Denon SC-307 (1980)
The Denon SC-307 is a 3-way, 5-driver sealed bookshelf loudspeaker released in 1980 at ¥85,000 per unit. It sat near the top of Denon's five-model 1980 speaker line. Only the flagship SC-5000 (¥350,000) ranked above it, with the SC-304 (¥44,800) and SC-306 (¥59,800) beneath. Every model except the SC-5000 used a sealed enclosure.
The SC-307's big idea was the "Twin Drive" low-frequency scheme. Two 25 cm cone woofers sit on a shared frame and present a radiating area equivalent to a single 35 cm driver. Denon developed the woofers jointly with Peerless of Denmark. The diaphragms are non-pressed Scandinavian pulp, and the voice-coil bobbins are aluminum, chosen for heat dissipation. The midrange is a 10 cm cone driver with a die-cast light-alloy frame and a back cavity filled with ring-shaped glass wool. The highs come from two vertically stacked 5 cm cone tweeters - arranged so as not to create horizontal directivity. Level controls for mid and high frequencies were continuously variable.
The enclosure is a 65.5-liter sealed box of hard particle board. The internal volume was reportedly settled on by repeated listening tests in 0.5L increments. Three types of damping material are layered inside, and aluminum-foil-laminated butyl rubber on the back panel suppresses harmful resonances. Woofers and tweeters mount through aluminum die-cast sandwich rings that clamp the full circumference of each driver to the baffle. The crossover uses parallel-connected capacitors throughout, a ferrite bobbin coil for the woofer section, and air-core coils for the mid and tweeter sections.
Rated specs: 8 Ω impedance, 92 dB/W/m sensitivity, 35 Hz - 20 kHz playback, crossover at 500 Hz and 4 kHz, and a maximum program input of 120W, with a separate instantaneous power rating of 600W. Distortion is rated at 1.5% or less above 50 Hz at 5W. The cabinet measures 392 × 700 × 355 mm and weighs 22 kg.
Surviving documentation is mostly period catalogs and spec listings. No contemporaneous reviews or owner impressions have surfaced in the research. A used example has appeared on Yahoo Japan Auctions, noted as scratched, and a parts listing for replacement cross-edge surrounds exists. No reliable current market pricing is documented.
- Type: 3-way, 5-driver, sealed bookshelf
- Drivers: 25 cm cone ×2, 10 cm cone ×1, 5 cm cone ×2
- Impedance: 8 Ω
- Sensitivity: 92 dB/W/m
- Frequency response: 35 Hz – 20 kHz
- Crossovers: 500 Hz / 4 kHz
- Dimensions: 392 × 700 × 355 mm; 22 kg
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