"Who Stole The Bass?" asked Anthony H. Cordesman, writing about minimonitors in the April/May 1987 Stereophile (Vol.10 No.3). And for the designer of a box loudspeaker, the fundamental design decision, at any price level, is how much bass extension to aim for. It will always be possible to design a speaker with extension down to 20Hz, but will the result be musically and commercially successful? Will the designer end up with a speaker hypertrophied in that one area at the expense of every other? Will, indeed, the result be feasible technically? For example, for a given cabinet volume, gains in low-frequency extension have to be balanced against corresponding drops in sensitivity, and it is quite possible that to go for 20Hz extension will result in a 60dB/W/m sensitivity, equating with a speaker that only plays extremely quietly, and thus of no use to anyone.
As mentioned by two readers in this month's "Letters," amplifiers are used to drive loudspeakers but are almost exclusively measured into resistive loads. The reasons for this are twofold: 1) real loudspeakers both produce neighbor-annoying sound levels and tend to break when driven with typical amplifier test signals; and 2) the question as to which "standard" loudspeaker should be used is impossible to answer---at least the conventional resistive loads are consistent and repeatable.
In the fall of 1982, I had just become the Editor of the English magazine Hi-Fi News & Record Review. Hi-fi was in a state of flux. The Compact Disc had just made its debut in Japan, but the British and American launches were six months and a year away, respectively. The Linn orthodoxy prevailed about the role of the source in system performance, but there was no agreement about what was and was not important when it came to enhancing the musical experience. "Objectivists" insisted that amplifiers and even loudspeakers had pretty much reached a design plateau where no further improvement was necessary or even desirable, while "subjectivists" were fragmented. All I was aware of was that my system, based on Celestion SL6 loudspeakers, needed more of an undefinable something.
One of the great imponderables in hi-fi is how much the vibrations of a dynamic loudspeaker's cabinet walls contribute to its overall sound quality. Studies by William Stevens in the mid-1970s showed that, with some speakers, the acoustic output of the enclosure could be almost as much as that from the drive-units. Since then, responsible speaker designers have worked hard either to damp cabinet vibrations or to shift them to higher frequencies where their effect on the music will be less deleterious.
In recent years, computer modeling, finite-element analysis, and laser interferometry have brought about a huge increase in our knowledge about what makes the moving-coil loudspeaker drive-unit work. Nevertheless, it has remained fundamentally unchanged since it was invented by Rice and Kellogg more than 60 years ago. That doesn't mean that it hasn't been refined considerably; in this review I examine the performance of a design whose drive-unit technology has been taken to the limit of what is currently possible, the B&W Silver Signature.
From London, England, to Santa Fe, New Mexico, is a pretty big jump, both geographically and culturally. From Hi-Fi News & Record Review to Stereophile, however, is a mere hop; the similarities overwhelm the differences. Unlike the US, mainstream magazines in the UK have managed to keep in touch with the fact that hi-fi components sound different; to edit and to write for an ostensibly "underground" American magazine presented no major philosophical problems. (I say "to edit," but as mentioned in "The Big Announcement," Vol.9 No.3, my editing is done in harness with Stereophile's founder and guiding light, J. Gordon Holt.)
I must admit, right from the outset, that I find reviewing electronic components harder than reviewing loudspeakers; the faults are less immediately obvious. No preamplifier, for example, suffers from the frequency-response problems endemic to even good loudspeakers. And power amplifiers? If you were to believe the older generation of engineers—which includes some quite young people!—then we reached a plateau of perfection in amplifier design some time after the Scopes Monkey Trial but well before embarking on the rich and exciting lifestyles afforded us by Reaganomics. (In the UK, it is generally felt by these people that the date coincided with the introduction of Quad's first current-dumping amplifier, the 405, in 1976.)
Following my reports on 13 mainly inexpensive loudspeakers that have appeared in the last four issues of Stereophile, I thought I would give myself a treat this month by reviewing the latest incarnations of a model that has stood the test of time: the two-way Celestion SL600Si...This is a carefully tuned infinite-baffle design, sacrificing ultimate extension for upper-bass and lower-midrange quality. Its crossover is conventionally British in that it puts flatness of on-axis amplitude response ahead of time coherence, while everything about it, from drive-units to the cabinet itself, is flagrantly "high-tech."