Dr. Edgar Choueiri explains BACCH

[Newman]

The rabid arm wavers on this forum are doing no favours whatsoever in terms of "promotion" for this product. Quite the opposite in fact.

It's turning into a bit of an issue. I have largely left it alone and treated this thread as a fans-gotta-have-a-place-to-play thread, but if the overdefenders want to start lashing out all over the rest of the site, calling everything 'bogus' except their apostle-guru-approved tech, then the safe haven status might have to be reconsidered.

It's a pity because cross talk and HRTF are very legitimate and well-researched issues, and not fully addressed by current mainstream sound reproduction tech, but if the response here (to a reality check delivered by an esteemed audio researcher) is to launch into dismissive shooting of the messenger, then you know that someone is not here in good faith, or at the very least, lost the ability to listen and learn on this particular topic with a balanced and neutral perspective.

And like you say, that's actually counterproductive, even for those with a keen interest.

cheers

 

[Lion♡]

About 2.5 meter.

nice!

You mean the speakers? They are ESL about 6 x 3 feet each. Speakers are just about 3cm from one another.

I was asking about the size of the space. For example, in a room of 10m x 10m, the listening distance between the speaker and myself is 3m

20 degrees.

very suitable!

Above 40dB attenuation. Room RT is below 0.2s. Didn’t really hear any diff with the XTC even when it was above 0.3s.

I think what you feel is right because XTC follows and works with most responses and characteristics within 5-10ms.
Even if more than 1000 ms of Late Reflection was added, it was not related to XTC. But I was curious. I wanted to hear the environment of multiple people, like I wrote.

3.2m between MLP and speaker. The speakers are set up on the long wall of a 6m x 7m room in an equilateral triangle.

nice. I'm looking at your setup thread well.

60 degrees. Both speakers toed in to the listener.

You mean 60 degrees each, right? You put it quite wide. I think the ASW will be stimulated well. Interesting!

Thank you to both of you @STC @Keith_W for providing, share the information.

 

[Justdafactsmaam]

It's turning into a bit of an issue. I have largely left it alone and treated this thread as a fans-gotta-have-a-place-to-play thread,

And yet here you are with nothing to offer on the actual subject making derogatory comments about other forum members.

but if the overdefenders want to start lashing out all over the rest of the site, calling everything 'bogus' except their apostle-guru-approved tech, then the safe haven status might have to be reconsidered.

Now that is ironic. Given the guru status of Dr. Toole accusing others of having an apostle-guru. Please do cite examples of someone “calling everything bogus” actually happening “all over the rest of the site”

It's a pity because cross talk and HRTF are very legitimate and well-researched issues, and not fully addressed by current mainstream sound reproduction tech, but if the response here (to a reality check delivered by an esteemed audio researcher)

Reality check? You mean the researcher who quite literally offered opinions on the BACCH without testing it? And refused an invitation to even audition it? I thought reality checks had to be based on reality. Where’s the science? Where’s data in support of these opinions?

An esteemed researcher should know better than to offer opinions that aren’t backed by actual data.

is to launch into dismissive shooting of the messenger, then you know that someone is not here in good faith, or at the very least, lost the ability to listen and learn on this particular topic with a balanced and neutral perspective.

Again with the irony. Where is the good faith in attacks on technology without any actual testing to back it up?

Dr. Toole built a career on blind preference listening tests and his “devoted” followers seem to be on board with his every utterance. And yet neither Dr. Toole nor any of his followers have expressed even a remote interest in putting the BACCH up to blind preference comparison to conventional 2 channel stereo.

If good faith is really of interest here then blind preference tests would be the way to demonstrate it.

But Dr. Toole wasn’t even interested in any kind of audition much less an actual blind preference test.

And all time I thought that was supposed to be the gold standard.

I have a hunch as to why there was a such a lack of interest in actually putting the technology to the test.

I’m not going to shoot the messenger but I am going to call out the message for what it is.

 

[theREALdotnet]

You mean the researcher who quite literally offered opinions on the BACCH without testing it? And refused an invitation to even audition it? I thought reality checks had to be based on reality. Where’s the science? Where’s data in support of these opinions?

The researcher doesn’t believe in the value of stereo and posits that pretty much everything you need to know about a speaker can be obtained from mono listening and measurements of a single speaker. He also doesn’t think that room treatment is necessary or effective. So there.

As for BACCH, I’ve at least dipped my toe in. To the extent that the uBACCH plugin has anything to do with BACCH, I found it severely lacking. It did almost the opposite of most of the things it is advertised of doing.

 

[STC]

was asking about the size of the space. For example, in a room of 10m x 10m, the listening distance between the speaker and myself is 3m

Been years since I paid attention to those. Room was built during my stereo era. The dimension length is about 16 feet, height around 10 ft and width about 13 or 14 feet.

 

[STC]

Now that is ironic. Given the guru status of Dr. Toole accusing others of having an apostle-guru. Please do cite examples of someone “calling everything bogus” actually happening “all over the rest of the site”

I don’t think Toole is against XTC itself. Not sure what he said about BACCH. Any reference?

 

[Newman]

I don’t think Toole is against XTC itself. Not sure what he said about BACCH. Any reference?

1. "For those who cannot accommodate a quality multichannel system, it serves a purpose."

2. "In this mode (speakers 20 deg apart) it is really a sound-effects generator and opinions of like or dislike will predictably vary."

 

[STC]

2. "In this mode (speakers 20 deg apart) it is really a sound-effects generator and opinions of like or dislike will predictably vary."

Toole was giving an opinion. He even emphasized the word “think”. It is unfair to equate all XTC to BACCH. BACCH was developed or adapted the XTC for conventional stereo triangle. Regarding his other opinion to comparing his own VMAX with others I am not sure what is the purpose because XTC is not meant to be 5.1 or 7.1 or multichannel. It supposed to deal with the stereo errors and nothing more than that.

 

[audiofooled]

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

if you want your speakers to dissapear you must go with one that uses reflections, dipole or omni. normal box speakers dont even compare in that regard.

audiosciencereview.com

Here Dr. Toole said a lot in a very few lines.

IMHO, if you have sufficient information on how a single speaker would perform, then you still need the other one which is manufactured within tight tolerances. You may or may not find out that you don't need room treatment, depending on how you set it up. As usual, there will be setup limitations. I'm sure most of us can recognize the benefits of DSP as a tool. All I can say is that I was impressed with technology Yamaha engineers were able to incorporate in one of the flagship models of the last century. I just realized I don't need it for mostly practical reasons and some inconsistent results.

That said, I don't think any form of new technology should be dismissed without further testing. If you can hear nothing but benefits, by all means do it.

 

[STC]

You cannot make a single speaker disappear because it is the source of sound. It emits sound and our ears/brain evolved to find out where the sound is coming from. When it comes to speakers then we need to state clearly what are we referring to when we say the speakers disappear. If the sound source is so pristine like the original then can we also say the same when a guitarist playing in the room he disappears?

 

[Lion♡]

Been years since I paid attention to those. Room was built during my stereo era. The dimension length is about 16 feet, height around 10 ft and width about 13 or 14 feet.

Thanks for Info! very kind. Certainly rooms in other countries (including your rooms) seem to have high ceilings by default.

As for BACCH, I’ve at least dipped my toe in. To the extent that the uBACCH plugin has anything to do with BACCH, I found it severely lacking. It did almost the opposite of most of the things it is advertised of doing.

This is one of the reasons I wanted to ask you about the characteristics of the room and what you listen to.
ubaach, bacch, other xtc, physical xtc, virtual xtc, etc. The conditions of the room must also be met in order to perform properly.
If head tracking is supported, inaccurate filters can be smothered to some extent, but if the in-room conditions are very difficult, the results may fade.
Reflective sounds created by hitting somewhere other than a clean response meet, combining, mixing, and repetition of them, resulting in unpredictable results. That can also come as a change in tone that some people say.
response is shaken even with a difference of 0.01 ms and uncontrolled initial impulse peaks.

But on the contrary, I also think about this these days.
I don't think everyone has a clean response, so I expect there will be more cases where it's not a complete XTC.
Nevertheless, I think the reason for the high satisfaction is that the kind of effect that comes from mixing both channels in the reverse phase also affects.
Even if it's not canceled correctly, to a certain extent, something affects each channel. And the people I asked were surprised, amazed, and satisfied with the inaccurate cancellation.
Of course, the difference between an accurate cancellation and one that is not is too big.

 

[Davide]

To answer those who say that people speak without having listened to it.
I would say that even a classic stereo widener plugin can be preferred in a blind test.
But the same for a saturator or exciter...
But what would be the purpose of that test?
Some numbers are needed...
Leaving aside that long-term preference may vary (it happens to me often), we have no apparently a direct metric associated with spatiality with which to extrapolate a preference value (there is the spectrum of cancellation but to me it is not clear whether it can represent a subjective preference in addition to accuracy to the audio track. But if there is any information let's indicate it please so the discussion is constructive).

It's like taking a test to determine if an expensive bottle of wine is better than one from discount... probably it will be like this for most testers... but then?
For me we can only say that between the two bottles, in terms of price, there are many equally/differently appreciable wines.
Or that if vehicle specific wine molecules on specific taste receptors on the tongue I will get a better experience... to the detriment of have to put an uncomfortable contraption in my mouth... or having to sit rather firmly with the tongue (just examples).
Some compromises can already be contemplated before...
Obviously it is not a question of generalizing, only of putting conceptual elements on the table in the absence of numbers, which shouldn't mean going against it, but just trying to make constructive considerations with available info. Since we only have the theory, let's consider all the theory. Then if anyone has any relevant information on the matter I think it is the most welcome thing here. I think everyone is thrilled to see evidences of a super effective/preferable XTC that do justice to its cost. This should make it more desirable.
All this is the basis of ASR.

EDIT: My epilogue

 

[audiofooled]

You cannot make a single speaker disappear because it is the source of sound. It emits sound and our ears/brain evolved to find out where the sound is coming from. When it comes to speakers then we need to state clearly what are we referring to when we say the speakers disappear. If the sound source is so pristine like the original then can we also say the same when a guitarist playing in the room he disappears?

Yes you can. In a room that is normally reflective, with a single loudspeaker that doesn't have audible resonances or distortion, that has no spectral variance in the reverberant field and is phase coherent, especially in the crossover region, so no directivity mismatch. Early reflections alone would shift and draw away attention from the loudspeaker as an apparent sound source, running a bit late but having spectral cues that are closely matching direct sound. In an anechoic chamber, with a single speaker of such quality, so direct sound alone, you cannot localize, with sonic image ending up right in the middle of your head.

 

[STC]

I would say that even a classic stereo widener plugin can be preferred in a blind test.
But the same for a saturator or exciter...
But what would be the purpose of that test?
Leaving aside that long-term preference may vary (it happens to me often), there is no metric associated with spatiality with which to extrapolate a preferred value.
It's like taking a test to determine if an expensive bottle of wine is better than one from discount... probably it will be like this for most testers... but then? Should we say that everyone has to drink the more expensive one or that it is worth what it costs?

For me we can only say that between the two bottles, in terms of price, there are many differently appreciable wines.

XTC is not supposed to enhance or sweetened the sound like other DSPs. The only reason why we have digital XTC because physical barriers are impractical. Unless physical barriers are considered sound effect.

Yes you can. In a room that is normally reflective, with a single loudspeaker that doesn't have audible resonances or distortion, that has no spectral variance in the reverberant field and is phase coherent, especially in the crossover region, so no directivity mismatch. Early reflections alone would shift and draw away attention from the loudspeaker as an apparent sound source, running a bit late but having spectral cues that are closely matching direct sound. In an anechoic chamber, with a single speaker of such quality, so direct sound alone, you cannot localize, with sonic image ending up right in the middle of your head.

Reflection can slightly alter the exact spot of the emitter but that also applies to a real instrument or source unless you are saying we cannot tell the direction when blindfolded of a finest instrument or someone talking to you in the room.

Not sure why you cannot localize in an anechoic chamber since localization is primarily determined by ILD and ITD. Could you explain how this values altered in an anechoic chamber?

 

[audiofooled]

Reflection can slightly alter the exact spot of the emitter but that also applies to a real instrument or source unless you are saying we cannot tell the direction when blindfolded of a finest instrument or someone talking to you in the room.

That's the whole point, either real or recorded instrument is localizable by real or whatever recorded cues, if the reproduction qualities allow for this for the latter. Loudspeaker response nonlinearities, especially harmonically uncorrelated resonances quickly draw attention to the source of the culprit (box, driver(s), port(s)).

Not sure why you cannot localize in an anechoic chamber since localization is primarily determined by ILD and ITD. Could you explain how this values altered in an anechoic chamber?

I don't have a personal experience from anechoic chamber. But, in my normally reflective room, with my system, central image containing only pure tones, so signals with flat envelope, ranging from about 700Hz up to highest frequency of my audible band, are localized completely inside my head, right in the middle. As if loudspeakers are not a part of the equation at all.

This phenomenon in terms of auditory mechanism I have learned is far too complex, but I suspect it's closely connected to cues that are missing from the environment, rather than the ones that are present from the actual sound source, but supposedly equal for the left/right ear.

 

[STC]

I don't have a personal experience from anechoic chamber. But, in my normally reflective room, with my system, central image containing only pure tones, so signals with flat envelope, ranging from about 700Hz up to highest frequency of my audible band, are localized completely inside my head, right in the middle. As if loudspeakers are not a part of the equation at all.

This phenomenon in terms of auditory mechanism I have learned is far too complex, but I suspect it's closely connected to cues that are missing from the environment, rather than the ones that are present from the actual sound source, but supposedly equal for the left/right ear.

Without reflection we are unable to judge distance because judgment of distance is learned by exposure just like localization. We need to learn level difference and spectral changes. Some individuals localize sound better than others because of the exposure. In anechoic room listeners are experiencing sound without reference so the stage is stuck inside the head initially as cues for distance were missing.Toole referred to stereo playback with hard panned sound which would have contributed further confusion. I do not have the research but I believe if we live long enough in anechoic chamber we would able to judge distance based on level difference. However with amplified sound such reference is lost as the level could be very different from what should be a real sound at the given distance. Basically, anechoic chamber is something new to human who did not have enough exposure in a non reflective environment for proper judgement of sound characteristics to judge distance. There is no reference of actual sound level at a given distance for us to decode the sound in an anechoic room.

Having said that, pinna will still able to localize since its role is for direction finding. Even a single pinna can do the job especially for higher frequencies but we need to be exposed and learn them. So for new listeners to anechoic environment sound without the usual reflection contradict with all the reference in real world.

Human frontal localization is poor and that’s exactly the reason why the original idea of XTC places the speakers in Ambiodiople position, i.e., infront of the listener.

 

[Justdafactsmaam]

To answer those who say that people speak without having listened to it.
I would say that even a classic stereo widener plugin can be preferred in a blind test.
But the same for a saturator or exciter...
But what would be the purpose of that test?

The same purpose for all of Dr. Toole’s and Dr. Olive’s blind speaker testing. To find out what listeners like.

Leaving aside that long-term preference may vary (it happens to me often), there is no metric associated with spatiality with which to extrapolate a preferred value.

There are metrics. Preference tests have been done with spatial audio

And there certainly is room for more testing to better establish specific values for preferences

But it’s not that hard for us to figure it out for ourselves

It's like taking a test to determine if an expensive bottle of wine is better than one from discount...

blind tests is the gold standard for wine tasting and is used in all competitions

probably it will be like this for most testers... but then? Should we say that everyone has to drink the more expensive one or that it is worth what it costs?

Testing shows that it isn’t always a function of price or labels. It also gave wine makers objective data to help them make better wine

For me we can only say that between the two bottles, in terms of price, there are many equally/differently appreciable wines.
Or that if vehicle specific wine molecules on specific taste receptors on the tongue I will get a better experience... to the detriment of have to put an uncomfortable contraption in my mouth... or having to sit rather firmly with the tongue (just examples).

Or just do what they actually do. Blind preference tests and chemical analysis

 

[Davide]

The same purpose for all of Dr. Toole’s and Dr. Olive’s blind speaker testing. To find out what listeners like.

Agree with this. But those test have metrics (frequency response above all) from which a target derived from statistical preference is defined.

There are metrics. Preference tests have been done with spatial audio

Which metrics? (are related to preference I mean)

blind tests is the gold standard for wine tasting and is used in all competitions

Yes, in fact it only says which wine is preferred. So is a statistical preference.

EDIT: My epilogue

 

[audiofooled]

Without reflection we are unable to judge distance because judgment of distance is learned by exposure just like localization. We need to learn level difference and spectral changes. Some individuals localize sound better than others because of the exposure. In anechoic room listeners are experiencing sound without reference so the stage is stuck inside the head initially as cues for distance were missing.Toole referred to stereo playback with hard panned sound which would have contributed further confusion. I do not have the research but I believe if we live long enough in anechoic chamber we would able to judge distance based on level difference. However with amplified sound such reference is lost as the level could be very different from what should be a real sound at the given distance. Basically, anechoic chamber is something new to human who did not have enough exposure in a non reflective environment for proper judgement of sound characteristics to judge distance. There is no reference of actual sound level at a given distance for us to decode the sound in an anechoic room.

Having said that, pinna will still able to localize since its role is for direction finding. Even a single pinna can do the job especially for higher frequencies but we need to be exposed and learn them. So for new listeners to anechoic environment sound without the usual reflection contradict with all the reference in real world.

Human frontal localization is poor and that’s exactly the reason why the original idea of XTC places the speakers in Ambiodiople position, i.e., infront of the listener.

I agree that humans are great at adaptation. I watched somewhere an experiment about modifying pinna shape using modeling clay and indeed people lose the ability to judge elevation, even front to back is messed up. It doesn't say how long would it take for people to recalibrate to new spectral cues or how this would even work. Probably a slow process. On the other hand, we adapt to the listening environment fairly quickly. But I don't know about anechoic chambers, that would be interesting because it's supposedly annoying to even stay there for too long. Speaking for myself, pure tones that are not externalized, so hearing them inside my head when I know I'm not wearing any headphones, seems weird to say the least.

 

[Justdafactsmaam]

Without reflection we are unable to judge distance because judgment of distance is learned by exposure just like localization.

When we are out in open spaces and we hear a fly buzzing around our head we can judge with tremendous accuracy the direction and proximity of that fly. It’s not learned, it’s not reliant on reflections and anyone who has experienced it knows what I am talking about. There is no mistaking the proximity of the sound of a fly buzzing around your head.

In the near field we hear direction and proximity very clearly and accurately. With greater distances we lose precision and start to rely more on reflections and learned sonic characteristics