Fig.1 Spica TC-50 with Servo-Subwoofer, calculated group delay vs frequency…
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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.
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…
It would be a mistake to say that the bass was missing, however; indeed, when the program scoring omitted upper-mid and treble sounds, the bass section sounded quite even and extended; the problem was simply that its level was slightly subdued, overshadowed by the stronger output higher up the frequency range.
Its stereo performance was very good for the price. The sounds were not localized at the speaker positions, and image width was impressive. Interestingly, when compared with similarly sized direct-facing speakers, the TC-50 center image, though well focused, seemed quieter—as if…
Sidebar: 1988 Measurements
Anechoic data were available for the review, providing a foundation on which to base the technical analysis. The LF system resonance was noted at 65Hz, with a -6dB free-field response at 48Hz, indicating a desirably slow, well-damped rolloff. In-room, well sited within the boundaries, the response extended down to 35Hz, provided that excessively loud demonstration levels were not demanded.
Although the speaker is rated at 4 ohms, the impedance curve (fig.1) related to a 6 ohm nominal rating with minima at 4 ohms and above, while the peaks remained…
John Atkinson reviewed the Spica TC-50 in October 1989 (Vol.12 No.10):
"Why does John Atkinson devote so much of his time to loudspeakers selling for under a [sic] $1000?" wrote a correspondent to The Audiophile Network bulletin board in August, there being a clear implication in this question that "more expensive" always equates with "better" when it comes to loudspeakers. While it is true that the best-sounding, most neutral loudspeakers possessing the most extended low-frequency responses are always expensive, in my experience this most definitely does not mean that there is an…
A boost above 8kHz or so will not be perceived as "brightness" per se, but adds a lispiness to sibilants and almost a whistle to recorded hiss that makes the TC-50 sound very thin. If you were to walk into a room where a pair were playing and listen standing up, as you might at a show, you would come away with a very poor idea of the speaker's true tonal balance. I am sure that it was this off-axis emphasis of the high treble that led the venerable J. Gordon Holt (in whose ears we trust) to characterize the TC-50s as having rather a "cold," analytical balance (footnote 2). Even on the…
Sidebar 1: 1989 Review context
With small speakers, the first and most important consideration is what stands to use. Often treated as an afterthought, a good pair of stands is fundamental to getting optimum performance from even inexpensive loudspeakers. With my listening chairs placing my ears 36" from the ground, 24"-high stands were appropriate to use with both the Celestions and the Spicas (Spica actually makes a point of recommending Chicago Speaker Stands Hercules stands), but I used a $300 pair of Celestion SLSi models which were handy (footnote 1). These are single-pillar…
Sidebar 2: 1989 Measurements
Fig.1 shows the way in which the TC-50's impedance changes in amplitude (solid line) and phase (dotted line) from 10Hz to 50kHz. [Note that the phase scale is the opposite way around from what the magazine adopted in 1991, with negative (capacitive) angles at the top.—Ed.] Although its magnitude drops to a hair under 4 ohms in the low bass, lower midband, and mid-treble, the speaker shouldn't present any drive problems. It would be unwise, however, to connect more than one pair in parallel with a typical low-powered receiver. The single LF resonant peak due…
Sidebar 3: Specifications
Description: Two-way, stand-mounted loudspeaker. Drive-units: 1" soft-dome tweeter, 6.5" pulp-cone woofer. Low-frequency alignment: sealed-box with Q=0.78. Crossover frequency: 2kHz. Crossover: high-pass slope, approximately first-order, 6dB/octave; low-pass slope, fourth-order, 24dB/octave, Bessel; both drivers connected with the same polarity. Frequency response: 60Hz-17kHz -3dB. Sensitivity: 84dB/W/m. Nominal impedance: 4 ohms (3.6 ohms minimum at 4kHz). Amplifier requirements: 25-100W. Maximum power handling: 50W continuous, 100W peak.
Dimensions: 15.5" (…