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Evidence-based Speaker Designs

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Ilkless

Ilkless

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I didn't realize Amir was able to do speaker measurements... haven't kept up with developments here.

Right now I am doing some product development work, "evolving" in a particular direction. Once I'm reasonably satisfied that the evolution has run its course (and assuming we're satisfied with the results), I would DEFINITELY be interested in exploring the possibility of independent measurements.

Of course - I should have known! I once came thiiiiiis close to ordering a dozen or so 18" fiberglass SEOS waveguides... instead decided that the thing to do was make my own Oblate Spheroids. Easier said than done. Figuring out the best manufacturing technique for our situation, then working out the specifics, has taken a long time. We just took delivery of some custom tooling last week, so there is light at the end of the tunnel.

Excellent article - very educational and enjoyable! Definitely stretched my brain but didn't quite snap it. I'm not much of a headphone guy but have watched David's headphone calibration video, so I was waiting for that to show up in your article. I watch pretty much anything David has uploaded because every now and then he drops little nuggets of unique insight which are applicable to home-audio loudspeaker design, in my opinion anyway.

Informed by (my interpretation of) some of David's ideas, I hope one of my forthcoming designs will compete sonically with the latest version of the hORNS Universum. But I don't have a chance of competing aesthetically... the Universum would be completely at home in a museum of modern art.
Hi Duke,

Yes, Amir bought a very sophisticated measurement setup that allows full-range anechoic measurements without gating in a typical room. Here are example measurements. There have been some slight teething issues (as expected with such an advanced rig), but many users smarter than me have helped Amir troubleshoot the issues very effectively and they are largely ironed out.

Earl's website mentions that someone is "preparing" to make speakers from his product line. Would that be you by any chance? Would you be able to use Earl's foam plug?

I can't wait to see what you have in store for a massive waveguide design. Modern compression drivers and low-diffraction waveguides have come a long way, and the market sadly hasn't really caught up.
 

Duke

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Yes, Amir bought a very sophisticated measurement setup that allows full-range anechoic measurements without gating in a typical room. Here are example measurements. There have been some slight teething issues (as expected with such an advanced rig), but many users smarter than me have helped Amir troubleshoot the issues very effectively and they are largely ironed out.
I see now that he has reviewed many speakers, including at least one floorstander. So I made very very preliminary contact with him on the subject. THANK YOU for the suggestion - I wouldn't have thought it was possible.

Earl's website mentions that someone is "preparing" to make speakers from his product line. Would that be you by any chance?
That's not me. But whoever it is, I certainly wish them well with it.

I can't wait to see what you have in store for a massive waveguide design. Modern compression drivers and low-diffraction waveguides have come a long way, and the market sadly hasn't really caught up.
We hope to help the market, or at least one little sliver of it, catch up a bit.
 

Duke

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"If I could just get those Imperator 667s, it would sound so great I could finally get laid!"
It works.

I was nervous the first time my girlfriend came over and saw my SoundLabs. She was a drummer so I put on a drum solo track, and she immediately started playing air-drums and explaining to me what the drummer was doing, how he was getting this sound and that effect.

We've been married eighteen years now.
 

SIY

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Not for me. My wife (a professional musician for many years) was totally indifferent, other than complaining about the size and color of my speakers.

Now, the first time she had one of my pizzas... that was the hook. We've been married 12 years now.:D
 

Duke

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Only the person armed with the idea can produce a better speaker. And ideas are not science, nor "evidence". [emphasis Duke's]
Cosmik, I really like the way you have identified the idea as where creation happens. If the art is to be advanced, it will start with an idea.

For example, Toole's research started as an idea... a very good idea, to find correlations between measurement and perception. He probably had that idea before knowing whether or not it could be done. And he absolutely advanced the art, and in particular the psychoacoustics, of loudspeaker design for home audio.

It's the designing to "evidence" aspect that is circular. I am attempting to break out of the circle
I think I understand what you mean. At the risk of indulging in the cliche', IDEAS are what will take us outside our current box, not data (though data re-examined can inspire ideas). But ideas are also like genetic mutations - MOST of them will fail. Then those which succeed eventually become part of the NEW box, to be transcended by still better ideas some day.

Or (much better) they could approach it from the other direction: define what the ideal speaker should do and design something to realise it (as close as practical). In this case, the design would not be based on evidence at all, except for final confirmation and (this being the real world) refinement.

How many people would be prepared to define what the ideal speaker should do before they go looking for evidence? Not many.
I'll give it a shot:

The ideal speaker would get two things as perceptually correct as possible, within applicable constraints:

1. The first-arrival sound; and
2. Everything that follows it.

This does not tell us WHAT to do, nor HOW best to do it. Answering those questions are where research and refinement come in.

[edit] The question of "WHAT to do" is not about loudspeakers and rooms. It is about ears and performance venues, to inform ourselves about where the goals posts are. HOW best to do "it", whatever "it" turns out to be, is about loudspeakers and rooms. [/edit]

Cosmik, last year I learned the hard way that you and I do not agree on WHAT or HOW, and we probably disagree about "what the ideal loudspeaker should do", but I THINK we agree that

Only the person armed with an idea can produce a better speaker.
 
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tuga

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The ideal speaker would get two things as perceptually correct as possible, within applicable constraints:

1. The first-arrival sound; and
2. Everything that follows it.
If you are referring to the reproduction of the original soundfield of a live musical event over speakers (the listener is "transported" to the original acoustic space) then the only option is to use a spherical mic array and listen inside a spherical array of speakers:





If one would rather reproduce the instruments as if they were playing in the listening room then one would need to record each instrument inside a spherical array of mics and reproduce each instrument with a spherical speaker array:





What would be the best way to create and reproduce a studio mix? Multi-channel stereo?
Most of such music is created to be reproduced over a pair of earbuds, laptop speakers or a monaural bluetooth speaker and broadcasted over DAB so one would always have to produce a 2-channel stereo mix. Labels might not be willing to spend money on a multi-channel mix for most music.
 
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Cosmik, I really like the way you have identified the idea as where creation happens. If the art is to be advanced, it will start with an idea.

For example, Toole's research started as an idea... a very good idea, to find correlations between measurement and perception. He probably had that idea before knowing whether or not it could be done. And he absolutely advanced the art, and in particular the psychoacoustics, of loudspeaker design for home audio.
....
Only the person armed with an idea can produce a better speaker.
And if the idea it's to go, no against Toole :) but further than this idea of Toole, and consider more the influence of the listening room ?
My experience of sound engineer is if I put a very good loudspeaker in a very poor listening room , I get.... nothing :(
Said that listening room contribue 30 % only in bass frequencies it's reducer.
 
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Duke

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If you are referring to the reproduction of the original soundfield of a live musical event over speakers (the listener is "transported" to the original acoustic space) then the only option is to use a spherical mic array and listen inside a spherical array of speakers...
I only mentioned "applicable constraints", and didn't spell out what I think they are. Here are some of them, at least from my point of view as a small business owner.

1. Should be feasible without a prohibitive development cost.
2. Should do the things that matter to me at an acceptable production cost.
3. Should work with normal two-channel audio recordings.
4. Should work in a wide variety of rooms.
5. Should be practical (shippable, sellable, reliable, repairable, compatible with other equipment).
6. Should be desirable.

So while I do not doubt the superiority of your spherical array, it's outta my league!
 

SIY

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I suspect that something like Ambisonics will work nearly as well. The demos I’ve heard were spectacular. Unfortunately, it was not acceptable to consumers...
 

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My experience of sound engineer is if I put a very good loudspeaker in a very poor listening room , I get.... nothing :(
In my opinion room interaction is the essence of "everything that follows the first-arrival sound". So once we've gotten the first-arrival sound right, everything is about beneficial room interaction, or working "with the room" instead of against it.

For example, putting out energy which needs to be absorbed in order to get good sound is arguably "working against the room". Not putting out that energy in the first place would be "working with the room".
 
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tuga

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I suspect that something like Ambisonics will work nearly as well. The demos I’ve heard were spectacular. Unfortunately, it was not acceptable to consumers...
I wonder if it will ever sound un-processed or un-synthetic. I'm not really looking for spectacular, it strays too far away from music and into the realms of stage. If you can get the latter without messing up the former fine but if not then no thanks.
 

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I wonder if it will ever sound un-processed or un-synthetic. I'm not really looking for spectacular, it strays too far away from music and into the realms of stage. If you can get the latter without messing up the former fine but if not then no thanks.
It was the most realistic rendition of 3D sound I’ve ever heard.
 

Duke

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What I'm talking about [from a wide-baffle speaker] is the impression of size, body and weight of the actual instruments and voices within a soundstage. The sonic richness, the sense that you are hearing something closer to a full sized, fully-weighted acoustic guitar, or sax, or piano, or drums, vs a smaller or less subsantial instrumental reproduction (even if placed in an immersive soundstage).
I believe you.

I have built roughly a dozen different designs using the same large midwoofer. Some have been for prosound, some for home audio. I recognize the characteristic you are describing, and my observation is that it correlates with baffle size (especially width) rather than with low-end extension.

I am wondering how the baffle-step issue may or may not come in to play in explaining the characteristics I'm talking about.
I think the baffle step explains it. You can think of the baffle as a 180 degree horn, with the minimum dimension (typically the width) predicting how far down in frequency it "loads" the midwoofer.
 

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It was the most realistic rendition of 3D sound I’ve ever heard.
I agree SY, in my experience also (and I have used it in VR productions). Wavefield Synthesis is fabulous for pin-point localisation precision, but it is 2D only and it scales badly with spatial aliasing, not to mention being ridiculously resource-heavy and having zero production tools.... Higher Order Ambisonics (HOA) scales better, works probably better in the middle of the speaker array. WFS generally has a larger (sometimes very slightly larger) listening area, but can be more coloured... There are several papers comparing them, here is a decent one https://www.researchgate.net/public...atial_Discretization_Artifacts_in_Time_Domain
 

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I would say that the only room where [a speaker without dispersion control] wouldn't sound coloured would be an anechoic chamber. The suggestion otherwise is that the room can somehow be treated in an ideal complementary way that somehow fixes the poor dispersion of the speaker. I think this is a misunderstanding: poor dispersion cannot be fixed with room treatments or anything else.
Well said!

You can absorb the early reflections with acoustic panels.
Yes, but it's not quite that simple.

Absorptive material is far more effective at short wavelengths than at long ones, so foam just kills all the short wavelengths. What's left of your reflection is much weaker of course, and it has a very dull spectral balance.

Broadband absorption typically combines absorption with reflection or diffusion, which reduces the amplitude of the reflection, but does not correct its spectral balance.

Absorption which selectively affects a particular frequency region, such that it can "target" a specific excess of off-axis energy, would be a custom product IF it exists.

And what if your problem is a dip in the off-axis energy? You can't fill a dip with room treatments; you'd have to absorb everything around the dip, and that would not be easy.

Probably the most practical solution is indeed what you suggested: Just absorb the reflection so that it no longer colors the sound, but now you have this uber-absorptive panel which utterly kills the shorter wavelengths of any reflection that hits it. This can suck too much high frequency energy out of the in-room sound and make the perceived tonal balance dull and the presentation less interesting (high frequencies convey a lot of information even when they are in reflections, and we tend to like that).

Or... we can reconsider controlled directivity.

Quoting acoustician Matthew Poes: "A speaker that has controlled dispersion does basically the same thing you'd expect an acoustic panel to do, but it does a better job. And it allows you to get away with no panels on the wall.”
 
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tuga

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I would say that the only room where it wouldn't sound coloured would be an anechoic chamber. The suggestion otherwise is that the room can somehow be treated in an ideal complementary way that somehow fixes the poor dispersion of the speaker. I think this is a misunderstanding: poor dispersion cannot be fixed with room treatments or anything else.
Listen nearfield, setup speakers long wall in wide room, treat early reflections with specific narrowband absorption, all deal with the typical wide at the bottom of the passband dispersion of a non-waveguided tweeter.
 

Duke

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I hope to share about more affordable loudspeaker designs and manufacturers that have a demonstrable commitment to releasing evidence-based designs consistent with acoustical physics and psychoacoustics, even if they do not quite reach the levels of unsurpassed excellence often appearing in that other thread.
I'd like to nominate Earl Geddes' NS15 (NS is for "New Summa"). He no longer builds the smaller Abbey and Nathan, but apparently will still accept orders for the NS15.

For those of you more familiar with Olive and Toole, at the January 2009 ALMA symposium they both participated in a panel discussion entitled, “What loudspeaker specifications are relevant to perception?” Earl Geddes was on that panel with them.

Here is a link to the web page for the NS15, which includes a polar map. His website also reports that someone is preparing to offer his other designs.

Here is his paper on his loudspeaker design philosophy, which is imo the most educational such paper I have encountered: http://www.gedlee.com/Papers/Philosophy.pdf

And here is a YouTube video which imo supports my claim that Earl's designs qualify as "Evidence Based". You'll find that he and Toole usually agree, but not always:

https://www.youtube.com/watch?v=fE2nWVwFT9k

I suggest you pause if necessary to read the contents of the slides if what he's saying interests you.

Note in particular his "Loudspeaker Specs" slide which first shows up around 2:50. It's a bit different from most manufacturer's loudspeaker specs.
 
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Ilkless

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I'd like to nominate Earl Geddes' NS15 (NS is for "New Summa"). He no longer builds the smaller Abbey and Nathan, but apparently will still accept orders for the NS15.

For those of you more familiar with Olive and Toole, at the January 2009 ALMA symposium they both participated in a panel discussion entitled, “What loudspeaker specifications are relevant to perception?” Earl Geddes was on that panel with them.

Here is a link to the web page for the NS15, which includes a polar map. His website also reports that someone is preparing to offer his other designs.

Here is his paper on his loudspeaker design philosophy, which is imo the most educational such paper I have encountered: http://www.gedlee.com/Papers/Philosophy.pdf

And here is a YouTube video which imo supports my claim that Earl's designs qualify as "Evidence Based". You'll find that he and Toole usually agree, but not always:

https://www.youtube.com/watch?v=fE2nWVwFT9k

I suggest you pause if necessary to read the contents of the slides if what he's saying interests you.
Hi Duke, I'm well aware of Earl's designs and excellent engineering, but refrained from putting it on the list because of the uncertainty surrounding its availability. Earl retired soon after the NS15 came out, to my knowledge, and I don't know of anyone who got an NS15 on special order after his "retirement". I still check in from time to time on the Gedlee website on updates about whoever is taking over Gedlee production, but there doesn't seem to be any. In any case, Earl seems to be enjoying a much-deserved retirement and indulging in his stained glass hobby.

https://www.audiosciencereview.com/forum/index.php?threads/dagogo-interview-of-earl-geddes.6554/

Another excellent resource is Dagogo's interview with Earl.
 
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