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not much out there on these speakers. someone recently asked me what the zu sound is like. cause ive been talking about them for a few weeks now. Kev told me about these when i said i was looking for speakers that will run on 8-11w amps. i never heard of them before . i do not yet know what they sound like and the only place i can audition them is sold out and waiting for a couple pairs to come in soon.
zu sells internet direct and gives a full 60 day money back guarantee, they even pay the return shipping. so all you have to lose is the original shipping cost. they also sell what they call dirty zu's, on occasion. new cabinets with refurbished drivers, very inexpensive and then if you decide you like them , they give you 100% trade in value on you next pair of zus. pretty cool i think aside from the not being able to hear them before you purchase. lol.
but here is there company answers to some questions.
and a few pics ill add
What is nanotech to Zu and what do you mean by nano-sanctification?
Zu’s full-range nanotech loudspeaker drivers use pulpwood as a core material along with adhesives and nanometer engineered structural materials to create a very high performance driver membrane.
Why paper as a core? Because wood fibers have an excellent blend of strength, weight and damping for use as a dynamic speaker’s cone, the material is easy to work with and these fibers provide much greater service life compared to plastics, glass fibers and thin metal alloys. (The wave dynamics in cones of loudspeakers being played loudly are intense and will rapidly breakdown the vast majority of fibers and plastics.) But with advances in nanometer engineered structural materials it’s now possible to improve the wood fiber’s strength without hindering damping or performance over time.
Zu’s “nano sanctified” drivers feature a nano materials pallet developed to compliment and improve the wave dynamics of the paper cone—increased stiffness and shear, increased propagation velocity and better control of modes and damping behavior. While damping is improved it is not due to properties of the materials but rather to the reduced weight of the membrane over what was required without the use of nano material fortification—Zu’s nanotech cones are lighter than the pervious generation and better power transfer of waves on cone to waves in air results in reduced damping needs as more energy is transferred from one medium (the cone) to another (sound in air). So, better strength, lighter weight and this gives you better dynamics, greater bandwidth with less modal noise—clearer, more extended, more dynamic and natural, simply better sounding sound.
Nanometer material pallet on first generation Zu nano doped drivers (ZuND/G1, sans engineering detail): ceramic spheres, fumed silica, cristobalite nanofibers. Application: aerosol within a custom formulated epoxy matrix.
Dialog and additional insight as the above is an overview; in response to customer inquiry on nano sanctification:
The vagueness is not really intended but we think appropriate, the nano-level world behaves different than the normal structural world and what is happening down there is rarely visible. Maybe all this will make more sense after additional explanation, so here goes. The cone makeup is actually lighter by several grams compared to it’s predecessor, as we are reducing the need for other binders and damping compounds. We use epoxy so we can handle them (and handle them safely )and so the nano infused matrix lays more atop the fiber structure than penetrating it—the nanometer particles are so small that the bond with the material is via van der waal forces, primarily anyway depending on size/form and materials. Most of the time nano structure are added to epoxies or vinyl-esters to help further strengthen the matrix of synthetic and organic high-performance composites (graphite/carbon, Kevlar, glass, wood and other fibrous materials generally in heavily engineered close-mold resin infused stuff). Water is often used as a carrier on surface applications but in our case the water swells the paper core considerably and the particles are attracted/driven deep into the structure. There are other problems with waterborne solutions relative to our application like no sealing of the natural fibers and a lack of a defined skin/core, we want more of a skin on the cone structure so the paper can continue to act as a good damping force—only a portion of the energy is transferred to air and the loudspeaker’s surround, spider, frame and cabinet cannot damp or transfer all that much wave energy. The another reason for using epoxy as a carrier is that it makes it safe to spray. There are other ways to apply it but the sprayable mix works really good for our application, tools and level of sophistication.
For UV protection (epoxy degrades rapidly from UV exposure) we use UV absorbing compounds within the mix that rise to the surface of the super thin skin protection the epoxy from the sun. The matrix (not really a film but sort of, just very rough as it follows the structure of the core) is so thin that it’s extremely difficult to see the difference between the old cone and the nano imbued cone, or nano sanctified (we like sanctified, not so tech sounding and we think it sounds cool, but that’s just us being fun) but in the right light the nano sanctified cone reflects/refracts light differently and has an odd distant shimmer to it, like looking at the nearly starless cloudy parts of the Milky Way on a dark night in the middle of nowhere.
Zu’s “nano sanctification” ratios, epoxy compound and UV protectants are not released.
Posted on February 4, 2014 by Sean Casey and filed under Loudspeaker, Show All, Technical.
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What makes Zu loudspeakers so good?
(A bit of—us vs. them—done for perspective.) For us, a good loudspeakers play all genres of music, with real intensity, is dynamically expressive of tone and texture and is in time—all with convincing tone, putting the music out in a way that hooks you and pulls you in, or rips your guts out—good loudspeaker almost force your attention, and make you want to live life bigger, with greater effect. Today those that want full and hard hitting efficiency are cursed with a market full of unnatural sounding speakers, most featuring three or more speaker-drivers, complex crossover networks, low efficiency, and all claiming to sound perfect, lifelike, and better than the rest. Empty rhetoric if you ask Zu. Modern hi-fi speakers sound amazingly similar, and nothing close to engaging. Tweeters that make your ears bleed, woofers smaller than pancakes making all drums sound fake, and the stereo image they cast compares on a visual level to early ‘80s computer animation. The way the majority of loudspeakers are being done in hi-fi today is whacked.
We think a loudspeaker must have a wide dynamic range, which is the ability to play from very low to very high levels, with a linear, distortion-free dynamic behavior. This is held as the fundamental rule on which all Zu loudspeakers are based. In any loudspeaker there are five fundamental areas that make up its quality or tone: frequency, bandwidth, time, dispersion, and dynamic range. An engineer can, in most cases, borrow (or diminish) dynamic range to fix problems that exist in a loudspeaker’s bandwidth, frequency, and time domains, but the opposite is not true, leaving dynamic range as the defining character. Either a speaker has it, or it doesn’t. (Not forgetting dispersion, but this is application specific.) When playing music these domains do not behave in a linear way and it’s the deficit, or linearity between them that must be the engineers focus if real tonal and dynamic fidelity is to be had.
In addition to dynamic realism, a good hi-fi loudspeaker will also create a uniform, full-range wave front, with all notes emanating in the same time, so fidelity can be had throughout a listening area. Tone-textures, density, resolution and spatial qualities are all degraded if this is not realized. Nearly all of today’s loudspeakers fail to meet these criterion with linear dynamic behavior.
A full-range, direct-radiating loudspeaker driver can provide better timing than a multi-driver loudspeaker and, when properly designed and built, can eliminate the distortions introduced by crossovers and filters. Zu hi-fi loudspeakers do not use crossover or filter components on its full range drivers, and believes you will notice the clarity, aliveness and presence—even if you are used to much more expensive brands. This might take some time if you have grown up with dicked up modern hi-fi speakers but we think most of you that live with our stuff will come around—you need to do more than just taste the “Zu sound”.
Tests and measures can easily show all five facets of a loudspeaker’s performance, however, current practices in measuring loudspeakers—steady-state, odd FFT and data processing, single point mic location—result in little correlative data as to how it will perform under dynamic conditions, like music, and have little relevance to how it might sound in a living room. Technically, bandwidth does fall within amplitude domain but since bandwidth is so important, and can be engineered around amplitude goals, Zu handles it as a primary feature.
How are Zu loudspeakers different?
In a market where nearly all speakers are the same it would seem either Zu is wrong or everyone else is. There are many additional points that make Zu loudspeakers remarkable, but the following five distinctive traits lay the foundation.
Zu’s high efficiency full-range 10” loudspeaker driver platform plays nearly all the musical scale with stunning dynamic range, and with linear behavior, creating such a natural and vivid sound that you will no longer focus your attention on the speaker, just the music.
There are no crossovers sucking life out of the music like 99% of today’s loudspeakers.
Zu-Griewe driver/box/acoustic loading technology developed by Sean Casey and the late Ron Griewe allows improved driver-to-room coupling, fidelity, and bandwidth.
Zu’s own B3 internal cabling archetype and solderless termination offers significant improvement in amplifier / loudspeaker interaction, increased resolution and reduced noise.
In-house manufacturing ensures quality, consistency and long-term viability.
Zu’s 10” high efficiency, high power handling driver platform. With high power amplifiers saturating the market, why would anyone looking at loudspeakers consider high efficiency as an essential design feature? In addition to the technical reasons stated high efficiency is necessary for low power amplifiers; and the Zu + tube combination, especially single ended triodes, is certainly addictive. Same holds true for the more interesting solid-state designs, most of which is coming from Nelson Pass’s head and hands. Regardless of amplifier selected, a wide bandwidth driver with high efficiency, combined with wide dynamic range results in very real resolution and contrast. Combine dynamic range with good frequency and time behavior, and get sound that is so effortless and engaging that you find yourself making excuses to spend time listening. Zu loudspeakers give an owner the option to connect just about any amp, from a little 1 watt single-ended triode, through the super high-output transistor amps. Zu’s resolution and intimacy allow users to explore amplification at a whole new level. And this brings us to another side of the Zu speaker, that of high power handling. The main percussive feature in today’s music is the kick-drum and most hi-fi speakers can’t even look at a one, let alone reproduce it. They are either grossly inefficient, can’t play transient bass, or can’t handle power. Many loudspeakers have power handling, a few have high efficiency, Zu has both. Moderate to high power (twenty watts) combined with the high efficiency of Zu results in a dynamic range able to recreate concert level playback, or thunder claps, or car crashes, or jet flybys.... Zu believes in having the ability to do real levels without risk of damage to your gear or ears—its high sustained SPL levels plus noise that is the destroyer of gear and hearing. You won’t have to turn up the volume to uncomfortable levels to get convincing bang from a soundtrack, shove from your favorite electric guitar recordings or crescendo from Wagner.
No crossover. Zu loudspeakers are designed and built well enough not to need “fixing” with crossover and other electronics parts. Today, nearly all home audio loudspeakers use plastic or metal cones and crossovers. They do this as a cost savings measure, plastic cones are easy to work with and crossovers allow you to fix and tweak without the expense of heavy time and tooling. We also think plastic and metal cones are used as a gimmicky sales tool, new and different equals better. Loudspeaker drivers today are designed to look good first and produce a salable sound second. In the ‘50s, budgets and living room spaces were being split between television sets and audio, and it was during this time that acoustic suspension speakers were introduced. Consumers began to gravitate to small speakers that gave the impression of big sound, and today’s speaker builders continue in this convention. Real fidelity has all but disappeared in today’s living rooms and anyone who has tried to playback rock, big orchestra, even piano recordings on their home speakers at moderate to real levels knows it’s a long way from lifelike. For over fifty years now it has been, out with the big well-made speakers and in with the new smaller and cheaper ones featuring cost mandated imported drivers, engineered to sound impressive but not really delivering realism. Zu on the other hand has continued on the course set out by Western Electric, RCA, Westinghouse and others, using paper based cones, even leaning heavily on the exceptional 1930s RCA research and designs. Not being afraid to design and produce their own speaker-driver has allowed Zu to create a modern device that is capable of playing bass, mids and lower treble with better overall fidelity than the multi-driver designs of today, and without filter parts injecting noise, robbing efficiency, and sucking the soul from the music.
Zu-Griewe technology. Zu’s driver/box/acoustic impedance matching technology. Zu has designed a speaker-driver/box/room loading technology that reduces the acoustic impedance ratio of loudspeaker cone to room, thereby increasing efficiency and reducing cone motion. This original technology significantly widens the usable bandwidth and reduces distortion. It does not introduce distortions common to horn loaded speakers and is operable through several octaves.
With other speakers and technologies, if bandwidth is widened distortion is increased. Bass-reflex speakers are infamous for this, as are transmission lines, and acoustic suspension designs.
Zu cable inside. Zu does not skimp on the internal cable of its loudspeakers; no zip-cord running about, no cheap imported wire, nothing that will get in the way of performance. Zu manufactures its own cable and places considerable attention to this aspect of design. Zu’s own B3 internal cabling, combined with solderless and cold forged termination techniques lower noise and increase resolution, and significantly enhance amplifier/speaker intimacy. Within Zu loudspeakers you will find original Zu-designed and built cable assemblies using nothing but the highest-grade Zu cable product.
Zu builds what it sells. Today’s audio companies focus more on product style and packaging than fidelity or lasting quality. Its a, profit first, never mind performance or craftsmanship so long as they sell, business. Zu on the other hand makes audio gear with performance and build quality first; trusting that if it builds the best products, with a duty to community, sales and success will follow. Imagine, products selling themselves.... To maintain its inventiveness and realize its long term goals, Zu chooses to use critical components and sub-assemblies that have been developed by, and are made at Zu. Simply, our products are made by us at Zu, tested, listened to and packaged at Zu—If it wasn’t invented or made by us we have a serious problem putting our brand on it. Really, how much difference is there between loudspeakers that all sport nearly identical speaker drivers? If a manufacturing company is not continually reinvesting in production and tooling you can bet they will fall behind, maybe lose everything. Just look at the history of Tesla’s company or Western Electric.
Oddly, Zu is the exception today, most outside the aerospace/military companies no longer make product themselves, choosing instead to outsource the majority of their product. For every ten loudspeakers sold in the US at least nine are made in China. If you are a Chinese company, you should build it in China, and if your company is in Ogden, Utah you should build your products in Ogden. Sure there is a huge temptation to outsource and to get some of that cheap labor, but not for something you really care about, something you build that will be used nearly everyday of its and your life!
There are several other features that are original to Zu, but really, what it all comes down to is how the thing sounds to you and in your own living room.
Posted on August 18, 2013 by Sean Casey and filed under Loudspeaker, Philosophy, Show All.
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What is a full-range driver?
First, a loudspeaker driver is the part of a loudspeaker that converts electrical energy into acoustic (transducer), generally incomplete without the supporting enclosure and tuning system that together make up what is known as a loudspeaker system, “speaker” for short. The loudspeaker driver is nearly always of the electrodynamic type, consisting of a frame that supports a magnetic circuit, a cone and suspension system and voice coil.
In usage, Harry F. Olson, helped define the term full-range driver: as any loudspeaker drive unit capable of quality reproduction of bass through treble (musical terms, musically defined) with usable dynamic range when matched to the supporting acoustic space such as the speaker cabinet or mounting baffle.
Traditionally, single drive units capable of covering the bandwidth of roughly 60 Hz to 8 kHz have for over six decades been distinguished and marketed as full range. Zu specifically defines its use of the term full range in its marketing efforts, stating that its 10.3” full-range driver has an in-room bandwidth capacity of 35 Hz to 12 kHz, roughly eight and a half octaves. Super-tweeter covers the top octave; harmonics on muted trumpet, pan flute, a bit of shimmer on cymbals, and burnish on strings.... For more info and perspective on full-range driver terminology and some history please see Wannabe Curation Communication listed under Forum Claptrap.
Posted on August 18, 2013 by Sean Casey and filed under Loudspeaker, Technical, Show All.
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Tell me more about Zu's 10" full-range driver.
Zu is responsible for the net parameters of the driver, designed to sound good to us—and hopefully others—with heavy bias on dynamic expression, dynamic resolution, tone and texture, baritone weighted and designed to work with Zu-griewe acoustic loudspeaker loading technology.
Zu’s 10” Driver Chronology
Original Development on this 10” platform by Olson at RCA in the 1930s
CURRENT PRODUCTION
Zu103/ND/G1–16 16 ohm, 5336 grams (2011–). Model engraved on center cone.
Zu260FRD/ND-12 12 ohm, 4650 gram, (2013–), model engraved on center cone. Warm tone, less shove, undercut magnet.
Zu103CX/ND/G1–8 8 ohm 10” full-range co-ax, axially mounted super tweeter rolls in at 12kHz.
DISCONTINUED
Zu260FRD/G1 12 ohm, 5010 grams (2001–2003). Original design. Used in original Druid and Definition loudspeakers.
Zu260FRD/G2 12 ohm, 4660 grams (2003–2006). Second generation with changes to the motor and surround to improve bass.
Zu260FRD/G3 12 ohm, 4660 grams (2007). Changes made to the cone, assembly technique, and batching / matching process.
Zu260FRD/G4/Essence 12 ohm, 4807 grams (2008–2012). Essence specific, stiffening/weighting ribs on cone.
Zu103FRD/G1 16 ohm, 5193 grams (2007–2009). Used on Presence. Max shove / low Qes motor assembly.
Zu260FRD/Experience 16 ohm, 5350 grams (2011). Model engraved on center cone.
Zu260FRD/G4/HO 16 ohm, 5338 grams (2009–2013). Model engraved on center cone.
Zu machines and assembles the final motor work, finishes the driver frames, performs the final cone prep, binds and treats the cone, soak tests and proves the completed driver with a minimum of 600 hours of burn-in, final QC, testing, and tolerance matching. Our driver is made primarily by us and Eminence, with a few parts coming from other suppliers. It has many things finished by Eminence: the voice coil/former assembly, the charging of the magnet and the riveting of the yoke/magnet/frame. As stated, the driver is based largely on the 1930s technologies and research of Harry Olson. One of the greats that had his hands all over this format: the cone geometries, jib factors and suspension, voice coil size.... From what we can find the original cones were made by the Hawley paper company, and this full-range platform originated from RCA in Harry circa 1934. To say this is Eminence's or Zu's is delusional. Zu has certainly added it's feature to the platform, modern materials, improvements to bandwidth, power handling, power transfer.... All versions of the Zu 10” platform are unique, with differing applications and Thiele/Small electromechanical parameters. It’s funny that in 70–80 years audio hasn’t been able to really improve the basic design of a this rock solid 10” full range platform (we are however entering the age of nano engineering...).
Zu full-range drivers utilize diamagnetic materials in its motor to influence and shape the inductive dynamics under power of the interaction of static field and field of the coil. Considerations and design features relative to frequency, the eddy currents formed (the shape of the B fields of the coil relative to frequency and waveform) are also designed into our driver. These features are fully operative and designed to continue to be effective even under extreme SPL demands.
The center cylinder (phase plug) in a Zu 10” driver
A machined phase plug assembly, which is not in motion, directly connect to the frame/motor assembly, with both visible and hidden features allowing for the following benefits:
Extending high frequency limits of the driver assembly through a combination of whizzer cone and center pole detail profile and acoustic impedance matching.
MLS diffuser function of pole piece profile and rings aids in the widening of the high frequency (polar plot or beam pattern).
Aids in control of dynamic behavior through diamagnetic shunting (shorting) of spurious B fields.
Zu’s implementation of shunting is regulated, providing virtually no dynamic damping at low level play and increasing logarithmically to maximum in high SPL play.
Dramatic improvement in cooling as the assembly is press fit and uses thermally conductive adhesive. (Only significantly in play when you are pushing huge power, but there nonetheless.)
NOTE: layup is post centering/aligning/shimming of the motor/voice coil assembly, a process that then requires the hand removal of the center dust cap.
Posted on August 18, 2013 by Sean Casey and filed under Loudspeaker, Technical, Show All.
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Why doesn't Zu use crossovers in their speakers?
We think crossovers are tone suckers, especially when done at speaker-level as are 99% of hi-fi and home audio speakers. We believe the speaker-level crossovers rob tone from the system; that designing a full-range driver and loudspeaker system that does not need the heavy-handedness of a crossover is preferred and will sound better. Our full-range 10” drivers are designed around this objective and implemented into loudspeaker systems that do not require them—network components or bandwidth limiting elements are not used on any of our full-range 10” drivers. Cable comes in and runs full bandwidth directly to the voice coil—no inductors, resistors, capacitors, nothing. There is a high-pass network on the super-tweeter. Zu’s full-range drivers do exhibit aggressive high frequency attenuation from around 12k and up (high treble), but this is a function of the intrinsic behavior of the transducer (speaker driver) which cannot be defined as a component within a crossover network.
If a driver is running within its usable bandwidth without any network filtering or resistive influences, its low/high roll off or slope (knee, also referred to it as phase angle—dynamic behavior of the transducer as resistive elements, i.e. mechanical, acoustic and electrical functions of the motor...) should not be referred to as a crossover function. There is of course an acoustic crossing point between our super-tweeter and full-range driver, which can certainly be described as the acoustic crossover point, but the term crossover used in this way is attributive and not a definition of technology. The definition of a crossover as used in the audio lexicon, short for crossover network, must function as an isolated component and cannot require external reactive elements to complete it. A crossover network must perform the following functions: split a single input signal into at least two output signals, one output limiting bandwidth to the lower frequencies and the second output limiting bandwidth to the upper; having a “crossover" point between the two bands which will (hopefully) sum close to zero attenuation. In a three-way crossover network you would have the addition of a bandpass—one input signal, three output signals; low frequency band, mid band, high frequency band, with each crossing point between then summing to roughly zero.
Apologies. We did use an impedance modifying parallel filter on our first model of Definition, a zobel network, and its the only make and model to have used such a filter.
Posted on August 18, 2013 by Sean Casey and filed under Loudspeaker, Philosophy, Technical, Show All.
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What does Bob Moog thing about loudspeakers?
High efficiency, big fat dynamic range, wide bandwidth. Big dynamic range is realized through correct design of the driver’s motor system and the loudspeakers impedance match ratio to the room. In the early days of audio, inefficient loudspeaker drivers were made much more efficient through the use of horns. Horns are acoustic transformers, able to couple a high acoustic impedance like a dynamic driver, to the relatively low impedance of our atmosphere thereby radically improving power transfer. Western Electric and others were getting 50% efficiency with their monumental horn systems designed for the early theaters and yet hear we are nearly a hundred years latter happy with 1% efficiency in our homes.... But theatrical perfection and horns don’t really fit in normal homes, and even if they did there would still be fidelity issues, even in the largest of living rooms. Since horns are bandwidth limiting, only able to cover a few octaves without introducing high levels of distortion, an array of specific horns must be built to adequately cover the musical scale. The most basic is a two horn system, bass/midrange and midrange/treble. Large systems able to cover the entire musical scale were made up of five horns or more. Bandwidth optimization and splitting the music also resulted in timing issues and the introduction of the loudspeaker crossover network. The two technologies did allow for some improvement in fidelity back in the day as related to home playback. So, after roughly eighty years of band-aids and increasing complexity, Zu is continuing the search for real solutions for underlying problems. through researching the work of the pioneering giants, application of modern physics, innovation, the use of a highly developed materials pallet and making combination and assemblies repeatable through high-precision manufacturing.
Others on this similar path include the legendary Bob Moog—engineer with an ear. His comments are all relevant and applicable though in the context of what makes a good loudspeaker for plugging your Moog synthesizer into. His bottom line: “Use spec sheets as a guide, but rely primarily on your ear."
First, let's talk about acoustic power output. What we want out of a speaker is sound (acoustic power). As converters of electrical power, loudspeakers are generally inefficient. Most of the high-price juice going into a speaker cabinet winds up as heat instead of sound. Good, wide-range speaker systems typically have an efficiency of from 1/2 to 5%. That is, 100 watts of amplifier power may yield 1/2 to 5 acoustic watts of sound power. How loud is one acoustic watt? Well, a premium home music bookshelf speaker will generally burn out before it produces one acoustic watt continuously. A typical full-size professional studio monitor will produce three acoustic watts at rated power. And a supergroup's stadium sound reinforcement rig may produce a total of 100 to 1,000 acoustic watts, wide open. In a typical club environment, a speaker emitting one acoustic watt will produce a sound pressure of around 110 dB SPL onstage. Ten acoustic watts will produce an additional 10dB, which, as the textbooks say, is loud enough to hurt.
How about frequency response? The lowest F on a bass guitar is 42Hz, the C below that is 32Hz, and low A on an acoustic piano is 27-1/2Hz. Below 60Hz or so, every hertz of response is a significant addition in speaker system size, weight, and price. One person can move a moderately efficient speaker cabinet with a low-frequency cutoff of 45Hz, but it will take two people to handle a 30Hz cabinet of the same moderate efficiency. To my ears, response to 45Hz is necessary for a good "commercial" sound, while a 30 or 32Hz low-frequency cutoff adds a fullness that is sure nice to have. At the high end, you can hear the difference between 12kHz and 15kHz. A 12kHz high-frequency cutoff (and flat response below) gives a smooth, sparkly quality to bright timbres; extending the response to 15kHz adds a touch of brilliance and tinkle that can be significant in recording, or in small clubs.
Distortion becomes important when more than one pitch is played through the sound system. If you're feeding two or more keyboard instruments through the same speakers, you will have to be concerned about distortion. Unfortunately, speaker distortion characteristics are not given on spec sheets. You'll have to listen for yourself. It's generally audible when loud, low notes are played. To test for distortion, play a loud bass note along with a midrange chord. Speaker distortion will produce a "muddiness" that arises from sum and difference frequencies generated by the distortion component. In general (but not always), high-efficiency speaker systems and large speakers distort less than low efficiency speaker systems and small speakers.
Without a doubt, a typical good 100-watt guitar amp has the efficiency and stamina to put out a few acoustic watts. However, its frequency response and distortion characteristics are optimized for guitar: no significant response below 100Hz, a broad spectral "hole" around 500Hz, and sharply rising response above 1kHz, with some "warm" (low order) distortion. Guitar amps, therefore, are generally not suited for synthesizer sound reproduction. Similarly, most PA. systems are designed to make the human voice sound good. The P.A. frequency response (determined largely by the speakers) generally has a broad peak in the "presence" region of the spectrum (2–3kHz) and decidedly weak bass. Professional studio monitors, on the other hand, have more-than-adequate frequency response distortion characteristics, but often lack the stamina to produce loud, sustained, steady tones without over-heating. This is doubly true for some music speaker systems.
Keyboard amplifiers come closest to meeting our power, frequency response, and distortion requirements. High-frequency response is sometimes a problem. Many keyboard amplifier-speaker systems are designed primarily for tone-wheel organs, electric pianos, and similar instruments with little harmonic content. Such systems rarely have adequate high-frequency response for synthesizers. However a keyboard amplifier-speaker system with good speaker response to 12kHz or so is likely to meet all of our requirements for synthesizer sound production. If the speaker system itself is efficient, a 50– to 100–watt power amplifier will produce 2–5 acoustic watts, which is plenty for rehearsal or club work, while a 200- to 400-watt power amplifier will produce upwards of 20–25 acoustic watts, which is adequate for 95% of indoor gigs. When selecting an amplifier-speaker system for your synthesizer, it is a good idea to pick a few speaker systems that are efficient (that is, they sound just plain loud when fed with the output of a modest power amplifier) and then select the speaker from that group that sounds the smoothest and fattest. Use spec sheets as a guide, but rely primarily on your ear. —Bob Moog
Posted on August 18, 2013 by Sean Casey and filed under Loudspeaker, Philosophy, Technical, Show All.
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What is Zu-Griewe loudspeaker technology?
This technology is used in the majority of Zu’s loudspeakers. Its concepts can be used in any loudspeaker where there are internal velocity changes. The technology concept was introduced in Zu’s very first loudspeaker, Druid. The Zu-Griewe technology is a multi-octave impedance modifying acoustic model that can be applied to any acoustic system with alternating velocities; electro-acoustic, electromechanical, internal combustion engines, and so on. It is developed exclusively by the late Ron Griewe and Sean Casey. The original concept is Ron Griewe’s, a motorcycle legend that had a nice bit of engineering insight as he sat inching through Los Angeles traffic one afternoon. (More about Ron Griewe below.)
Let’s outline a few basic principles expressed in the technology and contrast them with bass reflex (ported) designs, as well as transmission lines, pipes and horns. A bass reflex loudspeaker uses a simple Helmoltz resonator to augment lower frequencies via the air “spring” in the cabinet and the “mass” in the port, tuned to add amplitude response, and control cone motion. A Helmoltz resonator consists of a rigid-walled cavity (the volume) with a neck (“port”) with an area and length. The fluid (air) moves as a unit within the port tube to provide the mass element and the acoustic pressure within the loudspeaker box provides the stiffness or spring element; the resistive element is provided by the opening that radiates the simple source sound. All Helmoltz resonators contain these basic elements, and all create sinusoidal waveforms but cannot recreate the complex and dynamic waveforms typical of music.
Zu-Griewe technology is expressed, on a fundamental level, like that of a waveguide with expanding acoustic cross section and terminated and driven at one end. Propagation within the Zu loudspeaker is mostly planer and standing waves are not as stimulated as in other similarly sized designs. Development of acoustic models accounting for driver introduced dynamic variables within horns, pipes, and transmission lines revealed areas of non-planer propagation. This turbulence (noise) is wavelength relational and proportional to amplitude. Zu-Griewe can reduce many of these problems.
Applied to loudspeakers, this new technology reduced noise in varying degrees over the majority of the audible bandwidth. These new ideas in acoustic impedance transform function, and the designs they realize are proprietary. The basic idea however is acoustic impedance matching of the high Z of the cone to the low acoustic Z of the room; the reduction of non-planer propagation in more than just a single octave; the reduction of internal cabinet standing waves.
Ron “Ogre” Griewe 1939–2005
Original concept as applied to exhaust systems for internal combustion reciprocating engines, is the brain child of the late great Ron “Ogre” Griewe—two wheels and a fist full of throttle. Sean had the pleasure of working and riding with Ron back in the nineties at ATK motorcycles.
Ron was a well-known and well-respected character and professional in the motorcycle world. Known in his younger days for desert racing, always running a bit too close to the edge, but always with a grin and a cigar. Later, Ron made a significant contribution to bikers, street and dirt, in his writings, projects and leadership at Cycle World magazine. While there he rose to Editor-In-Chief, a position he held for 16 years. But the Ron Sean knew was really an inventor and engineer, a guy that didn’t get his knowledge from a can. For him, leaving Cycle World—a bikers dream job, getting payed to ride all kinds of bikes all over the globe—to drag ATK America out of custom one-off dirtbikes shop and into a real production based American made dirtbike factory made perfect sense. Yeah, it was a while back when Ron and Sean tore it up together and only a season long, but Sean will never forget the time spent riding, talking and working with him. Ron turned seventy the month before Sean returned to audio; Ron was one fast mother, forget about age. Seriously fast, technical single track or super fast fire road. Riding the desserts of Southern California? Hit the Husky Monument.
Posted on August 18, 2013 by Sean Casey and filed under Loudspeaker, Technical, Show All.
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Impedance and its influence (electrical)
Many types of amplifiers will benefit greatly from a 12, 16 or even 32 ohm loudspeakers—even solid-state and even if they are only printed to work with 4 or 8 ohm speakers; going higher is generally not a problem, higher impedance presents less load to the amp, going too low is typically the problem. Higher impedance loudspeaker designs can and often do sound better than demanding low impedance designs. Here’s why:
First, it’s Ohm’s law. Many loudspeaker designers, reviewers, hobbyist, and consumers, fail to recognize some basic points about how a loudspeaker should be measured and what effects the amplifier can have on tests and measures as well as the musical performance, timbre, bandwidth, presence and so on. This article address the basic electrical relations between amplifier and loudspeaker, which together form an intimate relationship—get it wrong and your sound will suck. The Article does not attempt to detail the more complex dynamic behavior of the loudspeaker system, thermal changes at the transducers motor, loudspeaker cable influences, environmental conditions, nor how an audio power amplifier’s design will react to these dynamic impedance variables.
2.8 volts equal 1 watt, right? Only for true 8 ohm loudspeakers.
Ohm’s law, power, and SI units of measure:
V=IR I=V/R R=V/I
W=IV I=W/R R=V2/W
efficiency = output / input
Electric potential is voltage V, current is amperes I, resistance is ohms R, power is wattage W.
Loudspeakers are generally reactive AC devises. Power factors and impedance differentials between amplifier and loudspeaker must be considered. Solving for power, watts not voltage, is essential for understanding relationships. Power in watts is current times voltage. Phase angles can be ignored in basic loudspeaker testing but does factor in more complex dynamic behavior modeling. Without the correct understanding of basic power transfer, a complete detailing of the system and device under test, measures and data cannot be accurately correlated into observed fidelity. It should also be pointed out that without a basic understanding of test system, device, procedure and marketing can easily manipulate the tests, data and you.
The amplifier is a major factor in how a loudspeaker system performances, both technically and sonically. If testing the efficiency of a driver in an infinite baffle, correctly mapping the impedance across its bandwidth, then at least distilling the string of points into a nominal number is essential. You cannot simply pump in 2.8 volts and call it. Data acquired this way has little correlative meaning. Once impedance is known and plotted power and system efficiency can then be tested and the results can be useful.
Many Zu loudspeakers measure 12 ohms nominal. (Remember, the speaker driver’s measures and performance are in large part determined by the acoustic impedance system: box, horn, baffle... that they are mated with and raw driver or infinite baffle plots are not system impedance measures.) To get a basic measure of system efficiency we first solve for current, then voltage, all measures being at the loudspeaker’s input.
First solve for amperes; square-root of wattage over resistance (ignoring phase) which equals 0.289 amps. Then take amps times resistance to solve for voltage and we arrive at 3.5 volts input. So a 12 ohm load (older Zu Druid, Omen, Essence...) requires 3.5 volts at input to reach 1 watt. An input of 2.83 volts into a 12 ohm load yields 0.66 watts. Nearly all modern tests and measures on loudspeakers simply input 2.8 volts (assumption of an 8 ohm standard) which has almost no lay correlation to actual transduction efficiency and power. If all loudspeakers had a nominal impedance of 8 ohms then a 2.83 volt input would be fine and does in fact result in a nominal 1 watt of input power. With 4 ohm nominal loudspeakers we get; 2.83 volts input which equals 2 watts of electrical power at input, at 16 ohms its 1/2 watt and 32 ohm you are down to a 1/4 watt. Knowing power in and accurately measuring power out of a system you can then know efficiency. Voltage sensitivity is not efficiency, it is a subset of efficiency. Voltage sensitivity is a useful tool in specific applications and conditions but is typically the domain of the engineer.
Now add the amplifier and its design—it’s all about the matchup
Designers and reviewers should be working with power and impedance and not sensitivity and uncorrelated measures. Let’s take an ideally optimized class-A solid-state direct transistor drive power amplifier running wide open, best case when properly matched up to a loudspeaker designed for that amp is 25% electrical power efficiency, this is amplifier only efficiency and not system or loudspeaker. But when you take the same or similar class-A design and transformer couple the output transistors to the loudspeaker you can reach an electrical power efficiency up to 50%, again amplifier only. This is if everything is optimally designed and once understood a designer can then apply similar engineering and reason to transformer/loudspeaker optimization to further improve power transfer to the loudspeaker and net additional fidelity gains. With vacuum tubes this whole matchup is even more critical.
These are maximum percent efficiencies for series-fed class-A amplifiers occurring only under ideal conditions and for maximum signal swing.
Note, with class-A solid-state it’s important to always have your loudspeakers connected, driving your class-A amps without the load will result in excess heat generation within the power transistors. If the loudspeaker draws some of the power then the transistor has to handle proportionately less. The transistor has to dissipate the most power when the loudspeaker is disconnected. It’s always preferable to keep the load connected as long as the class-A amplifier, transformer coupled or not, is switched on.
Understanding power transfer dynamics will hint to why power amplifiers have such a huge impact on the playback systems timbre, dynamic range, bass response, presence, treble, how loud it sounds, and so on. Remember, the reactivity of a dynamic driver is dramatically effected by the loudspeaker design and the driver loading used (box, horn, baffle...) and the necessity for measuring the device as a complete loudspeaker system. This also reveals how the exaggerated “sensitivity” measures are being generated by the majority of brands. Now that we understand the basic relations between impedances voltage and current we can approach how a given power amplifier might behave and influence the tone, power, and presence of playback.
Posted on August 18, 2013 by Sean Casey and filed under Loudspeaker, Technical, Amplifier, Show All.
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What's the correct gap height?
All floor standing Zu loudspeakers that do not have a powered subwoofer need a bit of gap between the bottom of the loudspeaker and the floor. While they are not a ported design (bass reflex) the finger port detail on the bottom needs to see the acoustic impedance of the room to correctly function. Setting the gap height is relative to your amp matchup, your room and your tastes—it’s tunable. Yes, optimum gap height will change from amp to amp and person to person.
Start with 1/4” [6mm]
Min. 1/32” [1 mm]
Max. 5/8” [16 mm]
Increasing the gap height, depending on amplifier, usually results in increased bass weight in kick drum and wood timbre, but it nearly always results in less output in deep bass. More gap height usually increases bass noise as well, causing the timbre to be a bit thick or wooly sounding. Less then 1/4” [6mm] will increase bass articulation / attack, increases bottom octave amplitude, but does reduce overall bass amplitude a bit. Typically, most arrive at gap height to be just about 3/16” [5mm], which is the size of those skinny half-hight CD jewel cases, perfect for a quick and easy gauge. But again, each amp will respond differently as the gap height influences the load impedance, a good thing because you can now better match amp and speaker and room, a bad thing because there’s one more thing you can fiddle with. Here is a great time saving idea regarding adjusting your gap height....
How to make adjusting gap height simple.
Zu knows you have music to listen to and that you really hate fiddling with the gap height—getting down on your knees, looking up at the bubble level, checking to make sure all four spikes are solid... it gets old fast. So, once you get your speakers where you like ‘em—making sure the left and right channels are spaced the same distance from the listeners center line, that they have the same toe-in, that they are both level, and that the spikes are equally weighted, with no cabinet wobble—set the gap height to roughly 1/4”. Likely they will sound great, but still, you should mess around with the gap height, with some amps it makes a huge difference. The easy, and best way to do this is shimming the gap with standard letter sized paper. The paper will be placed on the floor centered under the loudspeaker between all four spikes—don’t lift the speaker up you don’t want your spikes on the paper you want them firmly coupled to the floor. Best place to start is with a stack of paper that will take up roughly half the gap space, listen and go from there. You might want to take sheets out, increasing the gap height a bit, or add to reduce the gap height, experiment. Do the gap height shimming with just your left channel connected (or right) it reduces the work to half. After you get the left side sounding the way you want, mirror the changes on the right channel. You might find the difference to be huge, we usually do. It’s easy and free, mess with it.
gap-height.png
zu sells internet direct and gives a full 60 day money back guarantee, they even pay the return shipping. so all you have to lose is the original shipping cost. they also sell what they call dirty zu's, on occasion. new cabinets with refurbished drivers, very inexpensive and then if you decide you like them , they give you 100% trade in value on you next pair of zus. pretty cool i think aside from the not being able to hear them before you purchase. lol.
but here is there company answers to some questions.
and a few pics ill add
What is nanotech to Zu and what do you mean by nano-sanctification?
Zu’s full-range nanotech loudspeaker drivers use pulpwood as a core material along with adhesives and nanometer engineered structural materials to create a very high performance driver membrane.
Why paper as a core? Because wood fibers have an excellent blend of strength, weight and damping for use as a dynamic speaker’s cone, the material is easy to work with and these fibers provide much greater service life compared to plastics, glass fibers and thin metal alloys. (The wave dynamics in cones of loudspeakers being played loudly are intense and will rapidly breakdown the vast majority of fibers and plastics.) But with advances in nanometer engineered structural materials it’s now possible to improve the wood fiber’s strength without hindering damping or performance over time.
Zu’s “nano sanctified” drivers feature a nano materials pallet developed to compliment and improve the wave dynamics of the paper cone—increased stiffness and shear, increased propagation velocity and better control of modes and damping behavior. While damping is improved it is not due to properties of the materials but rather to the reduced weight of the membrane over what was required without the use of nano material fortification—Zu’s nanotech cones are lighter than the pervious generation and better power transfer of waves on cone to waves in air results in reduced damping needs as more energy is transferred from one medium (the cone) to another (sound in air). So, better strength, lighter weight and this gives you better dynamics, greater bandwidth with less modal noise—clearer, more extended, more dynamic and natural, simply better sounding sound.
Nanometer material pallet on first generation Zu nano doped drivers (ZuND/G1, sans engineering detail): ceramic spheres, fumed silica, cristobalite nanofibers. Application: aerosol within a custom formulated epoxy matrix.
Dialog and additional insight as the above is an overview; in response to customer inquiry on nano sanctification:
The vagueness is not really intended but we think appropriate, the nano-level world behaves different than the normal structural world and what is happening down there is rarely visible. Maybe all this will make more sense after additional explanation, so here goes. The cone makeup is actually lighter by several grams compared to it’s predecessor, as we are reducing the need for other binders and damping compounds. We use epoxy so we can handle them (and handle them safely )and so the nano infused matrix lays more atop the fiber structure than penetrating it—the nanometer particles are so small that the bond with the material is via van der waal forces, primarily anyway depending on size/form and materials. Most of the time nano structure are added to epoxies or vinyl-esters to help further strengthen the matrix of synthetic and organic high-performance composites (graphite/carbon, Kevlar, glass, wood and other fibrous materials generally in heavily engineered close-mold resin infused stuff). Water is often used as a carrier on surface applications but in our case the water swells the paper core considerably and the particles are attracted/driven deep into the structure. There are other problems with waterborne solutions relative to our application like no sealing of the natural fibers and a lack of a defined skin/core, we want more of a skin on the cone structure so the paper can continue to act as a good damping force—only a portion of the energy is transferred to air and the loudspeaker’s surround, spider, frame and cabinet cannot damp or transfer all that much wave energy. The another reason for using epoxy as a carrier is that it makes it safe to spray. There are other ways to apply it but the sprayable mix works really good for our application, tools and level of sophistication.
For UV protection (epoxy degrades rapidly from UV exposure) we use UV absorbing compounds within the mix that rise to the surface of the super thin skin protection the epoxy from the sun. The matrix (not really a film but sort of, just very rough as it follows the structure of the core) is so thin that it’s extremely difficult to see the difference between the old cone and the nano imbued cone, or nano sanctified (we like sanctified, not so tech sounding and we think it sounds cool, but that’s just us being fun) but in the right light the nano sanctified cone reflects/refracts light differently and has an odd distant shimmer to it, like looking at the nearly starless cloudy parts of the Milky Way on a dark night in the middle of nowhere.
Zu’s “nano sanctification” ratios, epoxy compound and UV protectants are not released.
Posted on February 4, 2014 by Sean Casey and filed under Loudspeaker, Show All, Technical.
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What makes Zu loudspeakers so good?
(A bit of—us vs. them—done for perspective.) For us, a good loudspeakers play all genres of music, with real intensity, is dynamically expressive of tone and texture and is in time—all with convincing tone, putting the music out in a way that hooks you and pulls you in, or rips your guts out—good loudspeaker almost force your attention, and make you want to live life bigger, with greater effect. Today those that want full and hard hitting efficiency are cursed with a market full of unnatural sounding speakers, most featuring three or more speaker-drivers, complex crossover networks, low efficiency, and all claiming to sound perfect, lifelike, and better than the rest. Empty rhetoric if you ask Zu. Modern hi-fi speakers sound amazingly similar, and nothing close to engaging. Tweeters that make your ears bleed, woofers smaller than pancakes making all drums sound fake, and the stereo image they cast compares on a visual level to early ‘80s computer animation. The way the majority of loudspeakers are being done in hi-fi today is whacked.
We think a loudspeaker must have a wide dynamic range, which is the ability to play from very low to very high levels, with a linear, distortion-free dynamic behavior. This is held as the fundamental rule on which all Zu loudspeakers are based. In any loudspeaker there are five fundamental areas that make up its quality or tone: frequency, bandwidth, time, dispersion, and dynamic range. An engineer can, in most cases, borrow (or diminish) dynamic range to fix problems that exist in a loudspeaker’s bandwidth, frequency, and time domains, but the opposite is not true, leaving dynamic range as the defining character. Either a speaker has it, or it doesn’t. (Not forgetting dispersion, but this is application specific.) When playing music these domains do not behave in a linear way and it’s the deficit, or linearity between them that must be the engineers focus if real tonal and dynamic fidelity is to be had.
In addition to dynamic realism, a good hi-fi loudspeaker will also create a uniform, full-range wave front, with all notes emanating in the same time, so fidelity can be had throughout a listening area. Tone-textures, density, resolution and spatial qualities are all degraded if this is not realized. Nearly all of today’s loudspeakers fail to meet these criterion with linear dynamic behavior.
A full-range, direct-radiating loudspeaker driver can provide better timing than a multi-driver loudspeaker and, when properly designed and built, can eliminate the distortions introduced by crossovers and filters. Zu hi-fi loudspeakers do not use crossover or filter components on its full range drivers, and believes you will notice the clarity, aliveness and presence—even if you are used to much more expensive brands. This might take some time if you have grown up with dicked up modern hi-fi speakers but we think most of you that live with our stuff will come around—you need to do more than just taste the “Zu sound”.
Tests and measures can easily show all five facets of a loudspeaker’s performance, however, current practices in measuring loudspeakers—steady-state, odd FFT and data processing, single point mic location—result in little correlative data as to how it will perform under dynamic conditions, like music, and have little relevance to how it might sound in a living room. Technically, bandwidth does fall within amplitude domain but since bandwidth is so important, and can be engineered around amplitude goals, Zu handles it as a primary feature.
How are Zu loudspeakers different?
In a market where nearly all speakers are the same it would seem either Zu is wrong or everyone else is. There are many additional points that make Zu loudspeakers remarkable, but the following five distinctive traits lay the foundation.
Zu’s high efficiency full-range 10” loudspeaker driver platform plays nearly all the musical scale with stunning dynamic range, and with linear behavior, creating such a natural and vivid sound that you will no longer focus your attention on the speaker, just the music.
There are no crossovers sucking life out of the music like 99% of today’s loudspeakers.
Zu-Griewe driver/box/acoustic loading technology developed by Sean Casey and the late Ron Griewe allows improved driver-to-room coupling, fidelity, and bandwidth.
Zu’s own B3 internal cabling archetype and solderless termination offers significant improvement in amplifier / loudspeaker interaction, increased resolution and reduced noise.
In-house manufacturing ensures quality, consistency and long-term viability.
Zu’s 10” high efficiency, high power handling driver platform. With high power amplifiers saturating the market, why would anyone looking at loudspeakers consider high efficiency as an essential design feature? In addition to the technical reasons stated high efficiency is necessary for low power amplifiers; and the Zu + tube combination, especially single ended triodes, is certainly addictive. Same holds true for the more interesting solid-state designs, most of which is coming from Nelson Pass’s head and hands. Regardless of amplifier selected, a wide bandwidth driver with high efficiency, combined with wide dynamic range results in very real resolution and contrast. Combine dynamic range with good frequency and time behavior, and get sound that is so effortless and engaging that you find yourself making excuses to spend time listening. Zu loudspeakers give an owner the option to connect just about any amp, from a little 1 watt single-ended triode, through the super high-output transistor amps. Zu’s resolution and intimacy allow users to explore amplification at a whole new level. And this brings us to another side of the Zu speaker, that of high power handling. The main percussive feature in today’s music is the kick-drum and most hi-fi speakers can’t even look at a one, let alone reproduce it. They are either grossly inefficient, can’t play transient bass, or can’t handle power. Many loudspeakers have power handling, a few have high efficiency, Zu has both. Moderate to high power (twenty watts) combined with the high efficiency of Zu results in a dynamic range able to recreate concert level playback, or thunder claps, or car crashes, or jet flybys.... Zu believes in having the ability to do real levels without risk of damage to your gear or ears—its high sustained SPL levels plus noise that is the destroyer of gear and hearing. You won’t have to turn up the volume to uncomfortable levels to get convincing bang from a soundtrack, shove from your favorite electric guitar recordings or crescendo from Wagner.
No crossover. Zu loudspeakers are designed and built well enough not to need “fixing” with crossover and other electronics parts. Today, nearly all home audio loudspeakers use plastic or metal cones and crossovers. They do this as a cost savings measure, plastic cones are easy to work with and crossovers allow you to fix and tweak without the expense of heavy time and tooling. We also think plastic and metal cones are used as a gimmicky sales tool, new and different equals better. Loudspeaker drivers today are designed to look good first and produce a salable sound second. In the ‘50s, budgets and living room spaces were being split between television sets and audio, and it was during this time that acoustic suspension speakers were introduced. Consumers began to gravitate to small speakers that gave the impression of big sound, and today’s speaker builders continue in this convention. Real fidelity has all but disappeared in today’s living rooms and anyone who has tried to playback rock, big orchestra, even piano recordings on their home speakers at moderate to real levels knows it’s a long way from lifelike. For over fifty years now it has been, out with the big well-made speakers and in with the new smaller and cheaper ones featuring cost mandated imported drivers, engineered to sound impressive but not really delivering realism. Zu on the other hand has continued on the course set out by Western Electric, RCA, Westinghouse and others, using paper based cones, even leaning heavily on the exceptional 1930s RCA research and designs. Not being afraid to design and produce their own speaker-driver has allowed Zu to create a modern device that is capable of playing bass, mids and lower treble with better overall fidelity than the multi-driver designs of today, and without filter parts injecting noise, robbing efficiency, and sucking the soul from the music.
Zu-Griewe technology. Zu’s driver/box/acoustic impedance matching technology. Zu has designed a speaker-driver/box/room loading technology that reduces the acoustic impedance ratio of loudspeaker cone to room, thereby increasing efficiency and reducing cone motion. This original technology significantly widens the usable bandwidth and reduces distortion. It does not introduce distortions common to horn loaded speakers and is operable through several octaves.
With other speakers and technologies, if bandwidth is widened distortion is increased. Bass-reflex speakers are infamous for this, as are transmission lines, and acoustic suspension designs.
Zu cable inside. Zu does not skimp on the internal cable of its loudspeakers; no zip-cord running about, no cheap imported wire, nothing that will get in the way of performance. Zu manufactures its own cable and places considerable attention to this aspect of design. Zu’s own B3 internal cabling, combined with solderless and cold forged termination techniques lower noise and increase resolution, and significantly enhance amplifier/speaker intimacy. Within Zu loudspeakers you will find original Zu-designed and built cable assemblies using nothing but the highest-grade Zu cable product.
Zu builds what it sells. Today’s audio companies focus more on product style and packaging than fidelity or lasting quality. Its a, profit first, never mind performance or craftsmanship so long as they sell, business. Zu on the other hand makes audio gear with performance and build quality first; trusting that if it builds the best products, with a duty to community, sales and success will follow. Imagine, products selling themselves.... To maintain its inventiveness and realize its long term goals, Zu chooses to use critical components and sub-assemblies that have been developed by, and are made at Zu. Simply, our products are made by us at Zu, tested, listened to and packaged at Zu—If it wasn’t invented or made by us we have a serious problem putting our brand on it. Really, how much difference is there between loudspeakers that all sport nearly identical speaker drivers? If a manufacturing company is not continually reinvesting in production and tooling you can bet they will fall behind, maybe lose everything. Just look at the history of Tesla’s company or Western Electric.
Oddly, Zu is the exception today, most outside the aerospace/military companies no longer make product themselves, choosing instead to outsource the majority of their product. For every ten loudspeakers sold in the US at least nine are made in China. If you are a Chinese company, you should build it in China, and if your company is in Ogden, Utah you should build your products in Ogden. Sure there is a huge temptation to outsource and to get some of that cheap labor, but not for something you really care about, something you build that will be used nearly everyday of its and your life!
There are several other features that are original to Zu, but really, what it all comes down to is how the thing sounds to you and in your own living room.
Posted on August 18, 2013 by Sean Casey and filed under Loudspeaker, Philosophy, Show All.
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What is a full-range driver?
First, a loudspeaker driver is the part of a loudspeaker that converts electrical energy into acoustic (transducer), generally incomplete without the supporting enclosure and tuning system that together make up what is known as a loudspeaker system, “speaker” for short. The loudspeaker driver is nearly always of the electrodynamic type, consisting of a frame that supports a magnetic circuit, a cone and suspension system and voice coil.
In usage, Harry F. Olson, helped define the term full-range driver: as any loudspeaker drive unit capable of quality reproduction of bass through treble (musical terms, musically defined) with usable dynamic range when matched to the supporting acoustic space such as the speaker cabinet or mounting baffle.
Traditionally, single drive units capable of covering the bandwidth of roughly 60 Hz to 8 kHz have for over six decades been distinguished and marketed as full range. Zu specifically defines its use of the term full range in its marketing efforts, stating that its 10.3” full-range driver has an in-room bandwidth capacity of 35 Hz to 12 kHz, roughly eight and a half octaves. Super-tweeter covers the top octave; harmonics on muted trumpet, pan flute, a bit of shimmer on cymbals, and burnish on strings.... For more info and perspective on full-range driver terminology and some history please see Wannabe Curation Communication listed under Forum Claptrap.
Posted on August 18, 2013 by Sean Casey and filed under Loudspeaker, Technical, Show All.
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Tell me more about Zu's 10" full-range driver.
Zu is responsible for the net parameters of the driver, designed to sound good to us—and hopefully others—with heavy bias on dynamic expression, dynamic resolution, tone and texture, baritone weighted and designed to work with Zu-griewe acoustic loudspeaker loading technology.
Zu’s 10” Driver Chronology
Original Development on this 10” platform by Olson at RCA in the 1930s
CURRENT PRODUCTION
Zu103/ND/G1–16 16 ohm, 5336 grams (2011–). Model engraved on center cone.
Zu260FRD/ND-12 12 ohm, 4650 gram, (2013–), model engraved on center cone. Warm tone, less shove, undercut magnet.
Zu103CX/ND/G1–8 8 ohm 10” full-range co-ax, axially mounted super tweeter rolls in at 12kHz.
DISCONTINUED
Zu260FRD/G1 12 ohm, 5010 grams (2001–2003). Original design. Used in original Druid and Definition loudspeakers.
Zu260FRD/G2 12 ohm, 4660 grams (2003–2006). Second generation with changes to the motor and surround to improve bass.
Zu260FRD/G3 12 ohm, 4660 grams (2007). Changes made to the cone, assembly technique, and batching / matching process.
Zu260FRD/G4/Essence 12 ohm, 4807 grams (2008–2012). Essence specific, stiffening/weighting ribs on cone.
Zu103FRD/G1 16 ohm, 5193 grams (2007–2009). Used on Presence. Max shove / low Qes motor assembly.
Zu260FRD/Experience 16 ohm, 5350 grams (2011). Model engraved on center cone.
Zu260FRD/G4/HO 16 ohm, 5338 grams (2009–2013). Model engraved on center cone.
Zu machines and assembles the final motor work, finishes the driver frames, performs the final cone prep, binds and treats the cone, soak tests and proves the completed driver with a minimum of 600 hours of burn-in, final QC, testing, and tolerance matching. Our driver is made primarily by us and Eminence, with a few parts coming from other suppliers. It has many things finished by Eminence: the voice coil/former assembly, the charging of the magnet and the riveting of the yoke/magnet/frame. As stated, the driver is based largely on the 1930s technologies and research of Harry Olson. One of the greats that had his hands all over this format: the cone geometries, jib factors and suspension, voice coil size.... From what we can find the original cones were made by the Hawley paper company, and this full-range platform originated from RCA in Harry circa 1934. To say this is Eminence's or Zu's is delusional. Zu has certainly added it's feature to the platform, modern materials, improvements to bandwidth, power handling, power transfer.... All versions of the Zu 10” platform are unique, with differing applications and Thiele/Small electromechanical parameters. It’s funny that in 70–80 years audio hasn’t been able to really improve the basic design of a this rock solid 10” full range platform (we are however entering the age of nano engineering...).
Zu full-range drivers utilize diamagnetic materials in its motor to influence and shape the inductive dynamics under power of the interaction of static field and field of the coil. Considerations and design features relative to frequency, the eddy currents formed (the shape of the B fields of the coil relative to frequency and waveform) are also designed into our driver. These features are fully operative and designed to continue to be effective even under extreme SPL demands.
The center cylinder (phase plug) in a Zu 10” driver
A machined phase plug assembly, which is not in motion, directly connect to the frame/motor assembly, with both visible and hidden features allowing for the following benefits:
Extending high frequency limits of the driver assembly through a combination of whizzer cone and center pole detail profile and acoustic impedance matching.
MLS diffuser function of pole piece profile and rings aids in the widening of the high frequency (polar plot or beam pattern).
Aids in control of dynamic behavior through diamagnetic shunting (shorting) of spurious B fields.
Zu’s implementation of shunting is regulated, providing virtually no dynamic damping at low level play and increasing logarithmically to maximum in high SPL play.
Dramatic improvement in cooling as the assembly is press fit and uses thermally conductive adhesive. (Only significantly in play when you are pushing huge power, but there nonetheless.)
NOTE: layup is post centering/aligning/shimming of the motor/voice coil assembly, a process that then requires the hand removal of the center dust cap.
Posted on August 18, 2013 by Sean Casey and filed under Loudspeaker, Technical, Show All.
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Why doesn't Zu use crossovers in their speakers?
We think crossovers are tone suckers, especially when done at speaker-level as are 99% of hi-fi and home audio speakers. We believe the speaker-level crossovers rob tone from the system; that designing a full-range driver and loudspeaker system that does not need the heavy-handedness of a crossover is preferred and will sound better. Our full-range 10” drivers are designed around this objective and implemented into loudspeaker systems that do not require them—network components or bandwidth limiting elements are not used on any of our full-range 10” drivers. Cable comes in and runs full bandwidth directly to the voice coil—no inductors, resistors, capacitors, nothing. There is a high-pass network on the super-tweeter. Zu’s full-range drivers do exhibit aggressive high frequency attenuation from around 12k and up (high treble), but this is a function of the intrinsic behavior of the transducer (speaker driver) which cannot be defined as a component within a crossover network.
If a driver is running within its usable bandwidth without any network filtering or resistive influences, its low/high roll off or slope (knee, also referred to it as phase angle—dynamic behavior of the transducer as resistive elements, i.e. mechanical, acoustic and electrical functions of the motor...) should not be referred to as a crossover function. There is of course an acoustic crossing point between our super-tweeter and full-range driver, which can certainly be described as the acoustic crossover point, but the term crossover used in this way is attributive and not a definition of technology. The definition of a crossover as used in the audio lexicon, short for crossover network, must function as an isolated component and cannot require external reactive elements to complete it. A crossover network must perform the following functions: split a single input signal into at least two output signals, one output limiting bandwidth to the lower frequencies and the second output limiting bandwidth to the upper; having a “crossover" point between the two bands which will (hopefully) sum close to zero attenuation. In a three-way crossover network you would have the addition of a bandpass—one input signal, three output signals; low frequency band, mid band, high frequency band, with each crossing point between then summing to roughly zero.
Apologies. We did use an impedance modifying parallel filter on our first model of Definition, a zobel network, and its the only make and model to have used such a filter.
Posted on August 18, 2013 by Sean Casey and filed under Loudspeaker, Philosophy, Technical, Show All.
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What does Bob Moog thing about loudspeakers?
High efficiency, big fat dynamic range, wide bandwidth. Big dynamic range is realized through correct design of the driver’s motor system and the loudspeakers impedance match ratio to the room. In the early days of audio, inefficient loudspeaker drivers were made much more efficient through the use of horns. Horns are acoustic transformers, able to couple a high acoustic impedance like a dynamic driver, to the relatively low impedance of our atmosphere thereby radically improving power transfer. Western Electric and others were getting 50% efficiency with their monumental horn systems designed for the early theaters and yet hear we are nearly a hundred years latter happy with 1% efficiency in our homes.... But theatrical perfection and horns don’t really fit in normal homes, and even if they did there would still be fidelity issues, even in the largest of living rooms. Since horns are bandwidth limiting, only able to cover a few octaves without introducing high levels of distortion, an array of specific horns must be built to adequately cover the musical scale. The most basic is a two horn system, bass/midrange and midrange/treble. Large systems able to cover the entire musical scale were made up of five horns or more. Bandwidth optimization and splitting the music also resulted in timing issues and the introduction of the loudspeaker crossover network. The two technologies did allow for some improvement in fidelity back in the day as related to home playback. So, after roughly eighty years of band-aids and increasing complexity, Zu is continuing the search for real solutions for underlying problems. through researching the work of the pioneering giants, application of modern physics, innovation, the use of a highly developed materials pallet and making combination and assemblies repeatable through high-precision manufacturing.
Others on this similar path include the legendary Bob Moog—engineer with an ear. His comments are all relevant and applicable though in the context of what makes a good loudspeaker for plugging your Moog synthesizer into. His bottom line: “Use spec sheets as a guide, but rely primarily on your ear."
First, let's talk about acoustic power output. What we want out of a speaker is sound (acoustic power). As converters of electrical power, loudspeakers are generally inefficient. Most of the high-price juice going into a speaker cabinet winds up as heat instead of sound. Good, wide-range speaker systems typically have an efficiency of from 1/2 to 5%. That is, 100 watts of amplifier power may yield 1/2 to 5 acoustic watts of sound power. How loud is one acoustic watt? Well, a premium home music bookshelf speaker will generally burn out before it produces one acoustic watt continuously. A typical full-size professional studio monitor will produce three acoustic watts at rated power. And a supergroup's stadium sound reinforcement rig may produce a total of 100 to 1,000 acoustic watts, wide open. In a typical club environment, a speaker emitting one acoustic watt will produce a sound pressure of around 110 dB SPL onstage. Ten acoustic watts will produce an additional 10dB, which, as the textbooks say, is loud enough to hurt.
How about frequency response? The lowest F on a bass guitar is 42Hz, the C below that is 32Hz, and low A on an acoustic piano is 27-1/2Hz. Below 60Hz or so, every hertz of response is a significant addition in speaker system size, weight, and price. One person can move a moderately efficient speaker cabinet with a low-frequency cutoff of 45Hz, but it will take two people to handle a 30Hz cabinet of the same moderate efficiency. To my ears, response to 45Hz is necessary for a good "commercial" sound, while a 30 or 32Hz low-frequency cutoff adds a fullness that is sure nice to have. At the high end, you can hear the difference between 12kHz and 15kHz. A 12kHz high-frequency cutoff (and flat response below) gives a smooth, sparkly quality to bright timbres; extending the response to 15kHz adds a touch of brilliance and tinkle that can be significant in recording, or in small clubs.
Distortion becomes important when more than one pitch is played through the sound system. If you're feeding two or more keyboard instruments through the same speakers, you will have to be concerned about distortion. Unfortunately, speaker distortion characteristics are not given on spec sheets. You'll have to listen for yourself. It's generally audible when loud, low notes are played. To test for distortion, play a loud bass note along with a midrange chord. Speaker distortion will produce a "muddiness" that arises from sum and difference frequencies generated by the distortion component. In general (but not always), high-efficiency speaker systems and large speakers distort less than low efficiency speaker systems and small speakers.
Without a doubt, a typical good 100-watt guitar amp has the efficiency and stamina to put out a few acoustic watts. However, its frequency response and distortion characteristics are optimized for guitar: no significant response below 100Hz, a broad spectral "hole" around 500Hz, and sharply rising response above 1kHz, with some "warm" (low order) distortion. Guitar amps, therefore, are generally not suited for synthesizer sound reproduction. Similarly, most PA. systems are designed to make the human voice sound good. The P.A. frequency response (determined largely by the speakers) generally has a broad peak in the "presence" region of the spectrum (2–3kHz) and decidedly weak bass. Professional studio monitors, on the other hand, have more-than-adequate frequency response distortion characteristics, but often lack the stamina to produce loud, sustained, steady tones without over-heating. This is doubly true for some music speaker systems.
Keyboard amplifiers come closest to meeting our power, frequency response, and distortion requirements. High-frequency response is sometimes a problem. Many keyboard amplifier-speaker systems are designed primarily for tone-wheel organs, electric pianos, and similar instruments with little harmonic content. Such systems rarely have adequate high-frequency response for synthesizers. However a keyboard amplifier-speaker system with good speaker response to 12kHz or so is likely to meet all of our requirements for synthesizer sound production. If the speaker system itself is efficient, a 50– to 100–watt power amplifier will produce 2–5 acoustic watts, which is plenty for rehearsal or club work, while a 200- to 400-watt power amplifier will produce upwards of 20–25 acoustic watts, which is adequate for 95% of indoor gigs. When selecting an amplifier-speaker system for your synthesizer, it is a good idea to pick a few speaker systems that are efficient (that is, they sound just plain loud when fed with the output of a modest power amplifier) and then select the speaker from that group that sounds the smoothest and fattest. Use spec sheets as a guide, but rely primarily on your ear. —Bob Moog
Posted on August 18, 2013 by Sean Casey and filed under Loudspeaker, Philosophy, Technical, Show All.
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What is Zu-Griewe loudspeaker technology?
This technology is used in the majority of Zu’s loudspeakers. Its concepts can be used in any loudspeaker where there are internal velocity changes. The technology concept was introduced in Zu’s very first loudspeaker, Druid. The Zu-Griewe technology is a multi-octave impedance modifying acoustic model that can be applied to any acoustic system with alternating velocities; electro-acoustic, electromechanical, internal combustion engines, and so on. It is developed exclusively by the late Ron Griewe and Sean Casey. The original concept is Ron Griewe’s, a motorcycle legend that had a nice bit of engineering insight as he sat inching through Los Angeles traffic one afternoon. (More about Ron Griewe below.)
Let’s outline a few basic principles expressed in the technology and contrast them with bass reflex (ported) designs, as well as transmission lines, pipes and horns. A bass reflex loudspeaker uses a simple Helmoltz resonator to augment lower frequencies via the air “spring” in the cabinet and the “mass” in the port, tuned to add amplitude response, and control cone motion. A Helmoltz resonator consists of a rigid-walled cavity (the volume) with a neck (“port”) with an area and length. The fluid (air) moves as a unit within the port tube to provide the mass element and the acoustic pressure within the loudspeaker box provides the stiffness or spring element; the resistive element is provided by the opening that radiates the simple source sound. All Helmoltz resonators contain these basic elements, and all create sinusoidal waveforms but cannot recreate the complex and dynamic waveforms typical of music.
Zu-Griewe technology is expressed, on a fundamental level, like that of a waveguide with expanding acoustic cross section and terminated and driven at one end. Propagation within the Zu loudspeaker is mostly planer and standing waves are not as stimulated as in other similarly sized designs. Development of acoustic models accounting for driver introduced dynamic variables within horns, pipes, and transmission lines revealed areas of non-planer propagation. This turbulence (noise) is wavelength relational and proportional to amplitude. Zu-Griewe can reduce many of these problems.
Applied to loudspeakers, this new technology reduced noise in varying degrees over the majority of the audible bandwidth. These new ideas in acoustic impedance transform function, and the designs they realize are proprietary. The basic idea however is acoustic impedance matching of the high Z of the cone to the low acoustic Z of the room; the reduction of non-planer propagation in more than just a single octave; the reduction of internal cabinet standing waves.
Ron “Ogre” Griewe 1939–2005
Original concept as applied to exhaust systems for internal combustion reciprocating engines, is the brain child of the late great Ron “Ogre” Griewe—two wheels and a fist full of throttle. Sean had the pleasure of working and riding with Ron back in the nineties at ATK motorcycles.
Ron was a well-known and well-respected character and professional in the motorcycle world. Known in his younger days for desert racing, always running a bit too close to the edge, but always with a grin and a cigar. Later, Ron made a significant contribution to bikers, street and dirt, in his writings, projects and leadership at Cycle World magazine. While there he rose to Editor-In-Chief, a position he held for 16 years. But the Ron Sean knew was really an inventor and engineer, a guy that didn’t get his knowledge from a can. For him, leaving Cycle World—a bikers dream job, getting payed to ride all kinds of bikes all over the globe—to drag ATK America out of custom one-off dirtbikes shop and into a real production based American made dirtbike factory made perfect sense. Yeah, it was a while back when Ron and Sean tore it up together and only a season long, but Sean will never forget the time spent riding, talking and working with him. Ron turned seventy the month before Sean returned to audio; Ron was one fast mother, forget about age. Seriously fast, technical single track or super fast fire road. Riding the desserts of Southern California? Hit the Husky Monument.
Posted on August 18, 2013 by Sean Casey and filed under Loudspeaker, Technical, Show All.
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Impedance and its influence (electrical)
Many types of amplifiers will benefit greatly from a 12, 16 or even 32 ohm loudspeakers—even solid-state and even if they are only printed to work with 4 or 8 ohm speakers; going higher is generally not a problem, higher impedance presents less load to the amp, going too low is typically the problem. Higher impedance loudspeaker designs can and often do sound better than demanding low impedance designs. Here’s why:
First, it’s Ohm’s law. Many loudspeaker designers, reviewers, hobbyist, and consumers, fail to recognize some basic points about how a loudspeaker should be measured and what effects the amplifier can have on tests and measures as well as the musical performance, timbre, bandwidth, presence and so on. This article address the basic electrical relations between amplifier and loudspeaker, which together form an intimate relationship—get it wrong and your sound will suck. The Article does not attempt to detail the more complex dynamic behavior of the loudspeaker system, thermal changes at the transducers motor, loudspeaker cable influences, environmental conditions, nor how an audio power amplifier’s design will react to these dynamic impedance variables.
2.8 volts equal 1 watt, right? Only for true 8 ohm loudspeakers.
Ohm’s law, power, and SI units of measure:
V=IR I=V/R R=V/I
W=IV I=W/R R=V2/W
efficiency = output / input
Electric potential is voltage V, current is amperes I, resistance is ohms R, power is wattage W.
Loudspeakers are generally reactive AC devises. Power factors and impedance differentials between amplifier and loudspeaker must be considered. Solving for power, watts not voltage, is essential for understanding relationships. Power in watts is current times voltage. Phase angles can be ignored in basic loudspeaker testing but does factor in more complex dynamic behavior modeling. Without the correct understanding of basic power transfer, a complete detailing of the system and device under test, measures and data cannot be accurately correlated into observed fidelity. It should also be pointed out that without a basic understanding of test system, device, procedure and marketing can easily manipulate the tests, data and you.
The amplifier is a major factor in how a loudspeaker system performances, both technically and sonically. If testing the efficiency of a driver in an infinite baffle, correctly mapping the impedance across its bandwidth, then at least distilling the string of points into a nominal number is essential. You cannot simply pump in 2.8 volts and call it. Data acquired this way has little correlative meaning. Once impedance is known and plotted power and system efficiency can then be tested and the results can be useful.
Many Zu loudspeakers measure 12 ohms nominal. (Remember, the speaker driver’s measures and performance are in large part determined by the acoustic impedance system: box, horn, baffle... that they are mated with and raw driver or infinite baffle plots are not system impedance measures.) To get a basic measure of system efficiency we first solve for current, then voltage, all measures being at the loudspeaker’s input.
First solve for amperes; square-root of wattage over resistance (ignoring phase) which equals 0.289 amps. Then take amps times resistance to solve for voltage and we arrive at 3.5 volts input. So a 12 ohm load (older Zu Druid, Omen, Essence...) requires 3.5 volts at input to reach 1 watt. An input of 2.83 volts into a 12 ohm load yields 0.66 watts. Nearly all modern tests and measures on loudspeakers simply input 2.8 volts (assumption of an 8 ohm standard) which has almost no lay correlation to actual transduction efficiency and power. If all loudspeakers had a nominal impedance of 8 ohms then a 2.83 volt input would be fine and does in fact result in a nominal 1 watt of input power. With 4 ohm nominal loudspeakers we get; 2.83 volts input which equals 2 watts of electrical power at input, at 16 ohms its 1/2 watt and 32 ohm you are down to a 1/4 watt. Knowing power in and accurately measuring power out of a system you can then know efficiency. Voltage sensitivity is not efficiency, it is a subset of efficiency. Voltage sensitivity is a useful tool in specific applications and conditions but is typically the domain of the engineer.
Now add the amplifier and its design—it’s all about the matchup
Designers and reviewers should be working with power and impedance and not sensitivity and uncorrelated measures. Let’s take an ideally optimized class-A solid-state direct transistor drive power amplifier running wide open, best case when properly matched up to a loudspeaker designed for that amp is 25% electrical power efficiency, this is amplifier only efficiency and not system or loudspeaker. But when you take the same or similar class-A design and transformer couple the output transistors to the loudspeaker you can reach an electrical power efficiency up to 50%, again amplifier only. This is if everything is optimally designed and once understood a designer can then apply similar engineering and reason to transformer/loudspeaker optimization to further improve power transfer to the loudspeaker and net additional fidelity gains. With vacuum tubes this whole matchup is even more critical.
These are maximum percent efficiencies for series-fed class-A amplifiers occurring only under ideal conditions and for maximum signal swing.
Note, with class-A solid-state it’s important to always have your loudspeakers connected, driving your class-A amps without the load will result in excess heat generation within the power transistors. If the loudspeaker draws some of the power then the transistor has to handle proportionately less. The transistor has to dissipate the most power when the loudspeaker is disconnected. It’s always preferable to keep the load connected as long as the class-A amplifier, transformer coupled or not, is switched on.
Understanding power transfer dynamics will hint to why power amplifiers have such a huge impact on the playback systems timbre, dynamic range, bass response, presence, treble, how loud it sounds, and so on. Remember, the reactivity of a dynamic driver is dramatically effected by the loudspeaker design and the driver loading used (box, horn, baffle...) and the necessity for measuring the device as a complete loudspeaker system. This also reveals how the exaggerated “sensitivity” measures are being generated by the majority of brands. Now that we understand the basic relations between impedances voltage and current we can approach how a given power amplifier might behave and influence the tone, power, and presence of playback.
Posted on August 18, 2013 by Sean Casey and filed under Loudspeaker, Technical, Amplifier, Show All.
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What's the correct gap height?
All floor standing Zu loudspeakers that do not have a powered subwoofer need a bit of gap between the bottom of the loudspeaker and the floor. While they are not a ported design (bass reflex) the finger port detail on the bottom needs to see the acoustic impedance of the room to correctly function. Setting the gap height is relative to your amp matchup, your room and your tastes—it’s tunable. Yes, optimum gap height will change from amp to amp and person to person.
Start with 1/4” [6mm]
Min. 1/32” [1 mm]
Max. 5/8” [16 mm]
Increasing the gap height, depending on amplifier, usually results in increased bass weight in kick drum and wood timbre, but it nearly always results in less output in deep bass. More gap height usually increases bass noise as well, causing the timbre to be a bit thick or wooly sounding. Less then 1/4” [6mm] will increase bass articulation / attack, increases bottom octave amplitude, but does reduce overall bass amplitude a bit. Typically, most arrive at gap height to be just about 3/16” [5mm], which is the size of those skinny half-hight CD jewel cases, perfect for a quick and easy gauge. But again, each amp will respond differently as the gap height influences the load impedance, a good thing because you can now better match amp and speaker and room, a bad thing because there’s one more thing you can fiddle with. Here is a great time saving idea regarding adjusting your gap height....
How to make adjusting gap height simple.
Zu knows you have music to listen to and that you really hate fiddling with the gap height—getting down on your knees, looking up at the bubble level, checking to make sure all four spikes are solid... it gets old fast. So, once you get your speakers where you like ‘em—making sure the left and right channels are spaced the same distance from the listeners center line, that they have the same toe-in, that they are both level, and that the spikes are equally weighted, with no cabinet wobble—set the gap height to roughly 1/4”. Likely they will sound great, but still, you should mess around with the gap height, with some amps it makes a huge difference. The easy, and best way to do this is shimming the gap with standard letter sized paper. The paper will be placed on the floor centered under the loudspeaker between all four spikes—don’t lift the speaker up you don’t want your spikes on the paper you want them firmly coupled to the floor. Best place to start is with a stack of paper that will take up roughly half the gap space, listen and go from there. You might want to take sheets out, increasing the gap height a bit, or add to reduce the gap height, experiment. Do the gap height shimming with just your left channel connected (or right) it reduces the work to half. After you get the left side sounding the way you want, mirror the changes on the right channel. You might find the difference to be huge, we usually do. It’s easy and free, mess with it.
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