Taming/Damping Electrostat Backwave

Has anyone ever tried mounting maggies or stats inside a wall that divides two different rooms, so that you get a monopolar wave in each? Just curious if anyone has tried it and what your results were, in particular whether the reflections from one room came back through the panel into the other.

Didn't Genesis or Infinity do something like this? Any one ever try using two pairs back to back to cancel the out of phase rear wave and create an in phase back wave? Just curious.

Room Lenses work wonders behind 'stats. DIY lenses using 5 or 6 tubes are even better or you might want to make noodle lenses. Check out Audio Asylum for info. I recently heard of using bi-fold louvered doors from Home Despot. These are said to be great diffusers and are easy to set up. Just fold them enough to stand up and place them behind the speakers. WAF might be a factor.

T Bone -

I'm pretty much going to say the same things Rives and Sidssp said, just in a different way. So feel free to skip over this post.

Assuming the "holy grail" is to recreate the concert hall experience, let's look at what's going on in the concert hall, and then see what we'd want to do with your SL3's to incorporate some of that into the listening room.

In the concert hall, first thing you hear is the direct sound of the instruments (duh). Then there's a considerable time lag - up to several tens of milliseconds - before the reflected energy starts to arrive. This reverberant energy is very powerful but also very diffuse, and lasts for several hundred milliseconds. This powerful, diffuse, late-arriving reverberant field is largely responsible for the rich timbre and enveloping sense of ambience in a good hall.

The backwave of your SL-3's can be your secret weapon in creating a better approximation of the concert hall than most speakers can.

Ideally, you want to position your SL-3's about 6 feet out into the room. This will allow adequate path length for the backwave energy to arrive late enough (10 milliseconds minimum) that it won't screw up the imaging, but will instead enrich the timbre and the feeling of ambience. Assuming your room's tonal balance is good, you'd want to use diffusion on the first backwave reflection points, to the inside of the speakers along the wall behind them (I use fake ficus trees). You might also want to treat the first sidewall reflection points, though with the fairly directional SL-3's this might not be necessary. Once again diffusion is preferable to absorption, unless your room is too bright. And even then, a little absorption goes a long way. The reason of the diffusive treatment of the first reflection points is that strong, distinct early reflections can skew the imaging, but we'd like to preserve that energy to enrich the timbre and spaciousness.

Okay, now let me come at the same issue again, this time focusing more on voice and instrumental timbre than on concert hall-ish acoustics. The tonal balance of the reverberant field has a significant impact on the perceived timbre. The bass of your hybrid SL-3's is essentially omnidirectional, which means there will be lots of reverberant energy in the bass. The panels are much more directional, and so put less energy into the reverberant field, relatively speaking. If we use absorption to soak up the backwave of the panels, there will be a severe shortage of mids and highs in the reverberant sound field. As a result, the speakers will tend to sound precise, but uninvolving and lifeless, and eventually fatiguing. You see, a significant discrepancy between the direct and reverberant fields contributes to listening fatigue, so we want to keep 'em as much alike as possible.

My advice is always free, and worth every penny.

Duke

Although I disagree somewhat with Audiokinesis' theory about ambiance recreation, I do agree with his point concerning power response. (I believe speakers should ideally reproduce the actual ambiance captured on the recording, not introduce spurious additions of their own, something which the listening room is already going to be unavoidably doing anyway - although one can always make the argument that recordings fail to adequately capture all of the natural ambiance, and therefore we are forced to 'add some back' through any means necessary. My problem with that is the fact that the added 'ambiance' will be constant in character [as indeed are all listening room signatures] and unrelated to the soundfield of the actual event recorded, so that while it may sound pleasant in certain instances, it is still a distortion. However, that's a disagreement about ideals, not about panel speakers per se, which can offer fewer side reflections than monopoles, and properly positioned and diffused, I do agree that dipoles can offer their own intrinsic strengths which allow them to more than compete with typical box radiators under the right circumstances.) But to affirm his admonition against over-damping in different words, the speakers you buy are balanced for optimal in-room frequency and power response *without* having to resort to a LEDE (live end, dead end), quasi-anachoic listening room set-up, so if you over-damp by absorbing the backwave, the resulting frequency balance will not be as intended.

From my own (admittedly limited - I've never owned any, yet!) experience with 'stats, I have found that placement is highly critical, especially distance from the front wall, with practically every inch potentially making a difference. I also have found that, even with curved panels, a little judicious toe-in can still have a beneficial effect in redirecting the reflections and altering the perceived direct/reflected sound balance, even when diffusion treatments are being employed.

Unsound, to address your typically creative suggestion about using two pairs of panels back-to-back to achieve bi- instead of di-polar propagation, the phase inversion aspect in a dipole really matters the most not in the reflected waves bouncing around the room - where the phase will quickly become all jumbled up with any radiation pattern or ?-pole design anyway - but at the sides of the panels where the waves wrap around and cancellations occur. If one were to take speakers designed for dipolar operation and alter the figure-8 radiation pattern through the introduction of out-of-phase interference, then presumably the side cancellations accounted for in the original design and voicing of the speaker would be violated, upsetting the correct response. I think.

I've always been interested in the ideas Sean and Karls mention. I believe the Wisdom Audio planar-magnetics incorporate a monopolar panel radiator through the use of a damped rear cabinet (in their current form - the first generation were dipoles with open backs). But considering the inherent problems introduced by all cabinets, the in-wall, open on both faces, infinite side-baffle configuration seems fascinating (and what a cool way to get multi-room sound!).