Denon SC-507 (1983)
The Denon SC-507 is a big three-way bookshelf speaker released in 1983 at ¥65,000 per unit. It's a bass reflex design with a 70-liter enclosure. Drivers are a 32 cm cone woofer, a 6 cm dome midrange and a 2.5 cm dome tweeter. The cabinet measures 390 × 700 × 385 mm and weighs roughly 23 kg. Rated input impedance is 6 Ω, maximum allowable input is 140W (program source), and the stated playback band runs from 30 Hz to 50 kHz with crossover points at 800 Hz and 5 kHz. Sensitivity is rated at 92 dB/W/m.
The interesting part is the driver material. Denon positioned the SC-507 as following the tech of the earlier SC-A7, with particular attention paid to the woofer. The midrange and tweeter both use what Denon called an α-Boron diaphragm - a hard dome made by fusing boron compound and alumina particles onto aluminum alloy foil with a plasma jet welding process. Denon claimed this gave roughly three times the rigidity of titanium and about ten times the internal loss of a conventional metal diaphragm. The woofer uses a polypropylene diaphragm with a corrugated rib structure, a large flat damper, a long-stroke heat-resistant voice coil, and a 135 mm barium ferrite magnet. The midrange and tweeter both got aluminum die-cast frames and strontium ferrite magnets, and the midrange used a double suspension support system. The cabinet has continuously variable level controls for the midrange and high range.
The German publication Stereoplay (1984, Heft 11) included the SC-507 in a comparative loudspeaker test alongside models from Electro-Voice, Kirksaeter, Magnat, and Pioneer. The surviving fragment is brief. It says the bass gathered plus points for reaching deep and only softening in the lowest registers, and that the Denon placed "clearly better." The full context of that comparison isn't documented.
Surviving information beyond this is thin. No production end year, no detailed measurements, and no comprehensive review data are recorded. Used listings over the years have appeared in Germany, Russia, Australia, and Serbia, with asking prices varying widely. One Japanese auction noted edge deterioration (surround rot) on a pair, so check for that on any example.
Known specs, in brief:
- 3-way, 3-speaker bass reflex, bookshelf type
- 32 cm cone woofer / 6 cm α-Boron dome midrange / 2.5 cm α-Boron dome tweeter
- 30 Hz - 50 kHz; 140W max input; 6 Ω; 92 dB/W/m
- Crossovers at 800 Hz and 5 kHz
- 390 × 700 × 385 mm; approx. 23 kg
- ¥65,000 per unit (1983)
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