1928 duplex patent

[bfish]

Herman J. Fanger filed this patent in 1928;

http://www.google.com/patents?id=SOB5AAAAEBAJ

First shoot-thru duplex?

The Bostwick/Bell Labs duplex patent;

http://www.google.com/patents?vid=USPAT1907723

...wasn't filed until a full year later, though approval was granted to Bell Labs' patent first.

Looks like Fanger also had a very early grasp of the dual voice coil concept as well.

[bowtie427ss]

Interesting stuff!

Thanks for posting!

There are some interesting links in the references especially in the second patent. One from Renkus Heinz for multiple drivers in a common horn, a similar patent from Turbosound for a similar arrangement as well as one for some sort of phase plug type device, for a while TS used to push advertising for their "patented Turbosound device". Also a patent from Altec for a piezoceramic tweeter.

[bfish]

You're welcome.

Yeah, the citations and "cited by" features are invaluable, in fact, that's how I found the Fanger patent. I've been studying Danley's Unity patent (at GM's suggestion) for awhile, which cited the Fanger patent. While there were a few other patents that predated production of the Altec/Lansing Duplex, most were merely tweeters strapped in front of woofers.

What I found most interesting was Fanger's employ of a single magnetic source (as used in The Engine), versus the widely produced Altec/Lansing dual magnet iteration. It seems to me the dual mag version is really a step backwards...not only do you have the extra expense of another magnet or field coil, but there's the added delay and dimension that design incurs. Fanger's design has flaws too though, primarily directivity mismatch and potential IM distortion.

Since my initial post, I've been searching for more info on Fanger, but haven't found much. None of his patents were assigned to a company or entity that might have resulted in actual production. Some of his patents, which included xfmrs, various artillery-related devices, and even rail spikes did have percentages assigned to individuals. As often happens with this type of thing, I'm left with more questions than answers...