The Spica SC-50 is a two-way bookshelf speaker system. Spica's first design, the speakers cut-away tube design is finished top and bottom in oak panels. The brochure describes the SC-50 as a compact speaker with truly amazing performance. The SC-50 produces clear inviting sound with pinpoint imaging and excellent dynamic range.
There were two designations the for the SC-50 , the Sc-50 and the SC-50i. When I questioned Bau about the differences, he responded:
"The SC-50 was a product that continually morphed along the way, mostly in driver treatment and crossover design. There were about a dozen different SC-50 crossover topologies used at one time or another, 2nd order, third order, Linkwitz-Riley, asymmetrical 4th. There was a lot more "ear" tweaking in the SC; because it wasn't a phase-aligned design, the targets were "fuzzy", leaving me with a lot more guesswork and subjective evaluation, which, though I did a ton of it, I had a basic distrust of. As much as anything, the "i" designation was a pronouncement that the tweaking was nearing a conclusion and the design had become stable."
John Atkinson interviews Spica designer John Bau in February 1988 issue of Stereophile. The article titled Interstellar Overdrive is a great read, that discusses not only the design of SC-50, but also the early beginnings of Spica.
Spica SC-50i V-7, Archibald
The Boston Audio Society (BAS) Speaker
1981, Spica SC-50 CES Report, Vol 9, No 10
by Unterbrink and Meyer
Released: 1979 CES Chicago
Drive-units: 6.5" woofer, 1" tweeter
Description: Two-way, Acoustic Suspension
Drive-units: 1" soft-dome tweeter, 6.5" long-throw concave cone woofer.
Crossover frequency: 2.5kHz.
Crossover: Second order Linkwitz
Frequency response: 56Hz-20kHz (+-3dB).
Nominal impedance: 4 ohms (2.9 ohms min. at 13kHz).
Amplifier requirements: 20W min.
Maximum power handling: 50W continuous, 80W peak.
Dimensions: 13.25"(33.7) H x 9"(22.9) W x 11.25"(28.6) D
Weight: 11 lbs each.
SC-50 Schematic Sketch from John Bau
Woofer: HIF 17JS 2 CA12, 4 Ohm Audax (FR) / Polydax (US) (specs for 8 ohm)*
Tweeter: HD 100 D25, 8 Ohm Audax (FR) / Polydax (US) (specs)
*The spec for HIF 17JS 2 CA12 provides correct response curves etc. however, the 4 ohm version of this driver was used in the SC-50.