Sony SS-7300 (1971–1974)
A 3-way bookshelf speaker system from Sony with Ultra Linear Magnetic (ULM) drivers and a bass reflex enclosure.
Overview
The Sony SS-7300 is a 3-way, 3-speaker bookshelf system from the early 1970s. Sony marketed it as the ULM3. It is a bass reflex design with a walnut-finished enclosure and a streamlined baffle that cuts acoustic reflections. Sony built it from the ground up on its own speaker research, aiming for low distortion and high power handling.
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 came out of Sony's fundamental research into speaker design. The Ultra Linear Magnetic (ULM) circuit uses a notched center pole and thick copper plating to hold down magnetic distortion. The voice coils use a heat-resistant synthetic resin adhesive, and the woofer has a metal bobbin for better power handling. The cone material and the cloth edge, treated with thin rubber, are made for smooth response near 400 Hz. The lead wires are high-purity copper foil, which helps durability. A special diffuser improves frequency response. The baffle uses a Saran frame with no decorative edges, to reduce reflections. A continuously variable level control gives ±3 dB adjustment of the tweeter and mid-range. A multi-selector switch disconnects the LC network so each driver can be driven directly.
Context
The Sony SS-7300 was a standard bookshelf speaker system from the early 1970s.
Market
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