Sony SS-7300 (1971–1974)
A 3-way bookshelf speaker system developed by Sony featuring Ultra Linear Magnetic (ULM) driver technology and a bass reflex enclosure.
Overview
The Sony SS-7300 is a 3-way, 3-speaker bookshelf system developed by Sony in the early 1970s. Marketed as the ULM3, it features a bass reflex design with a walnut-finished enclosure and a streamlined baffle to reduce acoustic reflections. Designed from the ground up using fundamental speaker research, the system emphasizes low distortion and high power handling through advanced magnetic and mechanical engineering.
Specifications
| Product type | 3-Way, 3-Speaker, Bass reflex system, Bookshelf Type speaker system |
| Unit For low band | 30 cm cone type |
| Unit For Medium Range | 12 cm cone type |
| Unit For high-pass | 2.5 cm dome type |
| Playback frequency band | 50 Hz to 20,000 Hz |
| Output sound pressure level | 90 dB/W/m (New JIS) |
| Impedance | 6 Ω |
| Maximum allowable input | 100W (weighted pink noise, 24-hour guarantee) |
| Crossover frequency | 600 Hz, 4500 Hz |
| External dimensions | Width 390 mm x Height 636 mm x Depth 300 mm |
| Weight | Approximately 19 kg |
| Original price | ¥35,000 (per unit, circa 1971) — note: source conflict; not corroborated by additional research |
Design
The SS-7300 was developed based on Sony's fundamental research into speaker design. It features the Ultra Linear Magnetic (ULM) circuit, which uses a notched center pole and thick copper plating to minimize magnetic distortion. The voice coils use heat-resistant synthetic resin adhesive, and the woofer includes a metal bobbin for improved power handling. The cone material and cloth edge, treated with thin rubber, are engineered for smooth response near 400 Hz. High-purity copper foil lead wires enhance durability. A special diffuser improves frequency response, and the baffle uses a Saran frame without decorative edges to reduce reflections. The system includes a continuously variable level control for ±3 dB adjustment of the tweeter and mid-range, and a multi-selector switch allows direct drive of individual drivers by disconnecting the LC network.
Context
The Sony SS-7300 was a standard bookshelf speaker system developed by Sony during the early 1970s, representing the company's commitment to high-fidelity audio through advanced engineering.
Market
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