Electro-Voice 15TRXB

Name: Electro-Voice 15TRXB
Brand: Electro-Voice

Seventy-nine dollars bought a fifteen-inch triaxial driver that E-V's own catalog ranked below its pricier TRX siblings. Thousands of builders put it in a folded-horn corner anyway.

Overview

The 15TRXB was Electro-Voice's working-class triaxial: a fifteen-inch extended-range integrated three-way loudspeaker, listed at a net price of $79 in the company's 1957 catalog pages. The same advertisement spread ran in Audio (May 1957, p.87) and in High-Fidelity (May 1957, p.19). It put the 15TRX at $145, the 12TRX at $120, and the 12TRXB at a lower figure still. So the 15TRXB sat well down the TRX ladder. E-V's own copy called the whole TRX family "Extended-Range Integrated 3-Way Loudspeaker Systems," with the Radax coaxial two-ways listed separately beneath them.

For $79 the buyer got a coaxial assembly with a mechanical crossover at 2,000 cps and a built-in electrical crossover at 3,500 cps feeding a T35B very-high-frequency tweeter. The fifteen-inch Radax-type woofer carries a "Whizzer" high-frequency propagator cone. The mechanical crossover at 2,000 cps hands the upper midrange to that whizzer, and then the electrical network at 3,500 cps passes the signal to the separate T35B VHF unit. Two crossovers, two different jobs. This predates the single-crossover approach that later coaxial drivers settled into, and it is why the 15TRXB is described as a three-way rather than a two-way with a helper tweeter.

Power handling is documented at 20 watts, and the response is quoted as 30 to 15,000 cps when the driver is installed in the enclosure E-V recommended for it. E-V's Regency folded-horn corner cabinet was the natural home for the 15TRXB. The company's literature said the Regency could be used against a wall away from the corner for essentially flat response, or pushed into the corner to use the room's walls for augmented bass. The enclosure came in mahogany or Korina blonde, and the Regency itself was priced at $130 - more than the driver going into it. E-V sold the combination as a system, and the cabinet cost more than the speaker.

Builders who wanted to save on the cabinet could get the Regency as a kit, Model KD-4. It is a low-boy folded-horn enclosure usable in a corner or flat against one wall, finished at 29⅜ inches high, 33½ inches wide, and 19 inches deep, shipping at 70 pounds. The same kit literature lists the Empire (KD-5), Aristocrat (KD-6), and Baronet (KD-7) as the other enclosure options in the line. The Regency kit is called out as suitable for the SP15 coaxial and the 15TRX, while the Empire kit is called out as suitable for the SP15B coaxial and the 15TRXB. Because of that cross-compatibility, the driver turns up in Regency cabinets, in Empire cabinets, and in home-built corner horns. The enclosure it arrives in will shape the sound more than the driver's own spec sheet does.

Reception in the period press was advertising-driven rather than independently measured. The 15TRXB appears in dealer and manufacturer pages rather than in test reports. The Audio (July 1957, p.45) spread that placed it in the Regency was Harvey's own pitch about translating specs into sound in their listening rooms, not a review with measurements. The surviving record does show that E-V positioned the 15TRXB as the entry point to its triaxial line. It also shows the driver was common enough by the late 1990s to still be changing hands in the classifieds of the audiophile press. A 1995 issue of Vacuum Tube Valley carried a pair of 15TRXB triaxials in large enclosures offered at $150 for the pair, so the secondhand market never treated them as precious.

For a collector today, the 15TRXB is a good driver in a category where the good ones are not rare. The $79 list price, the 20-watt rating, and the 30-to-15,000-cps response in the Regency all point to a speaker built to fill a room efficiently rather than to chase the last octave. The whizzer cone is the part that will need attention first. Those propagator cones are the wear item on any Radax-type driver, and a dented or detached whizzer changes the upper-midrange behavior noticeably. The T35B tweeter is a separate, replaceable unit, which helps. Expect to find these drivers in period cabinets rather than bare, and price accordingly: the driver alone is a modest purchase, and the Regency enclosure is the part that has held whatever value the system retains.