Ambiophonics, What it is

[Orb]

Not wanting to complicate this, but it may be fair to say that stereo channel playback using ambisonics algorithm/principles does exist today in Trifield, which exists in some form within several products, products by Meridian the best known.
But as Ralph mentions ambisonics is best known for its attempt to define a multichannel/soundfield recording process and standard overcoming the limitations found with quadrophonics, anyway sadly it never was adopted for valid reasons, one primarily relating to business side and not the technology.
Saying that the mic technology (multicapsule) Soundfield microphone is still around today.

Cheers
Orb

 

[Steve williams]

Hi Ralph

Totally my fault and correction made to Forum title

Nice to see you here again Ralph. If there is any advancement in your field please feel free to share them here with the members

 

[Ralph Glasgal]

Not wanting to complicate this, but it may be fair to say that stereo channel playback using ambisonics algorithm/principles does exist today in Trifield, which exists in some form within several products, products by Meridian the best known.
Cheers
Orb

Sorry, but the only thing Trifield and Ambisonics really have in common is Michael Gerzon although there is some deference given to Ambisonic precepts in the original Trifield paper. But Trifield is just a superior way to add a center speaker to an ordinary stereo system playing standard 2.0 recordings. It does not expand the width of the stage or provide surround sound as can Ambisonics playing 4.0 discs (or as some would claim UHJ 2.0 encoded media). The Trifield processor takes the sum of the left and right channels, splits it into high and low frequency bands around 5000 Hz. These two signals are then processed differently in phase/delay/level and then combined to form a signal for a center speaker. A different combination of these two signals is then combined with the original difference signal to form a new left and right speaker pair.

For the life of me I cannot see how all this relates to basic Ambisonics.

Now for the commercial. If you use Ambiophonics with the speakers close together or either side of the TV set, you never need a center speaker even if playing 5.1 movies.

Ralph Glasgal
glasgal@ambiophonics.org

 

[Kal Rubinson]

Sorry, but the only thing Trifield and Ambisonics really have in common is Michael Gerzon although there is some deference given to Ambisonic precepts in the original Trifield paper. But Trifield is just a superior way to add a center speaker to an ordinary stereo system playing standard 2.0 recordings. It does not expand the width of the stage or provide surround sound as can Ambisonics playing 4.0 discs (or as some would claim UHJ 2.0 encoded media). The Trifield processor takes the sum of the left and right channels, splits it into high and low frequency bands around 5000 Hz. These two signals are then processed differently in phase/delay/level and then combined to form a signal for a center speaker. A different combination of these two signals is then combined with the original difference signal to form a new left and right speaker pair.

For the life of me I cannot see how all this relates to basic Ambisonics.

Agreed. Two additional points: Trifield in the Meridian 861 will expand 2 channel to 5 channel. Also, the 861 does have a separate Ambisonics mode.

Now for the commercial: Any word from Ambio4You, Ralph?

Kal

 

[Orb]

Hmm,
maybe how I wrote my post was confusing but I was not suggesting Trifield and Ambisonics are the same for the reasons you outline; one deals with stereo channel decoding while Ambisonics is a format for recording multiple channel info.
What I was suggesting is that there is an overlap of technology from the Ambisonics that is found inside Trifield, and possibly also Dolby (but in the classical 5.1 setup) from what I remember although never proved or denied.
Here is part of an academic page that used to be compiled by Michael Gerzon:

*** M.A. Gerzon, 'Optimum Reproduction Matrices for Multispeaker Stereo', J. Audio Engineering Society, vol. 40 no. 7/8, pp. 571-589 (1992 July/Aug.) (A fundamental paper on the application of Ambisonic ideas to frontal stage stereo using more than two loudspeakers. This technology is now known as the 'Trifield' system.)

I feel what I said is being blown out of proportion, and while what I said is rather short I have mentioned ambisonics in the past and did not feel the need to re-iterate it.
Hope this helps to clarify what I was saying.
Cheers
Orb

 

[Orb]

Ralph,
I see where some of the misunderstanding is coming from on my end and why your wondering why I raised Trifield.
It stems from when you said:

There is no such thing as ambiosonics at the moment.......

I took this as a typo and thought you were suggesting that there was no current aspects of ambisonics in use (hence my mention of Trifield), I now see it was not a typo on your part and that you were explaining a possible mistake on section title.
Cheers
Orb

 

[Orb]

Agreed. Two additional points: Trifield in the Meridian 861 will expand 2 channel to 5 channel. Also, the 861 does have a separate Ambisonics mode.

Now for the commercial: Any word from Ambio4You, Ralph?

Kal

Just for closure, here is the specific Trifield stereo upconversion patent to multiple speakers:
Sound reproduction system having a matrix converter:
http://www.patents.com/us-5594800.html

Cheers
Orb

 

[Roger Dressler]

I don't see a way to get notice of replies so if you want me to seee a reply or get a reply from please me let me know directly.

I think that you can either go to Settings-->General Settings and change the Default Thread Subscription Mode to one of the email notification options, or go to Quick Links-->Subscribed Threads and check the Notification box next to the thread. Then at the bottom of the page, open the Selected Threads window to set the desired notification method.

BTW, what are the particular differences between Ambiophonics and Cooper/Bauck's Transaural? On the surface they seem quite similar to me: LPF-based XTC. But I tend to oversimplify.

 

[Ralph Glasgal]

Time marches on. There are a lot of earlier attempts to do crosstalk cancellation. Carver's sonic hologram is one and Lexicon's panorama mode is another, then there is POLK and AR, etc. Modern high speed DSP chips or just plain computers now make it possible to implement recursive crosstalk cancellation in real time, at any data rate, where the cancellation cancels previous crosstalk cancellation all the way to inaudibility. With full recursive functionality, filters to correct for strange things are no longer necessary and the whole thing becomes much less critical as to the speaker angle, room, and the type of speaker or recording. Also, most previous implementations were analog. The RACE equations are quite simple and easy to implement.

Some RACE implementations do provide an adjustable lowpass filter but this is not really necessary in most situations. It just allows you to have stereo at the high frequencies and Ambio at the lower ones, if you like. It is a subjective tweak that has nothing to do with localization or stage width since the ear does not use the very high frequencies for ITD or ILD localization. The pinna really don't care if the high treble is stereo or Ambio if the speakers are relatively frontal. I probably should never have included this feature in my original RACE AES paper block diagram.

Another difference from all the earlier protocols is that the idea of having the speakers really close together at one third the stereo speaker spacing or less was a basic change from all the earlier arrangements. One other difference is that RACE is in the public domain, and free for anybody to use, whereas the others were proprietary and you had to pay or get sued. I think also except for the old Carver or new Sunfire, there are now probably more RACE gizmos now out there than any of the other earlier CTC products. Jambox now offers a RACE-like feature built-in to their speaker.

I am getting notices now. Thanks.

Ralph Glasgal
glasgal@ambiophonics.org

 

[Ralph Glasgal]

October 2012 Stereophile, page 21 David Chesky is serious about binaural (encoding) and is using BACCH filters now, and in all future CHESKY recordings, and I am excited big time.

This quote from stereophile article says it all...from David Chesky...

"I am going to do all Chesky recordings this way" "We've done this two -mircophone stereo thing for 50 and 60 years. We need to start doing things differently. I absolutely believe we can put you right in the center in Carnegie Hall, with all the perspective and density of the live performance"

HOT DAMN, now we're getting somewhere, and CHESKY is leading the way, again!

And of course, thank you to our WBF member Ralph Glasgal big time too.

Yes, and thanks to David Chesky for getting Ambiophonics some mention in Stereophile. Atkinson has steadfasly refused to come for a demo or review Ambiophonic gizmos, components, or priciples in Stereophile. On November 4th we will be hosting a meeting of all the audiophile Societys in Rockleigh, NJ where some eight different Ambiiophonics systems can be auditioned. Like stereo, Ambio can be implemented in lots of different ways, tweaks, and costs. All members of this list are welcome.

Both RACE and BACCH are examples of recursive crosstalk cancellation. You can read about the slight differences between them at www.ambiophonics.org. Chesky uses mostly BACCH because he thinks audiophiles will not move their speakers closer together to achieve greater perfection. Both RACE and BACCH do work better at what they do if the speakers are about one third the angle used in most stereo systems. RACE is easily adjustable by the end listener for speaker angles and recordings, while the Chesky versiion of BACCH is fixed for the 60 degree angle and cannot be tweaked for non Chesky (or Chesky) recordings. Unfortunately for confirmed stereophiles, the 60 degree angle induces pinna direction finding pattern errors that not even RACE or BACCH can correct. So if you want perfection, think postiviely about moving your speakers closer together.

The Ambiophonics web page has just been updated and there are some really great pictures, tesimonials from new users in Europe, and a whole bunch of new products, mostly free, that allow you to play your existing library of LPs, CDs, and DVDs. the loudspeaker binaural way. It is just not true that you need purpose made binuaral recordings made with a dummy head to get a fantastic result by switching from the 60 degree loudspeaker triangle to the Ambiodipole. I am always amazed by how much ILD and ITD data is on the exisiting discs just waiting to be auralized. I know this stuff is technical and hard to believe but read the papers and tutorials and then try some of the demos or downloads. If you are well heeled there are the pioneering TacT Audio components or the little miniambio processor from Hong Kong!

Ralph Glasgal
www.ambiophonics.org