Trinaural decoding equations for 3 speaker stereo matrix ?

[SEdwards]

Last week I was listening to a 2-> 3 matrix with coeff 0.5 in Reaper (I'll upgrade to Markus' script, thanks for posting that). For the afternoon I'm using Dolby PLIIx from my soundcard (Xonar) output.

What exactly does it do frequency wise? It cuts up processing band by band, but how? The Wikipedia article doesn't really say. Or am I totally mistaken and it is just a sqrt(2) center if I'm using 3 speakers.

[Elias]

Originally Posted by lolo

What about directivity? I finally had 2 hours for myself last night and experimented with three quickly made pipe speakers, matrix from my old denon receiver and dayton RS100. It works!

I also started with cardboard tubes (diam about 12cm, length about 40cm) and FRS8 full range elements I lifted the tubes so that elements are on ear height. First listened with elements aimed to the listener, then aimed the elements towards the ceiling. This was with passive matrix wiring with coefficient of 0.5. So they were kind of omnis.

Then I placed a large (60*80cm) baffles just behind each tube to make them 2pi radiators, and it was much better !

Omni midrange ? I don't like it very much. It sounds too ambigouos and not very clear. Half space midrange is better, also with matrix.


- Elias

[Elias]

Originally Posted by lolo

maybe?

Is it anywhere like this you made ?

[a_tewinkel]

Originally Posted by Elias

Omni midrange ? I don't like it very much. It sounds too ambigouos and not very clear. Half space midrange is better, also with matrix.

I currently have cardioid mids. Much better and more clarity than with narrow boxes or dipoles too close to the wall.

[markus76]

Originally Posted by SEdwards

I'll upgrade to Markus' script, thanks for posting that

If you use the energy-preserving code then remove the 3dB attenuation for the center. Simply replace

c_out = 0.7071*m_c;

with

c_out = m_c;

[lolo]

Yep, something like that, but with three separate pipes and a 90 deg angle so they come out as three flowers. I really have to redo it there is just too much omni leakage in the mids, will report back.

Originally Posted by Elias

Is it anywhere like this you made ?

[markus76]

Just for the sake of completeness here's the "final" Reaper code for a energy-preserving matrix decoder after Gerzon:
http://mehlau.net/audio/matrix_decoder/

[Elias]

I found some more confirmation on Trinaural matrix coefficients from here

http://www.nubert-forum.de/nuforum/v...42a5023fc0a493


And the matrix coefficients according to them are:

L -> L - R/2
R -> R - L/2
C -> (L+R)/2

Which are the same as referenced earlier from another source.


The thing I don't know is how they know it


- Elias

[markus76]

That's TriSonic (AES Preprint: "An Optimum Linear-Matrix Stereo Imaging System") with a matrix factor of 0.5.
Just a sub-version of Gerzon's energy-preserving decoder.

[markus76]

A post by Elias just got lost?