Dynaco A-30mkII (circa early 1970s)
The Dynaco A-30mkII is a 2-way, 2-speaker bookshelf system that appears to have been sold mainly in the Japanese market. Most of what survives about it comes from Japanese audio databases, not American hi-fi press. It was priced at ¥41,000 per unit, which suggests it sat above the more familiar A-25 in Dynaco's speaker lineup.
The interesting part is the "damped bass reflex" loading. Instead of choosing between a sealed enclosure and a conventional ported design, Dynaco filled the opening of the lower baffle grating with special glass fiber. It's a semi-braking arrangement. The woofer gets air to move, and the resonance problems of an ordinary bass reflex cabinet are suppressed. The enclosure walls are lined with two layers of glass fiber and rock wool with different absorption coefficients, to cut internal reflections. The stated goal was to avoid both the over-braking of a fully sealed box and the port resonance of a standard reflex design.
The drivers follow the same thinking. The 25 cm cone woofer uses a light vibration system with small amplitude, not the heavy, long-voice-coil assemblies common in sealed-box designs. The dome tweeter likewise uses a lightweight diaphragm. Crossover is at 1 kHz. Rated frequency response is 25 Hz to 20 kHz, maximum input is 100W, and impedance is 8Ω. The sensitivity figure of 98dB, if accurate, would make this an unusually efficient speaker for its size. The cabinet measures 320 × 570 × 250 mm and weighs 11 kg, slightly larger than the A-25mkII.
Surviving information on this model is thin. There's no confirmed production year. The sources say "around the early 1970s?" with an explicit question mark, and one unverified listing claims 1970. No period reviews, no owner accounts, and no collector pricing data have surfaced.
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