The technical report is excellent, I have heard an All range, and indeed it is an excellent gramophone, though interestingly an EMG Xb oversize despite it's slightly smaller horn (33 ½" vs the All Range's 36") did win out in a comparison, though that was a hot jazz record, different records may well turn the tables, I still love the all range though, such a striking machine to see, interestingly the image in that article seems to represent a Senior.
Regarding soundboxes, here are my two Expert 4 spring 'Dynamic' soundboxes, these could be an example of the newer and older versions.
The one on the left is from my Junior (10a Soho Square 1933-36) and the right from my Senior (64 Frith Street 1936-1939), the difference is slight, but the later one on the right is ever so slightly larger, possibly with a slightly larger diaphragm? I haven't my calipers here to check currently, with a slightly different shaped body, notice how the earlier body is longer with a cut out for the needle bar, the later is flat bottomed, this doesn't seem to be an isolated thing as I previously rebuilt another later Expert 4 spring which was also of the larger type, perhaps they started like mine on the left, progressed to the slightly larger one then became the type Chunny has (Of which I have never seen another, very interesting!) in the war time and post war years? all speculation however.
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