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Is the tubing from the tone arm to the horn exponential? and what material is it made from paper mache type material ,metal or wood?

Thanks, Jake

The tube is metallic, and at least externally looks to be of a single diameter. I never disassembled it to check the internal diameter, but we have an expert in the forum - emgcr - that actually built full fiberglass horns with the same dimensions as the originals and rebuilt several machines, so he can provide more precise response.

12jslater wrote:Is the tubing from the tone arm to the horn exponential? and what material is it made from paper mache type material ,metal or wood?

Thanks, Jake

The internal conduit is usually made from cast aluminium of a low-resonance grade---in the case of my reproduction examples LM6. Originals appear to have been of similar material but I have not had this tested metallurgically. Some of the earlier models employed cast brass or bronze which are also materials offering low acoustic reverberation but more expensive, of course. I have also seen use of cast iron occasionally. Thick-wall casting (approximately 5/32") is the key for this application compared to say a drawn or folded material which, due to thinner possibilities, could result in unwanted echoes within the tube (cf HMV 32 etc).

The expansion is not exponential at these smaller diameters but conical/linear as shown in the drawing contained in the following link:

Please scroll down to the post on Oct 19th 2014--3.53 pm.

http://forum.talkingmachine.info/viewto ... 6&start=20