JBL 2408H

A 1.5-inch annular-diaphragm compression driver that spent decades inside JBL's PA cabinets and is only now getting attention as a standalone part.

Overview

The JBL 2408H is not a speaker you buy to sit on a shelf. It is a high-frequency compression driver, a bolt-in component that threads onto a horn and disappears inside a professional loudspeaker cabinet. Collectors mostly run into it as a replacement part number, not a product, which is why the naming gets confusing. The research turns up three closely related variants: the base 2408H, the 2408H-1, and the 2408H-2. Each has its own JBL part number and its own set of host cabinets. The base 2408H is listed under part number 361549-001X, the 2408H-1 under 365011-001X, and the 2408H-2 under 5020337X. None of them were ever sold to consumers as a boxed hi-fi product, and that shapes how they trade today.

Physically, it is a 1.5-inch compression driver built around an annular polymer diaphragm and a neodymium magnet. Polymer instead of the older aluminum or titanium domes, and neodymium instead of ferrite, is the signature of JBL's modern professional line. The polymer diaphragm is the reason these can be driven hard night after night without the metallic edge that older compression drivers develop when pushed.

The 2408H-1 is specified with a 38 mm (1.5 in) exit and a 38 mm (1.5 in) voice coil, with a nominal impedance of 8 ohms. Some JBL documentation for the MD55 describes the same driver as having a 1.5-inch diaphragm with a 1-inch exit, so JBL's own spec sheets were not always written by the same hand. The 2408H-2 is listed as a 1.5-inch compression driver with a poly-annular diaphragm and neodymium magnet, and one parts listing describes its diaphragm assembly as a "38Core Aluminum Assembly 64mm." The base 2408H is documented as a 37.5 mm (1.5 in) annular polymer diaphragm, neodymium compression driver, 8 ohms.

JBL was founded in Los Angeles, California in 1946 by James Bullough Lansing, and the company has been part of Harman International, itself now a Samsung company, for years. The 2408H sits in the professional sound-reinforcement tradition, not the home hi-fi tradition that produced the L100 Century and the studio monitors of the 1960s.

Key Features

Annular Polymer Diaphragm with Neodymium Motor

The defining feature of the 2408H family is the diaphragm and magnet combination. JBL's own spec sheets for the MRX612M and the MRX515 describe the driver as a "37.5 mm (1.5 in) annular polymer diaphragm, neodymium compression driver 8 ohms." The polymer suspension gives the driver its smoothness in the upper midrange and lower treble, the region where compression drivers tend to get shouty.

Phase Plug Differences Between 2408H and 2408H-1

This is the detail that trips up buyers. According to The Speaker Exchange, the JBL 2408H and 2408H-1 drivers differ in their phase plugs: the 2408H-1 has a square phase plug and a shorter screw-on connector compared to the 2408H. That means the two are not drop-in interchangeable in every application. If you are buying a replacement for a specific cabinet, you need to know which variant the cabinet was designed around. A 2408H will not simply screw onto a horn that expects a 2408H-1, and vice versa. Verify this before you buy.

PT Progressive Transition Waveguide Compatibility

In JBL's installation products, the 2408H-1 is paired with a "Large PT™ Progressive Transition waveguide for excellent pattern control and low distortion." In the AM5215/66 and AM5212/66, that waveguide is rotatable for vertical or horizontal orientation, and the MD55 uses a 90° x 50° rotatable PT Progressive Transition waveguide. The waveguide is not part of the driver, but it is the reason the 2408H-1 sounds coherent rather than beamy. Anyone who pulls a 2408H-1 out of a cabinet and mounts it on a generic horn should expect the pattern control to change.

Image Control Waveguides on the 2408H-2

The 2408H-2 generation moved to what JBL calls "innovative new horns with updated JBL Image Control Waveguides" that "provide optimum beamwidth and directivity." JBL's marketing for the PRX912, PRX935, and PRX915 describes the 2408H-2 as providing "clear, detailed high-frequency response even at maximum volume." That is marketing copy, not an independent measurement, but it points to the design intent. The 2408H-2 was built for powered PA boxes where a Class-D amplifier with DSP limiting drives it, and the waveguide geometry was tuned to work with that signal chain.

Diaphragm Replacement and Serviceability

The diaphragm is a serviceable part. For the base 2408H, the replacement diaphragm is listed as D8R2408. For the 2408H-2, a diaphragm repair kit is sold on the Russian marketplace Ozon, described as a "finished product, easy installation without special equipment or preparation." A blown diaphragm does not write off the whole driver. A competent tech can swap the assembly and put the unit back into service.

Historical Context

No production years, original manufacturer pricing, or historical development information turned up in the research for any of the three variants. What the sources do establish is where the driver was used. The base 2408H is described by retailer Bax Music as an "HF driver for MRX5, PRX5, VT4887," and JBL's own spec sheets place it in the MRX612M and MRX515. The 2408H-1 appears in the AM5215/95, AM5215/66, AM5212/26, AM5212/95, AM5212/66, AM5212/26-WRX, AM5212/64-WRC, MD55, and CV3025-66. The 2408H-2 is described by Ubuy as "primarily designed for the PRX700 and PRX800 series, but it may also fit some older JBL models," and a Russian listing states it is used in the "MRX, PRX, Vertec" series. AVL Gear adds that the 2408H-2 is used in "PRX and AC series speakers."

This pattern suggests, and this is interpretation, not documented fact, a driver that was iterated across JBL's professional lines over a span of years, with the suffix changing as the host cabinets changed. The research does not establish a hierarchy between the three variants, and no source states which came first.

Collectibility & Value

These are working parts, not collector's items, and the market reflects that. The only price found in the research is a used/private sale listing on Avito for a 2408H-2 at 12,000 rubles each. It is undated, and that market does not translate cleanly to US or Western European pricing. No original manufacturer price was found for any variant, and no common failure modes, maintenance procedures, or discontinued-parts warnings turned up either.

The market does offer parts availability. The 2408H-1 is sold as a replacement part under number 365011-001X by reconingspeakers.com. The 2408H-2 is available under part number 5020337X from AVL Gear, and Ubuy lists a "JBL Factory Replacement Driver 2408H-2, PRX700, PRX800." AVL Gear's marketing copy argues for genuine parts - "Using genuine JBL replacement parts ensures your speaker system continues to perform to manufacturer specifications" - and that is marketing, but matching the original phase plug and diaphragm assembly is a real concern given the 2408H/2408H-1 differences above.

One conflict is unresolved for anyone shopping the 2408H-2. JBL's own spec sheets for the PRX912, PRX935, and PRX915 describe the diaphragm as "poly-annular," while a Russian Avito listing describes it as "титановая диафрагма" - titanium. The manufacturer documentation is the more authoritative source, so the poly-annular description should be treated as correct, but listings in some markets describe the material differently. There is also a forum opinion from a diyAudio user who described the 2408H-1 as "basically a BMS 4540ND with a different phase plug." That is one person's visual comparison, not a measurement.