Superex TRL-77
Not much is documented about the Superex TRL-77, an open-air stereo headphone that turns up in period sources from the late 1970s. The best record is a Hirsch-Houck lab test in Stereo Review (May 1977, p.34). Impedance measured about 80 ohms. Distortion stayed low up to roughly 90 dB SPL, and it reached 5% only at the 5-volt maximum input, which corresponds to a very loud 125 dB. The review called the sound well balanced and musical. It also noted the usual open-air trade-off - the phones radiated sound outward and let room noise in.
A year later, a Stereo Review equipment directory (1978, p.196) still carried the TRL-77, listed as a "Trans-Linear" open-design headphone. That is where the record ends. No production dates, original price or full specification sheet have surfaced in the Archive's material.
Similar items on eBay
No exact Superex TRL-77 listings are live right now — these searches show current Superex and similar vintage audio gear on eBay:
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.