Review: Audio Magazine, December 1995
Reviewer: James T. Frane
Article: “Direct Acoustics Silent Speaker” pp. 72-76
“Room surfaces and their proximity to a speaker can have a significant effect on the reproduced sound, depending on the reflection or absorption characteristics of the surface. Sound that bounces off these surfaces is delayed with respect to the direct sound from the speaker. The closer the speaker is to the surface, the shorter the delay of the reflected sound. Reflected sound can augment or cancel the direct sound at certain frequencies. Many people prefer to place speakers well away from as many room surfaces as possible, and some sit relatively close to the speakers so that the direct sound dominates. This practice can, with many speakers, increase the apparent width and depth of the stereo image and also better define the location of the performers.
A few speakers, however, are specifically designed for optimal performance when placed in close proximity to one or more room surfaces. Winslow Burhoe of Direct Acoustics (formerly with Acoustic Research and KLH, and founder of EPI) has designed such a product, the Silent Speaker-a two way model in a somewhat unusual cabinet. It has a small (9 1/2 x 12 3/4 inch) footprint, and a forward sloping top on which are mounted a 1-inch dome tweeter, and a 6 1/2-inch woofer. The cabinet front is 21 1/8 inches tall, and the back is 25 inches tall. The grille, a sheet of 1/4-inch0thick hardboard with a cutout around the drivers, is covered by black double-knit cloth. The grille is attached to the speaker baffle with double-sided tape and is intended to be left in place to enhance the performance of the drivers.
A bass reflex design, the Silent Speaker has an internal duct, rectangular in cross section that curves upward within the cabinet from a vent (11 1/2 inches wide and 7/8 inch high) at the base of the front panel. The duct extends well up into the enclosure and across the full width of the cabinet.
Direct Acoustics says the Silent Speakers got their name “because their sound is so lifelike that you cannot tell that you are listening to speakers.” This is further explained by the premise that “when speakers make sounds which are not on the recording or don’t make sounds that are on the recording, they are making their own sound, that is, they are not silent.” The owner’s handbook discusses placement, design details, cables, amplifiers, and other equipment and also includes definitions of many relevant terms.
Silent Speakers are designed to be placed with their backs up against the wall. They are mirror imaged, and the tweeters are to be placed to the inside. Speaker logos are on the cabinet fronts, underneath the woofers, to make left and right identification easy. The drivers are mounted on the sloped tops of the speakers to minimize standing waves and room resonances. The woofer has a long voice coil and soft suspension to enable long excursions for deep bass reproduction. The European-designed soft-dome tweeter uses magnetic fluid for voice-coil cooling. The drivers are crossed over at 18 dB per octave. The approximately 5/8-inch-thick cabinet material is described as “heavy, non-porous wood.” My review samples were finished in black vinyl that had the appearance of ash wood grain. The finish was first-rate, and one would be hard pressed to determine by eye that it was not black-painted wood. A genuine wood-veneer version is offered at extra cost. The speakers are available directly from the manufacturer at $486 per pair for the vinyl-covered version.
Everyone who saw the speakers in my system commented favorably on their appearance, as well as their designated placement against the front wall. One friend commented that the slanted baffles will prevent people from setting drinks or other objects on the speakers and from using them for seats.
The speakers were driven from a Carver TFM-42 power amp via Kimber 4PR cables. At the front end, I used a Carver CT-17 tuner/preamp. The speakers used for comparison were Mach 1 M-Two’s-two way acoustic suspension models with front-baffle driver placement. Sources were a Sony CDP-C315 CD player, a Dual CS5000 turntable used alternatively with Shure V15 Type V and Ortofon X1CM cartridges, and the Carver tuner. I listened to acoustic jazz, vocals, classical music, and vintage rock.
I first tried the Silent Speakers on the floor, well away from any walls, and then, as recommended in the owners manual, with their backs only about 3 inches from the wall. I liked the sound both ways, although there were differences. (Most of my listening was with the speakers in the recommended position against the wall, where they nearly disappear visually.) The sound was a bit warmer with the speakers close to the wall, and the soundstage was not quite as deep. In either position, the Silent Speakers’ bass was strong down to 40 Hz and still very much present at 20 Hz, although down a few dB.
The Silent Speakers created a wide and spacious soundstage, with imaging that was a bit diffuse and a sound that was slightly less detailed that of the Mach 1 M-Two speakers. The sound extended well beyond the outside edges of the Silent Speakers and was a bit recessed, as if heard from a distance, with the soundstage slightly lower than the listener. It reminded me of the sound of a live performance from front-row balcony seats. Bass was very good, and remarkable in view of these speakers’ size. The strong bass and good dynamic range added to the realism of the reproduction. The speakers reached deep enough to vibrate the floor with timpani, organ, and double bass. I had a sense of hearing the orchestra spread before me, with good center fill. The character of pink noise and of music with prominent highs changed between the seated and standing positions, becoming slightly softer when I was seated (and thus farther off the driver axes). The soundstage was not as deep and layered as with the Mach 1 speakers but still had a three dimensional character.
I tried a few cuts from Jazz Sampler & Audiophile Test Compact Disc, Vol. 1 (Chesky JD37). The sound from the “Over” track of the stereo-image test reached a height of about 5 feet; “Lateral” was smooth and even, and “Depth” gave a good sense of the acoustics of the recording space at different distances from the mike. “Up” curved slightly inward from each speaker. On Ana Caram’s “Viola Fora de Moda” from Rio After Dark (Chesky JD28), the highs were sparkling and clear, the bass solid, and Caram’s voice warm. The piano sound was full on David Chesky’s Club de Sol (Chesky JD33), but the initial keystrokes were a bit soft. Various cuts on Dave Brubeck’s Jazz Impressions of New York (Columbia CK-46189) were rendered with appealing smoothness and breadth. Beethoven’s Symphony No. 3, “Eroica,” by the Met Orchestra under James Levine (Polygram POL 925), was re-created with appropriate majesty and emotion. The orchestra was spread in front of, and slightly below, my listening position. Julie London’s voice on All Through the Night (Liberty LST-7434) retained the characteristic textures that are evident from other fine speakers.
The Silent Speaker’s sensitivity was a bit lower than that of the Mach 1s, possibly a trade-off for deeper bass, but they played quite loudly with sufficient amplifier power. The sound was warm and full, mellow and forgiving, with addictive smoothness and spaciousness. Highs were never harsh or fatiguing. Although performers were properly located on stage, the imaging was not of the pinpoint variety, again typical of sitting at a distance from a live performance, particularly in a reverberant space. A solo performer could thus sound a bit “wider” than with the Mach 1 speakers.
The Silent Speakers have the ability to transport you back to a favorite concert hall’s balcony seat while spreading the performers before you. They do not have the analytical “up-front” character or finely etched detail of many high-end speakers, but that may not be your preference. And for such attractive sound and appearance, they are unquestionably a fine value.“