Electro-Voice T35B
A four-ounce magnet, a 180-degree horn, and twenty-two dollars - the little VHF driver for budget hi-fi systems.
Overview
The T35B is the cheap seat in Electro-Voice's Super-Sonax family, and it is the one most people actually bought. The flagship T350 carried a full one-pound magnet. The T35 sat in the middle with seven ounces. The T35B got by on a four-ounce magnet and a 9,000-gauss gap, and Electro-Voice priced it at $22.00 net. That one number tells most of the story: a very-high-frequency unit a teenager on a paper-route budget could afford to bolt onto an existing speaker.
The money bought a diffraction horn covering roughly 2 kc to 18 kc at ±2 db, with a RETMA sensitivity rating of 54 db. That is three decibels down on the T35's 57 db and six down on the T350's 60 db. Collectors who have run all three side by side describe the T35B as the slightly quieter, slightly less extended sibling, which is what the spec sheet promises. It shares the family's 180° dispersion pattern, one-inch voice coil, 16-ohm impedance, and 50-watt program / 100-watt peak capacity. The parts that matter for system-building are identical across the line.
Electro-Voice's own advertising said the Super-Sonax line delivered flat, extended high-frequency response "beyond the very limit of audibility." The argument was that folded-horn and phase-loaded systems with strong first-octave bass need that top-end extension to stay musically balanced. The pitch leaned on the diffraction principle and the company's Avedon throat design as the way to get there without distortion. That is marketing copy and should be read as such. The T35B was sold less as a standalone product than as a building block.
Electro-Voice positioned it that way. Period advertising laid out a step-by-step upgrade path: start with an SP12B coaxial full-range speaker, then add the T35B with an AT37 level control and an X36 crossover "for those silky highs." The same copy notes the T35B needs only the X36 to attach to an existing music system, with the AT37 optional. The driver was also specified as the high-frequency section of the Stereon 1A three-way system, paired with the MJ30B mid-bass coaxial assembly. Audio (October 1955, p.83) described the T35B as intended for lower-powered systems and for existing quality AM-FM radios and radio-phonographs, finished in flat matte black.
That flat matte black finish says who the buyer was. This is not a component meant to be admired on a shelf. It is a driver meant to disappear into a cabinet or perch on top of one, wired in and forgotten.
Today the T35B turns up in period-correct restorations of entry-level and mid-line Electro-Voice systems from the second half of the 1950s. A Stereon 1A without its T35B is an incomplete system, and the driver shows up in the do-it-yourself Aristocrat builds that Electro-Voice pushed hard in its catalogues. The company sold the Aristocrat corner folded-horn enclosure as a $72 finished cabinet or a $39 kit, and the T35B was the recommended high-frequency step in the build plan that started from an SP12B. Collectors chasing a budget E-V system of the era will find the T35B far easier to source than the T350 and considerably cheaper, which is the same arithmetic that made it popular in 1956.
The caveats are the ones the spec sheet already gives. Eighteen kilocycles is the ceiling here, against twenty-one on the T350. The lower sensitivity means the T35B wants a level control to blend properly with whatever it is crossed over to. The 16-ohm impedance and 50-watt program rating also mean this is a driver for valve-era systems and modest solid-state amps, not for anyone planning to throw modern power at it.
The T35B is the least glamorous member of the Super-Sonax trio and the one with the least collector heat around it. Twenty-two dollars bought a genuine diffraction horn with the family's dispersion and power handling in 1956. Today the same driver costs less than the T350 premium.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.