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.
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Sidebar 5: Specifications
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…
The reasoning behind this thinking is summarized in three graphs. Figs.1 & 2 show the group delay of an inverting and noninverting Servo-Subwoofer; the inverting unit is clearly better. Fig.3 shows the combined frequency response of a properly set up Spica Servo-Subwoofer and TC-50 speaker, using Spica's 100Hz crossover. These graphic results are good by any standard, and provide just a hint of the amount of sophisticated modeling and experimentation that has gone into the Spica Servo-Subwoofers.
Fig.1 Spica TC-50 with Servo-Subwoofer, calculated group delay vs frequency…
Spica offered the following Manufacturer's Comment:
Editor: Thank you for offering us the opportunity to get a "second opinion" on the subjective performance of our TC-50/Servo combination. While I find AHC's impressions to be much more akin to our own than were JGH's in Vol.9 No.5, I do not experience the lack of dynamics in the upper bass/lower midrange. I have experienced this when the Servo placement was incorrect, which is why I treated this subject in great detail in the manual. And we have received no comments regarding this apparent lack from our dealers, nor from the 700+ owners…
Martin Colloms reviewed the Spica TC-50 in January 1988 (Vol.11 No.1):
The "transatlantic price penalty" means that a speaker appropriately priced according to performance for one market needs to be something rather special to survive the increase in price when exported to the other side of the Atlantic. One US miniature which has sold well in its home country is the Spica TC-50, now also available in the UK at a selling price of around £600/pair ($1000). Given the UK income level, this means that it rates as an expensive model over here, falling a little short of the legendary Celestion…