Sony SS-7220 (around 1973)
A 3-way bookshelf speaker system using Sony's Ultra Linear Magnetic Path (ULM) technology for reduced distortion.
Overview
The Sony SS-7220 ULM22 is a bookshelf speaker made around 1973. It is a 3-way, 3-speaker bass-reflex design, sold under the full name "SONY SS-7220 ULM22." The drivers are a 25 cm woofer, a 10 cm midrange and a 2.5 cm dome tweeter. Sony built it with several advanced materials and techniques for its time. It was designed for high-fidelity audio and noted for clear, powerful sound with tight bass, and it pairs easily with amplifiers.
Specifications
| System | 3-way, 3-speaker bass-reflex system |
| Woofer | 25 cm cone type |
| Midrange | 10 cm cone type |
| Tweeter | 2.5 cm dome type |
| Frequency Response | 40 Hz to 25000 Hz |
| Impedance | 6 Ω |
| Sound Pressure Level | 88dB/W/m (New JIS) |
| Maximum Input | 70W (weighted pink noise) |
| Crossover Frequencies | 600 Hz, 4.5 kHz |
| Dimensions | 350 mm (W) × 590 mm (H) × 290 mm (D) |
| Weight | 15 kg |
| Cabinet Type | Bass-reflex with 20 mm thick hard particle board |
| Grille | Detachable |
Design
The SS-7220 uses Sony's Ultra Linear Magnetic Path (ULM) magnetic circuit. It cuts distortion by adding a notch and copper plating to the center pole. The woofer has a metal bobbin and a special alloy resin adhesive to increase input tolerance. The cone is made from Scandinavian pulp using Sony's proprietary paper technology. A dust-proof cap minimizes abnormal noise radiation. The surround is rubber-coated cloth with an airtight treatment, which eliminates a dip near 400 Hz. The lead wires are high-purity copper foil with special resin. The crossover uses large air-core coils with low DC resistance. A continuously variable level control adjusts the mid and high frequencies.
Context
The SS-7220 gives clear, powerful sound with tight bass. It is noted as easy to match with amplifiers, which makes it friendly to beginners. It was priced at ¥27,000 per unit around 1973.
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