Dahlquist Acoustix System One Dynamic Array

      Date posted: February 24, 1998

Dahlquist Acoustix System One Dynamic Array

Size: Towers: 37″Hx 4″W x 10″D;
Centre: 22″W x 4″H x 6″D;
Subwoofer: 17″H x 10 1/2″W x 15 1/2″D
Sugg. Retail: $2299 (CAN)
Manufacturer: Audiosphere Technologies Corp.
25 Esna Park Drive, Markham, Ont. L3R 1C9
(905) 474-1843
FAX 474-9812
(Reprinted from the Winter 1998 Audio Ideas Guide)

      This stylish home theatre speaker struck me visually more as a kind of art deco skyline than as a bunch of speakers. When setting up the shot (at right) I had mental visions of Chicago, or the Manhattan Trade Centre towers, and the photographer, conveniently, had a kind of Botticelli or Turner canvas sky for background. It’s definitely a winter sky.

      As speakers, the 4 identical towers share a diminutive footprint and very narrow baffle, and all share the same drivers, a fabric dome tweeter, and 3 3 1/2″ cones for bass and midrange; the centre speaker is similarly slim laterally, with 4 of the 3 1/2″ drivers flanking the same tweeter. All of these are designed to operate down to a lower limit of 80 Hz. They are front-ported, but the real bass is reproduced by the subwoofer.

      That sub is also a ported design, a quite compact cube with its 8″ driver on the front and port and amplifier at rear. The driver has a “polypropylene injection-moulded cone with butyl rubber surround.” The amplifier is a “discrete mosfet output stage Class AB operation” type with a “Thermally compensated bias network” and “driver compensated EQ circuitry.” It turns on and off automatically via a signal sensor, or can be left on continuously. Amplifier power is rated at 100 watts rms, with 400 watt peak capability.

      The Low Pass crossover is adjustable from 40 to 150 Hz, but with this system’s limited bass from all other speakers, should be set quite high, something I’ll explore further below. The High Pass is fixed, all frequencies below 120 Hz kept out of the main speakers. A Video toggle switch introduces low end boost, which is also worthy of further comment below, while a second toggle reverses phase.

      This system has some inherent advantages not always seen even in matched home theatre systems. With identical drivers all around, it should have exceptional timbre matching of all channels. An extra midrange in the centre should provide a little additional intelligibility from dialogue, and the tweeter height should match most big screen TVs’ picture for good audio-to-video correlation. There’s been some careful ergonomic and industrial design put into this product to make it elegantly unobtrusive and operationally user friendly. Frequency Response

      Looking at the measurements, we can also see some serious technical design effort, the responses of sub and towers seen in the top graph at left. Except for a dip in the midrange, the Pink Noise Sweep and Summed Axial response curves overlay each other closely, as do the axial curves below, indicating good dispersion to 30 degrees, where output is a little lower, with a midrange suckout; this may be a good thing because these speakers will be less likely to interact with side walls. The quasi-anechoic measurement shows the same crossover artifact, but in the important lower midrange and upper bass, response is exceptionally smooth.

      Rolloff begins at 300 Hz, hence the need for the subwoofer’s upper crossover to be set quite high; it can be seen that the 150-Hz position provides a nice dovetail with the tower’s response. The subwoofer is here +/-3 dB from 30 to 100 Hz with the Video boost on; when it’s defeated we see the more mountainous curve just below, which is +/-2 dB from 40 to 100 Hz. The Video switch not only extends bass, but also increases its level by 5 dB from 100 Hz down. Looking at the half- and minimum-rotation sub measurements below (also done with the Video boost on for flattest response), we can see that the greatest deep bass extension comes at the half-rotation setting, a remarkable +/-1 dB from below 30 Hz to 70 Hz. It’s an irony that the best audio performance of the sub occurs in the Video setting. At bottom is the minimum setting with Video boost on, which provides a concentration of energy around 30 Hz. Clearly, this subwoofer (also sold separately as the PDQ-100 at $499 sugg. retail) is more versatile than necessary for this system, and can serve well also in a budget audio system. In my view, its best setup for this system is full-rotation/Video boost as seen at top. Centre Channel Frequency Response

      That seemed to be confirmed in listening tests, but before getting to that, a look at the centre channel’s measurements. Though its driver complement is the same except for an additional bass/midrange, they are on their sides relative to the towers, so what interactions there are vertically between tower drivers will be lateral on the centre channel and affect off-axis listeners.

      Though the crossover dip on axis seems extreme, especially in the quasi-anechoic curve, it actually makes some sense for the centred listener, and can be seen to be compensated for in the 15 and 30 degree curves in the axial measurements by a bump in the same region. That’s why the Pink Noise Sweep and Summed Axial Responses look quite different in this area: while the former reflects the overall energy radiated into the room, the latter simply adds the axial responses together; this gives the on-axis dip a disproportionate weight in the summed curve. To determine the actual listener audibility of this dip (which could simply be lobing among drivers at the 1-metre measuring distance), I did a PNS measurement at 2 metres, that seen bottom; this shows good midrange smoothness, with a little extra energy above, which could be heard in listening as a slight brightness, and even some extra intelligibility of speech and narration. Off axis, dialogue remains firmly centred. The response of this speaker is indeed tailored somewhat, but I would say it is done in a positive manner. Tower Impedence Curves

      And just before discussing the sound of the Dynamic Array system, a few words about the impedance/phase curves. The impedance of the tower is very linear, though somewhat high, ranging between 15 and 25 ohms over most of the range, dropping to 8 above 10 kHz. Electrical phase is extremely smooth, suggesting both an easy load for even budget A/V receivers (though this system deserves better), and the prospect of very coherent sound with excellent imaging. The curves for the centre channel show higher impedance in the midrange, and greater phase shift, but again, values are in a range which will pose no difficulty for any amplifier. Centre Channel Impedence Curves

      Listening to the system as a whole, I heard seamless integration in all 5 channels, and excellent reproduction of ambient and discrete surround effects. The tonal balance in all quarters is maintained very well, this enhancing the realism considerably. The system did image very well, too, with a fine sense of depth in all planes. This is a benefit of the near absence of front baffles and resulting diffraction in the horizontal plane; these tweeters operate largely as point sources, and image like they should, while the multiple midrange drivers provide line-source energy as well.

      The subwoofer worked well with the system, though with discrete Dolby Digital both speaker-in and line-in connections will be required for DVD use to accommodate the special LFE output.

      In general, I liked the tonal balance of this system. It was never aggressive, but clean and clear to quite high levels, with bass that held up to 30 Hz, something you wouldn’t expect from the compact subwoofer and speakers this size and shape.

      It’s also very unobtrusively handsome with its black vinyl finish. I think Dahlquist has a real winner for real living rooms in the Acoustix System One Dynamic Array home theatre package.

Andrew Marshall

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