Denon SC-A5 (1982)

The Denon SC-A5 is a 3-way, 3-speaker bass-reflex bookshelf speaker from 1982. It inherits the technology Denon first worked out in the larger SC-A7. Denon conceived it with the CD age in mind, as a speaker that could reproduce digital-era sources with high fidelity. That explains the unusually extended top end.

The drivers are where the SC-A5 gets interesting. The low end is handled by a 26 cm cone woofer with a polypropylene diaphragm, chosen because it is light and hard. A special material is added to control internal loss and rigidity. The diaphragm is molded into a corrugated rib structure for extra stiffness, and it sits in a powerful magnetic circuit with an aluminum die-cast frame. Above that, the midrange (4.3 cm) and the tweeter (1.6 cm) are both hard-dome types using Denon's α-Boron diaphragm. It is made by fusing boron compound and alumina particles onto aluminum alloy foil with a plasma jet welding method at over 10,000°C. Denon claimed roughly three times the rigidity of titanium and about ten times the internal loss of a conventional metal diaphragm. Both the mid and high frequencies get continuously variable level controls.

The enclosure is a rigid particle board, bass-reflex design with 42-liter internal capacity. The cabinet measures 324 x 589 x 325 mm and weighs 15.3 kg. Frequency response is rated at 35 Hz to 65 kHz, with crossover points at 1 kHz and 8 kHz. Nominal impedance is 6 Ω, sensitivity is a healthy 92 dB/W/m, and maximum allowable input is 130W (program source). The original price was ¥48,000 per unit.

The record on this model is thin in a few places. Production year is given as 1982, but no confirmed production run dates exist. There's no period review commentary in the archive, and no corroborated information on common failure modes. One classified listing from a Russian seller, who had the low-frequency surrounds replaced, suggests foam or rubber surround deterioration is a known maintenance item for these now. The same listing gives weight as 16 kg per speaker, slightly above the documented 15.3 kg, which may reflect the replacement work.