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-   -   EP21 - Single Stereo Loudspeakers (http://www.diyaudio.com/forums/multi-way/222698-ep21-single-stereo-loudspeakers.html)

gainphile 2nd November 2012 03:37 AM

EP21 - Single Stereo Loudspeakers
 
For my 21st loudspeaker build, I would like to implement Elias Pekonen's SSS.

Quote:

Originally Posted by Elias (Post 3224364)
2 speaker stereo is dead :cool:

The concept is very unique and interesting.
dl.dropbox.com/u/2400456/html/Elias_Pekonen/SingleSpeakerStereo.html

I have ordered 3x HiVi B3N / B3S for this endeavour !

I will compare it with my personal reference:
gainphile.blogspot.com.au/2012/03/s19-4-way-dipole-radiator.html

Fun times ahead :cheers:

Moondog55 2nd November 2012 05:54 AM

Can I say "Hmmmm" ??
Interested to hear your impressions

Perhaps "Wide-field single speaker box" would be a better name

lolo 2nd November 2012 09:46 AM

Please do keep us posted! :wave2:

Elias 3rd November 2012 02:59 PM

Quote:

Originally Posted by gainphile (Post 3224590)
For my 21st loudspeaker build

21 is a popular number nowadays ;)


If you got any experience of matrix stereo, you'll already have a hint what to expect. Single speaker stereo is a simulation of three speaker matrix stereo. The room side walls are an essential part of the system:
http://dl.dropbox.com/u/2400456/html..._0x5_huone.png


See also my FDTD soundfield simulations of SSS. They'll serve as a proof of it's achieved intended functionality.
Elias Pekonen Home Page - FDTD simulations on Single Speaker Stereo SSS


Yes, fun you'll not be lacking :D


- Elias

dewardh 3rd November 2012 03:58 PM

Quote:

Originally Posted by Elias (Post 3226511)
Single speaker stereo is a simulation of three speaker matrix stereo.

It is a simulation, however, that depends on a directivity of the L and R speakers that is not clearly in evidence, and which is also dependent on a high degree of symmetry in sidewall reflections. An alternate scheme (which would be easy to implement and test) is suggested by your "M/S" example (at you web site). A pair of Magnaplanar MMG dipoles could easily provide a M/S source of well defined directivity . . .

Elias 3rd November 2012 05:45 PM

Quote:

Originally Posted by dewardh (Post 3226572)
An alternate scheme (which would be easy to implement and test) is suggested by your "M/S" example (at you web site). A pair of Magnaplanar MMG dipoles could easily provide a M/S source of well defined directivity . . .

I found an old figure of mine from the Stereolith thread describind MS stereo playback of two crossed dipoles:
https://dl.dropbox.com/u/2400456/diy...ointstereo.png

What matters is the response to the 45 angle direction to generate the side wall reflections towards listening position. We need angle independent summation from the two dipoles. I don't think wide ESL is any good in this regard due to their beaming nature at high freqs.

Anyway, as you know the matrix coefficient of 0.5 is the optimal one, so MS stereo is then.. suboptimal ;)


- Elias

graaf 5th November 2012 09:37 AM

Quote:

Originally Posted by Moondog55 (Post 3224667)
Perhaps "Wide-field single speaker box" would be a better name

why? if it produces stereo imaging - and it does - then it is stereo

cT equals piD 6th November 2012 12:02 AM

In the two different systems of Elias' post #4, an essential difference is that with the single speaker stereo system, the (L-0.5R) and (R-0.5L) signals are time-delayed in arriving to the listener, relative to the (0.5L + 0.5R) signal. That is, for single speaker stereo set-up, the summed signal has precedence over the difference signals. If the time delay is several milliseconds, then the listener recognizes the sound reflected off of the side walls as non-direct ambient sound and there is no stereo imaging.

It would be great if this really did work, but I don't think so.

Possibly a solution would be to use signal processing to delay the summed signal so that all three signals arrive to the listener simultaneously....

Regards,
Pete

Elias 6th November 2012 08:22 AM

Quote:

Originally Posted by cT equals piD (Post 3229848)
It would be great if this really did work, but I don't think so.

Why don't you try it and you will change your mind.


There are several aspects you neglect.

First the precedence is not simply an one dimensional phenomena but it includes both time and amplitude, and usually known as time intensity trading. For this reason there is a psychoacoustic filter involved in the speaker which steers the high freq energy from the center to the sides.

More shocking aspect is that precedence effect (Haas) is only valid with one reflection. In a small room acoustic space a cluster of reflections eminating from about the same lateral angle will override Haas effect completely.

There are issues with current psychoacoustic theories within small rooms that need some rethinking. There would be a good opportunity for someone research minded to write a couple of academic papers on these issues (hint) ;)


- Elias

cT equals piD 7th November 2012 12:24 AM

Elias, your post #9,

Colloms cites precedence only of the direct sound in allowing the listener to hear a stereo image (in his book High Performance Loudspeakers). He says that if the listener is 3 to 5 meters distant from stereo speakers, then "most of the sound energy heard is reverberant". The arrival time of the direct "focused" sound ahead of the "diffused" reflected sound he claims is the only thing that allows for the perception of stereo.

I don't understand why the precedence effect should be valid for only a relatively focused reflection where all of it arrives to the listener at about the same time. Even if the arrival times of reflections from a side wall are spread out over a fairly large time interval, still the direct sound of the summation signal arrives prior to any of the reflections off of the side wall.

In the patent literature I've seen a proposal at least similar to your SSS from some time ago. Certainly the fact that your SSS will only work in some listening rooms reduces its commercial viability. But as far as I know a system like your SSS has never been commercialized, suggesting that it is lacking as a method of stereo reproduction.

One other critique that I can make is that reflectivity of the walls of the room would need to be taken into account. That is, I think that the level of the directly radiated summation signal should be reduced relative to the level of the difference signals reflected off of the side walls.

Regards,
Pete


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