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does anyone has tried this before ? aluminum ring around the mica

http://cgi.ebay.com/HMV-No4-soundbox-re ... 2eb6dcf798

Paul

I've never heard of such a thing before, and quite frankly, I dont understand what purpose it would serve.

The Aluminum ring is not a flat ring, but a stamped form the obviously was purpose made. I have zero experience with HMV machines so I can only speculate that maybe this diaphragm was for some other off brand repro that just happened to fit.

It might be interesting to ask the seller a question and request he post a picture of the picture of the packaging the NOS diaphragm came in.

Brad wrote:The Aluminum ring is not a flat ring, but a stamped form the obviously was purpose made. I have zero experience with HMV machines so I can only speculate that maybe this diaphragm was for some other off brand repro that just happened to fit.

It might be interesting to ask the seller a question and request he post a picture of the picture of the packaging the NOS diaphragm came in.

The same composite diaphragm turns up on late production VV 2-60 portables. I have a couple gilt pot-metal No. 4 sound boxes in my junk box with these diaphragms. The aluminum edge appears to have been an attempt to increase edge compliance, and to encourage the center of the diaphragm to move more as a piston. In this it is a more or less qualified success. I installed such a diaphragm in the HMV No. 4 on my Model 32 gramophone, and found a most noticable improvement, with slighly increased bass, better trebel and a lass prominent midrange.