Three-Piece Ensemble from 3D
---- 3D Acoustics Model 3D-610B loudspeaker system
----ROOM RESPONSE CHARACTERISTICS
3D Acoustics Model 3D-610B three-piece loudspeaker system (two satellite speakers and a floor-standing bass module), in walnut veneer enclosures. Satellite dimensions: 8 by 13 1/2 inches (front), 6 3/4 inches deep. Bass module dimensions: 15 1/2 by 23 inches (front) 11 1/2 inches deep (max.). Price: $450 (east), 5500 (west); optional stands for satellites, $65 per pair (east), $75 per pair (west). Warranty: "full," five years parts, labor, and shipping. Manufacturer: 3D Acoustics, Inc., 5 Sunrise Plaza, Valley Stream, N.Y. 11581, USA.
There is an obvious symbiosis between a so-called subwoofer and a pair of mini-speakers--which are easy to place but invariably bass-shy in comparison with big full-range systems. The combination theoretically offers audiophiles the best of both worlds: full-range music reproduction without the clutter of a pair of large, ungainly boxes in the living room. Unfortunately, most of these satellite/subwoofer systems have been considerably more expensive than conventional models of similar performance. But this is not the case with 3D Acoustics' three-piece loudspeaker system, which sells for about the cost of a good pair of full-range two-way speakers.
The first product from this new company (scarcely a year old), the 3D 610B comprises a pair of compact speakers, each with a one-inch dome tweeter and a six-inch driver in an acoustic suspension enclosure, and a single bass module built around a resistively loaded ten-inch woofer with a dual voice coil. Amplifier connections are made to the woofer module via a set of spring-loaded clips on the rear of the enclosure. Leads to the satellites are strung from a second set of clips on the woofer box, which are connected in parallel to the first set for full-range operation of the satellites. The inputs to the woofer itself are rolled off above 100 Hz by a passive crossover filter. Because the woofer has a separate voice coil for each channel, the crossover is spared the costly task of matrixing stereo signals into mono for delivery to a conventional driver with only one voice coil.
Driven with 2.8 volts (equivalent to 0 dBW or 1 watt into 8 ohms) of band-limited pink noise, the system showed itself to be moderately efficient. If we had to rate the impedances of the satellite and woofer modules separately, we would call the former 8-ohm units and the latter a 6-ohm unit. The system as a whole stays very close to 4 ohms from 20 to 90 Hz, meanders between 5 and 6 ohms up to 200 Hz, rises smoothly to a maximum of 53 ohms at about 1.2 kHz, and then falls back to 5.7 ohms at 7 kHz. We would not expect any good amplifier to have trouble driving such a load.
Because the small satellite speakers are driven full range, with no electrical cutoff at the bottom end, they become the limiting factor in the 3D's power-handling capacity. Diversified Science Laboratories found that the system could accurately reproduce 300-Hz shaped tone bursts at peak drive levels as high as ± 14 volts (equivalent to 14 dBW or 25 watts into 8 ohms), which is similar to the performance of a typical good mini-speaker. The continuous output test was not performed, because "distortion"--actually extraneous noise created by air leaking from the cabinet-became intrusive at 95 dB SPL, though true harmonic distortion was still reasonably low.
Below the 300-Hz test frequency, distortion rises appreciably, with the second harmonic exceeding 1% below 200 Hz and the third below about 100 Hz at all test levels. The second harmonic also exceeded 1% in the 10-kHz range, but the third harmonic did so only at the highest drive level (for 95 dB SPL). In between, however, distortion is low. It averaged less than 1/2% at 95 dB SPL and less than that at lower output levels.
Our listening was done with the satellite speakers at ear level and well out from the walls of the room, simulating the use of 3D's own stands. (One test pair of stands did not survive shipping; a second pair did not fit the satellites very well.) After some experimentation, we settled on the position recommended by 3D for the woofer module, backed up against a wall away from any corners. We were immediately struck by the speaker's precise, spacious imaging. And integration of the bass and upper frequency ranges was excellent. Never was there any sense of listening to two small boxes situated some five feet from a separate woofer.
The system's balance was much as one might expect from the frequency-response plot. Bass was smooth and firm without being over-prominent (a common flaw in satellite/subwoofer systems) and extended down far enough to project with authority all but the most subterranean musical fundamentals. The midrange sounded equally natural; the dip centered on the range between 300 and 400 Hz was not particularly apparent in our auditioning. A few listeners did note a touch of brightness, evident in both the on- and off-axis response curves, which show a gradual rise beginning at 2 kHz. But a light hand on the treble control is all that's necessary to tame the high end.
The 3D-610B sounds at least as good as most other speakers in its price range, and it is competitive with satellite/subwoofer systems costing far more. If the format appeals to you-as it obviously does to a great many listeners--this certainly a model to include on your auditioning list.
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(High Fidelity, USA print magazine)
Also see:
The Critics Go Speaker Shopping [June 1981]