The well-known German speaker manufacturer MB Quart recently introduced its lowest-priced product to date, the Quart One, which is assembled in the United States using German and North American components. A small, two-way bookshelf speaker, the Quart One has a 6-1/2-inch woofer with a butyl-rubber surround that crosses over at 2,800 Hz to a 1-inch titanium-dome tweeter. A seven-element crossover network cuts off the woofer's response at 12 dB per octave and the tweeter’s response at 18 dB per octave.
Nominal impedance is 4 ohms, and the bandwidth is given as 49 to 32,000 Hz. Rated sensitivity is 88 dB sound-pressure level (SPL) at 1 meter with an input of 2.83 volts, and the power-handling rating is 60 watts.
The black cabinet, constructed of 3/4-inch high-density particle board, has injection-molded top and bottom plates and a removable black cloth grille. The woofer operates in a bass-reflex enclosure.
We placed the Quart Ones on 26-inch stands for our room-response measurements, with the microphone on the axis of the left speaker and about 12 feet away from it. The response was unusually smooth and uniform, with very small differences between the left and right curves from 400 to 20,000 Hz. Floor reflections and other room-boundary effects introduced some irregularity between 400 and 150 Hz.
A separate, close-miked measurement of the woofer-cone and port outputs produced a somewhat optimistic picture of the speaker’s bass performance (combining port and cone outputs often exaggerates a low-frequency response curve). The best splice we could make between the bass and room-response curves made the Quart One’s useful output appear to extend to below 30 Hz, which our ears and other measurements contradicted.
Response measurements at 1 meter with an input of one-third-octave random noise, stepping through the audio range, showed a relatively uniform output from 20,000 Hz down to about 60 Hz, with a variation of less than ±4 dB over that range. Horizontal dispersion was very good; the difference in output on-axis and 45 degrees off-axis was only 4 dB at 10,000 Hz and 8 dB at 20.000 Hz.
Quasi-anechoic response measurements at 1 and 2 meters also showed about a ±4-dB variation from 300 to 20.000 Hz. There was a drop of 4 dB between 2,000 and 3,000 Hz (the crossover region), a return to midrange levels between 4,000 and 6,000 Hz in a smooth 8-dB rise, and an almost perfectly flat output from 8,000 to 20,000 Hz. Group delay (an indication of phase linearity) varied only about 150 microseconds overall in the tweeter range of 3,000 to 19,000 Hz, and even through most of the woofer range the total delay shift did not exceed 700 microseconds.
The Quart One’s impedance curve showed minimum readings of 3.1 ohms at 180 Hz and 3.4 ohms at 50 Hz. Impedance rose to 11 ohms at the two bass resonances of 24 and 90 Hz and to 17 ohms at 1,900 Hz. It exceeded the 4-ohm rating over most of the range.
Sensitivity was 89 dB, slightly better than rated, and with an input of 3.17 volts (equivalent to a 90-dB SPL) the woofer distortion was between 0.5 and 1 percent at frequencies in the range of 100 to 2,000 Hz, averaging about 0.7 percent. At low frequencies the distortion increased smoothly to 4 percent at 50 Hz and 7.5 percent at 40 Hz.
The Quart One was able to handle a healthy power input without serious distortion or damage in our single-cycle tone-burst tests. The woofer cone reached its 100-Hz excursion limits at 330 watts, where the sound became noticeably hard. At higher frequencies, the limiting factor was our amplifier, which clipped at outputs of 700 to 1,100 watts without any prior signs of overload from the speaker.
The Quart One was as listenable as its measurements would imply. Its sound was balanced and uncolored, without artificial upper-bass boom. The highs were crisp but not at all shrill. In A/B comparisons with other small speakers, the Quart One sometimes had a bit more sparkle, possibly reflecting its slightly elevated output (about 5 dB) in the top octave.
The MB Quart One is more expensive than some other small speakers, but its sound is generally commensurate with its price. In side-by-side comparison with two similarly sized but somewhat lower priced models — the Signet SL250B/U ($300 a pair) and the Paradigm Titan ($199 a pair)—the Quart One delivered lower lows and higher highs. Based strictly on sound, I would rate it as the best of the three, and since the other two are excellent speakers in their own right, that makes the Quart One an outstanding performer in its class.
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