Ambisonics - WOW

[fjhuerta]

I think I talked about this before in other sections in the forum. Still, it bears repeating.

Ambisonics is simply FABULOUS. Incredible.

Don't know what Ambisonics is? Well, it's a technology developed in England in the 70's. Supposedly, they recorded using L-shaped microphones, and captured the overall sound pressure level, then substracted the respective left, right, up and down signals, created a signal called wxyz with them, and then encoded them into a J (stereo) signal.

Sounds complex, but the decoders are pretty simple.

I had an Ambisonics recording (Alan Parsons - Stereotomy) and I decided to decode the J signal into a 5.1 surround Dolby Digital mix. It took me close to two weeks, but...

1) The surround mix is so impressive, it leaves DTS in the dust. Not because of clarity or channel separation, but the overall ambiance was simply *perfect*. It wasn't as if "horns blared over *that* speaker". More like, "hey, a horn is sounding over there... like, to the left of the front channel, but a bit on the back". Wow.

2) The algorithm allows you to define the distance between listener and speakers. So I designed an Ambisonics mix with the exact position of my speakers. Which made the mix simply incredible.

3) Unfortunately, I had to set the levels perfectly. And if I moved a couple of centimeters from the sweet spot, the imaging was severely hurt.

4) People can't believe the decoded Ambisonics mix really started life as a stereo recording. It's *that* good.

Sadly, I don't have any other Ambisonics discs. Maybe it is for the better. I would end up decoding every CD in my collection, and 2 weeks is too long

 

[Dusty Chalk]

Coolness! I've always been interested in surround sound, and stumbled upon Ambisonics in my quest for more knowledge.

What do you mean by you decoded it?

I've got another one -- the Vincent Clarke/Martyn Ware's "Pretentious".

 

[Nick Dangerous]

Hang on there... Ambisonics is just a superset of surround-sound processing techniques. I've heard it referred to as mostly DOA on the development radar.

Ever heard of Ambiophonics? No special processing required:

www.ambiophonics.org

I think I posted about this before. To try it, place a pillow vertically at the end of your nose and put two speakers at the far end. Put each one on either side of the pillow facing your ears. Hear that? This is the basis for establishing a near-perfect soundstage using standard 2-channel stereo recordings and inexpensive audio gear.

The question is, how to talk the wife into installing the dividing wall!

 

[skippy]

pretentious is in binaural. it does sound pretty good over a matrix decoder though. you know clarke and ware put out another album in binaural called 'spectrum pursuit vehicle'.

 

[ai0tron]

Skippy when are you going to publicly bash those V6's you purchased?

 

[fjhuerta]

Quote:

Originally posted by Dusty Chalk Coolness! I've always been interested in surround sound, and stumbled upon Ambisonics in my quest for more knowledge. What do you mean by you decoded it? I've got another one -- the Vincent Clarke/Martyn Ware's "Pretentious".

Well... let me try to remember...

First of all, you need to get some software tools, which you can find in www.ambisonics.org. If you can't find them, e-mail me. They are basically 3 impulse signals (for the x,y,z coordinates). You need to convolute (convolve? can't remember the term) the impulse signal with the original stereo signal; then convert it to mono.

You do this for the x,y,z coordinates. And then you take the original signal and turn it into mono. That'll be your "absolute pressure" signal. You take the 4 tracks, mix them into a quad channel WAV file, and you run the Ambisonics software decoder. When configuring it, you create a bidimensional matrix (since it's a stereo original signal you are working with, the "z" coordinate, or "height" is non-existant) defining where your speakers are located around you. The decoder creates an "n" channel signal (in my case, a 5 channel signal), which you can then encode in DTS or Dolby Digital.

It's a very slow, tedious process, but the results are superb.

Also, it's been said the Ambisonic surround decoding works with a simple stereo signal. Although I think it sounds nice, it's nothing compared to the full surround decoding you can get with the software tricks.

If anyone's interested, I might be able to upload a song in Ambisonics / Dolby Digital. You would only need a CD burner, a CD/DVD player linked digitally to a Dolby Digital receiver, and that's it! It would be a 35 meg file, tho.

 

[jbannow]

Interesting stuff ... I have to try this out now. I'll let ya'll know how it goes.