Vintage Pair Altec Lansing 515B Speakers | eBay
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They also have vented dust caps unlike the aluminum caps on other Biflex I've seen. Maybe someone did a home biflex conversion.
I know the 420A frame/magnet is the same as the 416, which is also the same as the 515 so could be cobbled together.
Mind you after seeing that 604B magnet on a 604E white basket the other day, anything is possible.
Look at the glue on back of cones- bad recone job with cobbled together parts
here is an interesting thread on the Altec 420A, (I still say (as far as I can figure) they are an 8" woofer w/ a super magnet and with a 15" passive radiator attached at the hip):
http://www.hostboard.com/forums/f700...pressions.html
There are some strange hybrids out there, in part because Jim Lansing maintained some favored specifications across varied product lines. A JBL small format driver will bolt right up to the early Altec horns that maintained the three bolt mount, and a 288 pot will bolt right up to an 803 or 416 or 515 frame.