JBL LE21H
The LE21H is the big one in JBL's LE series — a 21-inch woofer built for serious low-end output. It's a cast-frame driver with a reinforced paper cone and a foam surround, powered by a 24 oz. ceramic magnet and a 2.5-inch edgewound voice coil. This is a pro-grade transducer meant for large reflex enclosures; JBL recommended a 300-liter box with a 1.5 kHz crossover point.
The Thiele/Small parameters that survive paint a picture of a high-efficiency, high-output design: 98 dB SPL (1W/1m) sensitivity, an Fs of 30 Hz, and a Qts of 0.27 — low enough to stay controlled in a big ported cabinet. The magnet gap flux was rated at 12,300 Gauss, and the whole driver weighs in at 48 lbs. It was marketed for both pro sound and home high-fidelity systems, and it's the kind of driver that found its way into large-format studio monitors and serious home setups alike.
A couple of spec discrepancies float around the forums. Power handling is listed variously as 700 watts peak / 350 watts RMS and 650 watts; frequency response appears as both 50 Hz – 2 kHz and 45 Hz – 2 kHz. Take your pick — either way, this is a lot of cone area moving a lot of air.
Audio (July 1980, p.40) covered the LE series around this period, though the specific review details are thin in the surviving record.
**Known specifications:**
- 21" woofer, 8 ohms
- 98 dB SPL (1W/1m) sensitivity
- Fs: 30 Hz · Qts: 0.27 · Vas: 480 liters
- Xmax: 6 mm · BL: 12.2 Tm
- Foam surround, reinforced paper cone, cast frame
- Weight: 48 lbs
- Recommended enclosure: 300-liter reflex
No exact production years or original retail price have surfaced in the documentation. The foam surrounds are the usual suspects for age-related deterioration, as with most JBL drivers of this era.
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