Dahlquist DQM-3 Speaker System Review

The Dahlquist DQM-3 is a compact two-way speaker system with an 8-inch acoustic-suspension woofer that has a flat-wound ribbon-wire voice coil and a polyvinyl-acetate cone. The sealed enclosure’s outside dimensions are 17-3/4 inches high, 11-3/4 inches wide, and 10-3/4 inches deep; it weighs 34 pounds. There is a crossover at 2,000 Hz to a 1-inch dome tweeter. The system impedance is rated at 8 ohms, with a 5-ohm minimum. Its sensitivity is specified as 90 dB sound-pres-sure level (SPL) at 1 meter when driven by 1 watt at 1,000 Hz. The DQM-3 is recommended for use with amplifiers rated to deliver between 20 and 100 watts per channel. Its nominal frequency response is 50 to 20,000 Hz, with no tolerances stated.

The cabinet is made of a laminated multilayer particle board identical to that used on Dahlquist’s larger DQM series speakers. This material, imported from West Germany, is said to reduce cabinet-panel resonance effects compared with more conventional particle boards. The front baffle board is covered with Nextel, a felt-like flocking material, to reduce high-frequency diffraction effects. The black cloth grille is retained by plastic snaps that hold its wooden frame about 1/4 inch away from the baffle surface. The vertically aligned drivers are located slightly to the left of the center of the speaker board. Available cabinet finishes are either walnut-grain vinyl veneer or gray Nextel.

The DQM-3 has no user-adjustable controls. Inset into the rear of the cabinet are a pair of heavy-duty five-way binding posts and two fuse holders. The entire system uses a 2-ampere fuse, and the tweeter is separately protected by an additional 0.8-ampere fuse. Price per speaker: $200 with the walnut-vinyl finish, $225 with the Nextel finish.

Laboratory Measurements

The close-miked woofer response of the DQM-3 reached its maximum at 75 to 80 Hz, falling 12 dB per octave at lower frequencies. The woofer output also dropped off, though at a much lower rate, with increasing frequency. The averaged room response from the two speakers was quite uniform in the upper-middle and high-frequency ranges, with a 5-dB overall variation between 750 and 20,000 Hz. Splicing this curve to the woofer curve resulted in a composite frequency-response curve that was flat within ±3.5 dB from 200 to 20,000 Hz but nearly 10 dB above the midrange average at its 80-Hz maximum level.

The general contour and smoothness of the middle- and high-frequency response was confirmed by quasi-anechoic response measurements made with our IQS FFT analysis system. In fact, the axial response was an excellent ±1.5 dB from below 1,000 Hz to about 22,000 Hz. Unfortunately, even the IQS system does not permit a true low-bass response measurement to be made in a room of normal size (except with the close microphone spacing used for our sweeping sine-wave low-frequency response measurement), so we could not use it to confirm the validity of our curve-splicing technique.

The system impedance hit a minimum of about 4 ohms at 20 and 130 Hz, with a peak of 10 ohms at the bass resonance of 80 Hz. It typically measured between 8 and 20 ohms in the 700- to 20,000-Hz range. We would classify the DQM-3 as a 4-ohm system based on these measurements. The system sensitivity was lower than rated, with a measured output of 85 dB at 1 meter with 2.83 volts of band-limited pink noise. Using the data to determine the drive level that would give a 90-dB SPL at 1,000 Hz, which was 5 volts, we drove the speaker at that level from 100 Hz down to measure the woofer distortion. The system’s distortion measured only 1 to 2 per cent from 100 to 60 Hz, rising to 4 per cent at 50 Hz and to 9.5 per cent at 40 Hz.

The system’s group delay was constant within ±0.1 millisecond over the upper part of the tweeter’s range (9 to 20 kHz) and varied within 0.5 millisecond overall through the lower part of the range. The tweeter’s dispersion was excellent, with less than 6 dB difference between the 0-degree (axial) and 30-degree response at any frequency up to 20,000 Hz.

Comment

Placed against the wall about 28 inches off the floor, the Dahlquist DQM-3 had a pleasant sound, with no hint of the measured 80-Hz bass peak. No doubt this was due, at least in part, to the low frequency of the bass rise. There is little energy in most music or voice sounds, in the range of this peak. It is more common to find speakers having a bass emphasis an octave higher than this (around 100 to 200 Hz), where it imparts an unmistakable coloration to male voices. This effect was notably absent in the sound of the DQM-3’s, which instead had a balanced, wide-range response with clean, well-dispersed highs and an uncolored midrange.

The speaker’s low measured sensitivity was obviously genuine, as was demonstrated by A/B comparisons with other speakers of similar or higher rated sensitivities. The DQM-3 is certainly not a low-efficiency speaker, but we would advise using it with amplifiers nearer the upper end of its recommended power range than with those in the 20-watt category. For our tests we used amplifiers in the 100- to 200-watt range, and the DQM-3’s always sounded fine at any level we cared to play them. (Since we never blew one of the speaker fuses, we cannot judge how much protection they offer, but fusing is always a desirable protection for any speaker that does not have a more sophisticated protection system.)

Considering the very modest price and dimensions of the Dahlquist DQM-3 together with its thoroughly musical and pleasing sound, we have no hesitation in recommending it for use in any moderate-priced music system.

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