Celestion SL700 loudspeaker

"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.

In his article, while Mr. Cordesman did allow that "it is still possible to make a loudspeaker with a midrange good enough to partially compensate for the fact that it will not play loud or low," he concluded that "virtually all of today's small 'monitor' speakers are measurably incapable of high-fidelity reproduction, and have no place in a decent audio system." If money were no object in both the design and purchase of loudspeakers, this would be a fair statement. But I suggest that it is unrealistic in terms of the laws of physics when constrained by the demands of budget.

When the designer is given his head, sure, he can go for the maximum low-frequency extension without worrying that something must be given up somewhere else. But when the speaker has to be affordable, then there are really only two strategies available. The first is to use the largest box available at the price, and a relatively small magnet for the woofer. A speaker with such a high-Q bass alignment will play loud and go deep, but at the expense of high levels of midrange coloration and a boomy, ill-defined midbass. (In addition, as I pointed out last month, a big enclosure will be inherently more colored than a small one due to the larger size of its panels.)

The alternative, which I suggest is more true to the needs of "high-fidelity reproduction" as defined by Mr. Cordesman, is to sacrifice a half octave, one octave, or even more, of deep bass to allow other important areas of performance—midrange clarity, evenness of dispersion, HF purity, stereo imaging—to be optimized. And, dependent on the tastes and preferences of every listener, this could well outweigh the loss of weight to bass instruments and the reduction in apparent hall size due to the LF truncation of the reverberation.

Such is the case with the Celestion SL600, which has remained my personal reference for five years now, a long time for a loudspeaker. Yes, it is a small speaker, with a miserly proportion of low bass. But, as Larry Archibald will testify, having listened to my system on many occasions, it has enough low frequencies not to offend, allowing its uncolored midrange and holographic imaging to shine forth. An area where I think it is flawed, in the sense that listeners will either love or hate it, is its depressed top octave, something that deprives recordings of sufficient "air" and reduces transparency in this region. The SL600 also compresses dynamics somewhat at the top of its loudness range. But as every loudspeaker, even the most expensive, has a signature, I do not think these negative aspects are bad enough to outweigh the positive and preclude recommendation. You have to spend a lot more money than the SL600's $1899 to get superior performance in the areas where it shines.

Which brings me to the subject of this review, a small two-way design, stand-mounting being mandatory to allow it to work as its designers intended. The Celestion will play reasonably loud, providing strain-free reproduction into the 90dB SPLs. However, it won't reproduce music's lowest octave below the lowest reach of the double-bass, the region between 20Hz and 40Hz, despite costing a hair under $3000—true high-end territory, where competing designs often have excellent bass extension.

System & Setup
The test procedure followed, with minor changes, that established for my previous loudspeaker reviews: each pair was used both with a Krell KRS2/KSA-50 combination and the Linn LK1/LK2 remote-control amplification system. A pair of VTL 100W tube monoblocks was also used to drive the Celestions. Source components consisted of a 1985 vintage Meridian Pro CD player—I've been feeling a little nostalgic of late for this classic 14-bit machine—a 1987 Linn Sondek/Ittok/Troika combination sitting on a Sound Organisation table, and a 1975 vintage Revox A77 (unmodified) to play my own 15ips master tapes. Interconnect for the Krell system was Monster M1000, with Monster M1 speaker cable. The Linn system was used with Linn interconnect and speaker cable.

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