Celestion SL600si loudspeaker & DLP600 digital equalizer Dick Olsher, January 1989

Dick Olsher wrote about the SL600 in January 1989 (Vol.12 No.1):

It has been some 250 years since Jonathan Swift's Captain Gulliver tangled with the inhabitants of the land of Lilliput. In the interim, it appears to me that a significant number of Lilliputians have succeeded in infiltrating the British Isles. How else am I to account for the uniquely British craze for miniature loudspeakers? The BBC, rumored to be a Lilliputian stronghold, started it all when they licensed commercial production of the LS3/5A minimonitor. The ProAc Tablettes followed shortly thereafter, and managed to infect the minds of audiophiliacs on this side of the Atlantic.

The situation has progressed to the point where recently the Acoustic Energy AE1 minimonitor, with a truly Lilliputian 4" woofer, made Stereophile's list of recommended components. A 4" woofer? Give me a break! How can anyone mistake a midrange driver for a woofer? Is it even fair to advertise these wooferless designs as loudspeakers? Well, maybe. Having by now punched a fair number of readers' buttons, I have to confess that I'm actually sympathetic to the Lilliputian Legacy: smaller can be more nimble and cunning.

A few years ago I reviewed the ProAc Tablette (Vol.7 No.4). When J. Gordon Holt, the champion of tonal accuracy, first heard them he was violently put off by their tonal imbalance. "Violins sound like children's toy violins, celli are emasculated," and on and on he went. My review was less than a rave, yet he castigated me as "having gone off the deep end" for my failure to trash them. Yet in my system, side by side with my reference speakers at the time—the helium-driven Hill Plasmatronics—the Tablettes were superior in defining the underlying bass lines and highlighting the pulse or heartbeat of the music. Thus, through the Tablettes the range below about 1kHz, while not as "accurate," was more "tuneful." Shortly thereafter, I sold the Plasmatronics. Not because the Tablettes became my new reference (I also value accuracy), but because they whetted my appetite for a speaker that could reproduce the lower mids and bass octaves with transparency and detail.

Much later, the Celestion SL600s arrived. Of course their imaging was superb, and although there was no deep bass, the tonal balance was a bit too lean for my tastes, and the highs, while extended, lacked air and transparency, what really captured my imagination was the speaker's ability to focus in on bass detail and clearly resolve bass information. I was almost willing to forgive all of the '600's shortcomings for the privilege of clearly hearing what I could not hear before.

The issue can now be appreciated and restated as one of quality vs quantity. The Lilliputians would argue that the finesse areas of bass reproduction are best served by minimizing the speaker. The Brobdingnagians, on the other hand, would argue that finesse is not enough, that power and extension are paramount for maximizing realism. The issue of bass quality has had a difficult gestation period in the US, even in the hands of veteran audio reviewers. Not too long ago Anthony H. Cordesman snubbed the Lilliputians with his "bass is bass" motto, finding them guilty of stealing the bass. More recently, a well-known reviewer on the comeback trail—OK, Peter Aczel—preferred the bass of the Carver Amazing speaker to that of the Apogee Scintilla and Celestion SL600s. Speak about a blatant preference for heavy and featureless bass!

For satellites in my subwoofer survey, I settled on the Celestion SL600. Driven full-range, these satellites were capable of excellent imaging and resolution of low-level detail. The SL600 had problems, however, which would preclude them from long-term residency in my system...In contrast with the MG-2.5, the tonal balance of the SL600 begins to look like a reference standard. Its in-room response is extremely tight from 200Hz to 20kHz. There is a modest suckout of about 4dB in the octave between 100 and 200Hz, which results in a "lean" sort of balance. And despite the frequency extension of the SL600's tweeter, the subjective impression was of a closed-in, lifeless, and slightly opaque upper treble.

The Celestion's in-room bass half-power response was at a frequency of 50Hz. The SL600 woofer can thermally sink quite a lot of power, able to suck dry the 150Wpc Boulder 500 amplifier into clipping without any apparent damage. Yet the power the woofer sinks is not going into acoustic output, but merely heating the voice-coil. It is obvious that, on heavy bass transients, the SL600s are unable to "rise" to the occasion because the woofer is excursion-limited. The resulting compression robs wide-range orchestral music of its full dynamic range and power. The SL600s, therefore, proved an excellent candidate for a subwoofer; and because of their facility in the finesse areas of bass reproduction, they turned out to be a very critical tool in assessing the impact of the subwoofer on mid- and upper-bass quality.—Dick Olsher

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