Stereophonic Sound from a Single Loudspeaker

[graaf]

problem with linked pictures so I am posting them below

[Soundminded]

The idea is hardly novel. The electrical circuit is virtually identical to Ralph Glasgal's Stereo Separation control issued as US patent no. 3170991 issued in 1965

System for stereo separation ratio control, elimination of cross-talk and the like

The idea has its genesis in the matrix circuit for the FCC approved Zenith method of frequency division stereo demultiplexing in which the L+R mono signal is added in and out of phase to the L-R signal detected by the multiplex adaptor to obtain 2L and 2R. This is undoubtedly the same circuit used on HT receivers to generate the "wide" mode. (Ambiophonics takes the same principle and uses it for acoustic cancellation by slightly attenuating and delaying each channel and feeding it to the opposite amplifier/speaker. When the two fields arrive at the same point 180 degrees out of phase, your ears if you are precisely in the right location, cancellation of the opposite speaker's field occurs and voila, increased separation.)

You could rewire a single bose 901 speaker to do the same thing and operate it from the three front channels of an HT receiver in the wide mode.

Another attempt at single speaker stereo is JBL Paragon. Side firing single stereo speakers are nothing novel either. All rely at least in part on reflected sound to increase separation. Results strongly depend on room acoustics and speaker placement requiring experimentation to obtain the best effect. Equalization of the side firing speakrs can compensate for differential spectral absorption by the room boundaries otherwise the reflected sound will not have the same spectral transfer function as the front sound.

[graaf]

I have to say that word demultiplexing is truly EPIC!

[Elias]

Originally Posted by graaf

have You considered/measured the effect of the back wave of one speaker superimposed on the output of other two speakers and of the output of each speaker diffracting around the box?
for me it looks like that for frequencies below about 700<1000 Hz the output from each of the speakers is equally all around just with little relative SPL differences plus small time delays

Yes I'm planning to do detailed measurements, but at the moment I'm just enjoying the sound from this prototype Rarely something this simple sounds so nice.

In theory the idea of this kind of speaker is the directivity pattern is steered according to the stereo input signals L and R.

It may be that conventional measurements do not fully reveal how this kind of speaker is perceived in a room.


- Elias

[weltersys]

Originally Posted by Elias

It may be that conventional measurements do not fully reveal how this kind of speaker is perceived in a room.

- Elias

Yes, conventional measurements do not reveal perception.

The console stereo in my parents living room in the 1960's had side pointing Heppner horns, and front facing cone speakers, basically a larger version of what your experiment is.

I have fond memories of music played on that console.
In the mid 1980's they replaced the console with bookshelf speakers, the console went out on the enclosed porch while they tried (unsuccessfully) to give it away.
On a visit, I turned it on again out of nostalgia, it amazed me how awful it sounded.

Perception is quite subjective .

[graaf]

Originally Posted by weltersys

The console stereo in my parents living room in the 1960's had side pointing Heppner horns, and front facing cone speakers, basically a larger version of what your experiment is.

hm... usually consoles had side firing woofers

or perhaps was it Magnavox Imperial shown in this catalogue?

but in such a case those two horns were toed out to a degree rather than side pointing
plus two woofers facing forward - all this not very similar to Elias' box, wouldn't You agree?

perhaps You parents' console was different, do You know the name of it or can You post any pictures?

[optic]

Originally Posted by Elias

Those coefficients have so many decimals it must be based on academic research Any references ? Gerzon ?

So your three speakers, are they integrated as one, or spread in front in conventional triangle ?


- Elias

Yes Michael Gerzon.. Search Google patents to find details..

And yes single box 3 speakers 1 forward, 2 on sides angled forward. hmm, i did mention 30 deg, but i checked and its only about 15

I have tried the lcr triangle. It works well with Gerzon's formulas... However i wanted a simple solution for my den. Hence i tried the single box method.

The LCR method i use atm is so much better than standard stereo triangle. Sweet spot is every where...... Instrument positioning is exact. I dont sit still in my den so i needed a solution that would allow me to move around. It works for me.... Thats what matters....

I admit.... It takes a day to get use to the setup.... My brain was not use to having the centre channel at first.... But when i listen on my main system (standard triangle) i miss the stability the LCR setup provides... This will change.... New main system on its way..

I can create some 3 channel songs (2 to 3 channel conversion done) in mp3 format for those that want to experiment. I am working on scripts to do the conversion via commandline atm. So i can just use a 3 channel player or 4 channel 3.1 format (if they exist) to eliminate the PC i use atm.

Cheers,

Optic

[markus76]

Originally Posted by optic

Yes Michael Gerzon.. Search Google patents to find details..

What's the title of the patent? Couldn't find it.

[graaf]

Originally Posted by KSTR

^^
Elias, you're right, thanks for correcting that.

The more generic equation, as given by Michael Miles from MilesTech and coined "Optimum Linear Matrix", is :

L' = L - kR
R' = R - kL
C = (1-k)(L+R)

With k = 0.5 it's "Trinaual

- Klaus

so what You proposed Elias can be also seen as a kind of one-box trinaural?

[optic]

Originally Posted by markus76

What's the title of the patent? Couldn't find it.

Patent no. 5594800

Sound reproduction system having a matrix converter

Cheers,

Optic