Westlake BBSM-6F loudspeaker

I've been musing much of late on what enables some hi-fi components to sound natural while others always seem to add an edge of artificiality to their sound. This dichotomy was examined in last month's "As We See It," where I asked a representative group of Stereophile writers to discuss the fact that many high-end components regarded as being neutral in their sonic character, with apparently little wrong in their measured performance, can actually sound quite unmusical. This would seem to suggest that the nature of what a component does wrong is of greater importance than the level of what it does wrong: 1% of one kind of distortion can be innocuous, even musically appropriate, whereas 0.01% of a different kind of distortion can be musical anathema.

The reason for this seeming paradox, as I see it, must lie in something Bob Stuart referred to in his recent interview with Robert Harley (footnote 1). When we sit down in front of a stereo system and listen, say, to a recording of Beethoven's Symphony 6—my current favorite is the Bruno Walter performance on CBS Masterworks MYK 36720—we think that we hear violins, violas, and cellos, joined at measure 13 by double basses, making up the orchestral string section, spread out, as in real life, across the stage between and behind the loudspeakers. At measure 20, a lone bassoon quietly accentuates the phrase that rises up to the work's dominant, while a little later, the same phrase on the flute is echoed by the oboe to return the music to the tonic. This is what we perceive.

In actual fact, none of this is real. There are no individual sounds of instruments being reproduced by the loudspeakers. Instead, you have two channels of complex audio-bandwidth voltage information that cause two pressure waves to emanate from the loudspeakers. The impression you get at measure 29 of the "Pastoral"—of an oboe positioned just right of center stage and set a ways back behind the violins stating the first movement's main theme—is something that exists only in your head, your brain back-interpolating from the twin pressure waves striking your ears that that must have been what happened at the original recording. In Bob Stuart's words, your brain creates totally subjective "acoustic models" as a result of the acoustic information reaching your ears (footnote 2).

You do this so naturally—after all, it's what you do when your ears pick up real sounds—that it doesn't strike you as incongruous that the illusion of the sounds and spatial aspects of a symphony orchestra can be reproduced by a pair of speakers in your own room. Yet there is no measurement or set of measurements that can be performed on those twin channels of information to reveal what I have just described and what you perceive with no apparent effort when listening to Beethoven's most accessible symphony. All the measurements that this and other magazines routinely practice examine changes in the voltage or pressure signals in normally just one of the information channels at a time, yet the defects of recording and reproduction systems affect not just one of those channels but both simultaneously. And the audible effect of those defects is not heard as their direct measurable effect on the signals but as changes in the perceived character of the oh-so-fragile acoustic models.

Tom Miiller recently referred in The Absolute Sound to the "microdynamics" of live sound (footnote 3); Linn Products' Ivor Tiefenbrun often talks about the "tune." It is my belief that they are using different vocabularies to talk about the same thing, that which makes live sounds—electric or acoustic—distinct from one another. That bassoon at measure 20 of the "Pastoral," for example, is played very quietly compared with the levels of the strings, yet on a good system you hear it unambiguously as a bassoon (if you take care to become familiar with the sounds of real instruments, footnote 4), which means that all the small wrinkles in its original live sound that identify it as a bassoon are preserved by the recording and playback systems. Without those wrinkles in the sound, you would be unable to perceive that a bassoon was playing at that point in the music, yet those wrinkles represent an incredibly tiny proportion of the total energy that reaches your ears. System distortions that may be thought to be inconsequential compared with the total sound level can become enormously significant when referenced to the "bassoon-ness" content, if you will, of the stereo signal: the only way to judge whether or not they are significant is to listen, with an informed and open mind.

Which brings me to the subject of this review, a "so-called" monitor loudspeaker, a speaker that enables the recording engineer to critically examine the acoustic information captured by the microphones, to determine how closely a recording's acoustic models coincide with the real thing. It might be thought that there should be no difference between a monitor and a domestic loudspeaker: both need to be accurate, right? In general, however, speakers that have proved their worth as professional monitors have not been successful as home speakers. There have been exceptions, of course: the Rogers LS3/5a and Spendor BC1 have crossed over in one direction most successfully, as did the Spendor S100 that I reviewed in December 1991. The Quad ESL-63 and the B&W 801, in their various incarnations, have crossed over in the opposite direction. This month, I will be listening to a model from an American manufacturer of professional monitors that is said to work well in the home, the Westlake BBSM-6F.

Westlake BBSM-6F: $2800/pair
Westlake is one of the big names in professional monitoring, their high-power designs featuring man-sized woofers and horn midrange/treble units being built into many studio control rooms. In recent years, they have ventured into the domestic arena with a range of loudspeakers including massive, beautifully made, expensive horn designs, as well as more conventional direct-radiator models. The BBSM-6F is one of the latter, a relatively small (but heavy) three-way design. Finished in oiled-walnut veneer, with a brown grille cloth (the otherwise identical BBSM-6 offers a utilitarian black cabinet and a black grille cloth), it brought back memories of the classic Gale monitor that I used for a while in the late 1970s, with its wider-than-tall aspect ratio and its pair of small woofers flanking a vertically arrayed tweeter and midrange unit.

The 6" woofers, which handle the signal up to 600Hz, are plastic-coned units with inverted rubber roll surrounds, tuned by twin 4"-deep ports to the edges of the front baffle. These ports are 1.5" in diameter, with some profiling to minimize wind noise at high levels. The 3.5" midrange unit stands out from the baffle a little to give a degree of time-alignment between it and the tweeter, and features a paper cone of 3" radiating diameter. It crosses over at a high 6kHz to a 1" doped fabric-dome tweeter. Revealing the speaker's professional heritage, replacement diaphragms for all the drive-units are available from Westlake.

The 24-element crossover is mainly constructed on the black-painted rear panel, with the components glued to it and connected with point-point wiring and tag strips. A separate board on the cabinet base just behind the righthand port carries the tweeter high-pass filter. Air-cored inductors are used exclusively, these oriented for minimal magnetic linking, while all capacitors appear to be expensive Siderealkap plastic film-dielectric types, including a physically monstrous 200µF cap in the woofer filter. Electrical connection is via four screwdown terminals, two each for the woofer and midrange/HF sections of the crossover. These will only take spade lugs up to 3/8" in width, which will rule out use of some audiophile connectors.

The BBSM-6F's enclosure is constructed from ¾" fiberboard, with diagonal braces running from the sidewalls to the top and a horizontal brace joining the rear panel—this held to the main frame with no less than 21 wood screws—to the front baffle. It is loosely filled with fiberglass, while the braces and the drive-unit chassis are damped with a putty-like substance. All in all, the speaker seems pretty substantially built for its price.

The horizontal design of the Westlakes mandates tall stands. I used the 26" Ensemble "Flamingo" stands, with large Tiptoes underneath their rear to tilt them forward a little and bring my ears midway between the speakers' tweeter and midrange axes. (The speakers were coupled to the stands' top-plates with small pads of EZ-Tak.) Though the Westlake application notes on speaker positioning go into some detail on arranging for the path lengths from each speaker to the listener to be equal, as well as examining what the optimal room acoustics should be, they don't mention what the speaker's relationship should be to nearby boundaries. I therefore used my instinct (and Sitting Duck Software's Listening Room PC program) to get the smoothest balance in the bass, the speakers being set a little closer to the rear wall than the Acoustic Energie AE3s that I also review this month, but the same distance from the sidewalls.

The BBSM-6F's grille is made from thick board with holes cut in it for the drive-units. Though the speaker looks much better with the grille on, the apertures for the tweeter and midrange unit would undoubtedly add some cavity effects. I therefore left it off for all the serious auditioning, as recommended by Westlake. The BBSM-6Fs were connected to the amplifier with 10' bi-wire sets of 4-gauge Westlake cable.

My first impressions of the speaker were very favorable. There was a striking immediacy to its sound, which seemed extremely open, detailed, and refreshingly free from midrange congestion. The speakers seemed to need only a handful of volts from the amplifier to reach high playback levels, with an excellent sense of unrestricted dynamics. The bass, however, is shelved down in level, and the speaker actually sounded quite lightweight at low levels, with tenor and bass instruments sounding too "small." Nevertheless, I wasn't made aware of any discontinuity in the crossover region between the woofers and the midrange.

Tonally, the BBSM-6's balance seemed to favor the midrange. While male voices were endowed with a little cupped-hands character and were projected forward of the line joining the speakers' acoustic centers, they had a delicious tangibility. Female voices were presented in a similar manner, except that at high playback levels they acquired a hardness, a slightly "shouty" quality that detracted from the otherwise superbly clean nature of the sound.

The high frequencies were also clean, without any tilted-up emphasis or sense of detachment from the midrange. Coupled with the speaker's excellent dynamics, this lent recordings rich in transient information an impressive sense of ease. The guitars on Michael Hedges's 1987 Live on the Double Planet album (Windham Hill WD-1066), for example, sent shivers down my spine. There seemed a wealth of detail, both direct and reverberant, that filled the listening room with sound; the speaker's superb "jump factor" allowed the percussive nature of Hedges's playing to lend a palpable edge of realism to what is otherwise quite an artificial-sounding recording. Given this combination of superb dynamics and midrange-forward balance, I can understand why Westlake does very well in the Far East, where this mix of virtues fits the local cultural needs well (footnote 5).

Play a recording already hyped-up in the midrange, however, such as Andreas Vollenweider's Dancing With the Lion (Columbia CK 45154), and the sound became too fatiguing too quickly.

Footnote 1: "The Increasing Importance of the Smaller Difference," Vol.14 No.9, September 1991.

Footnote 2: This way of looking at perception is examined in Edmund Blair Bolles's A Second Way of Knowing: The Riddle of Human Perception, Prentice Hall Press, 1991.

Footnote 3: The Absolute Sound, Issue 74, November/December 1991, p.76.

Footnote 4: Musicians tend to become so familiar with the sounds of instruments that they need very few aural clues to reconstruct the acoustic objects. This is why they can be satisfied with what in absolute terms is appalling reproduced sound quality.

Footnote 5: When I have visited audiophiles in Japan, for example, their systems have almost always been optimized in these directions.

Westlake Audio
2696 Lavery Court, Unit 18
Newbury Park, CA 91320
(805) 499-3686