JBL TL500 (Mid-1970s)

The JBL TL500 is a floor-standing, two-way loudspeaker from the mid-1970s, built on the transmission line (or "acoustic labyrinth") principle. It belongs to JBL's TL series, which also included the TL300 and TL600, and it was positioned as a lower-priced alternative to the company's L-series. "TL" stands for Transmission Line.

The drivers are simple: a 10-inch LE10A woofer and an LE20 tweeter, the same pair found in several of JBL's L-series models of the era. The TL500 is described as a direct descendant of the L50 and L100 designs, sharing those exact drivers. The crossover is at 2.5 kHz (per audioheritage.org; radiomuseum.org lists 3000 Hz) with a 12 dB/octave Linkwitz-Riley slope. The cabinet is 3/4-inch high-density particle board in walnut veneer, with a zip-lock removable grille frame and color-coded binding posts on the back.

Specifications as documented: 8-ohm impedance, 60 watts continuous program power, frequency response of 40 Hz to 20 kHz, and sensitivity of 88 dB SPL at 1 watt, 1 meter (anechoic). Dimensions are 24 × 14 × 11-1/2 inches (H × W × D). Each speaker weighs 31 lbs.

JBL's advertising for the "T" and "TL" series leaned on the professional heritage behind the designs, noting the company's decades of use in studios and at major live events. It also pushed the high polymer laminated, mineral-filled polypropylene low-frequency transducers as delivering smooth, uncolored, powerful bass that was resistant to the automobile's hostile acoustic environment - which put the TL series in car audio as well as the home. Audio (July 1987, p.61) ran this campaign copy.

Among collectors, the TL500 has a reputation as a "sleeper," a great-sounding speaker often overlooked in favor of the more famous L-series models. Owners describe the sound as warm and smooth, with good bass extension for a transmission line design. Some note the LE20 tweeter can sound a bit forward or harsh at high volumes. The foam surrounds on the LE10A woofer are known to deteriorate with age and need replacement. The LE20 tweeter itself is a known failure point, and original replacements are scarce, though aftermarket diaphragms are available. A good pair typically runs $200-400 USD.

No exact production years, original price, or official spec sheet have surfaced in the available documentation. The record is also thin on factory crossover component values, port tuning, and serial number ranges.