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Ambiophonic encoder - RACE algorithm
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Blue Hell
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PostPosted: Sat Apr 12, 2008 7:29 am    Post subject: Reply with quote  Mark this post and the followings unread

So basically you spin the headphones at 85 rev/sec and then get the the tree that falls to carve a double bass ... pretty smart Wink
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PostPosted: Sat Apr 12, 2008 7:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
So basically you spin the headphones at 85 rev/sec and then get the the tree that falls to carve a double bass ... pretty smart Wink



Cool

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PostPosted: Sat Apr 12, 2008 11:05 am    Post subject: Reply with quote  Mark this post and the followings unread

seraph wrote:
Kassen wrote:
Depends on the volume and the eigen-frequency of the tree.

the lowest eigenfrequency of a double bass is at 85 Hz.


Thanks quite interesting really.

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PostPosted: Sat Apr 12, 2008 11:20 am    Post subject: Reply with quote  Mark this post and the followings unread

bachus wrote:
seraph wrote:
Kassen wrote:
Depends on the volume and the eigen-frequency of the tree.

the lowest eigenfrequency of a double bass is at 85 Hz.


Thanks quite interesting really.


can you imagine an ambiophonically encoded eigenfrequency of a double bass at 85 Hz Question

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PostPosted: Sat Apr 12, 2008 1:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

seraph wrote:
bachus wrote:
seraph wrote:
Kassen wrote:
Depends on the volume and the eigen-frequency of the tree.

the lowest eigenfrequency of a double bass is at 85 Hz.


Thanks quite interesting really.


can you imagine an ambiophonically encoded eigenfrequency of a double bass at 85 Hz Question


As there is a 12dB/8ve hi-pass filter at the encoder input it would be down a little better than 20 dB at 85 HZ. Further, between your ears, the phase angel would be at most 0.31 pi radians. So I don't think the experience would be too much of a much.

But I didn't double check my figures on that.

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PostPosted: Sat Apr 12, 2008 1:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

bachus wrote:
But I didn't double check my figures on that.


The common advice seems to be to stuff the bass speaker under the sofa, so you can't be that far off

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PostPosted: Sat Apr 12, 2008 1:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

bachus wrote:
Further, between your ears, the phase angel would be at most 0.31 pi radians.




Quote:
The Angel Phase is an archaeological cultural manifestation of the Mississippian culture of the central portions of the United States of America.


an archaeological cultural manifestation of the Mississippian culture between your ears Question
unlikely Exclamation good thing that you did not double check your figures on that.

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PostPosted: Sat Apr 12, 2008 1:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

seraph wrote:
bachus wrote:
Further, between your ears, the phase angel would be at most 0.31 pi radians.




Quote:
The Angel Phase is an archaeological cultural manifestation of the Mississippian culture of the central portions of the United States of America.


an archaeological cultural manifestation of the Mississippian culture between your ears Question
unlikely Exclamation good thing that you did not double check your figures on that.


Hmmm not only did I not check my math I didn't check my spleling.

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PostPosted: Sat Apr 12, 2008 11:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hmm... I'm a bit sceptical of the whole thing.

That comes both from having seen a presentation by Glasgal, where he was supposed to preside a panel on multichannel audio on some AES convention, but basically dominated the whole thing with a sales speech for his thing, instead of giving each person time to present the different angles of approach in the field, and the lack of clear info I can find on that site on how it actually works.
I briefly skimmed over a few of the AES papers that are listed, but I don't get a clear idea of what is going on (didn't see any equations of any kind, which makes me wonder).

Having several speakers and adding some diffusion to the different channels will help give you a nicer experience, and trying to prevent unwanted reflections does help, and using high quality speakers can also make your sound better.

I'm however still unclear what is tried to be optimized and on what psychoacoustic basis it is. Are there any studies where the psychoacoustic advantages have been measured in any way? Other than testimonies?

Sorry, this is a bit of a rant...

(Let's look at tube amplifiers for our IPods now...)
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PostPosted: Sun Apr 13, 2008 1:35 am    Post subject: Reply with quote  Mark this post and the followings unread

I guess you mean Ralph Glasgal.
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PostPosted: Sun Apr 13, 2008 4:57 am    Post subject: Reply with quote  Mark this post and the followings unread

nescivi wrote:
Having several speakers and adding some diffusion to the different channels will help give you a nicer experience,


Your meaning here is unclear to me. Could you explain this with a bit more detail?

nescivi wrote:
I'm however still unclear what is tried to be optimized and on what psychoacoustic basis it is. Are there any studies where the psychoacoustic advantages have been measured in any way? Other than testimonies?


Are you referring to ICC or synthetic ambience? They really are two distinct issues.

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PostPosted: Sun Apr 13, 2008 9:57 am    Post subject: Reply with quote  Mark this post and the followings unread

I think it is a bad idea to confuse the person leading the forum discussion with the technology itself. That's the message of the play/movie Amadeus; how could such an obnoxious fool write such beautiful music?
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PostPosted: Sun Apr 13, 2008 10:19 am    Post subject: Reply with quote  Mark this post and the followings unread

mosc wrote:
I think it is a bad idea to confuse the person leading the forum discussion with the technology itself. That's the message of the play/movie Amadeus; how could such an obnoxious fool write such beautiful music?

Very good point.

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PostPosted: Sun Apr 13, 2008 10:40 am    Post subject: Reply with quote  Mark this post and the followings unread

mosc wrote:
I think it is a bad idea to confuse the person leading the forum discussion with the technology itself.


I believe the point here may be that the behaviour of the person can influence the availability of information on the technology. I too would like to know about the underlying principles. What is, for example, the link between the space between the speakers, their angles and the delay length? What phenomena is this based on and why?

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PostPosted: Sun Apr 13, 2008 11:09 am    Post subject: Reply with quote  Mark this post and the followings unread

Well, that's a good point. I just spent some time on the official ambiophonics.org site and skimmed through Ralph's book. I didn't get too much out of it. I've been involved with Robin Miller and Ralph for a few years running experiments using ambiophonic setups. As you already know, I'm very impressed with it compared to stereo, but the explanations are certainly wanting IMHO.

I'll talk this over with Robin in the coming week and maybe he and I can come up with something based on principles, not impressions or experience. While the latter are very valuable, they don't suffice as an explanation or understanding.

I could try to hack up something on the fly, but it would probably be better for everyone if it was a bit more deliberate.

Ralph didn't invent this, but I think he came up with the name ambiophonics. I don't think it is a trademark. The add-on of multi-channel convolution (which I don't think works) isn't ambiophonics and it tends to confused the issue.

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PostPosted: Sun Apr 13, 2008 3:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

Kassen wrote:
What is, for example, the link between the space between the speakers, their angles and the delay length? What phenomena is this based on and why?


I could certainly be wrong but it seems obvious from first principles that:


ICCFormula.jpg
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PostPosted: Sun Apr 13, 2008 3:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

Using Howard's "rule of two thumbs" for speaker placement this yields ~53 microseconds delay at a listening distance of 9 feet with k set to 0, thus k is fairly small.

k is not a constant but a function of D and d. I should be clear from inspection of the image that k is less dependent on d if D is small. This is one of the advantages of Ambiosonics over Sonic Holography.

Clearly if you make D large you will need to use a HRTF (equalization) that is a function of D and d.

Again this is not an area of expertise for me, it's just what seems the obvious and necessary consequences of the conceptual description of ICC. I hope to learn from any critiques of this.

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PostPosted: Sun Apr 13, 2008 6:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

More accurate drawing detail:

Edit:

To be clear 'D' is the distance between the centers of radiation of the two speakers and the listener is placed on the perpendicular bisector of that line.


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PostPosted: Mon Apr 14, 2008 2:54 am    Post subject: Reply with quote  Mark this post and the followings unread

Ok. So now it's clear how the speakers are to be placed, exactly. What's not so clear to me yet is how this will remove cross-talk. Maybe we *could* but only if the listener would set very still at a very well defined spot.

Another note on "K", am I right in assuming that K doesn't take into account how the way in which "sound wraps around the head" is frequency dependant?

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PostPosted: Mon Apr 14, 2008 5:52 am    Post subject: Reply with quote  Mark this post and the followings unread

Kassen wrote:
Ok. So now it's clear how the speakers are to be placed, exactly. What's not so clear to me yet is how this will remove cross-talk. Maybe we *could* but only if the listener would set very still at a very well defined spot.


Yes, I think it is made clear in all the literature that Abiophonics has a finite sweet line. Almost all other ICC systems have a sweet spot. I think I've read of a DARPA system that tracks the listener's position and dynamically adjusts the time delay and HRTF.

Kassen wrote:
Another note on "K", am I right in assuming that K doesn't take into account how the way in which "sound wraps around the head" is frequency dependant?


k only takes care of the *(head wrap) distance parameters .
bachus wrote:
Clearly if you make D large you will need to use a HRTF (equalization) that is a function of D and d.
The HRTF *(Head Related Transfer Function) takes care of that issue. If the speakers are close *(as they are in Ambiophonics) to each other an HRTF is not really an issue.

As to weather (or is that a neutered goat?) or not ICC works one only has to press the bypass button on such a system. The sound field immediately collapses and source positions become more vague. The loss of stage is absolutely dramatic. I would just do a search on Intraural Crosstalk Cancellation there are many papers on the subject.

As to how: the block diagram at the start of this thread should make that clear.

*Edits

also added link

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PostPosted: Mon Apr 14, 2008 10:04 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks, Bachus, for that explanation.
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PostPosted: Thu Apr 17, 2008 7:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
I believe the point here may be that the behaviour of the person can influence the availability of information on the technology.


yes.

My point was mostly that the manner in which the information has been presented has been lacking scientific quality, i.e. content, or the acknowledgement of the possibility that the posed theory may be disproved, which is the underlying principle in western science, a tradition from which - I believe - the researchers in question come.

If there were a proper paper on Ambiophonics explaining the underlying principle in a rigorous way, I could critique it better and compare it to other technologies of (spatial) sound reproduction.
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PostPosted: Thu Apr 17, 2008 7:50 pm    Post subject: Re: Ambiophonic encoder
Subject description: Anyone interested in coding this
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seraph wrote:

check this out


Here is a much cheaper one:

http://www.core-sound.com/TetraMic/1.php

For which there is already free open source software available by Fons Adriaensen!

Last edited by nescivi on Thu Apr 17, 2008 8:07 pm; edited 1 time in total
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PostPosted: Thu Apr 17, 2008 8:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

nescivi wrote:
Having several speakers and adding some diffusion to the different channels will help give you a nicer experience,


bachus wrote:
Your meaning here is unclear to me. Could you explain this with a bit more detail?


Adding some kind of synthetic ambience, which seems to be what is happening with the surround channels.

nescivi wrote:
I'm however still unclear what is tried to be optimized and on what psychoacoustic basis it is. Are there any studies where the psychoacoustic advantages have been measured in any way? Other than testimonies?


bachus wrote:
Are you referring to ICC or synthetic ambience? They really are two distinct issues.


I actually meant a well carried out listening test comparing ambiophonics with other systems which aim to improve the listening experience; that could include just the ambiophonics enhanced stereo, and the version with added ambience.
Listener preference tests for various other systems are available, so why not for ambiophonics? If they had done tests for that, they would surely reference them, right?


The ICC bit was a bit unclear to me, reading the website, so I was confused in general what they are actually doing.
This can be done to some extent, but it will depend on a lot of factors, such as the quality of your speakers (mainly their "sameness"), the aforementioned early reflections ("who put that atlas on the carpet before the speaker!"), your headsize, speaker displacements ("well, I was dusting the room, so I had to move it a bit") etc., etc...
Restriction of the listening position is a downside, and it may actually make things worse at other locations.
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PostPosted: Thu Apr 17, 2008 8:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

nescivi wrote:

Restriction of the listening position is a downside, and it may actually make things worse at other locations.


This is the easiest part of your post to address so with sloth I will start here. Based on my own experiences with several forms of ICC: Out side the ICC "sweet spot" imaging and sound stage are execrable.

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