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Post by Deleted on Oct 8, 2009 17:30:05 GMT
I measured the thickness of some cones: National 9.5" Original 1934 - 7 thou -weight-29g National 9.5" Pre Hot Rod - 8.5 thou -weight - 32g National 9.5" Hot Rod Cone - 7 thou thick -weight- 29g National Hotrod Tricone - 7 thou thick -weight - 7.5g Continental Tricone - 8 thou thick -weight - 11g
My measurments were non destructive of the cone taken on the lip in several places
Thickness of the metal is a major factor in the sound a cone produces along with the type of metal of course and how it is spun I expect, I thought it may be of interest to someone
Cheers , Josh
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Post by tark on Oct 9, 2009 17:06:04 GMT
As you probably found, measuring the thickness of a spun cone is quite tricky because the thickness and surface texture changes across the surface due to the spinning process itself. A more revealing measurement would be the thickness of the cone blank before its spun - information which is usually not available to us.
I find it is more revealing to weigh the cones - the National ResoPhonic cones being quite clearly the lightest. The other significant factor is the exact make up of the alloy used. As far as I know it is not usual to make cones from 'pure' aluminium. Finding the right alloy today which is similar to the alloy available in 1930 is part of the trick to making good cones. Something which National ResoPhonic have done only quite recently with their so called hot-rod cones.
Most cones look at least superficially the same - the biggest difference is whether or not they have the stamped spirals. Quarterman and I believe some Beard cones do not have spirals. Dobro cones apparently dont have spirals and some of them have four holes punched through them.
I have seen some very heavy Chinese made cones that I suspect were entirely stamped out - even including fake 'spinning' marks.
I read that John Dopyera said he felt - providing the processes were performed correctly he didn't think there was any difference between spun and stamped cones, although I think he was talking about the 10.5 inch Dobro cones. Some of these have stamped recesses to take the spider feet.
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Post by Deleted on Oct 9, 2009 17:24:32 GMT
I didnt find it too hard to measure cone thickness from the lip around the edge using a digital caliper i did it in several places to check my measurement too. I did weigh some a while back If I recal this was what I got Original National '34 9.5 cone - 29g National Hot Rod Cone - 29g National Pre Hot Rod cone - 32g
cheers
Josh
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Post by Deleted on Oct 18, 2009 17:35:55 GMT
just to added to my little list in the 1st post
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