LEDE Listening Room
Last month I reported on a somewhat radical idea in creating a new type of acoustical environment for listening to music. This was the LEDE or "live end, dead end" concept, in which the loudspeakers are placed in the acoustically dead front third of the room--with the remaining two-thirds of the room kept as live and reflective as possible. The dead end is achieved through use of a special open-celled polyurethane foam called Sonex, manufactured by Illbruck/USA of Minneapolis and sculpted in male and female anechoic wedge patterns.
There are three ways of applying Sonex sheets to a wall. For an extra $6.00 per sheet, they can be obtained with self-adhesive backings. You can also use a special gun to apply a type of mastic or adhesive to the back of the Sonex sheets; the gun costs $7.50 and extra cartridges of adhesive are $3.50 each. The third method, and in my opinion the easiest, is to use an electric power staple gun with half inch staples. The stapler is placed close to the base of the anechoic wedges so that the staples don't have to penetrate the full 2-, 3-, or 4-inch thickness of the Sonex. The adhesives are all right, but if the Sonex must ever be removed, it could be quite a mess.
The staples, on the other hand, can be pried out fairly easily with a small screwdriver. I experimented using this method and found that on plasterboard walls a coat of latex paint effectively hid the staple holes. Repairing wood paneling is more difficult, but a color-matched wood filler will hide the staple holes, and they can be finished off with a furniture touch-up stick.
In applying the 4 x 4 foot Sonex sheets to my side walls, I used only the male anechoic wedge pattern. This provided optimum propagation of the sound waves down the walls of the room and aided in attenuating standing wave modes. I used the indented or female Sonex pattern on the back wall behind the loudspeakers. The entire stapling procedure for my listening room took about five hours, with the installation of audiotiles on the ceiling accounting for a major portion of this time. The ceiling is literally a pain in the neck, and one might be tempted to leave it untreated. That is a big, fat "no no." The ceiling is a primary source of reflections and a major offender in terms of diaphragmatic flexure. Using Sonex on the floor is obviously impractical, but thick pile carpeting over thick rubber padding serves quite well.
It is true that if one had access to the elaborate equipment needed for TDS (time-delay spectrometry) measurements of TEF (time-energy-frequency) curves, it would be possible to determine precisely where the Sonex should be applied in the front dead end of the room. In other words, less Sonex could be used, but this assemblage of equipment currently costs about $22,000. (Although Crown International is expected to introduce a single dedicated TDS instrument this year with a price reportedly about $10,000.) Of course, one could also hire one of Don Davis' licensed TDS practitioners who have the requisite equipment, but they don't come cheaply either! What does it cost to create a live end, dead end listening room? The size of the room is the governing factor. I needed three six-sheet cartons of the 4 x 4 foot Sonex at $222.00 each.
I also required two 28-piece cartons of audiotiles for the ceiling at $195.00 each. Total costs came to $1,056.00 for Sonex and a $5.00 rental of the stapler. Not cheap, I'll agree, but I can't think of any comparably priced audio equipment that would even approach the dramatically heightened sense of realism afforded by Sonex in the LEDE configuration.
In my LEDE listening room, I use a pair of B & W 801F speakers driven by a Levinson ML-3 amplifier. The amp is between the speakers and connected by short lengths of Live Wire Big Red speaker cable made by Audioquest of Santa Monica, Cal. This cable is huge, about 1 1/4 inches in diameter and comprised of Litz wires in a special configuration. Quite incidentally, I have always been very skeptical about so-called super wires and the alleged improvements they make in music reproduction. Yet I must say Big Red seems to fly in the face of engineering theory and logic, for I certainly noted a smoother high-end response and, most especially, a cleaner bass, with more extension and plenty of weight and punch. But at $20.00 per foot, short lengths are the order of the day! Positioning the amplifier close to the speakers is not a new idea, but it appears to be gaining more and more favor among audiophiles. The speakers, while placed away from the walls, are nonetheless "surrounded" by the Sonex. Thus, those pesky close-order early reflections normally produced in all non-LEDE listening rooms are absorbed. Listening to a familiar loudspeaker in the LEDE environment, one is immediately aware of the great increase in the clarity and cleanness of the sound. Bass is singularly free of boominess or overhang. Instruments seem more clearly defined. Dense and complex musical textures are more articulate. Depth perception is greatly enhanced, as is the sense of ambience and the reverberant characteristics of the recording hall. Loudspeakers with superb imaging, like the B & W 801F, achieve new heights of instrumental localization and positioning; speakers with lesser degrees of imaging are considerably improved.
While most loudspeakers will benefit from the LEDE room, there are designs, like the Bose 901, which obviously would suffer from absorption of their rear sound output. On the other hand, dipoles like the Quad and the Acoustat electrostatic speakers perform exceptionally well. In a sense, these speakers "think" they are in a far bigger room. For those who have always yearned for a bigger room, in order to keep electrostatics well away from walls, LEDE is the answer.
The LEDE configuration allows you to get further into the music, be it performed in a studio or concert hall. However, therein lurk some annoyances. What once was masked by the interaction of listening room acoustics with loudspeakers is now all too clearly revealed. Poor mike techniques, especially multi-mike, can be devastating to hear-for example, some gross "pan potting" in which you can plainly hear left/right manipulations and "gain riding." In addition to all kinds of sonic anomalies, there are matters of performance. Poor intonation becomes easily apparent, as does inaccurate "unison" playing.
Needless to say, the LEDE room is not for everyone; it helps to live alone or with tolerant people. For those who can't go all out for an LEDE room at present, Sonex still can make an improvement. If you install one Sonex sheet on each side wall in the front of your listening room, and position your speakers so they are adjacent to the Sonex, some of the close-order early reflections will be absorbed.
I can truthfully say that my LEDE room has given me more unalloyed listening pleasure than I ever expected to hear in my home.
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(Source: Audio magazine, Jul. 1982; Bert Whyte )
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