Ambisonics, and listening to binaural via speakers

Doggyboy

Member
2010-06-14 8:31 pm
Are there any Ambisonics fans in this group? (who maybe could tell me some of what the hubbub is about?)

And is there a way to process audio recorded binaural (intended for headphone listening only) to work over loudspeakers in a normal room, without the normal issues of crosstalk and everything else? For instance 3d sound recordings with all their near-head effects and heightfield effects, to be played back through a 'quad' or 5.1 or 7.1 or whatever audio system, after processing.... i'm aware it's silly to ask about speakers in a headphone group, but it's about a headphone source so I figured headphone specific users would know if anyone would. Sometimes you want to share the content and can't afford $700 headphones for everyone..

I've heard some people talk about Meridian Trifield in relation to this topic elsewhere, if anyone has personal familiarity with that please say so as that's on the topic roster too but if it's too obscure/high end I don't know of another forum here to ask on it in.
 

31697B

Disabled Account
2012-05-19 12:53 am
I wish Ambisonics were more popular than it is... best realism/accuracy in sound field reproduction. The encode and decode circuits in the past cost too much and so only a few studios could afford it. Now, though, we should be able to do it cheap enough for everyone/everywhere try it and use it all the time.

THx-RNMarsh
 
There's a free or nearly free app on iTunes that will do it. I think it's called "ambio phonics". Do a quick search and I bet you find it.

Despite the similarity in names, Ambiophonics is unconnected with Ambisonics. For this application, Ambiophonics is probably better suited. It is intended for stereo sources, but should work well with binaural. (I have never used it.) I good place to start is the article on Wikipedia; this includes a link to the official website.

Regards,
Martin
 
Are there any Ambisonics fans in this group? (who maybe could tell me some of what the hubbub is about?)

A excellent place to start is the FAQ (which I created and maintain). The article on Wikipedia is also excellent.

And is there a way to process audio recorded binaural (intended for headphone listening only) to work over loudspeakers in a normal room, without the normal issues of crosstalk and everything else? For instance 3d sound recordings with all their near-head effects and heightfield effects, to be played back through a 'quad' or 5.1 or 7.1 or whatever audio system, after processing.... i'm aware it's silly to ask about speakers in a headphone group, but it's about a headphone source so I figured headphone specific users would know if anyone would. Sometimes you want to share the content and can't afford $700 headphones for everyone..

Another poster has pointed you towards Ambiophonics (which is unconnected with Ambisonics). Ambiophonics uses crosstalk cancellation, along the lines of the old Transaural system but updated for the digital age (and free).

I've heard some people talk about Meridian Trifield in relation to this topic elsewhere, if anyone has personal familiarity with that please say so as that's on the topic roster too but if it's too obscure/high end I don't know of another forum here to ask on it in.

Trifield reproduces two-channel stereo sources through three front speakers. (Meridian also tacks on some surround.) There is a Wikipedia article on Trifield, although it is only a stub. The underlying theory is explained in:
M.A. Gerzon, "Optimum Reproduction Matrices for multispeaker Stereo", J. Audio Engineering Society, vol. 40 no. 7/8, pp. 571-589 (1992 July/Aug.)​
Basically, the two-input channels are passed through a set of shelf filters with different gains above and below 5 kHz. From these, three new speaker feeds are derived. (I have never heard it; I can't afford Meridian kit.)

Regards,
Martin
 
Last edited:
And is there a way to process audio recorded binaural (intended for headphone listening only) to work over loudspeakers in a normal room, without the normal issues of crosstalk and everything else? For instance 3d sound recordings with all their near-head effects and heightfield effects, to be played back through a 'quad' or 5.1 or 7.1 or whatever audio system, after processing....



Hi Doggy,
I think most of your questions have been answered, so I will just try to address the 'loudspeaker binaural' issue..
If you want near-head effects and height you are probably better off sticking to headphones. Cross talk cancelling (XTC) does not result in left and right channels being heard by right and left ears, unless you have an anechoic chamber, and even then the cancellation is not perfect. In addition to the direct sound you get reflected sound when using loudspeakers. Where 'loudspeaker binaural' beats binaural is for frontal sounds where you tend to get a more natural sound and good distance perspective, when with headphones you often get reversals, in-head sound, or split front/back.
One problem with using XTC, such as the Ambiophonic RACE method, for binaural is that it is almost impossible to cancel at low frequencies, so that you cannot reproduce the low frequency Interaural Time Difference (ITD) of the original binaural recording, although it can sound pretty good regardless. To get sounds near-head yoiu also need to increase the ratio of direct to reflected sound, beyond what you would get from a simple speaker in a normal room. An anechoic room would help (or playing outside), or possibly focussed speaker arrays, but that is not likely to catch on...
I have made some dummy head recordings that have greater interaural level differences at low frequencies than normal for binaural, and a XTC filter that converts these to ITD but it is a prototype, I have only made the one demo, and there is zero interest in it..
Freesound.org - "bonfire ambio.mp3" by dwareing
Regards,
David.