Retro Watch: The First Powered Loudspeaker?
A “modern” idea’s time really came much earlier

By Keith Clark


Figure 1

Kiddies, there truly isn’t much new under the sun.

Our friend Ivan Schwartz recently pointed me to a very interesting page on the James B. Lansing (JBL) Heritage web site. (By the way, for the uninitiated, this is a superb site to check out, www.lansingheritage.org.)

Way back in 1965, JBL introduced what were called “Energizer” amplifier modules. They were built into loudspeakers, such as the D50SMS7 multi-way studio monitor system pictured at left in Figure 1.

Energizers had the capability of internal equalization, which could be achieved with the addition of a simple module. Crossover could also be adjusted and set.


Figure 2

“This was a very early version of full system integration that we see so much today. You had electronics packaged with, and tailorable to, the loudspeakers,” JBL’s Mark Gander told me. “These little EQ cards fit right into the amp, and they allowed you to do rudimentary bass boost or midrange equalization, or tweak the crossover.”

The technology was available for both studio monitor and sound reinforcement loudspeakers, as well as hi-fi systems.

Certainly, this was one of the first - if not the first - commercially available powered loudspeakers, and they had built-in processing capability to boot! (Yet another thing for me to keep in mind next time I receive one of those press releases touting a “new, revolutionary” technology…)


Figure 3

Also at the bottom left of Figure 1, you’ll see a polar response graph (nope - data acquisition isn’t new either) showing the horizontal dispersion of the high-frequency assembly in the JBL S7 loudspeaker. An automatic recorder traced the curves with the transducer located in a free-field environment.

Now, have a look at the chart on the bottom right of Figure 1. It shows the acoustic output of the JBL LE15A driver, when provided with 60 watts of continuous sine wave power at a frequency of 40 cps (cycles per second). A calibrated lab mic was used to pick up the sound, and this signal was fed directly to an oscilloscope, with the trace then photographed.


Figure 4

Pictured in Figures 2, 3 & 4 is the Energizer in action, part of a system implemented at the Mormon Tabernacle in Salt Lake City at some point in the ’60s.

In addition to the built-in powering and processing capability, these loudspeakers included large 15-inch woofers and passive radiators with large slant-like lenses helping with directivity.

 

Keith Clark is editor of Live Sound and is a history freak. He can be reached at kclark@livesoundint.com

October 2003 Live Sound International

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