Cambridge SoundWorks Model 11 Music System Review

The Cambridge SoundWorks Model Eleven transportable component music system is a direct descendant of designer Henry Kloss’s KLH Model 11, which was very popular in the 1960’s. The original Model 11, advertised as a “stereo phonograph in a suitcase,” consisted of a four-speed record changer, a low-power stereo amplifier (7-1/2 watts per channel), and two detachable speakers. The amplifier had conventional bass, treble, and balance controls as well as a pair of auxiliary input jacks with a switch to select the desired source. The complete $199 system weighed 26 pounds, qualifying it as portable if not exactly a featherweight.

The KLH 11 made no claim to high-fidelity performance, although it was a very respectable “mid-fi” system for its time. Ideal for children’s rooms and college dormitories as well as a convenient portable music source, it was not only a successful product in its own right but also inspired a host of “compact” music systems from many other manufacturers. (Even KLH produced several variants designed for fixed use in a home.)

As Cambridge SoundWorks tells it, Henry Kloss wanted to enjoy good music while on a recent vacation. Although a portable CD player and a couple of small powered speakers could fit into a suitcase, the combination was not convenient to carry, set up, and repack for transportation. And its sound quality, which lacked the deep bass of a good home system, was also not good enough to satisfy a serious listener or to do justice to CD’s.

Kloss set out to design a portable system compatible with the sound quality and dynamics of today’s digitally recorded music. Noting that a pair of small powered speakers and a portable CD player together occupy about the same volume as an acoustic-suspension woofer enclosure, he designed a carrying case of an appropriate size. Called the Bass-Case, it measures 19-1/2x 16-1/2 x 6-1/4 inches and is made of a composite material with a 5/8-inch-thick rigid foam core and outer layers of high-strength, luggage-grade plastic.

The BassCase holds a single 7-inch, long-throw acoustic-suspension woofer. Internal struts and a transverse rib add strength and form an airtight seal when the case is closed with its four heavy-duty, toggle-locking latches. Internal damping is supplied by a soft foam chosen for its acoustic properties. The foam has cutouts for the system’s two satellite speakers, its miniature amplifier, and a personal CD player or radio/cassette player. The supplied cables (two 15-foot lengths for the satellites and a 20-foot length for the BassCase) wrap around the woofer’s magnet structure for transportation.

There is an electronic crossover from the woofer to the satellites at 150 Hz. Each satellite has a 3-inch midbass/midrange driver and a 3/4-inch copolymer-dome tweeter in a black abs plastic case with internal damping and stiffening. Dimensions are only 6-1/4 inches high, 4-1/4 inches wide, and 3-1/8 inches deep. The back of each case has a keyhole slot and a threaded insert for mounting on a wall or stand. The black metal grille is not removable.

A three-channel amplifier powers the woofer and the two satellites. The frequency response of each amplifier channel is shaped to optimize the performance of the speaker it drives. This reduces the number of parts needed in the passive crossover between drivers in the satellites (although, according to the specifications, it is still a complex ten-element design) and is said to elicit extended bass response from a more efficient woofer than would otherwise be possible for the same performance.

The amplifier measures 7 inches wide, 3 inches high, and 5-5/8 inches deep. Its total output is given as 36 watts, without specifying how this is divided among the speakers. The three high-level inputs (auxiliary, tape, and CD) are balanced within the amplifier for minimum noise pickup and are selected by a knob on the front panel. Other knobs control volume, balance, bass, and treble (the last three are center-detented). Slide switches control power and mono/stereo mode, and there is a red led pilot light.

As befits its portable status, the Model Eleven can operate from 115- or 230-volt AC power (50 or 60 Hz) or a 12-volt DC supply. The amplifier also provides a 9-volt DC output for a portable CD or tape player. The system includes a 12-volt adaptor to power it from an automobile cigarette lighter, a stereo mini-plug adaptor, and wall-mounting hardware for the satellites. The speaker cables are fitted with polarized plugs at one end and stripped wire ends at the other; once connected properly to the speakers, correct attachment to the amplifier is assured. The complete Model Eleven system, ready to carry, weighs about 23 pounds. Price: $749.

Lab Tests

We tested the Cambridge SoundWorks Model Eleven as a system, measuring from the amplifier input to the acoustic output of the speakers. The satellites were placed on 26-inch stands about 2 feet in front of the wall, with the BassCase on the floor midway between them. The system’s averaged room response was smooth, uniform, and strong down to below 70 Hz. The Bass-Case’s close-miked (anechoic-equivalent) response was within ±1.5 dB from 50 to 160 Hz, falling at about 24 dB per octave below that range and about 14 dB per octave above it. Splicing the curves produced a composite frequency response of ±3.5 dB from 45 to 20,000 Hz.

We checked the amplifier’s tone-control range by acoustic measurements of the system output at the extreme control settings. The range was approximately ± 10 to 11 dB at 100 Hz and +10, — 20 dB at 10,000 Hz. Although speaker impedances are accounted for in the design of the system and therefore need not be of any concern to the user, we thought it would be interesting to measure them anyway. The satellites had a minimum impedance between 3 and 4 ohms, with a peak of 17 ohms at 170 Hz. The BassCase’s impedance peak was 14 ohms at 60 Hz, and its minimum was 4.6 ohms at 150 Hz. Its impedance rose steadily above 200 Hz, indicating the use of a passive inductor to remove high-frequency signals from the woofer circuit.

Output from the 3-inch driver of one of the satellites was greatest at 200 Hz. The tweeter’s horizontal dispersion was excellent, typically exhibiting less than 6 dB difference between the on-axis response and the response 30 degrees off-axis all the way up to 20,000 Hz. The satellites had very good phase linearity, with less than 0.1 millisecond (ms) variation in group delay from 1,000 to 20,000 Hz except for a single 0.5-ms jog at 4,500 Hz, which appeared only on the speaker’s axis and apparently was associated with its cabinet dimensions.

The integration of amplifier and speakers prevented our usual sensitivity and power-handling tests. We did make distortion measurements on the BassCase output, however, using the onset of audible buzzing at 100 Hz as a criterion for maximum signal-handling ability. With the drive set just below the buzzing point, the woofer’s distortion varied between 6 and 14 percent from 20 to about 48 Hz, dropped to between 3 and 4 percent from 50 to 85 Hz, and sloped off at higher frequencies to 0.6 percent at the bass driver’s nominal 150-hz crossover frequency. Reducing the drive level by 10 dB (which still left a healthy bass output) cut the distortion to 7 percent at 20 Hz, 4 to 5 percent from 25 to 48 Hz, 1 percent at 80 Hz, and 0.5 percent from 125 to 200 Hz.

Comments

The best way to judge an integrated system such as the Cambridge SoundWorks Model Eleven is by using it, since many measurements of its individual components are either impractical or meaningless. We chose to operate the Model Eleven as we would on a vacation (without traveling, however). Aside from the extremely stiff BassCase latches, which for a while resisted our efforts to open them, the setup was easy and straightforward. The most convenient program source was an inexpensive portable radio/ tape player. Since we didn’t have a portable CD player on hand, we used a home CD player as our source of digital program material.

The results were highly satisfactory, rivaling the performance of our main system in many respects. Like some other good three-piece speaker systems, the Model Eleven gave no audible clues to the size or configuration of its components. The BassCase could not be located by ear, even though it was usually most convenient to place it behind one of the satellites, and its output was perfectly integrated with that of the satellites. The hum field above the amplifier made it necessary to place the portable unit a few inches away while it was playing a tape, but no other anomalies came to light.

The sound was smooth and full-range, with a tendency toward brightness. The upper bass was subjectively flat, resulting in a non-boomy reproduction of male voices, and the low end—down to about 40 Hz—was clean and ample enough to provide a solid footing for the sound of an orchestra. The maximum volume level was as impressive as its quality. This system can easily produce much louder undistorted sound levels than we care to use, making conversation practically impossible in the same room.

Like all Cambridge SoundWorks products, the Model Eleven is sold direct from the factory, with a thirty-day return privilege. It carries a five-year limited warranty; problems resulting from a manufacturing defect will be repaired free the first year and for no more than $25 over the next four years.

The obvious conceptual connection between the Cambridge SoundWorks Model Eleven and the KLH 11 inspired us to set up our long-retired KLH Model 11 and test it with the same procedures and instruments. The results showed dramatically how much progress has been made in the last twenty-seven years. The KLH unit sounded like the mid-fi compact system it was (and still is—it did not seem to have deteriorated over the years in storage). By no stretch of the imagination could it be described as a hi-fi component. The new Model Eleven, on the other hand, is a true high-fidelity component system. Today’s improved program sources sounded thin, confined, and really not very pleasant through the older system, whereas the Model Eleven could easily hold its own with modem component systems selling for many times its price and occupying even more times its space. True, the Model Eleven’s price is three times that of its predecessor, but inflation is responsible for most, if not all, of that apparent increase. And it is a lot more of a music system, no matter how you look at it.

Although the Model Eleven probably would not satisfy many audiophiles as a main system, it was not intended to. But for use in dens, dormitories, or other limited-space installations, and especially for travel, it has no equal for its combination of performance, value, and portability.

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