MB Quart Quart Three Floor standing speakers
The products of MB Quart, a major German loudspeaker manufacturer, have been well received in the United States since their introduction here a number of years ago. The Quart Three, a recent addition to the company's line, is assembled in the United States using components made in both North America and Germany.
The Quart Three is a floor-standing columnar loudspeaker with two 6-inch woofers. One is at the top of the speaker panel, with a 1-inch metal-dome tweeter immediately below it. The other woofer is just below the midpoint of the panel, with a vent opening below it.
The installation instructions supplied with the Quart Three (and the smaller Quart Two and Quart One) are minimal, consisting only of general placement suggestions. The only technical information furnished is on a label affixed to the bottom of the speaker cabinet, which indicates a rated impedance of 4 ohms, a power-handling capacity of 90 watts (170 watts of music program), and a frequency range of 33 Hz to 32 kHz.
The input terminals, recessed into the bottom of the enclosure, are gold-plated binding posts, but they're spaced too widely for use with dual banana plugs (they will accept single banana plugs, however). A clearance gap is provided for the connecting wires, though it is not large enough to pass most specialty speaker cables other than flat ones.
Our initial measurements indicated somewhat unusual impedance and response characteristics, which led us to make separate frequency-response measurements of the two woofers. Those revealed that the upper cone had an effective range from well below 100 Hz to at least 2 kHz. Its response fell off at a steady 12 dB per octave below 100 Hz, indicating that it was operating in a sealed enclosure. The output of the lower cone, on the other hand, reached its maximum at 100 Hz and rolled off both above and below that frequency. A response null at 36 Hz showed that this driver was operating in conjunction with the vent, whose output augments that of the cone below about 50 or 60 Hz.
The room-response curve had the usual (and unavoidable) fluctuations in the midrange but was extraordinarily flat between 2 and 11 kHz (roughly +/-0.5 dB over that range). When we joined the room response with the combined close-miked responses from both cones and the port, the resulting curve was within +/- 2.5 dB from 40 Hz to 20 kHz, with the output slightly emphasized from 100 to 200 Hz and at about 13 kHz, where there was a small tweeter-resonance peak. A slight level change at about 2 kHz suggested that the crossover from the upper woofer to the tweeter was in that vicinity. A group-delay measurement showing a pronounced jog at 2 kHz reinforced that conclusion.
Quasi-anechoic MLS measurements confirmed the remarkable flatness of the Quart Three's response. At middle and high frequencies, where it is possible to effectively exclude room reflections from the measurement, the on-axis response was within +/-1.5 dB from 500 Hz to 17 kHz. The tweeter's high-frequency dispersion was also excellent, with less than 2 dB drop in output at 6 kHz measured 45 degrees off its central axis, increasing to 3.5 dB at 10 kHz and just 7.5 dB at 20 kHz.
The system impedance remained between 3.5 and 7 ohms from 20 Hz to 20 kHz except for a rise to 11.5 ohms at 70 Hz. Sensitivity was high, 93 dB sound-pressure level (SPL) at 1 meter with a 2.83-volt input of pink noise. At 2 volts (corresponding to a 90-dB reference SPL), distortion remained between 0.7 and 2 percent from 2 kHz down to 45 Hz, increasing to about 9 percent at 30 Hz. In single-cycle burst tests, the Quart Three absorbed the full output of the amplifier (1,240 watts) at 1 and 10 kHz without damage or significant distortion. At 100 Hz, however, the woofers began to sound slightly "hard" at about 30 watts input, bottoming audibly at 280 watts.
The Quart Three's measured performance essentially confirmed the manufacturer's somewhat sparse specifications. This moderately priced speaker not only had one of the flattest overall response characteristics that we have measured, but combined that with bass extension rarely found in its price range. Organ pedal notes were reproduced at useful levels down to the 30-Hz region. At the other end of the spectrum, the tweeter (which has what appears to be a diffusing plate in front of its dome) had unusually wide angular dispersion at the highest audio frequencies. Together with considerably higher than average sensitivity, these qualities make the Quart Three a strong contender in its price class.
