D130E

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D-130E Field Coil Speaker and Power Supply
Courtesy Paul Joppa

 


The D-130E is an extremely rare and fascinating driver from JBL. It is a driver based on the principles of the earliest loudspeakers - field coils. Since the mid 1940's, almost all loudspeakers have utilized permanent magnets to energize loudspeaker motors. This technology was the result of the war effort, during WWII, that saw the development of new permanent magnets with sufficient strength to generate high flux densities. Prior to this, the only practical way of generating the high magnetic energies needed for loudspeakers was with field coils. These required an external power source to keep the field coil energized which posed cost, operational and maintenance problems. For these reasons, field coils speakers were quickly supplanted with permanent magnet loudspeakers when the new magnet technologies became available.

Therefore, it was strange to find that JBL reintroduced field coil drivers for a very brief time around 1952. The reason behind this change is interesting. According to John Edwards, there was a rumor that the Alnico magnets used by most loudspeaker manufacturers would become unavailable due to wartime demands from the Korean conflict. In response, JBL designed field coil versions of their cone transducers. The first, and apparently only, field coil driver to actually be manufactured was the D-130E. This was meant to be a replacement for the permanent magnet D-130A.

Ultimately, the rumor proved to be false, and only a small number of D-130E's were ever produced.  Manufacturing quickly reverted to the permanent magnet version. No field coil compression drivers were ever produced since the rumor was dispelled before conversion of these drivers was begun. It appears that JBL was the only loudspeaker manufacturer to take these rumors seriously since none of their competition reverted to field coil drivers.


D-130E Field Coil
Courtesy Hal Cox

The D-130E drivers strongly resemble the early "flat back" D-130A's from the same era, and contain a 1,600 ohm field coil that requires 250VDC. The pot structure of this driver, with the field coil exposed, is shown in the photo to the left. This is from a driver that was given to Hal Cox by William Thomas.

Thanks to Paul Joppa and Joe Uyama, we have a number of photos below that illustrate this unique driver. Joe acquired a pair of D-130E's along with their field coil power supplies that he auctioned on Ebay. The photos from "Series 1" below are from that auction. The speakers were purchased by a friend of Paul Joppa. Paul provided the photos in "Series 2" below and the main photo at the top of this page.

 

 
Series 1

 


Series 2