JBL 4870

The JBL 4870 is a 3-way bass-reflex loudspeaker, and the documentation on it is thin. What the record shows comes almost entirely from a scanned owner's manual and a single ecommerce listing. No period reviews, no production years and no original price have surfaced.

Here is what is known. The 4870 pairs a 12-inch cast-frame woofer, with a treated paper cone and foam surround, with a 5-inch midrange in a sealed chamber and a 1-inch soft-dome tweeter with magnetic-fluid cooling. The crossover sits at 500 Hz and 3 kHz. The cabinet is MDF with internal cross-bracing and a rectangular front-firing port. It's a walnut-veneer box with a removable cloth grille held by plastic snap-in fittings, and it connects through standard 5-way binding posts. The manual recommends placing it away from room corners with the tweeter at ear height.

The 4870 was also a touring pro speaker, not only a living-room one. Recording-Engineer (April 1986, p.50) reported that each 4870 box weighed 214 pounds and measured 49.5 by 29.5 by 19.75 inches. The home version documented elsewhere weighs 38 pounds and stands 24 inches tall. So the 4870 name appears to have covered at least two very different boxes: a substantial touring enclosure and a more modest home loudspeaker. Which came first, or whether they shared anything beyond the name, isn't documented.

For the home version, the spec sheet lists 8-ohm nominal impedance, 90 dB sensitivity (1W/1m), and 150 watts continuous program power handling, with 20-200 watts RMS recommended. Frequency response is where the record splits. One source says 40 Hz - 22 kHz (±3 dB), while the owner's manual gives 30 Hz - 20 kHz. Both are left out of the summary below rather than picking one.

Type: 3-way bass reflex, front-firing port
Drivers: 12" woofer, 5" midrange, 1" soft-dome tweeter
Crossover: 500 Hz and 3 kHz
Impedance: 8 ohms
Sensitivity: 90 dB (1W/1m)
Power handling: 150 W continuous program; 20–200 W RMS recommended
Dimensions: 24" H × 15.5" W × 12.5" D
Weight: 38 lbs each
Finish: Walnut veneer, black grille

If you own a pair of 4870s, home or touring version, the Archive would like to hear from you. The record on these is sparse, and any additional documentation would help.