Sound-Lab A-1 electrostatic loudspeaker DO's last wing fling

Sidebar 3: DO's last wing fling

I wish I had a dollar for every time I've removed or installed these gigantic wings. During his visit last March, Roger West suggested that I try the wings mounted to the front of the speaker. So I went at it again. There's considerable logic to flip-flopping the wings to the front. This avoids creating a resonant cavity with the side and rear walls, and thus, in principle, should help alleviate the boxy character that rear-mounting the wings caused in my room. Second, it makes more sense to "horn-load" the front wave rather than the back wave. Dispersion of the rear radiation becomes easier to accomplish, and there's also a sensitivity gain in the lower mids.

In the frontal position, with arms outstretched, I found the wings actually less imposing—easier to accept visually. My first sonic impression was that imaging was essentially unaffected by the frontal wings. Certainly, the boxy nature of the presentation I had earlier complained of vanished. In moderately sized rooms like mine, I recommend that, if you must have wings, at least mount them frontally. However, take note that, over time, I became disenchanted with one specific aspect of the wingéd soundstage: Image outlines failed to bloom sufficiently. The sensation of 3-D, "in-the-flesh" instrumental outlines was lacking. Once I was aware of the problem, I became so focused on it that my listening enjoyment suffered considerably.

So back to the closet went the wings, for what I hope is the last time. Again, I was amazed at how much better the A-1s could float a soundstage without the wings in the way. With the new interface, the "tiptoe" feet, and mass loading of the array, I was perfectly happy with the resultant bass extension and definition.

Enter Sallie: SALLIE is quite a gal. At 77" tall, 12" wide, and 12¾" deep, she strikes oh, such a huggable pose. She does, however, have the peculiar impediment of having double cleavage. Front and back, running her full height, 6"-thick foam absorption wedges are mounted back to back, offset to always give a 6" absorptive path length through SALLIE. The wedges are very effective in attenuating sound from 250Hz up.

At a mere 15 lbs each, SALLIE is quite easily movable; she's intended to be positioned behind any dipole speaker to provide control over the backwave and its return reflections off the wall. SALLIE is quite efficient at this because she can be positioned quite close to the source, thus eliminating the need for extensive wall treatment behind the speaker. Reflection off the wedges is quite minimal; placements right up against the back of the speaker are okay, and will not color the front wave.

The amount of backwave absorption is adjustable by simply moving SALLIE toward or away from the back of the speaker. This turned out to be a critical adjustment in my room; it was possible to over-damp the back wave to the point that soundstage spaciousness disappeared. The objective is not to entirely kill the back wave, but to control it to the point that image outlines snap into focus. The point of maximum back-wave attenuation turned out to be with the foam in the diaphragm's virtual line source. If you put your ear behind the array and move it to a point over the binding posts, you'll notice a sharp increase in intensity. This line coincides with the focal line of curvature for the array. With SALLIE here, the back wave really died. However, the optimum placement in my room turned out to be with the foam about 6" away from the rear edge of the interface.

I verified to my satisfaction that SALLIE performed as effectively as a pair of ASC Studio Traps behind each speaker in controlling the A-1s' back wave. I imagine that any dipole speaker would benefit from a date with SALLIE. At a cost of around $1000/pair, SALLIE is worth getting to know well.

DO's final thoughts: There comes a point in every love affair when reality rears its ugly head. My infatuation with the A-1s was finally tempered by the realization that they're not perfect. Blemishes do exist. As much as it pains me, it must be pointed out that they are insensitive (footnote 1), dynamically limited in the bass, a bitch to drive (especially in the treble), and a room-matching challenge. The A-1 does, however, play much louder and digs deeper than any other full-range ESL I've heard to date. They blow away both old and new Quads in dynamic bloom, dynamic headroom, and bass extension. But ESLs they remain.

My level of frustration with this speaker increased after the Mylar episode's serious QA implications hit home. And the problems with the treble tonal balance and Brilliance Control cheered me up not at all. Because the impedance of both channels measured alike, I can safely assume that, rather than a manufacturing defect, the present BC represents faulty design. And what a booby trap this lays for the consumer: Under no circumstances should the user be allowed to present a virtual short circuit to the power amp. With the BC set to Maximum, I imagine that most of the impedance seen by the amp is actually due to the speaker cable. There ought to be a way to maintain a flat treble response while presenting a benign load to the amp. How 'bout it, Sound-Lab?

Yet when the A-1 is on its best behavior, I know in my heart that our relationship is secure. Its sonic imprint of concert-hall realism is so faithful to the real thing that I'm sure I'll remain captivated long after the honeymoon is over.—Dick Olsher

Footnote 1: Some might say inefficient, but actually the Sound-Lab's generally high modulus of impedance means that it doesn't require much current, hence power, except at very high frequencies. This means that, despite its insensitivity, the speaker is actually quite efficient. Still with me?
Company Info
Sound-Lab Corporation
153 N 400 W Street
Gunnison, UT 84634
(453) 528-7218
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remlab's picture
This was the first Stereophile...

...issue I ever bought. I never forgot about the Mylar thickness issue. I remember saying to myself, "what if John hadn't tested the speaker?" There would have been a whole bunch of screwed up A-1's out there, probably to this day. That's what made me realize how important the testing of all equipment is. How often has equipment malfunctioned or been out of spec  during Absolute Sound reviews without them even knowing. Obviously, having measured A-1's previously did help in this case.

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