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Who knows something about Tri-channel 3-channel stereo for music (not HT)?

I happen to have 3 Martin Logan 'Source' e-stats, and want to overcome one of my main complaints with these speakers... narrow sweet-spot.

Having heard of 3-channel stereo, had the idea that instead of using a stereo pair, I might incorporate all three to solve several issues (narrow sweet-spot and low impedance), while improving 3-dimensional holographic imaging for added benefit.

I know there was an era (before my time and before surround sound), when this was (considered by some) the pinnacle of hifi. I found this article on Magnepan site that details some history on the subject https://www.magnepan.com/betterthanstereo

I have tried connecting the 3rd speaker located in the center in series with the stereo pair - jumpered to positive speaker pole of one (say left) and negative to the other (say right) speaker. In this configuration, I'm not sure what signal is going to the 3rd (center) speaker, but it doesn't follow either left or right, and switching pos/neg connection to the other two doesn't cause a change. So as long as the 3rd speaker is connected pos-pos/neg-neg, it seems to be in-phase and not make either left or right channel dominant.

The effect does increase the sound stage width and impedance (this is a good thing for these low-impedance speakers); however, imaging is no more holographic than is typical for these (and most) electrostats.

So, I wonder what products like the Maggie/Bryston SP-3 and (likely) other similar products of the era offer, that would be an improvement over what I'm doing with series wiring? What about the benefits/pitfalls of various circuits L+R, L-R... etc., and what works best for imaging?

Happen to have some equipment (unused Denon AVR, miniDSP 2x4HD, Emotiva A800) that could potentially be used to try recommended schemes (play) and REW with calibrated mic (to measure results). Currently reconfiguring my 2-channel listening room with two single-stack racks to allow space for the center-channel floor-stander ML Source at center for progression of this endeavour.

Any history lessons on 3-channel stereo (from the good old days) or ideas to try are sincerely appreciated.
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Showing 1 response by mijostyn

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mijostyn
8,227 posts
 
Right. Klipsch started doing this for the simple reason that K horns had to go in corners and in many rooms this put them too far apart leaving a "hole" in the middle. So they developed the La Scala as a center channel speaker to run in the middle. The idea was that you would mono the signal to the center channel and turn up the volume just until the "hole" disappeared. It worked ok and made the system seem even more powerful. Nobody else did this because if you had a "hole" in the middle you just moved your speakers a little closer together which was a whole lot cheaper than buying a third channel.
In regards to your system a third middle channel will do nothing to increase the "sweet" spot. Draw it out on paper and you will see the dispersion stays exactly the same and you have shrunk the image dramatically. 
If you want a wider sweet spot buy speakers with wider dispersion. 
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