Onkyo U-3500 (circa 1971–1974)
The Onkyo U-3500 is a 3-way, 3-speaker bookshelf system from the early 1970s. It's a bass-reflex design, and Onkyo promoted its "slit-shaped special bass reflex port." The woofer is a 20 cm cone with a cross-roll edge, meant to improve linearity at large amplitudes. The midrange is a sealed-back 12 cm cone, and the enclosure behind it isolates the driver from woofer interference. The tweeter is a small 5 cm cone. Crossover points are 700 Hz and 7 kHz.
The specs describe a moderately efficient, compact speaker. Frequency response is rated at 45 Hz to 20 kHz, allowable input is 20W (40W maximum), impedance is 8 Ω, and claimed output is 100 dB/W measured at 50 cm. The cabinet is 322 × 534 × 290 mm, weighs 10 kg, and has an internal volume of 35 liters. Onkyo sold these for ¥17,500 per unit around 1971, then ¥18,300 around 1972 and ¥21,800 by 1974. Those prices are the only real dating evidence, since no production start or end dates are documented.
The historical record is thin otherwise. There's no surviving review commentary from period publications, no clear place within an Onkyo lineup, and no documented market context. A Japanese blog describes a variant with a 2.5 cm inverse-dome tweeter and a switchable 2-way/full-range mode. That conflicts with the 3-way spec above, and it's unclear whether it's a modified unit, a running change, or a different model entirely. A Russian marketplace listing notes the grilles had been recovered while the capacitors remained original, which hints that capacitor replacement is a consideration for these speakers today.
Known specifications:
- 3-way, 3-speaker, bass-reflex bookshelf system
- Woofer: 20 cm cone; midrange: 12 cm cone (sealed back); tweeter: 5 cm cone
- Frequency response: 45 Hz - 20 kHz
- Allowable input: 20W; max input: 40W
- Impedance: 8 Ω; output: 100 dB/W (50 cm)
- Crossover: 700 Hz, 7 kHz
- Dimensions: 322 × 534 × 290 mm; weight: 10 kg
- Original price: ¥17,500 (circa 1971), ¥18,300 (circa 1972), ¥21,800 (circa 1974)
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