Trinaural decoding equations for 3 speaker stereo matrix ?

[Elias]

Originally Posted by pos

An uncorrelated L/R stereo signal split into 3 speakers following this matrix will result in correlated sound between speakers, as they all have sums or differences of L and R...

The spatial comb filtering from 3 sources is not as severe as from 2 sources, since it almost never happens all the three signals to have exact amplitude and phase to cancel, whereas with two sources cancellation happens in every wavelength of spatial shift.

I've done comb filtering perception listening tests using mono pink noise (worst possible signal) and 3 speakers are much better than 2.

Here's some of my subjective results I did just recently:
Elias Pekonen Home Page - 2 vs 3 Speaker Stereo listening tests at high frequencies


- Elias

[pos]

very interesting, thank you

[Soundtrackmixer]

Originally Posted by a_tewinkel

Yes but that's still not very good. And even if ProLogic II is much better than standard linear matrixing, it did not impress me... don't know about you guys...

Personally, I am impressed with PLII. The first time I heard it was in Jim Fosgate's laboratory and it was a all analog implementation. It sounded wonderful and had absolutely no tonal coloration at all. The next time I heard it sound as good as the analog version was on a Arcam AVR600 I purchased last year. Once again, no colorations, and the speakers just disappeared, and I was immersed with pure uncolored sound.

These are the only two times I was impressed with PLII

[markus76]

Griesinger has some interesting PPT slides up on his webpage about "Pitch, Timbre, and Source Separation".

[markus76]

Originally Posted by Elias

Here's some of my subjective results I did just recently:
Elias Pekonen Home Page - 2 vs 3 Speaker Stereo listening tests at high frequencies


- Elias

Maybe more speakers isn't such a bad idea after all?

I strongly disagree with your statement "center phantom image weak or non existent" for 2-speaker stereo with high pass filtered music.
I do get a stable phantom center from high pass filtered (48dB@1.6kHz) stereo music tracks.

Possible explanations for your findings:
- Low direct/reverberation ratio. Is your room treated in any way? What kind of speaker directivity was used?
- Difference in localization perception. There are reports that some people can't localize phantom images. You've reported similar perceptions in the past. You should have other people listen to your test in your room and report their observations.

[Elias]

Originally Posted by markus76

Maybe more speakers isn't such a bad idea after all?

Nobody said more speakers are bad (think Ambisonics ) but certainly it is more efficient to use only one stereo speaker

It looks like 2 speakers is the worst scenario.

Originally Posted by markus76

I strongly disagree with your statement "center phantom image weak or non existent" for 2-speaker stereo with high pass filtered music.
I do get a stable phantom center from high pass filtered (48dB@1.6kHz) stereo music tracks.

I also don't have problems at 1.6kHz but the problems occur at higher freqs above about 6 kHz.

There is published scientific evidence that humans cannot perceive phantom images at very high freqs (the reference was given in another diyaudio thread). That is the problem of 2 speaker stereo.

3 speaker matrix stereo seems to solve this problem somehow.


- Elias

[markus76]

Originally Posted by Elias

It looks like 2 speakers is the worst scenario.

...in your personal priority list of what sound reproduction needs to be capable of. That list might not be the same for everybody. My priorities are certainly different.

Originally Posted by Elias

I also don't have problems at 1.6kHz but the problems occur at higher freqs above about 6 kHz.

Your page says "center phantom image weak or non existent" for frequency band 1-20kHz. It doesn't say 6-20kHz!? The cutoff in the track I've used is 1.6kHz (not 1kHz as in your example), still I get a perfect phantom center.

You skipped over my questions about room and speaker characteristics in your listening test.

[Elias]

Originally Posted by markus76

Your page says "center phantom image weak or non existent" for frequency band 1-20kHz. It doesn't say 6-20kHz!?

In 2 speaker stereo the phantom image is very weak, for the reason at freqs around 1 kHz there will be a phantom but at higher freqs above 6 kHz the image is split into the speakers. This happens if there is signal energy at both freq ranges.

When there is less signal energy at 1 kHz and more energy above 6kHz there is no phantom imaging and only the two speakers will be perceived.

So, overall the 2 speaker stereo does not work very well in terms of phantom imaging.

Originally Posted by markus76

I get a perfect phantom center.

That is highly subjective statement

[Rudolf]

Originally Posted by Elias

When there is less signal energy at 1 kHz and more energy above 6kHz there is no phantom imaging and only the two speakers will be perceived.

Must be weird kinds of music you are listening to.
I prefer music were - by and large - the harmonics roll off with rising frequency.

Rudolf

[Elias]

Heres my experimental matrix system at proto stage. Three FRS8 at reinforced cardboard dipole baffles Matrixed for coefficient of 0.5. Very old proto speaker has been forced laying on the floor to serve as a dipole bass below about 100Hz.


Sound... amazing


- Elias