JBL 2470 Compression Driver

Little is documented about the JBL 2470 in official sources. No datasheet, brochure, or manual surfaced in the research, and even its production years and original price are unrecorded. What the record does show, pieced together from collector discussions on the Lansing Heritage Forum, is that the 2470 is essentially a JBL-branded version of the Altec 288 compression driver. It uses the same 4-inch aluminum diaphragm (Altec part number 34647) and shares the 288's phase plug design, but swaps the Alnico magnet of the Altec for a ferrite structure. That made it the heavier, more affordable counterpart to the 288. It mates to a 1.4-inch throat horn, commonly the JBL 2350 in professional cinema and sound reinforcement setups.

The 2470 was used in JBL's professional cinema systems. Forum users report it as a solid, reliable driver that sounds close to the Alnico 288, though some find the ferrite version less "musical" and noticeably heavier on large horns. It's frequently recommended as a good-value alternative for DIY horn projects, especially since the 34647 diaphragm remains available from Altec parts suppliers. That matters because diaphragm failure is the most common issue, and the unit is user-serviceable in that regard. Other known failure modes include demagnetization from rough handling, clogged phase plugs, and stripped mounting bolts if over-tightened.

Known specs:

Diaphragm: 4-inch aluminum dome, Altec #34647 (shared with Altec 288)
Voice coil: 4 inches
Magnet: Ferrite (pot-style assembly)
Throat: 1.4 inches

Beyond these points, the record is thin. No frequency response, power handling, impedance, or sensitivity figures were found. The exact relationship to the sibling JBL 2471 also remains unclear. Modern Recording (July 1979, p.26) touched on the trade-off between the 2470's greater power handling and the extended frequency response of the Altec 2420 in a two-way biamping discussion. That at least confirms the driver was on working engineers' radar in the late 1970s.