3D Audio and individual Hearing.

[STC]

In this this context I refer to 3D audio that involves crosstalk cancellation.

[For readers, unsure what or how it supposed to sound, can get an idea with your recent iPhones when you play ‘Edgar the barber’ from Apple Music. Hold the phone close to your face and adjust until you hear the snipping is heard from the back of the head to the ears. Rotate the phone to change the left and right side speakers. For me it works when I rotate the phone so that the left is heard in the right ear. With the correct orientation I could only sense the snipping at the back when you moves towards the end. Ideally, it should sound like listening to it with headphones since it was a binaural recording.]

I have used almost all the crosstalk DSP such as RACE, AMTRA, Soundpimp, AmbiophonicsDSP and others while being developed. More recently, BACCH for Windows which didn’t work for my system. I don’t think anyone in my country is using BACCH4Mac or they are keeping low profile if they used it.

I have always thought BACCH SP is the gold standard because reading from the reviews and Choueiri claiming that he could make the fly circle around the head something I couldn’t do with other DSPs. Although, I could perceive the scissors snipping at the right and back of the head on the right side towards the tail end of ‘Edgar the barber’ but the left is always a frontal perception. I also refer to Howard Kneller’s review of BACCH where he said “ The scissors and shaver clearly circled the dummy head, moving from front to back and from top to bottom of the head.” Some users defined them to be near the ears.

After about 15 years, I finally perceived the “Edgar the barber” snipping from left to right behind my back when I auditioned Ruark R7 which came with its own crosstalk cancellations. It startled me because I couldn’t do it with other DSPs but here I am hearing the snipping clearly behind my head from left to right. This impressed me because there was no measurements or adjustments and it worked so well right out of the box. I then auditioned three other tracks that I am familiar with but they are not outstanding and probably just an incremental improvement then the standard stereo. This made me more curious. How does the cancellation work for binaural recording better than the stereo? The implementation should be the same but why one sounded so accurate while the other not so much?

BACCH Labs would have done their product testing before the release of BACCH for Windows yet it didn’t work for me. Is there something else beyond measurements?

I looked at my system. And then I tried something different and the magic happened. Yes, Edgar is now snipping behind my head. Musical tracks (some) have a layer just behind the head and the bee indeed circles the head. Although, I could never make the bee to circle around my head before this I have other listeners perceived it be so. They perceive it so based on my own hearing adjustment which didn’t work for me but worked for others or so they claimed as I am always skeptical of people’s localization and description ability when it comes to sound.

In conclusion, unless there is a standard that all listeners perceive the same location with XTC we are just playing a guessing game because I don’t think one can predict how someone hearing really works on measurements alone. It may work for some better than others. Individual adjustment is necessary but this involves proper reference and SOP so that the listeners really hearing what they are supposed to hear. Same measurements have given me different locations on different days. Unless, users actively involved in the settings and adjustment, the end users are just perceiving some better version but without ever knowing if that’s actually the correct settings. And this is where the trade secrets reside for crosstalk cancellation. This parameters involves more than ITD and ILD and allowing users to control them allows them to know how the program works.

 

[chjan]

Hi STC, I am the SoundPimp developer and I just discovered the various XTC discussions in this forum a few days ago. And so, I give you a quick remark to your interesting line of thoughts.

1. One needs to understand that acoustic crosstalk is fundamentally counter productive to audio quality. No way around that. Therefore, a system that counteracts crosstalk in a working manner, will improve many aspect of the audio quality. No way around that, either.

2. Normal stereo fences the audio soundstage to some +60 degrees, which is, beyond any doubt, a strong deviation from real life. The example is the conductor at the pole position of an orchestra. The conductors players are not within a 60 degree angle, merely 180 degrees. Most of the XTC software products will improve expand soundstage as 120 degrees is achievable in a steady manner, if you work with the setup and have a well damped room.

Hifi enthusiasts purchase expensive gear, but almost all of them forget the fact that 60 degrees soundstage is nothing else if not completely artificial, compared to reality. Kind of amazing.

3. I would not be so focused on the bee being behind your head, but focus on getting your room in shape and setting up any of these XTC products in a proper manner. If you were to evaluate and compare these XTC systems, you would need to make ABSOLUTELY SURE that your room is not creating artificial reflections and other artefacts that would start to interact with the XTC algorithms. And this is literally almost impossible, it just takes so much to achieve the perfect room.

Therefore, I often do my SoundPimp demos outside, on my large terrace where there are no walls diminishing the quality. We have, on a prototype level a (much) more sophisticated SoundPimp variant that will produce a full, real soundstage of 180 degrees, if the recording says so. I had a Scandinavian hifi magazin here last summer, and while they were supposed to visit me for half an hour, they stayed the whole days, because they just could not believe what they were hearing. They said: Like sitting in a giant headphone, only the front soundstage is not in your head as granted by a heapdphone, but in front of you, as in real life.

4. About the various parameters in an XTC system: I suggest there is a proper setting that will work for most settings, and it is mathematically calculated with ease. It will grant all the benefits of an XTC system, and you do not need to tune this on a per person basis. Just forget about that, and enjoy a wider soundstage with a more natural sound.

In this context there is one important fact, namely that an XTC system is based on the claimed fact that a human has only two ears. This is fundamentally wrong, and this error or misconception is "largely unknown" to even the most enthusiastic hifi person. What? Why?

A human has three ears!

There are two ears, and then there is bone conduction; the third ear. And therefore, when you start to tune e.g the delay involved in an XTC algorithm, as all these products do, things go awry. Why again? Because the algorithm is calculating setting to adjust for the time difference for the two ears and this is correct, but then comes bone conduction, which simply cannot be part of the equation, because, where the f.. is that ear? It is your whole body that bone conducts, and then the brain integrates that into a third ear perception in a manner not yet grasped by humanity. As simple as that, and as complicated as that.

I just explained the cause of the fundamental problem with a pair of headphones, i.e. that the front soundstage appears to be coming from INSIDE your head, whether you are listening to binaural or traditional recordings. One can understand this by understanding that, to PERCEIVE a point x,y,z in three dimensions, it is absolutely mandatory to have 3 points or meausure, i.e. three ears for the human case. It is absolutely and completely impossible to PERCEIVE correctly using only two ears. Please read and correct the explanation on ambiophonics.org in the light of this claim. (It is non disputable).

Therefore, to start to tune time delays beyond finding a delay that works in most setups (and more or less equally for all persons), is bordering on being uninteresting. I made the first VST plugin for ambiophoncis in 2009, and Ralph Glasgal and I agreed in that the sample delay parameter is really not that important. Ralph has done a lot of good work promoting the benefite of XTC systems, but his explanations on these things are not precisely correct. He does not understand bone conduction. (I left Ambiophonics back then because I do not believe a freeware strategy is the way of the winning team. Chouriery did the same, as far as I understood it).

So, STC, and others interested in discussing the optimal XTC algorithm, let it be known that bone conduction makes it impossible to achieve the perfect XTC system. We can only do it so good, but luckily, that is more than good enough compared to the alternative which is plain old Blumlein stereo.

Enjoy your XTC setup and happy new year!

 

[STC]

Please read and correct the explanation on ambiophonics.org in the light of this claim. (It is non disputable).

Hi Carl, Ralph has closed Ambiophonics non profit organization for good. I was following his work since early days of Ambiophonics. His idea of XTC and RACE meant to be freely available to the public.

The internalization of headphones perception is well documented. It is not about bone conduction. Smyth Realiser already done that pretty well externalizing headphones sound. They even did a demo in a HiFi show with multi channel setup and headphones. Ralph too was working with a University for something similar at lower price.

I agree bone conduction, skin and even eyeballs have a role but XTC for two stereo speakers, the ILD and ITD and attenuation of 10dB is more than enough. The value was picked based on research of actual attenuation in concert hall where it was established to be mere 8dB.

Optimal XTC is pretty much achievable. Although, some XTC like Ruark or BACCH seemed capable of projecting Edgar the Barber behind the ears but whether that is correct or not is another story.

Cheers and Happy New Year to you!

Edit:- Ralph was in this forum long ago but he left when his idea wasn’t welcomed then.

 

[chjan]

Hi Carl, Ralph has closed Ambiophonics non profit organization for good. I was following his work since early days of Ambiophonics. His idea of XTC and RACE meant to be freely available to the public.

The internalization of headphones perception is well documented. It is not about bone conduction. Smyth Realiser already done that pretty well externalizing headphones sound. They even did a demo in a HiFi show with multi channel setup and headphones. Ralph too was working with a University for something similar at lower price.

I agree bone conduction, skin and even eyeballs have a role but XTC for two stereo speakers, the ILD and ITD and attenuation of 10dB is more than enough. The value was picked based on research of actual attenuation in concert hall where it was established to be mere 8dB.

Optimal XTC is pretty much achievable. Although, some XTC like Ruark or BACCH seemed capable of projecting Edgar the Barber behind the ears but whether that is correct or not is another story.

Cheers and Happy New Year to you!

Edit:- Ralph was in this forum long ago but he left when his idea wasn’t welcomed then.

Thanks for info. I now see that ambiophonics.org is down. To be honest I think it is a good thing because we are more likely to get attention to products when people feel ownership because they had to pay for it. It is also a fact that freeware developers have a tendency to pop up once of a sudden, only to dissappear again just as quickly when they found a new freeware software project to work on. IMHO there should be a place (website) developed so that people get to know about it per rumour and articles, where all interested can discuss the benefits of XTC functions. That way, "all people" interested, including also the vendors, can get such products installed and have a better audio life, but I don't know how it could be made. Perhaps a facebook group. We have a low price on our product to make it possible for most people to purchase. The potential is that thousands of audiophiles take part in such discussions and interest, and then products would evolve at a faster pace because ideas, programmers and other things you need would flow better. Unfortunately, it has not been the case so far.

 

[STC]

Unfortunately, it has not been the case so far.

I think XTC will only appeal to very few audiophiles. We are dealing with people who grew up with stereo sound. Just like 3D TV, it is hard to change the acquired taste of stereo no matter how realistic the sound going to be.

 

[DVDdoug]

Since the sound is actually coming from the speakers, it's obviously an illusion to fake where the sound is coming from and different people will experience it differently. Different people experience regular stereo on headphones differently.

With multi-channel surround tracks, some people apparently get a good surround illusion with Dolby Headphone (or the newer Atmos version) but it didn't work that way for me. (Dolby only claims that it "enhances" the sound. They don't claim that you'll perceive sounds as coming from behind.)

Regular stereo (including the phantom center) is also obviously an illusion. Personally, I don't perceive a precise center. The only thing I perceive precisely-located are hard-panned, sounds which i perceive as coming directly from the left or right speaker. And I assume most people don't perceive s precise center, or home theaters (or movie theaters) wouldn't need a center speaker.

With real-life sounds or with surround speakers we often move our head consciously or subconsciously, sometimes to look where the sound is coming from. That allows us to to get multiple readings and triangulate. But still, if you've ever tried to locate a squeak or rattle in your car, or a cricket, etc., it's not always easy and we tend to over-rate our ability to locate sounds. I usually get a fairly strong sense of where the sound is coming from, but I'm often wrong!

 

[STC]

With multi-channel surround tracks, some people apparently get a good surround illusion with Dolby Headphone (or the newer Atmos version) but it didn't work that way for me. (Dolby only claims that it "enhances" the sound. They don't claim that you'll perceive sounds as coming from behind.)

You have get the pinna measured and fed real time for the illusion to take place.

Like what @chjan said, XTC purpose is not to create sound behind your head. it is about delivering stereo sound without the inherent interaural crosstalk. So far I have not seen anyone who couldn’t perceive the 3D with XTC while demoing my system and too without personalized cancellation.

 

[STC]

With multi-channel surround tracks, some people apparently get a good surround illusion with Dolby Headphone (or the newer Atmos version) but it didn't work that way for me. (Dolby only claims that it "enhances" the sound. They don't claim that you'll perceive sounds as coming from behind.)

You have get the pinna measured and fed real time for the illusion to take place.