JBL J620M (1973–1976)
The JBL J620M is a 12" three-way speaker system from the mid-1970s. It is a sealed acoustic suspension design in an oiled walnut cabinet. The "M" stands for Monitor. The drivers are an LE14A woofer, an LE5-2 midrange and an LE20-1 high-frequency driver, crossed over at 800 Hz and 3000 Hz. Impedance is 8 ohms, and JBL recommended a minimum of 10 watts of amplifier power. The cabinet measures 24" × 15-1/2" × 12" and weighs 42 lbs.
Documentation on this model is thin. The most complete technical record comes from an odd place: Ohio University's E.W. Scripps School of Journalism listed a pair of J620Ms in its 1976 federal grant equipment inventory for the Radio-TV program. That is a small piece of evidence that these speakers saw professional broadcast use, not just living-room duty. The same inventory is the source of the full spec set above, including the production years of 1973-1976. No original price was recorded there.
A marketplace listing for a pair of J620Ms included the original schematics and paperwork, which suggests the documentation that does exist circulates among collectors. The listing also called the speaker a "studio monitor," which fits the "M" designation and the Ohio University usage. The Scripps source itself simply calls it a 12" three-way system.
Beyond these facts, the record is quiet. No period reviews, sensitivity ratings, or frequency response figures beyond the crossover points have surfaced. What is known is consistent across sources, but it is not much for a speaker that clearly had some professional presence in its day. A 1996 issue of Audio magazine (February 1996, p.85) included the J620M in a direct-sales advertisement, so the model was still being sold years after production ended. The advertisement pushed direct purchasing as a way to cut out middleman costs.
- **Type:** 12" 3-way, sealed acoustic suspension
- **Drivers:** LE14A woofer, LE5-2 midrange, LE20-1 tweeter
- **Crossover:** 800 Hz / 3000 Hz
- **Impedance:** 8 ohms · **Min. power:** 10 watts
- **Dimensions:** 24" × 15-1/2" × 12" · **Weight:** 42 lbs.
- **Finish:** Oiled walnut
- **Years:** 1973–1976
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