Infinity PS-4
The Infinity PS-4 is a three-way, four-driver acoustic suspension bookshelf speaker sold in the mid-to-late 1970s. It was the "little brother" of Infinity's Quantum series, a smaller and more affordable alternative to those larger floor-standing designs. At $260 each in its era, it sat at a serious but approachable price for a company known for pushing into esoteric territory.
The driver complement is straightforward for the period: a 10" woofer, a 4.5" midrange, and a 1" dome tweeter, all in a sealed cabinet measuring 24-1/8" x 14-1/16" x 11-3/4" and weighing about 45 lbs. Rated sensitivity is listed as either 86 dB or 88 dB depending on the source, nominal impedance is 8 ohms, and Infinity recommended 10–100 watts of amplifier power. Frequency response is generally listed as 42 Hz–25 kHz, with crossover points somewhere in the 800 Hz / 5 kHz neighborhood (though at least one source lists 700 Hz / 4.5 kHz — the record isn't fully settled on that detail).
Documentation on the PS-4 is thin. The Vintage Knob, Hifi-Wiki, and Classic Audio all agree on the basic specs above, but there's no substantial period review in the archive, no owner commentary, and no service or repair history. Even the cabinet finish is disputed. Some sources say walnut veneer, others say walnut wood-grain vinyl. If you own a pair, the serial number plate and the crossover board are probably the best primary evidence of what your units shipped with. Audio magazine (November 1989, p.171) ran classified advertisements during that period, showing the secondhand market for vintage audio gear remained active.
Known Specs
- System: 3-way, 4-driver, acoustic suspension
- Woofer: 10" / Midrange: 4.5" / Tweeter: 1" dome
- Impedance: 8 ohms
- Recommended power: 10–100 watts
- Dimensions: 24-1/8" H x 14-1/16" W x 11-3/4" D
- Weight: 45 lbs (20.4 kg)
- Original price: $260 each
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