Cambridge SoundWorks is a recently established speaker company, but it actually provides a direct link to the earliest days of the high-fidelity industry. One of its principals is Henry Kloss, who was a co-founder some thirty-five years ago of Acoustic Research and later went on to found such well-known companies as KLH, Advent, and, most recently, Kloss Video.
Given Kloss’s technical expertise and distinguished record in designing high-quality speakers that could be sold at affordable prices, we were especially interested in hearing and evaluating CSW’s initial product, the Ensemble. It is a four-piece system in which two small satellite speakers reproduce the frequencies above approximately 100 Hz and a pair of separate bass modules roughly cover the octave from 120 to 50 Hz. Since each module contains its own crossover components, system wiring requires only simple parallel connections from each satellite to its bass section and from each bass module to the amplifier.
The satellites measure only 8-1/8 inches high, 5-1/4 inches wide, and 4 inches deep and weigh 5 pounds. Each contains a 3-1/4-inch low-/middle-frequency driver and a 1-1/2-inch cone tweeter (these dimensions are approximate). Heavy-duty multiway binding posts are recessed into the rear of the fully sealed enclosure, which also has a keyhole slot for wall mounting and a threaded bushing compatible with camera tripods and related devices. These features make the Ensemble satellites adaptable to a wide variety of mounting requirements. The cabinet is covered in a dark-gray flocked material (Nextal) and has a black metal grille.
Each bass module contains an 8-inch acoustic-suspension woofer protected by a metal grille. The enclosures measure 21 x 11-3/4 x 4-1/2 inches and weigh 16 pounds. They are finished in flat black. Multiway binding posts are recessed in one of the narrow sides of each module, near a corner. The bass modules can be mounted in any position or location as long as there is at least 1 inch of clearance in front of the grilles. Their shallow depth allows them to be placed under furniture or otherwise concealed from view. Short rubber mounting feet are supplied to raise the grille about an inch from the floor if the box is mounted with the speaker facing down. Smaller rubber feet are supplied with the satellites to protect furniture.
Because of the Ensemble system’s low bass crossover frequency (about 120 Hz), the bass modules cannot be localized by a listener and can therefore be placed almost anywhere in the room. To facilitate installation and experimentation with speaker placement, CSW provides 20- and 30-foot lengths of 18-gauge speaker cable with the system.
The extensive owner’s manual for the Ensemble provides considerable guidance for the nontechnical user in placing the system components as well as in connecting them to an amplifier or receiver. The manual includes few performance specifications, which are rarely of much value in judging the worth of a speaker system. CSW also has toll-free phone lines in the United States and Canada, with knowledgeable experts available to answer customers’ questions and help solve any problems that might arise.
The somewhat unusual design features of the CSW Ensemble are matched in novelty by the manner in which it is sold. The Ensemble is not available from dealers and must be ordered directly from the factory. Direct distribution contributes to the speaker’s low price—only $499 complete. The Ensemble system carries a five-year limited warranty covering parts and labor.
Lab Tests
The room-response curve for the Ensemble system was unusually smooth and uniform over its entire frequency range. We made this measurement with the satellites placed about 4 feet from the floor, 6 feet apart, and 2 feet from the wall behind them. The bass modules were placed upright on the floor, close to the wall, with the drivers near the bottom.
The close-miked response of a single bass module resembled a tuned circuit’s resonance curve with its maximum output centered at 75 to 80 Hz. The output at lower frequencies fell off at about 15 dB per octave and at about half that rate at higher frequencies. The bass curve spliced easily to the room curve, resulting in a composite frequency response that varied only about ± 3 dB from 50 to 20,000 Hz. Close-miked measurements of a satellite unit indicated that its larger driver operated from approximately 120 Hz (the crossover frequency from the bass module) to 1,200 Hz, where the crossover to the tweeter took place.
Our quasi-anechoic FFT response measurements confirmed the close-miked characteristics. The on-axis tweeter response was very flat from 2,000to 10,000 Hz, with a moderate irregularity at higher frequencies (which is typical of small-cone drivers in that frequency range). The horizontal dispersion was excellent up to about 6,000 Hz, above which the response measurements on-axis and 45 degrees off-axis began to diverge (though not severely under 15.000 Hz). The group delay of the satellite varied less than 0.1 millisecond overall from 4,000 Hz to over 20,000 Hz and was less than 0.4 millisecond down to 200 Hz.
The system’s sensitivity, measured 1 meter from the satellite with a 2.83-volt input of pink noise, was a rather low 83 dB sound-pressure level (SPL). Its impedance was about 3 ohms from 80 to 150 Hz, considerably below the rated 6 ohms, and reached a high of 13 ohms at about 5.000 Hz. With the bass module disconnected, the satellite’s impedance increased below 250 Hz, rising from 6 ohms at 120 Hz to 50 ohms at 20 Hz because of the high-pass crossover within the satellite.
The distortion of the bass module at a constant drive level of 6.3 volts (equivalent to a 90-dB SPL at 1 meter) decreased from 1.7 percent at 100 Hz to 0.6 percent at 65 Hz, and it rose to only 2 percent at 50 Hz and 4.5 percent at 40 Hz. High-power pulse tests showed that the woofer cone began to rattle with a 100-Hz input of 1,900 watts into its 3.2-ohm impedance. At 1,000 and 10,000 Hz, our amplifier clipped, at 900 and 500 watts, respectively, before there was evidence of speaker overload.
Comments
Although systems combining minispeaker satellites with separate bass modules are not new, and are currently enjoying renewed popularity, the CSW Ensemble is an exceptionally effective execution of the basic concept. The most obvious departure from similar products is the use of two separate bass modules. More commonly, two bass drivers are combined in a single enclosure or the low frequencies are electrically combined and used to drive a single woofer. Aside from any acoustic advantages it might have, the Ensemble’s configuration does provide more options for installation, since its shallow bass units can be located in places where thicker modules might not fit.
From our first hearing of this system, we had no doubt of its quality. There were no auditory clues to the locations of the woofers, whose output was subjectively linked firmly to that of the satellites. The effective lower limit of the bass speakers’ response is not much below 50 Hz, but it was sufficient to provide a good “floor” for the very smooth and balanced output of the satellites. Over most of the audible frequency range, the Ensemble satellites delivered a smoother output than many larger and more expensive speakers. Although nowadays small-cone drivers have been largely supplanted by dome radiators, these speakers provide convincing evidence of the capabilities of a well-designed cone. We noted a tendency toward a slight brightness at times, compared with some other speakers, but that may simply reflect the Ensemble’s very flat, extended high-frequency response.
We did not pamper the Ensemble speakers in our tests, driving them from a high-power amplifier and sometimes playing them at unreasonably high volume levels. Neither the speakers nor the listeners suffered unduly from the experience. Overall, the speaker system acquitted itself admirably. Few speakers we have seen in the Ensemble’s price range can offer it any serious competition. One of the only criticisms that might be leveled at the system concerns its low sensitivity, which is not uncommon in very small speakers. On the other hand, these are not the sort of speakers that most people will use to simulate jet planes or cannon shots; they were designed to play music—and to make it sound like music. This they do very well, in a most unobtrusive way, and at a bargain price.
The only mention of power requirements in the owner’s manual for the Ensemble indicates that amplifiers rated from 25 to 120 watts per channel have been found to be satisfactory. Our own experience confirms this advice, as well as CSW’s statement that the system is unlikely to be damaged by any higher-powered amplifier designed for home use (we used a 350-watts-per-channel amp without problems).
Normally, we recommend that a speaker be auditioned before purchase, preferably in your own home. Obviously, this is not possible in the case of the CSW Ensemble unless you have the opportunity to hear it at a friend’s home.
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