Power compression in lower efficiency speakers

Mike

Mike

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A very interesting read:

Power Handling Vs. Efficiency


"Even the limited tests I was able to perform show that flux modulation (magnetic compression) is quite capable of 'squashing' transients to some degree. In an extreme case (assuming low efficiency drivers and considerable amplifier power), where transients should jump out at you, they may blend into the overall mix, losing impact and removing some of the life from your music. The many owners of low powered Class-A amplifiers are forced to use high efficiency drivers to get an acceptable sound level in their listening room. Although the amplifier is often cited as the reason the systems sound good, one of the likely reasons should now be obvious - with no (or little) power compression of either form, high efficiency systems will give much better transient (impulse) response and dynamics. There can be no doubt that these systems will have dynamics that are very difficult to match by systems that require hundreds of Watts to achieve the same in-room SPL."


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Manufacturers of lower efficiency speakers came into vogue in the 80s+ with the advent of SS amplification (and hence more powerful amplifiers) and the view that watts are cheap. Although what they missed is that cheap watts sound exactly like what they cost :D High quality wattage is always expensive.

In any case, the problem with efficient speakers is that they have their own limitations too. Once you go multi-driver in a box-like enclosure you are immediately going to lower the efficiency of the speaker unless you have a huge box which presents its own problems.
 
Mike, I tend to agree to the general point of the article. Art Dudley often writes in other terms about the same thing. Few watts and very efficient speakers are the most logical way to reproduce " life like " music.
As Cyril stated, very high eff speakers also have their limits.
This is only my opinion : I did not buy any high eff speaker yet because I still have to find one that is not too aggressive to me and that sounds impressive at low volume. Our homes are not concert halls. Often high eff speakers tend to try to transform our listening rooms into concert halls. Impossible and high sound pressure in domestic rooms may be very dangerous to our ears.
Music is first a relaxation to me. I did not find any high eff speaker yet that relaxes me. But I am sure that they may exist.

I chose an intermediate way. Low eff speakers but very easy to drive. Giving a full sound at low volume and not pushed hard. Basically Alan Shaw theory. 50 W of power ( or even less : my 225 amp drives my Harbeths wonderfully, although they do go as low in the bass as my big Shindos...) and moderate volume listening. Near or intermediate field listening. Peaks of 85 dB maximum. Does not excite room resonances. Great compromise between sensations of the concert and the relaxation I want in my home.



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I just love this statement in the article
These power ratings for amplifiers and speakers are designed to appeal to those who have no understanding of efficiency, and think that power is the only thing that matters
Click to expand...

So If I read / understand this article correctly, please correct me if I'm not, using an amp like a SET / or something like a FirstWatt that will give you that SPL at lower wattage into a speaker that has high efficiency drivers should be very efficient.
 
You are correct. My understanding is, high efficiency speakers can give you greater dynamics or should I say, dynamic contrasts, because the woofers don't have to travel as far. That's why the article mentions "dynamics getting lost on low efficiency monopole speakers".

I've heard a high efficiency dipole point source system and the dynamics were breathtaking.

When you really start to listen to cabinet resonances which are not tuned to the speaker (like the Harbeth and to some extend Stradivari), you begin to appreciate just what music can sound like through and point source open baffle/dipole or omnipole (like MBL).

IMO, making a cabinet rock solid still produces some cabinet resonances in the lower mids. Not fighting the cabinet resonances and instead tuning the cabinet (like Harbeth and others) is a better way to go.

I need to research more on cabinet tuning by Tannoy and to see exactly what Raidho does as well as it relates to the cabinet.

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very good article. as someone on their 3rd day with high efficiency speakers in a huge cabinet, im still enjoying the added dynamics and how easy my 15wpc runs them. but like said above the big cabinets and big drivers are probably for a much bigger room than i have. and i also dont have the positioning right yet. but it has brought to my attention the need for some panels and traps and maybe even a total room redesign. of course im talking about a very inexpensive pair of horns. the imaging is a bit off and i dont hear as deep into the music as before, im guessing simply because the midrange is not the same as before. but the dynamics and sheer brawn of these big drivers make up for it and give it a more enjoyable and more well rounded sound. i guess its a trade off for now. making me think where i have to go to get the entire package lol. volti?, tannoy?
for now i will enjoy these for a few weeks, then go back to the less efficient ,smaller cabinet fabers and see if its really a big difference. and how much i miss the big sound im getting now. and probably sell the fabers for another efficient speaker.
but i will say being able to get the big bass and better dynamics and huge sound without gettng the ear fatigue ive experienced on most other big bass systems i heard in the past is incredible. and its all because of the nature of the efficient speakers and low watt tubes.
for me its exactly where i want to be. all i want to do now is bring in more 300b amps and efficient speakers.
 
I think Ralph Karsten's voltage vs power paradigm is a really good read- you can get good results with either, the key is knowing what you have:

Atma-Sphere music systems, inc.

High efficiency speakers have trade-offs as well....usually in the frequency response department. there is no magic bullet. i also think SETs distort easily which obscures how much power people think they need. for a 300B's typical 8 watts- i think efficiency has to be over 100dbs, preferably single driver-esque.

I did a test on the FirstWatt SIT's 10 watts in my room as SS distortion is quite easy to hear- the SIT-2 broke up at 93db+ (to my ears, so distortion began quite a bit lower). Clear headroom issue. The monos had more headroom, despite the same 10 watt rating and therefore the only choice.

On cabinets, i like my birch-ply versions- they retain musical life, but are very inert. I heard the Sony's at Newport and thought they sounded very good- they use birch-ply as well. Magico's original speakers were very good to my ears- I chose Zu over V3s in fact. I find many of the Audio Notes of the world colored sounding due to their design.
 
My interest is in amplifiers with zero feedback (local or global), amplifying elements with very low intrinsic distortion, and no switching artifacts. The Karna is one approach; Gary Pimm's is completely different, with MOSFETs, FETs, and bipolar transistors, but full (thermal) Class A and operating as a high-voltage differential steered current source.

Interestingly enough, both amplifiers sound pretty similar to each other, but both are sonically quite different than commercial SETs or transistor Class AB feedback amplifiers. (Gary Pimm built my Karna amplifiers, and we've done a lot of direct comparisons between the two. Both amplifiers use Gary's cascoded MOSFET current sources.) I'm contemplating a Mark II version with direct-coupling between the differential input and driver section, with a center-tapped reactor/audio-grade choke to keep the input section dynamically balanced and voltage offsets between the pair low.

Thermal Class A limits the power to 20 watts/channel or less if you want to keep heatsink size reasonable or B+ voltages less than 550V. Twenty watts isn't a limitation if the speaker efficiency is high enough, there is no requirement to fill an auditorium, and a separate amplifier is used to the cover the below-60 Hz range.

100+ watts/channel of (thermal) Class A power gets us into the rack-sized range, serious cooling requirements, and either very large heatsinks or B+ voltages in the 1 kV to 2.5 kV range ... something the size of a small radio-station transmitter.

Gary Pimm, Gary Dahl, and I are not building rack-sized amplifiers, and we like the sound of Class A operation (direct-heated triode, MOSFET or bipolar transistor). So ... a more efficient loudspeaker, which Gary Dahl is enjoying right now .. Lynn Olson ..
Click to expand...

Since optimizing one set of parameters in a loudspeaker may degrade others, a designer has to do some picking and choosing. A speaker designed for the lowest possible IM distortion may not have the flattest response, and a speaker designed for the fastest decay characteristic may not have the widest dynamic range. In other words, I don't think it's possible to optimize all technical parameters at once.

This is why I mentioned different types of music in the previous post. In my experience, acoustical music benefits the most from a rapid and resonance-free decay characteristic. Music that has an electronic source (going through a guitar amp, for example) may benefit from optimizing other characteristics, such as dynamic range. Acoustical music isn't morally or esthetically superior to hip-hop, stadium rock, or London dance music; it just has different technical requirements for the playback system.

My loudspeakers are optimized for acoustical music and moderate-power Class A amplifiers. That's the niche they're designed for. Other designers with different priorities will design different loudspeakers, and they've made plenty of posts right here in the diyAudio forums .. Lynn Olson ..
Click to expand...

Hmmm .. Dick Olsher astutely commented that, “If the first watt of an amplifier doesn’t sound good, why would you want 199 more of them?”
 
KeithR said:
I think Ralph Karsten's voltage vs power paradigm is a really good read- you can get good results with either, the key is knowing what you have:

Atma-Sphere music systems, inc.

High efficiency speakers have trade-offs as well....usually in the frequency response department. there is no magic bullet. i also think SETs distort easily which obscures how much power people think they need. for a 300B's typical 8 watts- i think efficiency has to be over 100dbs, preferably single driver-esque.

I did a test on the FirstWatt SIT's 10 watts in my room as SS distortion is quite easy to hear- the SIT-2 broke up at 93db+ (to my ears, so distortion began quite a bit lower). Clear headroom issue. The monos had more headroom, despite the same 10 watt rating and therefore the only choice.

On cabinets, i like my birch-ply versions- they retain musical life, but are very inert. I heard the Sony's at Newport and thought they sounded very good- they use birch-ply as well. Magico's original speakers were very good to my ears- I chose Zu over V3s in fact. I find many of the Audio Notes of the world colored sounding due to their design.
Click to expand...
great points, i almost feel 102db might be a little too much for my 15w amps in my smaller room. id love to try the even bigger 99db volti aluras. or try the sophia 91-01's @ 8w.
 
Mike said:
A very interesting read:
Power Handling Vs. Efficiency
Click to expand...

Hi Mike,

It's a decent article, but a bit simplistic. The issues are a bit more complex than that. If you really want to know more (or want your head to spin :D), the Klippel site is more comprehensive: Introduction (literature has all the articles).
Yes, generally speaking, higher sensitivity type designs will sound more dynamic, because the drivers are operating more linearly (not necessarily "moving less", though that's part of it, especially with bigger vs smaller drivers).
But there may be another reason. Typically, the low efficiency speakers are direct radiators (cone and domes, etc.), with little (or zero) directivity. The High sensitivity designs often feature horns/waveguides and larger drivers...which tend to be more directional. What we hear in a room is a combination of the "direct" radiation of the speaker and the reverberant or indirect radiation. The higher sensitivity designs will tend to have a higher direct/reverberant ratio, meaning that the level of "background noise level" if you will (not exactly), will be somewhat lower, allowing more contrast with the peak direct output.
Something along the lines of what Steve (Petro) is describing.
I think many here would be surprised to see the FR of their "monopole" box speakers measured from behind. A lot more radiation behind the speaker than some think with "forward" radiators, especially those with narrow baffles/small piston uncontrolled directivity drivers.

Oh..and high sensitivity (>100db) designs don't have to resemble a medium sized refrigerator.:)

Remember also with the low feedback tube designs (most 300b's, SETs, etc.), impedance matters!

cheers,

AJ
 
Thanks AJ....I'm reading as much as I can on different designs. Very fascinating.
 
Someone mentioned above about using lower eff speakers that are easy to drive.

How do you determine that by looking at the specs?
My Dynaudios are 86db @4ohm and not easy to drive to potential.
So what would one look for? 6 or 8ohm at a lower Eff rating? Or are there other numbers that tell you?
 
Shadowfax said:
Someone mentioned above about using lower eff speakers that are easy to drive.

How do you determine that by looking at the specs?
My Dynaudios are 86db @4ohm and not easy to drive to potential.
So what would one look for? 6 or 8ohm at a lower Eff rating? Or are there other numbers that tell you?
Click to expand...

Manufacturer's ratings are generally over simplistic.
 
Petro85 said:
great points, i almost feel 102db might be a little too much for my 15w amps in my smaller room. id love to try the even bigger 99db volti aluras. or try the sophia 91-01's @ 8w.
Click to expand...

No such thing as too much in this case as long as you have a volume control. I had a pair of 118db horns hooked up to a pair of 250w SS amps and it was fine. I eventually switched to a pair of 20wpc triode monoblocks and took a small hit to dynamics in exchange for a larger soundstage and better imaging.
 
Shadowfax said:
Someone mentioned above about using lower eff speakers that are easy to drive.

How do you determine that by looking at the specs?
My Dynaudios are 86db @4ohm and not easy to drive to potential.
So what would one look for? 6 or 8ohm at a lower Eff rating? Or are there other numbers that tell you?
Click to expand...

Hi Brian,

If manufacturers were honest with their "specs" and actually showed measurements, the (true) sensitivity and the impedance curve of the speaker would help you there. If this is your Dynaudio 82 impedance http://www.htguide.com/forum/attachment.php?attachmentid=17967&stc=1&d=1278971264 then the only issue might be the lowish sensitivity (is the 86db rating specified at 1w, or 2.83V ?).
Your Counterpoint should drive them pretty well. Why do you feel they don't?

cheers,

AJ
 
AJ Soundfield said:
Hi Brian,

If manufacturers were honest with their "specs" and actually showed measurements, the (true) sensitivity and the impedance curve of the speaker would help you there. If this is your Dynaudio 82 impedance http://www.htguide.com/forum/attachment.php?attachmentid=17967&stc=1&d=1278971264 then the only issue might be the lowish sensitivity (is the 86db rating specified at 1w, or 2.83V ?).
Your Counterpoint should drive them pretty well. Why do you feel they don't?

cheers,

AJ
Click to expand...

Thanks AJ

I did not say the 82s could not be driven with the Counterpoint. I just stated that they are harder to drive.
Hafler 9180 - OK sound no slam
Odyssey Stratos - plenty of slam and bass but lacking refinement
Counterpoint - Good all around sound but too forward at times

I guess the point I was making is that you need a big quality amp to get the best sound out of the 82s.

I am really curious as to how one is able to make the statement of "Easy to drive" if the numbers are 86db 4ohm. I was more of the understanding that 90db 8ohm would be considered easy to drive.

Case in point, all the Harbeth threads. 25watts to drive them, but really would want more. 86db, but touted as easy to drive. I am just not technical enough in this field to fully understand how to figure if a low sensitivity rated speaker is easy to drive.
 
And Brian, it has been my experience that SS and tube amps differ greatly on how they handle difficult loads.....and within those groups of amps, they can differ too - Class A/B vs Class A and push-pull vs SET. I'm not sure I could explain exactly why, but that has been my experience.


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Shadowfax said:
I guess the point I was making is that you need a big quality amp to get the best sound out of the 82s.
Click to expand...
I agree, especially for my tastes, which include music with wide dynamic range. I would consider the Counterpoints 200w/8 ohm 400w(?)/4 ohm (rms) to be more suitable that the other two lower power amps. However, rms ratings tell little, more important would be dynamic power vs load, as music (that I listen to) is dynamic, not rms. You could try a more powerful amp, but it's also possible that your speakers are beginning to compress even with the Counterpoint. Direct radiator/domes generally don't fare well with dynamics (unless you accept purely subjective opinions of cyber fans as gospel. Then, anything goes).
Unfortunately Soundstage does not have data on any Dyn towers, but here is one for a bookshelf:
thd_95db.gif
Note the obvious signs of distress from the dome tweeter. 95db @ 2m is quite loud...with a steady state signal. Music isn't steady state. It's quite easy to have dynamic peaks that loud when listening at much lower average levels (caveat about music tastes apply).
Btw, I'm not singling out Dyn at all, their drivers are pretty good amongst the cone/dome variety. This (generally) applies to that whole subset of lower sensitivity type designs. It's just that very, very, very few people require "real life" dynamics capability, hence the overwhelming popularity of low sensitivity/direct radiator speakers.

Shadowfax said:
I am really curious as to how one is able to make the statement of "Easy to drive" if the numbers are 86db 4ohm.
Click to expand...
Statements are easy to make...and tastes vary.:)

cheers,

AJ
 
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