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What makes speakers "disappear " and can it be measured?

I can’t back this up scientifically, but I think the phenomenon of speakers “disappearing” is related to hearing sufficient direct sound and stereo separation that the sound is apparently between the speakers. As reflected sound increases, the sound field becomes a more diffuse wall of sound and any central image less distinct.

I don’t think the effect is typically due to speaker distortion that causes you to locate the speaker in space as much as a weak center image.

Increasing direct vs reflected sound and having good frequency response off axis should both help achieve the effect.
I also think that hearing a sufficient amount of direct sound and a properly set up speaker positioning that locks in the phantom center will make the speakers "disappear".

As we all understand, a single speaker can never disappear no matter how much reverb sound our listening room adds to the equation, already there we have "the proof" that the listening room cannot be the factor that makes our speakers do the disappearing act. We need two speakers playing together, two sound sources properly set up that will give us "a window" to the recorded room, and for that to happen we need to reduce the reverberation from our listening room and get the positioning of the speakers just right.

My speakers can disappear depending on the recording. I have them set up in a 60-degree equilateral triangle with a distance between them small enough to get a distinct center image, the short distance to the listener position will also give me a fair amount of direct sound over the reverb from my listening room. But like I said it depends on the recordings, the speakers can of course never "escape" hard-panned dry sounds.
 
I wonder why this "headphone style" configuration never gets mentioned in speaker placement. In theory it should give you perfect stereo and eliminate any room effects.

Not really. Stereo is flawed whatever the setup may be. The best configuration would be an infinite number of speakers around you like a sphere. There are a few rare setups that operate in that principle: some of the earlier ones were temporary experimental installations, others more new and permanent with maybe fewer monitors eventually followed the lead. There have been a few pictures of such installations posted in the forum. Can't quite remember where... but they certainly do exist.
 
We have interesting discussion going on here.

Just for your interest and reference, my time alignment adjustment for sub-woofer is 16 msec delay of other drivers, i.e. 16 msec delay of woofer + midrange squawker + tweeter + super-tweeter. This corresponds to that I pushed subwoofers 5.5 m (345 ms x 0.016 s) ahead towards my listening position.

After reading about my 16 msec adjustment, one of my dear ASR Forum friends suggested that I may also try to physically move my L&R subwoofers about 4 m ahead to very near to or even beside my listening position instead of having the 16 msec digital delay adjustment. This would be an interesting suggestion, but I really did not like to try this. So, I wrote in my post #502 on my project thread;

At present, since I like the listening feeling as if I am sitting on the best S-class center seat in Concertgebouw Amsterdam, I do not like to have my SWs just beside me at my listening position; even with the "complete and perfect" time alignment of SPs I achieved, the orchestral big drum sound should be coming from the stage direction in front of my eyes and ears!

Of course, I know well that in real Concertgebouw Amsterdam (I have been there several times), I hear the entire hall tone (including the reflections, resonances, standing-waves) from all the directions surrounding me, from behind, above (ceilings), side (side walls) and floor. This is the the main reason that I insists we need suitable and preferable reverberations also in our home audio listening room which somewhat "simulates" the real hall tone, but never never to be perfect.

All of you may agree with me that our stereo audio music listening would not be enjoyable if our listening room is fully anechoic.
 
Not really. Stereo is flawed whatever the setup may be. The best configuration would be an infinite number of speakers around you like a sphere. There are a few rare setups that operate in that principle: some of the earlier ones were temporary experimental installations, others more new and permanent with maybe fewer monitors eventually followed the lead. There have been a few pictures of such installations posted in the forum. Can't quite remember where... but they certainly do exist.
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Not really. Stereo is flawed whatever the setup may be. The best configuration would be an infinite number of speakers around you like a sphere. There are a few rare setups that operate in that principle: some of the earlier ones were temporary experimental installations, others more new and permanent with maybe fewer monitors eventually followed the lead. There have been a few pictures of such installations posted in the forum. Can't quite remember where... but they certainly do exist.

Yes, I agree with you, and I also remember such experimental multiple speaker setup 3D spherically surrounding the listener. The real difficult issue in this case is that we need same number of multiple track recording and playback system for such 3D spherical setup...

I assume your point of multiple spherical SP alignment and my quasi-3D reverberation simulation of Concertgebouw Amsterdam mentioned in above #323 post are discussing the same issue from different angles.
 
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I wonder why this "headphone style" configuration never gets mentioned in speaker placement. In theory it should give you perfect stereo and eliminate any room effects.
While it would create “perfect” stereo, it would also completely eliminate the sound stage. To get the sense of performers at depth in front of you, there must be speakers in front of you. Otherwise, the sound is “in your head”. Headphones have this issue. Even the best collapse the soundstage significantly.
 
Anyone mention Audio Physic in this thread? Visiting one of my favorite Audio shops years ago, Audio Physic Tempo 3's were playing in one of the rooms. They completely disappeared within the sound field, like no other speaker I had heard prior. I was so impressed with that, that I bought a pair, though mine came from Audiogon. They were $3600 bucks on the showroom floor. Too rich for my blood at the time.
I don't think so in this thread, but @MattHooper did in a similar thread and I responded. They aren't well-known outside Europe, but in my experience the disappearing act reputation is justifiable.

Recall that Toole discusses speaker resonances as counter-productive in this aspect. Original Audio Physic designer (Diestertich) was particularly interested to control these via cabinet construction (your Tempo have the nice curved cabinet and various AP models employ plastic honeycomb, elastomer, ceramic foam and glass for their different densities and resonant behaviours) and similarly for the drivers themselves, decoupled mounting to the baffle and dual baskets (KEF just picked up the latter with a slightly different implementation in their new releases). Anyway, I like mine.
 
While it would create “perfect” stereo, it would also completely eliminate the sound stage. To get the sense of performers at depth in front of you, there must be speakers in front of you. Otherwise, the sound is “in your head”. Headphones have this issue. Even the best collapse the soundstage significantly.
This is probably going to depend on the mix, isn't it?

I mean the usual methods of FR shape, phase/delay, reverb etc will still apply, just implemented via Atmos (or equivalent) rather than stereo mix. So "in front" is traditional placement and applies to certain music types, but you can imagine other spatial presentations for (eg) electronic. Depth is an attribute independent from channel number (albeit more limited in mono, but we still have FR shape and reverb even then).

Edit: for the multichannel systems pictured in @youngho's post, all the depth cues present in the recording should be reproduced. For the Genelec-based system pictured in the anechoic room, the additional depth/reverb effects added by the listening room will be minimised (I see that as a more technically advanced system, but certain traditional recordings may lose the pleasing envelopment listeners to those types of music may be accustomed to).
 
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The BMR Tower speakers disappear more than I have seen with any other speaker. Especially, with classical music and a large orchestra. I credit that feature to the dual Tectonic Balanced Mode Radiator 2.5" midrange. I have the BMR Monitor too but in a larger room the BMR Tower dispersion of sound is at a whole new level. If you like classical music especially orchestra you will want to take a listen to the BMR Tower.

 
This is probably going to depend on the mix, isn't it?

I mean the usual methods of FR shape, phase/delay, reverb etc will still apply, just implemented via Atmos (or equivalent) rather than stereo mix. So "in front" is traditional placement and applies to certain music types, but you can imagine other spatial presentations for (eg) electronic. Depth is an attribute independent from channel number (albeit more limited in mono, but we still have FR shape and reverb even then).

Edit: for the multichannel systems pictured in @youngho's post, all the depth cues present in the recording should be reproduced. For the Genelec-based system pictured in the anechoic room, the additional depth/reverb effects added by the listening room will be minimised (I see that as a more technically advanced system, but certain traditional recordings may lose the pleasing envelopment listeners to those types of music may be accustomed to).
I didn't mean to imply only in front. Just that to create depth, the speakers can't Only be co-axial to your ears. Barring computer controlled office axis beaming/reflection technology. You can certainly have speakers in addition to (or in other off-co-axial locations) the front.
 
I hope this interesting thread is still alive and active.

Just for your reference, today I wrote my post here entitled "Perfect (0.1 msec precision) time alignment of all the SP drivers greatly contributes to amazing disappearance of SPs, tightness and cleanliness of the sound, and superior 3D sound stage." on my multichannel multi-way multi-driver multi-amplifier (with no LCR network) project thread.
I don't hear it. When I turn time alignment on and off with my room correction software, I cannot reliably tell a difference. Yes, sometimes I THINK I do, but usually I don't which makes me think I really don't, or maybe with only a few recordings. Blind listening tests are also inconclusive on the audibility of time alignment.
 
Yes, I agree with you, and I also remember such experimental multiple speaker setup 3D spherically surrounding the listener.

Scientists install such 3D something because of one reason, and another:
- a new theoretical solutions, once necessary compromises are chosen, shall be tested with real human listeners
- stereo is fundamentally flawed, hence the oportunity for improvement

Alas, the industry didn't get tired to press the audience into the idea that stereo was some kind of virtual reality. A trick of nature that would make the listener feel to "be there", effortlessly. This is plain fraud.

On one side the stereo imaging, which is an unlucky wording to begin with, is seen as the holy grail by enthusiasts. On the other side most of music lovers don't give a dime for it. Effectively mono is back in all honor. I couldn't tell when I saw a full stereo set-up lately, except for p/a--but was it stereo with the audience spread out widely?

Reiterated, stereo provides some artfull cues to trigger the listeners imagination. Not more, just triggers as seeds for an individual processing by the listeners imagination. There is no automatism! That investment, a concious activity, an active willingness to ignore the speakers as such is crucial. Best achieved by really interesting music.
 
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Scientists install such 3D something because of one reason, and another:
- a new theoretical solutions, once necessary compromises are chosen, shall be tested with real human listeners
- stereo is fundamentally flawed, hence the oportunity for improvement

Alas, the industry didn't get tired to press the audience into the idea that stereo was some kind of virtual reality. A trick of nature that would make the listener feel to "be there", effortlessly. This is plain fraud.

On one side the stereo imaging, which is an unlucky wording to begin with, is seen as the holy grail by enthusiasts. On the other side most of music lovers don't give a dime for it. Effectively mono is back in all honor. I couldn't tell when I saw a full stereo set-up lately, except for p/a--but was it stereo with the audience spread out widely?

Reiterated, stereo provides some artfull cues to trigger the listeners imagination. Not more, just triggers as seeds for an individual processing by the listeners imagination. There is no automatism! That investment, a concious activity, an active willingness to ignore the speakers as such is crucial. Best achieved by really interesting music.
I don't think suspension of disbelief wrt the stereo illusion is necessarily a conscious decision (although it can be). Also, calling stereo "fraud" is too hyperbolic to entertain.
 
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I didn't mean to imply only in front. Just that to create depth, the speakers can't Only be co-axial to your ears. Barring computer controlled office axis beaming/reflection technology. You can certainly have speakers in addition to (or in other off-co-axial locations) the front.
Got it. To explain what I was saying in that context, by "in front" you mean in any direction (as opposed to inter-cranial, say).

I guess I mean that, assuming the Atmos (or other multi-channel object-oriented) mix is done competently, a sound object can be positioned close to or distant from the listener in any direction (using the normal shaping and processing methods).
 
Also, calling stereo "fraud" is too hyperbolic to entertain.
My bitter verdict spelled: "Alas, the industry... press the audience into the idea ... stereo was some kind of virtual reality. ... . ... effortlessly. This is plain fraud."
And: " ... an individual processing by the listeners imagination. There is no automatism! That investment, a conscious activity, an active willingness ..."

I think we can agree, that stereo is not like virtual reality, any 'holo-deck' of Star Treck fame. It needs mental activity to puzzle a variety of cues together, while actively ignoring well-known contradicting cues. If such actions are conscious or at a certain degree automatic may be a matter of accommodation.
 
All of you may agree with me that our stereo audio music listening would not be enjoyable if our listening room is fully anechoic.

That would be very difficult if not impossible to achieve in normal domestic listening rooms anyway.

My room is quite dry, but with a flat RT. For live concert recordings, I will sometimes add additional DSP in order to artificially simulate a wider, more reverberant soundfield as it adds-in to the illusion of a much bigger space. The rest of the time, I'm perfectly fine with no additional reverb processing inserted into the mix.
 
That would be very difficult if not impossible to achieve in normal domestic listening rooms anyway.

My room is quite dry, but with a flat RT. For live concert recordings, I will sometimes add additional DSP in order to artificially simulate a wider, more reverberant soundfield as it adds-in to the illusion of a much bigger space. The rest of the time, I'm perfectly fine with no additional reverb processing inserted into the mix.
Many posts here mention reflections and envelopment as key to 'disappearing' but like you I have a dry listening room (RT30 is flat and < 200 ms until the bottom octave) and additionally speakers on the narrow directivity side of average. So I think the key elements of the speaker trick are more like flat FR and low distortion in the critical band, flat group delay and lack of revealing resonances.

Regarding the latter, and using a more familiar playback device, I like the way AirPods Pro do the in-front-of-you spatial audio thing quite convincingly when played from an iOS or iPadOS device. At all but the lower frequencies where some resonances in the earpieces break the illusion on certain notes. I imagine AirPods Max do it better.
 
I think we can agree, that stereo is not like virtual reality, any 'holo-deck' of Star Treck fame. It needs mental activity to puzzle a variety of cues together, while actively ignoring well-known contradicting cues. If such actions are conscious or at a certain degree automatic may be a matter of accommodation.
No I don't think we agree much.

The proposition that "stereo isn't a holo-deck so it's fraud" is as fallacious as any strawman.

I also think you wildly overstate any necessary accomodation (without knowing which specific meaning of accomodation you refer to, there are half a dozen that could apply). Stereo reproduces the cues of distance and direction sufficiently well that an untrained person can immediately ascertain left-to-right and (assuming the system is set up adequately and the recording likewise) some degree of depth. It isn't a puzzle that requires special effort to resolve, just the normal behaviour of our auditory system.
 
No I don't think we agree much.

The proposition that "stereo isn't a holo-deck so it's fraud" is as fallacious as any strawman.
... the normal behaviour of our auditory system.
Thanks, really, for rephrasing my argument. This is true gentlement's style.
So, we do not agree, because You may not get my argument right. I'm not saying that stereo as such was fraud. Instead, the idea that stereo is an automatic trick of nature, that is fallacy. The industry ventilated such misconception for decades. The latter, and just that latter is fraud.

I don't feel to view at myself as an auditory system. Such self-reference is prone to paradox, as Russell/Whitehead proved in the (in)famous book "Principa Mathematica".

Your criticism ist appreciated.
 
I think we can agree, that stereo is not like virtual reality, any 'holo-deck' of Star Treck fame. It needs mental activity to puzzle a variety of cues together, while actively ignoring well-known contradicting cues. If such actions are conscious or at a certain degree automatic may be a matter of accommodation.

I guess it depends on what one's threshold is for entertaining the "holo-deck" comparison.

I find 2 channel plenty holographic. And especially when I had the MBL omis, the sense of performers just appearing in 3 dimensions around the speaker, or (depending on the recording) being transported to the recording space, was pretty uncanny. Good enough for me to be impressed.
 
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