B&W DM305 Speaker System Review
B&W Loudspeakers, which was headed for many years by its cofounder, the late John Bowers, has earned an enviable reputation for high-quality loudspeakers spanning a wide range of sizes and prices. The new DM305 is a relatively small and affordable two-way tower speaker whose performance belies its size, weight, and cost. At the top of the enclosure, 31 inches above the floor, is a ferrofluid-cooled 1-inch soft-dome tweeter that crosses over at 3 kHz to a 6-1/2-inch cone woofer located just below it. The center of the woofer cone has a rigid conical dome, and both drivers are normally concealed by a removable plastic-framed grille.
The woofer's enclosure occupies the entire lower half of the cabinet. In addition to a conventional circular bass duct whose vent is on the rear of the cabinet, there is also a narrow ducted vent across the front of the cabinet below the woofer.
The rear of the cabinet presents an unusual appearance. It resembles an egg-crate, with more than fifty square openings. At the center are the input connectors. The manufacturer states that this patented "Prism System," designed to mimic the interior of an anechoic chamber, helps to break up the internal cabinet volume, which might otherwise support internal standing waves.
The input connectors are two sets of recessed binding posts, normally paralleled by removable metal jumpers. They allow the system to be biwired or biamplified, and apparently they are designed for use only with stripped wire ends, which must be passed through holes in the posts and then screwed down; dual banana plugs cannot be used, and even single plugs are extremely awkward to install because of the limited visibility and finger access to the connections.
Because the DM305 is a floor-standing system, it is not magnetically shielded. This should pose no problems in A/V installations, since the speakers should be placed at least a foot or so from a TV between them. Our measurement of the external magnetic-field strength at 4 inches from the front panel of the speaker showed a safe flux level of less than 2 gauss, indicating that the DM305s could be placed fairly close to a TV if necessary.
The system's impedance is rated at 8 ohms (nominal) or 4.2 ohms (minimum). We measured a maximum of 26 ohms at 65 Hz and a minimum of just over 4 ohms at 1.8 kHz. The measured sensitivity was a respectable 90 dB sound-pressure level (SPL) at 1 meter with a 2.83-volt input (rated 91 dB).
The averaged room response of the left and right speakers, placed 8 feet apart and a couple of feet in front of a wall, was an excellent ±3.5 dB from 50 Hz to 15 kHz. In quasi-anechoic (MLS) response measurements at distances of 1, 2, and 3 meters from the microphone, the response was (possibly coincidentally) also ±3.5 dB from 300 Hz to 15 kHz.
It is worth noting that the manufacturer's specifications for the speaker are reasonable and believable, in contrast to the somewhat optimistic ratings we encounter on occasion. As an example, the DM305's frequency response on-axis is given as 55 Hz to 20 kHz ±3 dB, which was essentially confirmed by our room-response measurement though it was made under very different (and nonstandard) conditions.
Unlike a tower system with either a built-in powered subwoofer or one or two large woofers, the B&W DM305 generates its entire bass output with a single unaided 6-1/2-inch driver - and with impressive results. In spite of this, our close-miked measurement of the woofer output, combining the outputs of separate microphones at the woofer cone and at the rear vent, showed a response variation of only ±3 dB between 40 and 150 Hz.
Except for its Prism System bass enclosure, the identifiable design features of the B&W DM305 seem quite conventional. Nevertheless, there appears to be considerably more to this loudspeaker than can be inferred from its plain exterior and modest price - in fact, it must be inferred, since the manual is surprisingly reticent about technical details of its design. However, the speaker's specifications are presented in considerable detail and, judging from our experience, with considerable conservatism.