Before I examined the measured effect of the DLP600, I ran the SL600Si through Stereophile's almost standardized test regime. Fig.1 shows the manner in which the speaker's electrical impedance magnitude and phase vary with frequency. The single peak of 30 ohms at 63Hz indicates the sealed-box tuning frequency. The speaker is an easy load, apart from the drop below 6 ohms above 4500Hz. Though this dips to 2.7 ohms at 34kHz, there is insufficient musical energy in this range to lead to any problems. Note the sharp impedance peak at 21kHz; this is due to the…
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Sidebar 5: 1992 Measurements
Fig.10 shows the impulse response of the SL600Si on its HF axis at 45" when corrected by the DLP. You can see that it is very much more like fig.9 than fig.8 (though inverted). Note also that the ultrasonic ringing has been eliminated, if for no other reason than the fact that there is now no signal content above 22kHz, and that the speaker's output has been delayed by a small amount.
Fig.10 Celestion SL600si equalized by DLP600, impulse response on tweeter axis at 45" (5ms time window, 30kHz bandwidth).
To look at what is happening from a different viewpoint, the MLSSA…
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…
Sidebar 5: Specifications
Celestion SL600Si: two-way, sealed-box loudspeaker with Aerolam (aluminum-honeycomb) enclosure. Drive-units: 1.25" copper-dome tweeter, 6.5" Kobex-cone (PVC) woofer. Crossover frequency: 2.3kHz, second-order, 12dB/octave slopes. Frequency response: 60Hz-20kHz ±3dB, low-end, -6dB at 60Hz in free-space conditions. Sensitivity: 82dB/W/m. Nominal impedance: 8 ohms. Amplifier requirements: up to 120W on program.
Dimensions: 14.5" (368mm) H by 7.75" (197mm) W by 9.25" (235mm) D. Enclosure volume: 12 litres (0.4 cubic feet). Weight: 11.25 lbs (5.1kg) each.
Serial…
High-quality, low-cost loudspeaker systems are not an everyday blessing. The Rogers LS3/5a has survived for more than a decade precisely because so few US manufacturers sought musical accuracy as distinguished from high output and powerful bass. The economics of loudspeaker manufacture also don't lend themselves to economy. The cost of woodwork is driving the price of speakers up almost as fast as the cost of sheet-metal work is escalating the price of electronics.
Both Spica and Dayton Wright, however, have come out with small affordable speakers that should earn the term "blessing"…
The Spicas have two minor problems in timbre that may or may not suit your taste. The first is a warm area extending from about 150 to 300Hz. The second is a hump from about 5.5kHz to 7.8kHz. These problems are minimized by very careful placement and proper choice of interconnects and electronics; they are perhaps more noticeable than usual because of the speaker's transparency and accuracy in other areas.
As for the soundstage, depth is slightly restricted by the limited bass response, but is otherwise excellent. Soundstage size is not equal to that of large arrays or planars, but is…
J. Gordon Holt reviewed the Spica TC-50 with its matching Servo-Subwoofer in August 1986 (Vol.9 No.5):
Like Audio magazine's Richard Heyser, Spica Speakers' John Bau is heavily into instrumentation for loudspeaker evaluation and design. His fully equipped, computerized lab allows him to assess just about every measurable aspect of loudspeaker performance, and to design towards perfection in all of them. Having toured Spica's manufacturing facility here in Santa Fe, I can vouch for the care and attention to detail that go into their loudspeakers. (The crossover in the TC-50 includes notch…
I went to crank the woofers up (from the levels set using the voltmeter), and promptly ran out of steam! There was only about 3dB of additional output level available. It was barely enough. With the woofers up full, mid-bass was just about correctly balanced with the upper range, but the bass below that sounded as if it tapered off all the way down to the speaker's (confirmed) 25Hz lower limit. I could hear 25Hz quite well, but its level was so far below the upper range as to be of little subjective value when listening to music.
Needless to say, I was even less happy with the sound…
Larry Archibald also wrote about the Spica TC-50 in August 1986 (Vol.9 No.5):
I think JGH misses some of both the positive and negative attributes of the TC-50/subwoofer combo. First, I think the subwoofers benefit from a lack of ambition as to awesomeness of performance. Bau has not tried to turn the system into an Infinity beater, but instead used the subwoofers to augment the TC-50's own virtues.
In this I think he has succeeded. In my room the subwoofers made the TC-50s into a more-or-less full-range system, with not much subjectively missing in terms of fullness through the…
Anthony H. Cordesman offered a Follow-up in November 1986 (Vol.9 No.7):
I was more than a little surprised to read JGH's recent review of the Spica TC-50 with Spica's powered Servo-Subwoofer. Gordon found the TC-50s to be bright and hard, which seemed to overshadow his impressions of the new combination of TC-50s and Servo-Subwoofer. In contrast, I have previously found the TC-50's highs to have a gentle rolloff, and the TC-50 to have one of the most listenable upper midranges of all small monitor speakers.
After discussing the subject with a distinguished panel in Santa Fe, I…