In Reply to: High efficiency speaker with great reproduction of speech posted by beppe61 on April 7, 2014 at 01:10:11:
Great question, beppe61. Correct, believable reproduction of human voice would seem to be a requirement in any high fidelity system, no?
Back in 1998 or so I bought a pair of ancient RCA field coil theatre woofers off ebay, and the seller offered to throw in a companion compression driver that shared the same motor for another $50. This RCA MI-1428B sat on my workbench for a few weeks until I connected its field coil to a lantern battery and fed it some audio from a table radio. I stood back and thought: DAMN, what is this thing? It offered the truest reproduction of the human voice I had ever heard! As I came to understand, this late 1930s RCA theatre compression driver was built under threat of patent infringement from Western Electric, and like other designs of its era went to elaborate lengths to avoid infringing AT&T's patents. Instead of AT&T's portion-of-sphere aluminum foil diaphragm with peripheral suspension and voice coil, this RCA used a silk cloth and phenolic resin center-suspended shallow cone diaphragm with wool cloth outer suspension and 2" voice coil located midway between center and outer edge. So although a bit heavy and challenged in the highest frequencies, the diaphragm was extremely well damped and well behaved in the critical midrange. As I came to appreciate, this enabled "big goose bumps" lifelike vocal reproduction. My machinist extraordinaire buddy Rich Drysdale and I began to manufacture modernized versions of this driver in 2004 and continue sporadically to this day. We have lost our shirts in this endeavor thus far but have sure had a lot of fun!
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Follow Ups
- RE: High efficiency speaker with great reproduction of speech - Steve Schell 22:49:20 04/12/14 (1)
- RE: High efficiency speaker with great reproduction of speech - beppe61 09:40:26 04/22/14 (0)