Dynaco A-25mkII (early 1970s)
The A-25mkII is the lesser-documented sibling of Dynaco's A-25, a bookshelf speaker that became one of the best-selling designs of the 1970s. The A-25 has a good paper trail. The mkII survives mostly through Japanese market records. What we know comes largely from a single Japanese audio database, which lists it as a 2-way, 2-speaker, dumped bass reflex bookshelf system priced at ¥35,000 per unit, circa the early 1970s. It was also sold in the UK, where one owner recalls it going for £64 - roughly £910 in today's money.
The "dumped bass reflex" is the mkII's defining technical feature. It's a semi-braking system. Special glass fiber fills the opening of the grating in the lower part of the baffle and provides airflow to the woofer. The inner walls of the enclosure are lined with two layers of glass fiber and rock wool, each with different sound absorption coefficients, to reduce internal reflection. The design intent was to eliminate the over-braking of the woofer common in fully sealed enclosures, while suppressing the resonance at the port opening that plagues conventional bass reflex designs.
The drivers follow the same lightweight approach. The 25 cm cone woofer uses a light vibration system with small amplitude, not the heavy long-voice-coil arrangement typical of sealed-box woofers. The tweeter is a dome type, also with a lightweight diaphragm. The crossover sits at 1.5 kHz. The speaker is rated for 90W maximum input at 8 ohms, with a frequency response of 30 Hz to 20 kHz and an output sound pressure level of 95 dB. Dimensions are 290 × 500 × 250 mm (W×H×D), and each unit weighs 9 kg.
Plenty is not documented. There are no production years beyond that "early 1970s" approximation. There is no confirmed driver manufacturer (Seas is often cited for the A-25, but not specifically for the mkII). Nobody has a clear picture of what actually changed between the A-25 and the mkII. The mkII appears to have been sold primarily in Japan and the UK, which may explain the thin record - it seems the mkII was a variant aimed at specific export markets rather than a major US release. No owner reviews, no common-failure lore, no collector pricing specific to this model.
- Type: 2-way, 2-speaker, dumped bass reflex, bookshelf
- Woofer: 25 cm cone
- Tweeter: dome type
- Frequency response: 30 Hz – 20 kHz
- Max input: 90W
- Impedance: 8 Ω
- Output SPL: 95 dB
- Crossover: 1.5 kHz
- Dimensions: 290 × 500 × 250 mm
- Weight: 9 kg
- Original price: ¥35,000 (Japan, early 1970s); £64 (UK)
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