No afilliation and all the usual caveats, just thought the members here would appreciate the detailed pics.
http://cgi.ebay.com/RARE-RCA-MI-1428...QQcmdZViewItem
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No afilliation and all the usual caveats, just thought the members here would appreciate the detailed pics.
http://cgi.ebay.com/RARE-RCA-MI-1428...QQcmdZViewItem
These RCAs are indeed remarkable drivers. I wrote an article on their history and design several years ago that is still up on my friend Jonathan Weiss's site. Here is the link:
http://www.oswaldsmill.com/id29.html
After a long dry spell there are a number of 1930s RCA field coil drivers on ebay right now. Easiest way to see them all is to search for "RCA MI". The MI-1444 woofers use the same motor structure as the compression driver, except that the top plate is modified for a deeper and wider voice coil gap. Both woofer and compression driver were built in both 13VDC and 115VDC versions.
Disclosure: My partner and I currently build and sell drivers based on the RCA design.
Steve Schell: Being a relative newbie to the legacy sound components, how does this RCA HF driver compare to the more modern JBL 375/376 and Altec 288 drivers?
In their day the RCA MI-1428B (13V field coil) and MI-1443 (115V field coil) drivers competed with the Western Electric 594A and Lansing 284, 285, 287 drivers in theatre service. An article in the RCA service literature of the time made comparisons and found (surprise!) that the RCA units offered superior power handling and considerably lower harmonic distortion than the competition.
These RCA units are very different animals than the more traditional Wente type metal dome diaphragm compression drivers. They use a 4.5" phenolic and silk cone shaped diaphragm which is suspended by a screw in the center and a clamped cloth outer surround, much like the early cone direct radiators. It is an inherently very well damped mechanism. People who use these drivers today enjoy their superb clarity of sound and take advantage of their ability to play down to 250 or 300Hz. with power and authority. The top end rolls off above 7kHz. or so, so a tweeter is called for.
So, compared to the metal dome diaphragm drivers old and new, they offer a bandwidth with more bottom and less top, and a overall sound quality that many profess to be the best they have ever heard. I think it is a shame that the center suspended cone compression driver concept disappeared into obscurity after WWII; it deserved a better fate.