Jamo Compact 120 Speaker System Review

Jamo’s Compact series of speakers is intended for applications where a large or distinctive-looking loudspeaker might seem intrusive or clash with the room decor. Although the Compact series will probably not appeal to ardent audiophiles (and it was not intended to do so), the speakers give a considerable measure of sound quality for their size and price.

At present, there are four models in the Jamo Compact series, from the subminiature Compact 50 to the bookshelf-size Compact 120. The Compact 120 is a three-way system whose 8-inch woofer operates in a ported enclosure. The first crossover, at 1,200 Hz, is to a 5-inch cone driver, and at 5,000 Hz there is a second crossover to a 1-inch dome tweeter. The tweeter is loaded by a short exponential horn whose mouth is 3 inches in diameter. The model name derives from the speaker’s rated power-handling ability—120 watts into its nominal 4- to 8-ohm impedance. The system’s sensitivity is rated as 92 dB sound-pressure level (SPL) at 1 meter with a 1-watt input. Its rated frequency range is 38 to 20,000 Hz, with an unspecified variation.

The speaker’s wooden cabinet is 16-1/2 inches high, 10-1/4 inches wide, and 8-3/4 inches deep. Each speaker weighs 14 pounds, 5 ounces. The molded-piastic front panel is barely large enough to contain the three drivers. The two cones are protected by fixed perforated-metal grilles, and the tweeter diaphragm is located out of harm’s way at the throat of its horn, more than an inch behind the panel. The woofer port is on the rear of the cabinet, which also has fittings to adapt it for wall mounting. The Compact 120 is available in a black or white finish. Price: $320 a pair.

Lab Tests

The room response of the Jamo Compact 120 speakers was generally smooth. Their output level decreased smoothly with frequency, dropping 5 dB between 300 and 10.000 Hz. There were the usual minor irregularities in the averaged response curve from the two speakers, but none of them deviated by more than a couple of decibels from a straight line joining the two end frequencies.

The woofer’s response, measured separately at the cone and the port and combined after correction for their relative diameters, peaked at 120 Hz and fell off at 6 dB per octave below and above that frequency. It leveled off at about 400 Hz, splicing smoothly to the room curve. The maximum output in the resulting composite frequency response was at 120 Hz, where it was about 5 dB higher than the level of the adjacent midrange portion of the curve. Overall, the system response varied ±6 dB from 26 to 19.000 Hz.

The minimum system impedance was 6 ohms at 200 Hz, and its maximum of 21 ohms occurred at 1,500 Hz. The impedance averaged between 6 and 8 ohms, and it never reached the 4-ohm minimum of the published rating. The measured sensitivity was 92 dB SPL, as rated.

When we drove the speaker with 2.25 volts (equivalent to a 90-dB SPL in our sensitivity test), the bass distortion measured 1.4 to 1.9 percent from 100 Hz down to 80 Hz and rose smoothly with decreasing frequency to only 4 percent at 40 Hz and 6.2 percent at 30 Hz. These figures were obtained from close-miked measurements at the port, which radiates most of the speaker’s output below 100 Hz.

Quasi-anechoic FFT frequency-response measurements showed that the speaker’s horizontal coverage was somewhat restricted. Frequency-response curves made on-axis and 45 degrees off-axis diverged above 500 Hz and were 6 to 10 dB apart over most of the audio range on one side of the speaker’s axis, but only between 3,000 and 6,000 Hz on the other side. The tweeter and midrange driver are placed side by side, which virtually insures some cancellation effects in the horizontal plane as well as the observed off-axis asymmetry.

The axial response showed narrow peaks of 5 or 6 dB at approximately 5,000 and 8,000 Hz. At some angles there were deep cancellations, or combinations of holes and peaks, at these frequencies, and most of the time there was a hole at 8,000 Hz. Since these effects occurred only in a few narrow frequency bands and at specific angles, they did not show up in the room response, which measures essentially the total output of the speaker in many directions.

A three-dimensional or “waterfall” plot of the speaker’s response, displaying the interrelations of time, frequency, and amplitude, clearly showed four distinct resonances—at approximately 5,000, 8,000, 14,000, and 18,000 Hz— which “rang” for several milliseconds after being excited. Although none of these resonances were evident in the room-response measurements, and the two highest ones would probably not be excited by most program material or be audible to most people, they were real and, we think, accounted for much of what we heard from the Compact 120 system.

In spite of the resonances, the Compact 120 had generally good group-delay characteristics. Except for narrow deviations at 8,000 and 18,000 Hz, the group delay was constant within 0.4 millisecond from 360 to 22,000 Hz. A separate low-frequency measurement showed a delay variation of 6 or 7 milliseconds from 100 to 1,000 Hz.

The speaker was able to handle large pulse-power inputs without distortion or damage. At 100 Hz, the woofer emitted a slight rattle at 220 watts into its 9-ohm impedance. At 1,000 Hz the amplifier clipped at 500 watts into 14.5 ohms with no sign of distortion from the midrange driver, and at 10,000 Hz the tweeter absorbed 825 watts (into its 8-ohm impedance) without difficulty before the amplifier clipped.

Comments

The Jamo Compact 120 had a surprisingly good subjective bass response. Initially we placed the speakers against a wall (“bookshelf’ mounting), and although we expected a slightly “thin” sound because of their size, the overall balance was good. The speakers were obviously much more sensitive than the others in our listening array at the time. Our early impression was of a rather good, listenable sound that seemed consistent with the size of the speakers.

More extended listening revealed an occasional tendency toward hardness, or a somewhat “forward” and strident sound in the treble and upper midrange. Tone controls were not very effective in correcting for this effect. These experiences, before we had made any measurements on the speakers, led us to expect a peaked, or emphasized, treble response. Our measurements, however, showed quite the opposite characteristic.

Some of those measurements suggested a possible explanation for this seeming inconsistency. The combination of several resonances—and, perhaps, the skewed polar pattern—appears to give these speakers their distinctive sound character. Also, much of our later listening was done with the speakers on pedestals, several feet from a wall. Although such a placement is usually beneficial (and frequently required) for speakers of this size, it did not improve the sound or imaging qualities of the Compact 120’s. In fact, it seemed to emphasize their treble hardness, possibly because the lower frequencies are not augmented in a free-standing installation compared with wall or shelf mounting.

An illustrated Jamo brochure describing the Compact speakers leaves no doubt that they are meant for shelf or wall mounting, although they should probably be at least a couple of inches from the wall for the bass port to function properly. It is also plain from our experience, as well as the manufacturer’s literature, that the speakers are not aimed at the typical hi-fi enthusiast but at a much broader market. Their very high sensitivity, small size, and attractive styling should make them a logical choice for improving the sound of TV sets, for example, as well as for less demanding audio applications. While their sound is not the equal of many high-quality speakers, it is unquestionably superior to that of the mass-market “hi-fi” units sold in department stores. Furthermore, as we verified when listening to CD’s having exceptional dynamic range, these speakers can handle very large program peaks without audible compression or distortion.

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