Stax SR-34
An electret "earspeaker" system that put Stax's electrostatic sound within reach. It still turns up in the classifieds for the price of a decent dinner.
Overview
The SR-34 is the working stiff of Stax's electret line. It is a complete earspeaker system built around an electret transducing element rather than a true electrostatic driver, and it was sold with an energizing adapter so it could be plugged into ordinary amplifier speaker outputs. Stax's own advertising placed it alongside the SR-84 (Lambda Junior) as a "cost vs. performance electret earspeaker system," and described the high-polymer film used for the diaphragm as "less than" the thickness of the Lambda's. The ad copy trails off mid-sentence in the surviving scan, but the pitch is clear enough: this was the affordable way into the Stax house sound (Audio, October 1982, p.103).
Per the same advertising, that house sound meant "the precise, transparent, and natural sound of an electrostatic system at an extremely affordable price." The Professional designation in the SR-34 Pro name referred to a new ultra-low-mass diaphragm (Audio, October 1989, p.319). Marketing copy is marketing copy, and Stax was selling hard in those pages. The electret approach was still a real engineering compromise.
A spec sheet in a 1989 buyers' guide gives the numbers: frequency response of 25-20,000 Hz ±2 dB, impedance 8 ohms, sensitivity 95 dB SPL with a 1 mW input at 1,000 Hz, and maximum power handling of 10,000 mW (HiFi-Stereo, 1989, p.179). The 8-ohm impedance and the 95 dB figure are the reason the SR-34 could be driven from a receiver's speaker taps through the adapter, rather than needing a dedicated high-voltage energizer. It was a headphone system designed to slot into a normal hi-fi. The ±2 dB window is tight for the money, and 25 Hz at the bottom is honest low-end reach for an electret.
It is not a true electrostatic, though. The electret element uses a permanently charged polymer film instead of the biased stator arrangement found in Stax's flagship designs. That is why the SR-34 and its Lambda Junior sibling were pitched as the budget tier rather than the reference tier.
The SR-34 shows up in dealer classifieds through the early 1990s at modest money. Audio's Audio Classics listings quoted the SR-34 at $96-99 in 1991-92, with the SR-34 Pro variant at $149-162 and the SR-84 at $149 (Audio, November 1991, p.319; Audio, January 1992, p.41). Those are dealer asking prices for used or demo stock, so treat them as a floor on what the system traded for, not a collector premium. The Pro version consistently commanded roughly fifty percent more than the base SR-34 in the same listings.
The energizing adapter is not optional. Without it the earspeakers are a paperweight, and adapters go missing or get separated from their headsets over four decades. Confirm the adapter is included and working before handing over money, because a replacement is not something you pick up at the corner store.
The SR-34 is not a collector's trophy. It is a sensible entry into Stax ownership for someone who wants to hear what the fuss is about without spending Lambda money, provided the adapter is there and the elements still work.
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