Definitive Technology DR7 Tower Floor standing speakers

The Definitive Technology DR7 loudspeaker system features the same styling and many of the technological features that were introduced in the company's first product, the BP10. The DR7, however, is somewhat smaller and considerably lower priced than the BP10 or its larger companion, the BP20. Also unlike them, it uses only conventionally forward-facing drivers.

The DR7 is a slender, columnshaped speaker that measures 38 inches high, 11-1/2 inches deep, and 8-1/2 inches wide. Like the BP10 and BP20, it is covered on four sides by a snugly fitting black cloth sleeve. The visible portions of the wooden base and the removable wooden top are finished in glossy black piano lacquer or golden oak. The input terminals-multiway binding posts that also accept single or double banana plugs-are on the bottom of the cabinet, whose base is slotted to clear the connecting cable.

The DR7 is a two-way vented system with a 6-inch woofer, a 1-inch ferrofluid-cooled tweeter, and a phase-coherent Linkwitz-Riley crossover network. The woofer is a little above the center of the front panel, the tweeter near the top, and the woofer port near the bottom. The manufacturer describes the system as having "computer-synthesized transmission-line tuning" for extended bass response. Its internally braced cabinet has special foam damping pads and 1-inch-thick Medite front and rear panels with rounded corners. In combination with the flush-mounted drivers and frameless "sock" grille, these features minimize cabinet resonances and diffraction.

The woofer is constructed with a cast-magnesium basket designed to have the largest possible open area behind the cone. Its butyl-rubber surround and dust cap are said to combine durability with a very low free-air resonance, a long maximum cone excursion, and effective damping of midrange energy in the cone.

The Definitive Technology DR7's specifications include a bandwidth of 22 to 28,000 Hz, a sensitivity of 90 dB, and a nominal impedance of 6 ohms. It is recommended for use with amplifiers rated between 20 and 200 watts per channel. Price: $750 a pair.

Lab Tests

The DR7's room response was exceptionally flat, varying only ±5 dB from 60 to 20,000 Hz before any corrections were applied. A close-miked woofer response, combined with the port output, varied only ±4 dB from 30 to 2,000 Hz and overlapped the room curve for more than two octaves to create a composite response curve flat within ±3 dB from 32 to 20,000 Hz. A separate response curve with the microphone 1 meter from the speaker, using a swept one-third-octave random-noise test signal, gave similar overall results, although many of the variations in output across the spectrum did not coincide with those in the composite curve.

We also took advantage of a new software release from Audio Precision to make quasi-anechoic response measurements with its MLS (maximum-length sequence) digital test program. Over portions of the frequency range where both test methods (swept and MLS) were valid, there was a rough agreement between them, but we will have to acquire more experience with MLS measurements to establish a meaningful correlation between them and the other types we use.

The DR7's measured sensitivity was 90 dB, exactly as rated. Total harmonic distortion plus noise (THD + N) from the woofer with a 2.83-volt constant input was between 0.5 and 1 percent from 80 to 2,000 Hz, increasing to 2.9 percent at 70 Hz, 3.5 percent at 38 Hz, and 10 percent at 25 Hz. The system impedance was a minimum of 3.75 ohms at 150 Hz, with peaks of 11 to 12 ohms at 62 and 25 Hz and 18 ohms at 1,400 Hz. Although the DR7's overall 6-ohm rating is not unreasonable, as its impedance was greater than 6 ohms over most of the audio range, users should be aware that the impedance does drop below that value in a range where considerable program power may be required.

We were not able to identify the exact crossover frequency, which was not given in the product specifications, from any of our measurements or from listening. Definitive Technology's claim of "seamless" response appears to be justified. Our best guess is that the crossover is in the vicinity of 2,000 Hz.

The tweeter's high-frequency dispersion was typical of 1-inch domes, with less than 3 dB difference between the output on-axis and 45 degrees off-axis up to about 6,000 Hz. The difference increased to 8 dB at 10,000 Hz and 14 dB at 20,000 Hz. Group delay varied less than ±0.1 millisecond from 3,000 to 18,000 Hz, with much larger swings from 3,000 to 1,000 Hz.

The DR7, despite its relatively small drivers, was able to handle very high short-term power levels. At 100 Hz, it required a 1-cycle burst of 1,260 watts into the speaker's 4.8-ohm impedance to give positive audible evidence of excessive woofer-cone movement, although some distortion could be heard at somewhat lower power levels. At frequencies of 1,000 and 10,000 Hz, where the speaker's impedance was in the 8- to 15-ohm range, our amplifier clipped first, at 460 and 750 watts, respectively.

Comments

For listening, we placed the Definitive Technology DR7's about 3 feet in front of a wall, 6 feet apart, and 4 to 5 feet from the side walls. They were slightly toed in toward the center of the room.

From first hearing, the DR7's sounded distinctly different from other speakers we had available. They were, most of the time, sonically "invisible," creating a stage of sound that was not obviously connected with the two slender black columns at the front of the room. Not only was there no sense of where, in each column, the sound originated, but there was usually no sense that it came from either of the two visible speakers. This impression was reinforced when we switched between the DR7's and any of several other speakers (some of which are considerably more expensive).

The DR7 sounds less like a speaker-or how we think of a speaker as sounding-than most others we have used. It was not always the brightest of the lot, nor the best in the low bass, but it always seemed to have just the right balance to encourage extended listening. There was an effortless, unstrained character to its sound that we have rarely experienced from speakers in this price range, or even at considerably higher prices.

Frankly, the last time we used speakers having this combination of qualities was during our test of the Definitive Technology BP10. Although the DR7 lacks the bipolar radiation pattern of the BP10 and BP20, and some of their deep bass, it somehow manages to create much of their total effect.

Even if you don't know the DR7's price or driver complement, its performance is impressive in its own right. But when you realize that a single 6-inch woofer and a 1-inch tweeter are generating the sound you are hearing, and that the DR7's price is not much more than that of many "budget" speakers, you can appreciate its real quality and value.