B&W Matrix 1 Speaker System Review

Although the theoretical design criteria for enclosed speaker systems are well known, they assume a perfectly rigid enclosure. Any vibration of the cabinet surfaces produces an acoustic output that may not be directly related to the driving signal’s waveform and whose phase and directional properties can degrade the overall system’s sound output. The conventional solution to this problem is to make the speaker enclosure of thick, heavily braced wood or particle board and to make liberal use of internal damping materials, such as glass fiber or wool, to minimize the effects of cabinet resonances. Other approaches have included the use of “sandwich” panels filled with sand, laminated-aluminum aerospace materials (Aerolam), and even concrete enclosures.

The new Matrix series from B&W Loudspeakers represents a different approach. Extensive listening tests and laboratory measurements by the well-known British manufacturer led to the conclusion that none of the conventional enclosure constructions was completely free from audible colorations. The major requirements for eliminating these effects are low cabinet-radiation amplitude and rapid decay (damping) of the radiated energy.

The solution proposed by B&W’s chief electronics engineer, Laurence Dickie, was to fill the interior of a conventional high-density particle-board cabinet with a matrix structure resembling a honeycomb, with long cells square in cross section. The matrix is formed of a series of interlocking, perforated members having relatively high damping qualities and high stiffness. The inner walls of the cabinet are grooved to accept the horizontal members of the matrix, which is then rigidly bonded to the cabinet. Finally, each cell of the matrix is filled with acoustic foam to damp any remaining resonances.

B&W engineers made lab studies of a number of speaker enclosures, attaching accelerometers to the outside of the cabinets to measure the vibration at many points on the surface and subjecting data obtained from these measurements to extensive computer processing. Comparisons of test results on similar enclosures made of different materials showed that the B&W Matrix structure was superior to the others in respect to vibration amplitude versus frequency and decay rate as a function of time. Its high mass also helped attenuate high-frequency cabinet radiation.

Completely new drivers were developed for the three new speaker systems designed around the Matrix enclosure. The woofer cones are shaped of a homopolymer form of polypropylene that was found to be 1.6 times stiffer than conventional copolymer materials and relatively free of breakup effects. The Matrix 1, smallest of the new family of speakers, has a single 6-inch woofer whose frame is cast as a unit with its magnesium-alloy front plate. The voice coil of the newly designed tweeter is cooled and damped by ferrofluid in its magnetic gap. The crossover, at 2,000 Hz, was simplified by designing a 12-dB-per-octave rolloff into the woofer so that only two components were needed in the external network to achieve the desired fourth-order Butterworth-squared characteristic.

A similar design was used for the tweeter’s crossover. The tweeter is protected against burnout by a signal-powered circuit that disconnects it with a fast-acting relay whenever the high-frequency signal level becomes excessive. When the signal returns to a safe level, tweeter operation is automatically restored.

The specifications of the B&W Matrix 1 include a free-field frequency response of 80 to 25,000 Hz ± 2 dB, a system resonance of 60 Hz (Q = 0.7), a sensitivity of 85 dB (2.83 volts), and an impedance of 4.5 ohms ±0.5 ohm (essentially resistive). The recommended amplifier power is 50 to 120 watts.

The Matrix 1 measures 16 inches high, 9 inches wide, and 12-5/8 inches deep, and it weighs 26-1/2 pounds (by our measurement—the specified weight is 22 pounds). Stands with loaded steel columns and heavy marble bases are optional. The speaker is available with walnut, black ash, or rosewood veneer finish or, on special order, high-gloss lacquer or natural oak. Price: $499 per speaker in walnut or black ash, $699 each in rosewood; stands, $199 per pair.

Lab Tests

We installed the B&W Matrix 1 speakers on their 20-inch-high stands and a few feet from the rear and side walls. The averaged room-response curve from the left and right speakers was smooth and extended in the tweeter’s operating range (above 2,000 Hz). There was the usual irregularity in measured output below 300 Hz, where room interaction is inevitable.

The close-miked woofer response, quite flat from 400 to 1,500 Hz, was down about 3 dB at 2,000 Hz. Below 400 Hz it rose to a maximum of +8 dB at 100 Hz before falling off at 24 dB per octave below 80 Hz. The composite response curve, formed by splicing the woofer curve to the overall room curve, varied only ±2.5 dB from 370 to 20,000 Hz but still showed the same strong emphasis at 100 Hz as the close-miked measurement.

Our quasi-anechoic FFT response measurements confirmed the smoothness and extended range of the system’s middle- and high-frequency response, but we could not reliably measure its low-frequency performance with this method because of unavoidable reflections in our listening room. We had to depend on listening tests to judge the reality of the measured bass emphasis. It was unquestionably real—the Matrix 1 sounded distinctly heavier (“bassier”) than any other speaker we had on hand, and it even seemed to have a subdued high-end response. The latter effect was obviously a psychoacoustic result of the frequency imbalance, since the highs were very much “all there,” as could easily be heard on program material with modest low-frequency content. Male voices, however, had the heaviness characteristic of an exaggerated bass response in the 100-Hz region.

The impedance of the Matrix 1 measured between 3.5 and 5 ohms, averaging 4 ohms over the entire audio range. This confirmed the manufacturer’s rating of an essentially resistive impedance, which any amplifier should be able to drive without difficulty. The speaker’s sensitivity was low, measuring 83.5 dB sound-pressure level (SPL) at 1 meter with a 2.83-volt input of pink noise. An input of 6 volts (9 watts) was required to produce our usual 90-dB reference SPL output.

The Matrix l’s distortion at the 6-volt input level was 2 percent or less above 80 Hz, increasing smoothly to 4.2 percent at 60 Hz, 6.6 percent at 50 Hz, and 11.2 percent at 40 Hz. The speaker’s group delay was exceptionally uniform in the tweeter’s range, varying about 0.1 millisecond overall from 5,000 to 20,000 Hz and less than 0.4 millisecond down to 500 Hz.

The B&W Matrix 1 performed exceptionally well in our pulsed power-handling tests. At 100 Hz, the woofer’s waveform began to distort visibly with an input of 1,800 watts, although it did not audibly “bottom.” At 1,000 Hz the amplifier clipped at 2,275 watts, and at 10,000 Hz the tweeter’s output was still undistorted when the amplifier clipped at 2,190 watts.

Comments

When we first heard the B&W Matrix 1 (and its larger relatives) at the June Consumer Electronics Show in Chicago, we were not aware of any bass emphasis. Our principal impression then was of the superb clarity of its sound, which hardly seemed to be coming from the fairly small loudspeakers that we could plainly see before us. In more familiar surroundings the same clarity was present, but this time with a noticeable bass emphasis. We cannot be certain how much of this emphasis resulted from differences in the listening rooms and how much from the different program material—probably it was a bit of both factors.

To put the matter into perspective, most speakers we have used in our room show bass coloration to some degree, but few have compensated for it with the extended high-end response and smoothness of B&W’s new Matrix 1. Its sound is completely consistent with its price, if not with its size! It is all too easy to lose sight of the fact that the B&W Matrix 1 is not much larger than a mini-bookshelf speaker, since it sounds so much larger than it looks.

This relatively inefficient speaker really deserves a powerful amplifier, and our tests indicate that it can absorb (for brief peaks) far more power than will ever be supplied to it in a home music system. In spite of the manufacturer’s power recommendations, we found its sound to be unstrained (but loud!) with musical program peaks of 350 to 500 watts. But don’t expect to get much more than background levels from these speakers if you drive them with a 25-watt amplifier.

Although its weight may have no bearing on its sound, the Matrix 1 is also surprisingly heavy for its size. The optional stands weigh a solid 18 pounds each, so the combined weight of about 45 pounds for stand and speaker places the Matrix 1 somewhat above the usual bookshelf range. So, of course, does just about everything else about the speakers. While we lacked a test setup for measuring cabinet vibration, rapping the cabinet sides with our knuckles produced little more than bruised knuckles. You could get about that much resonance by rapping a concrete block!

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