Music from a farther room

[kiwi_1282001]

Origins


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Much of the content of the first few pages of this thread was originally created in AudioEnz, which prior to a failed forum software upgrade was a beautiful place to be.


The journey continues.

.​

 

[kiwi_1282001]

March 2009​

The story of course begins well before March 2009 but it was around this period I discovered my love for really big panel loudspeakers. Until this time I’d been on a diet of conventional dynamic speakers – both bookshelf and floor standers including KEF C30’s, Polk Audio Monitor Series 2, KEF Cresta 2, Mission 780 & 780SE’s, Quad 12L, Totem Acoustic Hawks to name a few.

Photo 1: Quad 12L speakers replaced Mission 780 series

Photo 2: Totem Acoustic Hawks replaced Quad 12L speakers. The Totems excelled at vocals and Jazz​

The audition and subsequent purchase of Eminent Technologies EFT-8B planar speakers was revelatory. Here was a speaker that was very reasonably priced [about US$2.5k] yet offered near full range performance combined with a massive soundstage.

Photo 3: Perhaps the best value for money speakers I've ever purchased the Eminent Technologies LFT-8B planar​

Combined with a Unison Research Unico integrated source and fronted with Cary Audio CD-306 SACD professional music effortlessly flowed with touch of pleasing warmth. Equipment photo below on a SolidTech Rack of Silence reference rack and wired up with Nordost and Ecosse cables.

Photo 4: The Unison Research Unico Integrated, nice warmth but ultimately not incisive enough​

Around this time I was also trying to figure out what my next "super integrated" amplifier purchase might be. The final answer came in the form of amplification from Denmark - the Gryphon Diablo, but not before cycling through a pile of other fine integrated amplifiers including the Jeff Rowland C-500 Continuum and the Abbingdon Music Research AMR AM-77.

Photo 5: The Jeff Rowland produced amazing HiFi, but I just could not connect with the music

Photo 6: The AMR AM-77 produced wonderful vocals and piano but was not the last word in resolution or bass reproduction

​

Trying to find an integrated amplifier that was capable of producing intoxicating music - without compromise to HiFi reproduction proved much more difficult than expected!

​

 

[kiwi_1282001]

March 2010​

Just one year later just about everything had changed in my system.

First to be replaced was the equipment rack - the SolidTech Rack of Silence (reference version). I made the mistake of acting on lots of favorable reviews when I purchased this rack.

The Unison Research integrated amplifier had been replaced with a state of the art Gryphon Audio Diablo. I also started experimenting with ESL speakers; notably Kingsound (China) King and Prince II speakers

New amplification from Cary Audio; the SLP-05 pre-amp and CAD120S power amplifier offered great insight into music.

I was also having fun comparing direct types of planar speaker. Here the Eminent Techs are shown with Kingsound King electrostatic speakers at the rear.

I was also interested in comparisons between high quality tube amplification (Cary Audio) and high quality solid state amplification (Gryphon audio).

The Kingsound Kings were subsequently replaced with Kingsound Prince speakers which whilst more reliable could not offer much in the way of bass response leaving music sounding a bit thin.

Around this time I learnt one of the most important lessons I’ve ever learn in audio – that loudspeaker location and placement is everything.

Later in the year I moved house and it was an opportunity to review again equipment and for the first time create a dedicated audio room. The proposed room was however small (at 5m x 3m) and thus the opportunity arose to seek and find some high quality stand mount speakers. After an exhaustive search I settled on a virtually unknown brand – Raidho Acoustics. I was the first person in Singapore to purchase this brand.

 

[kiwi_1282001]

Music from a farther room


Just 8529km from Wellington sits my listening room, hence the unimaginative even if technically correct title of this thread – Music from a farther room.

Like most audiophiles I spent many years ignoring or otherwise taking for granted the importance of setting up a decent space in which to appreciate music. In naivety the only upgrades I ever imagined were related to hardware – bigger, better, more expensive etc. Naive, because I didn’t then appreciate that much of the sonic benefit derived from more expensive hardware was to a large extent being masked by poor room acoustics.

J. Gordon Holt once opined that “It is probably safe to say that 95% of the systems in audiophile homes are being degraded by a bad listening environment. Sound waves reflect from walls, floors, and ceilings, reaching our ears milliseconds after the direct sounds from the speakers and smearing those sounds. Echoes reverberate back and forth between parallel reflective surfaces, adding more smear and colouring the sound with spurious brightness or resonating bass hangovers. And reflections from side walls are heard as false stereo direction cues, impairing the accuracy with which a system reproduces instrumental locations.”

What then constitutes a good listening room? What is ideal and what is practical? The ideal according to Gordon would have brick or cinderblock walls, a concrete floor, and a concrete ceiling. Any flexibility in the room boundaries will cost you some deep bass, because some of the sound-wave pressure is lost through the flexing of boundary surfaces. The room would be symmetrical in shape, relative to an imaginary line running from the middle of the listening area to midway between the speakers. All room-boundary surfaces would be non-parallel. Why? Standing-wave frequencies are distance-dependent. With non-parallel boundaries, distances vary across each boundary. This broadens and smoothes out the resulting peaks and dips. The ceiling, for example, would slope downwards towards one end of the room the side walls would converge towards the listening area, and the end walls would slant away from one another as they approached the floor or ceiling. Obviously, wall tilting is easier to do with concrete or frame than with cinderblock or brick. The ceiling and floor would be heavily absorptive, with thick carpeting and under-liner underfoot, and efficient acoustical panels above. The walls, too, would be heavily absorptive, with deadening material covering 100% of the wall surface in the listening half, and 50% of the wall surface at the loudspeaker end. It is important to note that just like all things in audio, there is no real consensus on ideal listening room construction, perhaps in part to the fact that the “ideal” does not exist.
Photos of my system and room (at time of writing) are below.

Photo 1: Peeking into the audio room, view from doorway.​

Photo 2: The special Acoustic door. 3 inches thick with parameter and drop seals.​

Photo 3: The red listening chair. Warm hot blooded music?​

Photo 4: The completely fabulous Raidho Acoustics C1 loudspeaker


​

Photo 5: The equipment rack. Cary Audio & Gryphon Audio Designs (Denmark) amplification




​

My listening room is not ideal but at least upholds some of ideals opined above. The walls are brick and plaster, the flooring is solid concrete with timber strip overlay and the room is symmetrical in shape. I was not able to manage a concrete ceiling and I’m not sure I could relax in my listening chair knowing that several tons of concrete might one day fall on my head! In its place I have acoustic ceiling tiles which are 30mm thick high density fiberglass with a noise reduction coefficient of 0.8. This is followed by a second high density 100mm Rockwool layer. The window (windows are always problematic) at the front of the room was replaced with a double glazed type. This was more about keeping extraneous noises out rather than improving internal acoustics. The window was internally covered with a floor to ceiling acoustic curtain which was imported from the USA. While not shown in the photos a thick floor rug fills the space between the listening seat and the speakers. In order to seal the room properly a three inch thick acoustic door was added. The door is essentially made up of solid timber plates with two inch acoustic Rockwool infill. Raven parameter and heavy duty drop seals are incorporated. The room is served with three dedicated 20-amp circuits which take their feed directly from the main electrical panel. The room is also served with a dedicated earth.


SMALL ROOM PROBLEMS

There are lots of challenges with small audio rooms! It is common knowledge among those who’ve tried to find out, that the ideal listening room is rectangular and fairly large. The reason for the larger size isn’t so you can put your speakers farther apart, though that is beneficial, it is so that there is more space between your speakers and the reflective surfaces of your room. In a small room, wall reflections alter what you hear from your speakers and always in a negative way. A second challenge which was certainly relevant for my room is one of echo. This “ringing” quality is known as “flutter echo,” and if clearly audible can defeat the best efforts to produce decent sound. Flutter echo is due to the successive reflection of (generally) higher frequencies back and forth between flat, untreated, opposing walls. It may be cured either by damping those wall surfaces or by doing something to break up their flat surfaces—making the reflections less directional by dispersing them. The best solution is to provide the room with a reasonable balance of dispersion and absorption.

To cure the issues in my room absorption proved more effective than diffusion. With assistance from the design team at GIK Acoustics the solution comprised of Tri-traps for the room corners, Monster bass trap for the rear wall and three absorption panels for each side wall. Further panels are concealed in the ceiling and behind the curtain. A couple of the absorption panels where nicely dressed in a package called Art Panel, see GIK Acoustics ArtPanel for more details.

The room design follows a diluted “live-end”, “dead-end” philosophy; diluted because the prospect of completely deadening a portion of the room was not aesthetically pleasing but more importantly it has been my experience that rooms which employ this heavy absorption sounded a mite too dead for my taste. I won’t bore you with the measurements or the math but the room is broadly divided into thirds with the speaker’s approx. 1/3rd (of the room length) from the front wall and the listening seat approx. 1/3rd of the room length away from the rear wall. This means the listening position might be considered by some close to “near field” which for small rooms is often advisable, leading to improved perceived soundstage depth and solidity of the central image.

Photo 6: View from front wall to rear wall​

The room continues to be a work in progress as I experiment with different treatment types and placements.



Reference: Holt, J. Gordon (1983) Stereophile, The Listening Room: The Forgotten Factor, March 3rd Ed.

 

[kiwi_1282001]

Acoustics in my small audio room – Update One

“You’ve got the sound system to die for but a listening room that’s killing you.” Rives Audio


“The room is the first thing we start with and the last thing we think about.” Unknown

Photo 1: The equipment rack with acoustic treatments from GIK Acoustics​

This update is a continuation of my thoughts and experiments in setting up a good listening environment within the confines of a small listening room measuring approximately 5m x 3m x 2.8m (L,W,H). Philosophically the room design is LEDE with the speaker end being moderately diffuse and the listening end employing absorption and additional diffusion.

In my opening post I mentioned that one of the greatest challenges I faced in trying to derive positive acoustic values from my small room was flutter echo and this was resolved using absorption panels from GIK acoustics. However, flutter echo is far from the only challenge one faces in optimizing a small room. In my room linearity of mid-bass (or lack of) also raised its ugly head and this post contributes my thoughts together with some theory and measurements around this problem and the on-going solution thereof.


THE MID-BASS PROBLEM

Recollect that my loudspeakers were approx. 1/3rd of the way into the room and my listening position about 2/3rd into the room. While one rule of thumb suggests that this should be optimal for best bass response in my room this did not prove to be the case. Listening tests over an extended period using a mixture of recordings with a constant bass note of around 60-70Hz showed unequal pressure distribution caused by standing waves as evidenced by moving the listening chair forward and backward and observing heavier and leaner bass energy as a result.

While it is possible to find the critical optimal position of the listening chair by ear using such constant bass recordings I felt it important to undertake a number of relatively simple in room measurements to validate what my ears were telling me.

From the outset it needs to be said that one should expect unevenness in bass at some point(s) in the low and mid bass frequency range due to room modes. Room modes are natural resonances that occur in every enclosed space, and the frequency of each resonance is directly related to the room’s dimensions. For example, a room 16 feet long has a mode at 35 Hz because walls that far apart provide a natural resonance at 35 Hz. Additional modes occur at multiples of 35 Hz because those frequencies also resonate in the same space. Wall spacing that accommodates one cycle of a 35 Hz wave also fits two cycles of 70 Hz, three cycles of 105 Hz, and so forth. When you play a musical note having the same pitch as a natural resonance of the room, that note will sound louder and have a longer decay time than other notes. Of course, this is undesirable because some notes are emphasized more than others, and the longer decay times reduce clarity. Therefore, room modes are important because they directly affect the character of a room. Although room resonances can be reduced by adding acoustic treatment, in particular bass traps, they cannot be eliminated entirely.


CALCULATING ROOM MODES

If you don’t want to do the basic math Real Traps offers an on-line program that assists here; simply plug in your room dimensions into the “Real Traps ModeCalc” (note 1) and a plot will be generated showing the resonant modes graphically. Chart 1 below shows the results for my room. Input was in equivalent feet.

Chart 1: Calculated Room Modes for Authors Small Listening Room​

As evidenced above the smaller the room the greater the challenge in distributing room resonance modes and bunching or coincidence of modes is a result of the room height and room width being somewhat similar in measure. The audible unevenness in the bass (earlier observed) can be explained by height and width modes piling at 60Hz and 120Hz to create peaks in the response at these frequencies.

It is widely held that the “ideal” situation is one where modes are evenly distributed across the lower frequency range. (note 2)


INITIAL IN ROOM FREQUENCY RESPONSE

The frequency response plot of my “original” seating position is shown in Chart 2 below. This is followed in Chart 3 by smoothed SPL plot using 1/3rd Octave test tones from 20Hz to 20 KHz.

Chart 2: Frequency sweep with listening seat and speakers in original position​

Chart 3: Smoothed response plot of listening seat and speakers in original position​

The jagged lines you see in the “non smoothed” graph are the result of normal comb filtering which occurs in nearly all listening rooms. This plot shows peaks at 120Hz and 150Hz which not surprisingly are harmonics derived from a fundamental of 35Hz and room coincidence at 60Hz. Overall reasonable linearity can be seen above 200Hz but clearly remedial action is needed address the significantly greater energy in the lower octaves relative to the treble.

In my next update I will share what steps I took to address this problem.


Note 1: See RealTraps - ModeCalc
Note 2: Information sourced from Robert Harley, The Complete Guide to High End Audio. Other reference material drawn from F. Alton Everest, Master Handbook of Acoustics and resources and from Rives Audio, see Links

 

[kiwi_1282001]

May 2, 2011​

Acoustics in my small audio room – Update Two


This update is a continuation of my thoughts and experiments in setting up a good listening environment within the confines of a small listening room measuring 5m x 3m x 2.8m (L,W,H). Philosophically the room design is LEDE with the speaker end being moderately diffuse (and reflective) and the listening end employing absorption.

Recollect that my loudspeakers were approximately 1/3rd of the way into the room and my listening position about 2/3rd into the room. While one rule of thumb suggests that this should be optimal for best bass response in my room this did not prove to be the case. Listening tests over an extended period using a mixture of recordings with a constant bass note of around 60-70Hz showed unequal pressure distribution caused by standing waves as evidenced by moving the listening chair forward and backward and observing heavier and leaner bass energy as a result.

While it is possible to find the critical optimal position of the listening chair by ear using such constant bass recordings I felt it important to undertake a number of relatively simple in room measurements to validate what my ears were telling me.

The initial set of measurements can be found in my March update.

Using 1/3rd Octave test tones sweeping from 20Hz to 20KHz I set about moving the listening chair to the point in the room which gave the smoothest bass. Note here the priority is on listening chair position not on loudspeaker position which is tweaked later. After significant repositioning of first the chair then the speakers (with tweaks to both as the day wore on) the positioning outcome is illustrated in Figure 1 below.

Figure 1: Chair and loudspeaker positioning​

The revised response curves are illustrated in Charts 1& 2 below. By moving the listening chair closer to the rear wall and moving the loudspeakers further into the room (around 2 meters from the front wall) a dramatic measured improvement can be seen particularly in the problematic prominent resonant frequencies arena. Overall the frequency response is now broadly within a 10dB range across the spectrum, a big improvement over the original positioning which at less than 200Hz saw amplitude swings of more than 25dB. Audibly the evenness and the intelligibility of the bass have taken a giant step forward.

Chart 1: Frequency sweep with listening seat and speakers in revised position​

Chart 2: Smoothed response plot of listening seat and speakers in revised position​

REVERBERATIONS

Reverberation time is the time it takes for in-room sound to decay to inaudibility. The most common (but certainly not the only) measure is RT60 which looks at the time required for a direct sound to decay by 60dB.

It is not necessarily a case of low reverberation time is best. In my larger listening room downstairs reverb time not surprisingly measures much greater than my small listening room and one benefit of this is that one senses the music enveloping them i.e. seemingly wrapped around the listening position. Too short a reverb time leaves music sounding unnatural and too long a reverb time leaves music sounding confused and muddy.

Reverberation times can and will vary across the frequency range depending on the size of room. The objective here is to ensure decay is even across the frequency spectrum without favouring certain ranges. From the measurement point of view one tends to ignore measurements below 200Hz as in small rooms the measurement is flawed by the energy cumulated in room modes. The RT30 measurement of my room can be found in Chart 3 below:

Chart 3: Reverberation time (RT 30) for the room​

Reverb times can be altered with acoustic treatment and work continues on optimal placement of absorption and diffusion panels. At time of writing placements are shown in Figure 2 below.

Figure 2: Room treatment placement​

 

[kiwi_1282001]

28 August 2011​

Hmm, it has been a while since I last posted and there have been a few exciting discoveries…

The first is the Sanders Sound Systems Magtech Stereo Power Amplifier which now officially joins the inventory. It in my humble opinion a remarkable product at any price, but at US$5k it is a steal.

Photo 1: The Sanders Sound Systems Magtech Stereo power amplifier mounted on Stillpoints​

On first glance there is nothing on the outside of the Magtech to suggest that anything special lurks within. Indeed cosmetically the Magtech is quite unremarkable (even if pleasingly simple) and entirely lacks the butch machismo expected of muscle bound amplification. Many audiophiles like to have their equipment look as they expect it to sound and in this respect listeners really are in for a ‘Little Red Riding Hood’ experience.

From the first disc the attributes of the Magtech are clear. The Magtech sounds solid, powerful and extremely dynamic. Bass is tight and firmly controlled, yet full bodied and rich, while the treble is airy but focussed and clean. There is nothing sweet, mellifluous or euphonic about the way which the Magtech reproduces music, rather the Magtech appears to be a model of neutrality wearing clarity and dynamics very much on its sleeve.

Photo 2: The revised equipment rack. Magtech preferred shelf to floor​

Then there’s the new Nola Contender loudspeakers which go all the way down to the low 20Hz range in my room. Thankfully the room is designed to cope, because now I get to rumble with pipe organs. These are presently under review.

Photo 3: The Nola Contender Loudspeakers next to my Raidho Acoustic loudspeakers​

Photo 4: The Nola Contender Loudspeakers​

By way of postscript the Contenders didn’t last long in my system. While I loved their reach down into the low octaves I could not stand the dis-jointed bass – with the speaker sounding at times like each bass woofer was doing its own thing.

 

[kiwi_1282001]

September 11, 2011​

While waiting to receive an order for more diffusion products I thought I’d have a play with floor rugs. Many audiophiles have written to me saying that audio rooms need carpets or thick rugs on the floor to reduce unwanted reflections.

To be honest earlier attempts at introducing carpet to the listening room either produced mixed or inconclusive results.

Theoretically, carpet should indeed reduce reflection and it will absorb high frequencies and some of the mid-range – but of course will do nothing for the bass. I guess the question is – are all reflections bad and this for me is possibly what underpins my inconclusive results? There are instances, particularly with live recording of instruments like guitars and violins where I feel that slight reflections off the floor can give a more natural reproduction and a stronger illusion of the event being right there in the room.

Experiments continue and some updated photos are included below

Photo 1: View from entry door way​

Photo 2: View from listening chair​

So, any opinions and experiences out there on floor coverings?

 

[kiwi_1282001]

September 25, 2011​

Norse Series Jumpers have been added. Based on micro mono-filament technology – the same being utilized for the internal loudspeaker wiring – they are employed (in my system) in series and as an end point termination to my Nordost Heimdall speaker cables. These were recommended by the local Nordost dealer and after hearing the benefits during the dealers audition I jumped (pun intended) at the opportunity.

Photo 1: Nordost Norse Jumpers added to existing Nordost Speaker cable is the bizz…​

 

[kiwi_1282001]

November 6, 2011​

Acoustics in my small audio room – Update Three


This update is a continuation of my thoughts and experiments in setting up a good listening environment within the confines of a small listening room measuring 5m x 3m x 2.8m (L,W,H). Philosophically the room design is LEDE with the speaker end being moderately diffuse (and reflective) and the listening end employing absorption.

While generally pleased with the results to date which have seen giant strides in flattening frequency response, reductions in slap echo and audible improvements to the evenness and the intelligibility of the bass I have felt that more progress could be made and this update serves as a record to that end.

At time of writing my existing room treatment placement is shown in Figure 1 below.

REFLECTION vs. ABSORPTION AT FIRST REFLECTION POINT

My endless tinkering generated from untamed curiosity naturally led to questions on what type of treatment should be employed at the first reflection point? Note here that I am focused on the reflection point closest to each loudspeaker. A quick literature review on the topic of reflection vs. absorption vs. diffusion at the point of first reflection shows strong support for absorption but protagonists exist for reflection (no treatment at all) and diffusion. It needs to be stated for the record that my focus here is acoustic treatment for small rooms and large rooms play by very different rules.

Moreover, observations that follow should be read in conjunction with information provided in earlier updates and noting that the bass trap which resides under the diffusor will impact the sub 500Hz range.

In order to arrive at my own conclusions on the topic I embarked on a series of experiments which incorporated listening tests, LEDR tests and finally measurements.

First up was the listening tests which compared reflection (no treatment, brick, plaster and painted wall), absorption (GIK 242 panel) and diffusion (DIY 2D diffuser with bass trap base).

What follows are my observations.

Photo 1: Close up photo of the diffusion panel​

REFLECTION vs. ABSORPTION

This was an easy win for Absorption. Versus no treatment, absorption at the first reflection point produced a far superior central image with greater solidarity and focus. Furthermore, not only was there produced soundstage wider and deeper but instrumental localization was light years better. The improved focus also underpinned observations around resolution with micro-details being bought out more from the otherwise cluttered and homogenized mix. Bass too was also improved with far greater control and more realistic decays being observed on good orchestral recordings.

Were there any benefits to not treating the first reflection point? I observed two of note. First, while the central vocal image was more solid with absorption the more diffuse image rendered via reflection came across as more airy and live. Live recordings seemed more alive and more enveloping which with the right software was beneficial. Second, less amplifier power was needed to achieve the same SPL at the seating position. I was very surprised how much absorption attenuates perceptions of loudness or put another way – how much more amplifier power is needed when absorption is introduced.

Overall the benefits of absorption far outweighed those of reflection – though I can understand personal preference will play a role here.


ABSORPTION vs. DIFFUSION

Versus diffusion, absorption at the first reflection point once again produced a better defined central image with marginally better ambience also being noted. However, absorptions benefits seemed to end there because diffusion appeared (strangely) to offer overall better resolution combined with superior air in and around instruments and actors. Despite the benefits absorption created with image – the image observed via diffusion simply seemed more life-like, more real and whilst some dimensionality was lost this did not hinder either the articulation or the comprehension of vocals.
Overall the listening test nod went to the use of diffusion at the first reflection point which admittedly sets me at odds with literature and I dare say to the audiophile thought collective to.

Time then for some more tests….

Photo 2: Diffusion panel with bass trap underneath​

LEDR TESTS

Like most audiophiles (I’m guessing) I have a quiver full of Test CD’s including those from Stereophile [Test CD2], XLO [Test & Burn in CD], Chesky [Ultimate Demonstration Disc] and Sheffield Labs [The Sheffield / A2TB Test Disc]. The most useful disc to date has been from Nordost via its “System Setup and Tuning Disc”. On this disc Nordost includes what I have come to consider as one of the most enlightening, instructive and valuable of speaker / room interaction tests – LEDR. LEDR™ stands for Listening Environment Diagnostic Recording, a test to subjectively evaluate the accuracy of stereo image reproduction. LEDR test tones are a series of computer generated tones created by EASI to assess speaker positioning and room interaction.

“Lateral” and “Over” tests can provide valuable insights on important set up questions such as are my speakers correctly spaced apart, positioned and toed and are reflections from side walls or ceilings adversely impacting the image?
Test results showed here that diffusion at the first reflection point created a smoother motion both on lateral and over tests – with the left / right (lateral) in particular having greater symmetry and evenness.

In my next post I will provide some measured results for the room.

 

[kiwi_1282001]

November 6, 2011​

Continued:

ACOUSTIC MEASUREMENTS

Using a PC with Room Wizard EQ Software (REW) an M-Audio USB soundcard with phantom power and a calibrated Behringer ECM8000 microphone and a Sound Level Meter, I set about taking measurements from the seating position to plot frequency response, waterfall, energy-time curve (ETC) and reverb decay.

I believe that differences which can be audibly heard (between absorption and diffusion) should be measurable – so long as we know what and how to measure. The results of the various measurements can be found in charts 1-8 below.

Chart 1: Frequency response with absorption

Chart 2: Frequency response with diffusion

Chart 3: ETC with absorption

Chart 4: ETC with diffusion

Chart 5: Waterfall with absorption

Chart 6: Waterfall with diffusion & bass trap​

Chart 7: RT 30 with absorption

Chart 8: RT 30 with diffusion​

Analysis of these measurements will follow [when I get the time] but what is immediately obvious is the significant improvement in frequency response between 100 to 300Hz [as seen in the frequency response the waterfall charts]; reduced early (near-field) reflections as seen in the ETC chart, which underpin the observations around soundstage spaciousness and reduction in slow bass decay time.

Overall I am completely wrapped in the improvements this exercise has rendered. If audio is Everest, I feel that I have just arrived at a higher base camp.

Below is an updated view of my listening room

View from the listening chair


​

 

[kiwi_1282001]

November 29, 2011​

I have received a number of questions on the DIY diffusion panels I am using and I will use this post to address them.

The Panels were made by a third party in Singapore based on micro diffuser blocks sourced from China. I do not have details on the design save for the following information.

Each micro block measures 64 mm X 64 mm X 45 mm and is constructed from ABS (similar material to car bumpers). A photo of the block can be seen in photo 1 below:

I see many diffusers out there (for example RPG’s Hemiffuser tm & Skyline®) manufactured from polystyrene foam and I consciously preferred a material which was more rigid and fireproof. Furthermore the ABS is much easier to paint if desired and if one didn’t want to try that at home a local auto-shop (specializing in car damage repairs) quoted less than US$2 a block in virtually any choice of colour to match your decor.

Each micro block is claimed to diffuse from 2 kHz to about 9 kHz and this range is extended downwards by interconnecting and gluing multiple layers together. My panels vary from one to three layers and are effective from around 600 Hz. The combination of the varying cell depth and the staggering of the sections of blocks greatly assists with the temporal effects (phase) of the diffuser. The overall bandwidth of the diffuser is broader than commercial products like the RPG Omniffusor ®, a typical and similar 2D QRD design. The micro diffuser blocks are grouped and glued (epoxy or hot glue) back onto a piece of plywood which could be screwed onto the wall as-is, though I preferred framing which in my opinion looked better and allowed the panel to free-stand which was useful whilst trying to optimize positioning. Each grouping measures approx. 600 mm x 600 mm x 145mm (depth) and I use a 1×2 (wide/high) configuration for the side walls and a 2×2 configuration for the front wall. The side wall diffusers sit on top a bass trap which due to its restricted volume was most effective in addressing measured nulls between 100 – 300 Hz.


THE RESULT

I could not be happier with the impact of diffusion at the 1st sidewall reflection point. Continued listening has confirmed within the context of my room that compared with absorption the resolution, in particular resolved micro detail and ambient information, is far superior and this seems to benefit all recordings – but particularly poor CD recordings which often lack air and spatial depth and tend to decode as a thinly dimensioned central homogenized cluster or worse audibly appear tethered to the loudspeakers.

Admittedly these findings are at odds with my previous endorsement of absorption at the first reflection point for small room settings. :blush: Once again then I find myself eating earlier articulated views and so called canon on the topic and the only thing I can be certain of is that as time progresses I will find more things I need to change my mind on, or simply be flat out wrong about.

More happily, my overall objective of holistically assembling an audio playback system that provides no limits on your musical enjoyment – as evidenced by extended listening sessions and embracement of a wider diversity of musical styles and an ability to satisfyingly play any music in one’s library – has taken a further step forward with this project.

But more still can always be done and freshly armed with the recent acquisition of XTZ’s latest Room Analyzer Pro II measurement system, my attention now is turning to treatment of the rear wall. Stay tuned

 

[kiwi_1282001]

December 1, 2011​

omegaspeedy; wrote: Kiwi_1282001, I love how dedicated you are with your explorations of different room treatments! Great job particularly because it’s an area that isn’t really taken seriously enough by HiFi geeks like myself even though I know I really should!

Hi James,

Someone once quipped that “The room is the first thing we start with and the last thing we think about.”

While that statement is catchy and makes for good headline, I don’t believe it is absolutely true because we do from time to time think about our rooms and ponder “what if”?

My thesis is that the room tends to get neglected because it is one of the least understood influencers in the audio reproduction chain – and frequently one of the most challenging to change. Further, it does not help that equipment purchases are so damned exhilarating and that dealers can eagerly and readily demonstrate how cartridge X, DAC Y or amplifier Z is going to improve your world in a way that they can less easily with acoustic devices because of their room dependencies. More-over, often the very dealers upon which we depend for good advice have scant regard for room acoustics themselves – the proof of which can be seen by merely stepping into their show-rooms…

For years then, in naivety, the only upgrades I ever imagined were related to hardware – bigger, better, more expensive etc. Naive, because I didn’t then appreciate that much of the sonic benefit derived from more expensive hardware was to a large extent being masked or even completely annulled by poor room acoustics.

I hope my postings encourage all readers to pay more attention to the topic. That bloated bass, screechy treble or one dimensional soundstage might be better corrected with a few hundred dollars spent on acoustic treatments rather than a few thousand spent on new loudspeakers. The influence of the room on the overall reproduction of audio should not be underestimated or ignored and I have to declare with some degree of embarrassment that this fool of a scribe has learnt the expensive way….. Don’t follow me.

 

[kiwi_1282001]

February 6, 2012​

Acoustics in my small audio room – Update Four


This update is a continuation of my thoughts and experiments in setting up a good listening environment within the confines of a small listening room measuring 5m x 3m x 2.8m (L,W,H). Philosophically the room design is LEDE with the speaker end being largely diffuse and the listening end employing absorption.

In the last treaties I had indicated that my focus now was shifting to treatment options for the rear wall. The arrival of the XTZ Pro II room analyser system however placed this on hold as the software indicated via RT60 measurements that decay time at 8 KHz was a staggering 2 seconds! Was this a measurement anomaly which was a possible consideration since all the other RT60 values were nowhere near the 8kHz reading and when there is a high RT60 reading it is typically correlated to a higher SPL reading which in my situation wasn’t the case. Further, supporting the anomaly theory is the well-known fact that higher frequencies are very directional which makes it much harder for the microphone to properly pick it up and measure it.

Chart 1: Frequency response and RT60 for the room​

On the other hand it could also point to a slap echo artefact and the need to place additional absorption (i.e. GIK 242) in the room.

What to do and why hadn’t REW picked this up? Frankly I was at a loss. Surfing the web I came across an interesting document entitled “Acoustical Measurement Standards for Stereo Listening Rooms” (Mellor & Hedback, 2011).
http://blog.acousticfrontiers.com/storage/AMS for Stereo List. Rms.pdf


This document suggests that an acceptable T60 range is 0.2 to 0.5 seconds i.e. a decay of 60dB (250Hz to 4 KHz).
After a bit of farting around I decided to pace the room clapping my hands on the lookout for flutter echoes and sure enough between the rear of the speakers and the corner traps I found strong distinct echoes. To patch this problem I decided to re-deploy the diffusion panels from their first reflection point location to the area of bare wall between the speakers and the front wall.

Figure 1: Revised room treatment layout​

This not only fixed the problem but the newly placed side wall diffusors enhanced the impact of the diffusion already in place on the front wall allowing the soundstage width and depth to further expand. Sometimes problems can be blessings in disguise.

Below is the revised configuration. I am now re-looking at 1st reflection point treatment options and additional bass trapping. The project continues ….

Chart 2: Bass needs more work!​

Photo 1: Revised room treatment configuration​

 

[kiwi_1282001]

April 7, 2012​

Acoustics in my small audio room – Update Five


This update is a continuation of my thoughts and experiments in setting up a good listening environment within the confines of a small listening room measuring 5m x 3m x 2.8m (L,W,H). Philosophically the room design is LEDE with the speaker end being largely diffuse and the listening end employing absorption.

Photo 1: Revised room treatment configuration​

In the last update what was possibly an RT60 measurement anomaly or a slap echo artefact led fortuitously to the repositioning and employment of diffusion panels on the sidewalls in the front soundstage (behind the speaker plane).

Whilst earlier explorations had uncovered that if you diffuse the sound that reflects off the front wall you will have depth in your sound stage that appears to go right through the wall – this did not prepare me for the benefits that could be gained by placing additional diffusion in the front soundstage sidewalls. The audible effect of front soundstage diffusers enhanced the performance of those already placed on the front wall. In addition they allowed the sound stage width to expand in the same manner as the depth did when I treated the front wall. This discovery was not anticipated and somewhat of a shock when you consider we are talking of sound enhancements which fall behind the speaker plane and thus must be reflected and dissipated!


While I waited for the delivery of additional diffusion panels so I could check again on earlier observations made on absorption vs. diffusion at the first sidewall reflection point I experimented with different thicknesses of absorption at the first sidewall reflection. I had 2” and 6” thick panels (GIK 242 and GIK Monsters) to play with.

Toole[1] controversially suggests that treating first reflections are optional (wow!) But, if it is to be done treatment should be broadband when used, ideally uniformly effective above 200Hz. Toole points out that the typical 1 inch fibreglass sound panel most often affixed to walls works only at relatively high frequencies (>1 KHz) and acts to effectively turn down the tweeter with no effect on the midrange or upper bass, thus not preserving spectral balance. Uniform attenuation of the full spectrum of reflections is considered an important design goal. I thought it would be interesting to see if his comments on sound panel thickness applied also in my setting?

Listening tests which ran for the better part of one day tracked irrevocably towards the conclusion that additional absorption bandwidth (which in the case of the GIK Monster was effective down to about 80Hz) was welcome and audibly hallmarked by improved bass definition, transient response and decay. Furthermore on the question of absorption versus no treatment at all at the first side wall reflection point – my earlier preference for absorption remained unchanged. One possible explanation for this preference lies in the observation that the ambience already present in many recordings is that of a large space, such as a concert hall or movie scoring sound stage or recording studio. When played back in a small room having too little absorption, the strong small-room “early” reflections simply drown out the larger sounding ambience in the recording, thereby losing detail.

The eventual arrival of additional diffusor panels once again opened the ‘jack in a box’ on whether the earlier stated preference for diffusion (versus absorption) at the first side wall reflection remained valid and to cut to the chase – it did! Beyond earlier observations made, perceptively, one big difference between absorption and diffusion at the first side wall reflection point was the ‘view’ of the performance being played. The use of absorption gave the impression that one was viewing the performance from the back rows of a large auditorium – whereas, diffusion placed one more mid hall. One possible explanation for this is that variation in the amplitude of reflections may cognitively underpin and aid judgements the listener makes on the distance of sound.


SUMMARY

Thus far, I’ve drawn a conclusion that in the context of a small listening room, choosing what type of acoustic control you use at the first side wall reflection is important and treatment can be simplistically thought of as an ‘imaging versus spaciousness controller’. Using absorption on the side walls audibly narrows the soundstage and improves imaging. Leaving the sidewall reflective makes the sound spacious but loses out on pinpoint imaging and detail. Using a diffusor on the side walls is a reasonable compromise between the two approaches. So what you do with sidewalls really comes down to personal preference in musical presentation. For example, ‘Image freaks’, a term coined somewhat impulsively to describe audiophiles who place heavy emphasis on the quality of the image (usually girl and guitar music types in my experience) will likely prefer absorption for its ability to provide superior specificity and density to the image. ‘Orchestral and live event nerds’ on the other hand may prefer diffusion for its perceived ability to deliver a larger soundstage with a somewhat more listener enveloping experience.

This then nicely Segway’s into my next topic of discussion, “You are there” versus “They are here”. Stay tuned.


References
1. Toole, F, 2006. Loudspeakers and Rooms for Sound Reproduction – A Scientific Review. Journal of the Audio Engineering Society, 54 / 6, 451-476.

 

[Bruce]

Wow! Incredible perfection and dedication-- we are humbled keep up the good work!

Glad you got rid of those Nolas--they are over hyped-- sorry HP!

B

 

[kiwi_1282001]

April 7, 2012​

You are there vs. They are here


A thread on this topic posted on AudioGON in April 2010 peaked my interest. Given my recent obsession with room acoustics you may ponder what relevance the topic has to my room and system and on-going efforts in setting up a good listening environment?

The answer in short is everything.

Before I continue some definitions are in order. Borrowing from Mr Cunningham (the contributor on Audiogon):


“Sometimes a system sounds like “they are here.” That is, it sounds like the performance is taking place IN YOUR LISTENING ROOM.

Sometimes a system sounds like “you are there.” That is, it sounds like you have been transported to SOME OTHER ACOUSTICAL SPACE where the performance is taking place.”

Mr. Cunningham goes on to opine that whether a system sounds like “they are here” or “you are there” is principally determined by AMBIENT CUES during playback.


I am looking for a “you are there” experience when music is reproduced. I like the prospect of being transported to another space – even if such an objective seems hopelessly implausible given the physical confines of a small room.
My contribution on this subject is that listening room design has a weighty bearing on the illusion of “you are there”. As attested earlier, the employment of heavy absorption at early sidewall reflection points tended to make the presentation of the music somewhat aloof and distant. You are not there! My hypothesis is that absorption clearly reduces reflections as heard at the listening position thereby diminishing a sense of sound envelopment which is needed to give the illusion of “you are there”. This is to say, that direct sound only carries insufficient cues to convincingly transport us to another location and a degree of reflected sound is needed to underpin the you are there experience – though my findings have been that reflection via diffusion offers a superior experience to unconstrained reflections. I do my best to illustrate this point in diagrams 1 & 2 below.

Diagram 1: “They are here”​

Diagram 2: “You are THERE!”​

None of the above overlooks the fact that it is the actual recording which is the supreme commander of the “you are there” experience. You obviously cannot put into your listening room something that was not on the recording in the first place. It further assumes that any ambience contained in a recording is real and not synthetically created at a later stage in the recording chain and that the sound engineer has mixed sympathetically as again you cannot put back into the listening room something that the mikes may have picked up but the engineer subsequently mixed out. Moreover, I do not pretend that the recording and acoustic controls are the lone ingredients of a “you are there” experience as other system variables such as the quality and neutrality of the playback system and the noise floor of the room – to name put two examples – are surely stakeholders in this goal too.

 

[kiwi_1282001]

April 29, 2012​

Acoustics in my small audio room – Update Six


This update is a continuation of my thoughts and experiments in setting up a good listening environment within the confines of a small listening room measuring 5m x 3m x 2.8m (L,W,H). Philosophically the room design is LEDE with the speaker end being largely diffuse and the listening end employing absorption.

In my last update I had concluded that within the context of a small listening room, choosing what type of acoustic control you use at the first side wall reflection is important and treatment can be simplistically thought of as an ‘imaging versus spaciousness controller’. Using absorption on the side walls audibly narrows the soundstage and improves imaging. Leaving the sidewall reflective makes the sound spacious but loses out on pinpoint imaging and detail. Using a diffusor on the side walls is a reasonable compromise between the two approaches. So what you do with sidewalls really comes down to personal preference in musical presentation. For example, ‘Image freaks’, a term coined somewhat impulsively to describe audiophiles who place heavy emphasis on the quality of the image (usually girl with guitar acoustic music types in my experience) will likely prefer absorption for its ability to provide superior specificity and density to the image.

Orchestral and live event nerds’ on the other hand may prefer diffusion for its perceived ability to deliver a larger soundstage with a somewhat more listener enveloping experience.

As interesting as experimenting with different acoustic panels at the first reflection point may be – its importance borders on near insignificance compared to selecting where you seat in the listening room!


POSITIONING THE LISTENING CHAIR

Of all the choices one has to make in setting up a good environment in which to listen to music – by far the most important – is selecting the location of your listening chair.

Photo 1: Where you park your listening chair is critical​

While you will doubtlessly read of audiophiles who invest hours and in some instances days – and often on their hands and knees – (ouch) in tweaking the location of their loudspeakers their effort is ill-spent and near worthless (in my experience) if they then simply proceed to arbitrarily plonk the listening chair at a fixed distance away from the said speakers.

The key objective must be to discover where in the room you should sit to take advantage of the least negative room interactions such as obvious peaks and nulls in the bass.

Measurements (I recommend 1/12th Octave RTA) are the most effective – and quickest – way of achieving this goal and this latest round of adjustments interestingly saw the listening chair location move closer to the rear wall where the best combination of smoothest and deepest bass existed.

To objectively demonstrate the impact (and critical importance) of listening chair location consider the below measurements taken in my listening room last month.

Graph 1: Frequency response initial​

Graph 2: Frequency response after repositioning seat​

Graph 3: Spectrogram – a huge improvement over previous measure​

Measurements were performed using REW software with M-Audio external USB soundcard with phantom power and calibrated Behringer ECM 8000 microphone for frequency response and waterfall analysis and XTZ Room Analyser II Pro kit for Spectrogram analysis. The later depicts a colour spectrum with frequency, amplitude and time data and provides a quick glance guide of decay time as a function of time and frequency. Measurement methods are log sine sweep, full FFT and sliding CSD.

 

[kiwi_1282001]

May 2, 2012​

I find the importance of Stereo Imaging (generally defined as the production of stable, specific phantom images of correct localization and width) varies markedly among audiophiles. I attend a live concert every month and without fail I’m presented with a wall of sound – not tiny pin pricks of sound cleverly arranged on a large stage. Such concerts give me pause of thought on what goals we should have in mind when setting up a decent audio reproduction system. For some, critical listening means not just hearing the totality of the reproduced sound, but hearing into the sound – that is, desiring to observe the variety of sonic attributes that go to make up the whole. It is not at all uncommon to come across audiophiles who are more interested in a recordings revelation of ‘space’, that is the environment in which the performance was recorded, then the performance itself!

On the topic of measurements, one pet theory I have is that audio specifications and measurements have increased significance as they move from the source to your ear. Measurements of a DAC, CD player or amplifier won’t tell you a whole lot about how they will sound. Loudspeaker measurements are much more revealing and finally loudspeaker / room interface measurements offer quite vivid insights into how things are likely to sound. As my theory goes, master the room / speaker interface and Nirvana (liberation) awaits – even if prefaced by a very modest investment in equipment.



.

 

[kiwi_1282001]

June 9, 2012​

Music from “Another” Room


In times past I have made opaque references to ownership of a second audio system, this one located in a larger room on the ground floor. This is my ‘social’ system, deliberately conceived for the enjoyment of family and friends and proffering that all important space “for the girls to wiggle.”

This system is dominated visually by a pair of near 2 meter tall Electrostatic speakers (ESL’s) offering wide dispersion characteristics and the ability to create a massive soundstage. Other than the ESL’s and a 52 inch LED monitor which is connected to provide an A/V experience, all other components are concealed.

It must be said that I love panel speakers, especially ESL’s. Engineered properly, the most apparent benefit of ESL is its reproduction of high frequency content. The response of the lightweight diaphragm is in every way superior to the heavy moving coil used in a magnetic speaker. The sum of the mass of a magnetic speakers voice coil, suspension system and cone can prevent them from responding quickly enough to follow a rapidly changing audio waveform with perfect precision. In contrast the mass of an electrostatic speaker’s diaphragm is very small indeed and as a result it is far more easily able to respond to instantaneous audio signal changes even if it is still imperfect. ESL’s, at least those that valiantly endeavour to be “full range” (huh), do have one Achilles heel and that is their ability to deliver deep bass and my speakers bass might best be described as hung over, lumpy and boomy entirely lacking in definition. Still, its oft been said that in reality, all components are imperfect and the real subjective choice in assembling a good audio reproduction system will often come down to a choice of which particular imperfections or trade-offs you can live with over the long run. For whilst the bass response on these particular ESL’s leaves much to be desired – you forgive them almost immediately when you hear the sublime reproduction of that most important instrument of all – the human voice.

Photo 1: Descending from Music from a farther room to Music from another room​

Photo 2: The Speakers​

Photo 3: The engine room​

System Components

Tacima CS929 mains conditioner with Quantum Qv2 AC Line harmonisers
Ecosse Big Orange & Big Red power cables
Cisco HD Set Top Box
Oppo BDP-95 Universal Player
Modwright Instruments LS 36.5 tube line stage
Sanders Sound Systems ESL Mark II stereo power amplifier
Kings Audio Limited The Prince II Electrostatic loudspeaker
Nordost interconnect, speaker and jumper cables

Photo 4: From the listening sofa





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