KEF Model 102 Speaker System Review

The Model 102 from KEF, one of the company’s Reference Series loudspeakers, is a very compact two-way system with exceptional bass response for its size, which is close to minispeaker proportions. Its 6-inch Bextrene-cone woofer operates in a sealed enclosure, and the high frequencies are channeled to a 1-inch soft-dome tweeter. The walnut-finished wood cabinet is extremely rigid, and even the black cloth grille is stretched on a solid wood plate that is retained by plastic fasteners.

The frequency response of the KEF 102, at 2 meters distance on axis, is rated as 65 to 20,000 Hz ±2 dB and as down only 6 dB at 40 Hz. It is also rated to deliver a sound-pressure level (SPL) of 107 dB on program peaks under typical listening conditions. These figures are indeed impressive for a speaker that measures only 13 inches high, 8V4 inches wide, and IOV4 inches deep and weighs a mere 15 pounds.

The bass performance of the system is obtained by using a separate active (electronic) equalizer, the KUBE (KEF Universal Bass Equalizer), that boosts the bass drive signal by 5 to 6 dB below about 40 Hz while reducing the midrange drive signal in the 2,000-Hz region by about 5 dB. The KUBE Model 2088 supplied with the KEF 102 speakers is meant to be inserted in an amplifier or receiver tape-monitor loop or between a preamplifier and power amplifier. It has a set of tape input and output jacks and a monitor switch to replace those required for its connection to the amplifier.

Pushing in the extend button of the KUBE inserts an additional bass boost that complements the speaker’s natural rolloff in the bass region and gives it a nearly flat response to 40 Hz. Another control, marked contour, shifts the level of the entire bass range (below about 200 Hz) up or down as much as 3 dB to balance the low-frequency sound against the midrange level. The contour circuit operates independently of the extend control.

The rated sensitivity of the model 102 under anechoic conditions is 92 dB spl at 1 meter with a pink-noise input of 2.83 volts. Its nominal impedance is 4 ohms, and it is suitable for use with amplifiers capable of delivering between 50 and 200 watts into that load. KEF’s computer-designed passive crossover maintains a nearly resistive impedance over most of the audio range, making the Model 102 an “easy” system to drive.

The KEF Model 102, including its KUBE equalizer, is priced at $790 a pair.

Lab Tests

Although they are designed to be suitable for wall mounting, we placed the KEF 102 speakers on stands about 25 inches high and a couple of feet from any room wall. All our response measurements were made through the KUBE, whose frequency response we also measured separately.

In its normal setting, the KUBE boosts the drive signal at 20 Hz by about 10 dB relative to the average midrange level, and the boost increases to 18 dB in the extend setting. These figures must be kept in mind when using the KEF 102 speaker system, since almost any amplifier can be driven into clipping by this much bass boost if the playing volume is too high, and permanent damage to the speakers could result.

The averaged room response from the left and right speakers was unusually smooth and flat, varying only ±2.5 dB from 450 to 20,000 Hz. The directivity of the tweeters became significant only above 10,000 Hz. The close-miked woofer response reached its maximum in the 200- to 300-Hz range, falling smoothly by about 7 dB from 300 to 2.000 Hz. From 200 to 45 Hz, the output fell at 12 dB per octave in the normal mode and at 6 dB per octave in the extended mode. In both modes, it dropped off at 18 dB per octave below 45 Hz. The sharp cutoff of output above 2,500 Hz suggests that the crossover to the tweeter takes place close to that frequency, although the speaker’s specifications do not list the crossover frequency.

The composite frequency response, obtained by splicing the woofer curve to the room-response curve, was flat within ±2.5 dB from 450 to 20,000 Hz, or within ±3.5 dB from 40 to 20,000 Hz in the extended mode and from 80 to 20.000 Hz in the normal mode. The system’s impedance was 3.5 to 4 ohms from 300 to 20,000 Hz, with a maximum of 19 ohms at 85 Hz and a bass minimum of 5.8 ohms at 43 Hz. The linearity of the speaker’s phase shift was demonstrated by its above-average group-delay variation, only ±0.1 millisecond from 500 to 29,000 Hz.

The system’s measured sensitivity was 86 dB SPL at 1 meter with 2.83 volts of pink noise (through the KUBE in its normal setting). Bass distortion was measured with a constant input to the KUBE equivalent to a 90-dB SPL at 1,000 Hz. This input resulted in a very large drive signal at lower frequencies, which was reflected in the distortion readings: 2.5 to 5 percent from 100 Hz down to about 60 Hz but climbing steeply at lower frequencies where the equalizing boost increased rapidly. A 10 percent distortion reading was obtained at 41 Hz (normal) or 45 Hz (extended).

In our pulse-power tests (made without the KUBE), the woofer rattled audibly at 57 watts into its 14-ohm impedance at 100 Hz. At 1,000 Hz, our amplifier clipped at 1,600 watts into the woofer’s 3.6-ohm impedance at that frequency, before the speaker displayed any signs of distress. There was a similar result at 10,000 Hz, where the amplifier clipped at 1,560 watts without significant distortion from the dome tweeter.

Comments

Listening to the KEF 102 system, we quickly became aware of its smooth, easy sound—rarely experienced from speakers of its size, though it should be expected from speakers in its price class. The bass was not at all thin; in fact, the speakers had a tendency to sound “warm,” imparting an audible but not objectionable upper-bass boost to most voices. For the most part, however, the sound quality was as neutral as we have come to expect from KEF. The Model 102 even displayed some of the same minor colorations as the KEF 105.2 system we have used for years as our reference speaker.

An A/B comparison left no doubt of the close kinship between the Model 102 and the 105.2, which sells for about three times its price. The two have virtually identical sensitivities and, at least in our room, sound so much alike that in most cases only spatial clues enabled us to distinguish between them when switching back and forth.

It was not too surprising to find the Model 102 even better than the 105.2 in its high-frequency dispersion—its smaller, improved dome tweeter can take the credit for this. At modest listening levels, or when the program did not have unusual amounts of low-bass energy, there was virtually no difference between them. But when there was some high-level bass content, such as the drums in Stravinsky’s Rite of Spring, the physical limitations of the Model 102’s small cone became very audible (as they did in our pulse-power tests). This limitation is especially evident when using the extended-bass mode, which is unfortunately at its best when high-level bass is not present.

The KEF 102 is not a miracle, nor is it claimed to be. On the other hand, it can match or surpass the overall sound quality of many full-sized speakers, including some priced well above its range. It is not a “flashy” speaker, it does not have sizzling highs or room-shaking bass, but it is one of the most balanced-sounding speakers you are likely to find. If you have been attracted to one of the larger KEF Reference Series speaker systems but find its cost beyond your budget, listen to the Model 102. It might be just what you’re looking for.

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