Celestion System 6000 loudspeaker system Dick Olsher, January 1989
The System 6000 was previously reviewed in Stereophile, by Martin Colloms in Vol.10 No.2 (February 1987). What follows is simply meant as a quickie followup to that in-depth review.
Someone was bound to ask how Celestion's dipole subwoofer system ($2699/pair complete with electronic crossover) compared with the products surveyed herein, especially in view of the liberal use I've made of the Celestion SL600. So I endeavored to obtain a sample, which arrived just in time for a couple days' listening.
Here is a product designed to mate specifically with the SL600. Not surprisingly, therefore, the overall integration was very smooth—except for an annoying room mode at 60Hz which I couldn't eliminate. The improvements wrought by the introduction of the subwoofer were dramatic. Bass extension and dynamic headroom were much improved. Bass detail and pitch definition wee as good as ever. The range handled by the SL600s was much more effortless, with much reduced congestion on loud peaks, better detail, and, believe it or not, imaging stability was up a notch. The imaging was stable before, but now it's solid as a rock. The measured nearfield response of the subwoofer was well extended, with a –3dB point of 25Hz. However, there's not much dynamic headroom below 30Hz. An excellent subwoofer system, nonetheless.
Early on, I was bothered by grain and veiling in the upper midrange. It seemed reasonable to attribute this to the high-pass filter section of the line-level Controller, because the problem went away when the SL600s were operated fullrange. I'm surprised that MC did not comment on this in his review. After about a 48-hour warmup, the upper mids smoothed out quite a bit. But the problem was not adequately addressed until I replaced the Levinson amplifier with the Cochran Delta Modes as satellite amps. Is it possible that the tubed front-end of the Delta Modes filters most of the dirt generated by the Controller? I'm left with a nagging suspicion that perhaps the Controller could benefit from a discrete no-holds-barred design. Let's see, if I could talk Threshold into rebuilding the Celestion Controller...
Subwoofing makes good sense only if you're buying a sure thing, like upgrading to a Celestion System 6000, or if you are a risk-taker who can afford the cost of experimentation. If you decide to experiment, then the best strategy is to bi-amp using steep filter sections and a nominal 100Hz crossover point.—Dick Olsher