Note from EMGIAN
First cut the rubbers (I use soft tubular rubber as found in Bicycle shops in use for old style inner tubes valves) slightly longer than the diameter of the rebate so that they seal end to end when later inserted, then, with subtle setting in the sense of ensuring the longitudinal springs are just tight enough to stop the stylus bar from slipping in the knife edges and set so that the diaphragm is in a central position of rest, you then insert the rubber seals and assemble the housing, then apply light pressure to the cross biasing springs. You can then tune these biasing springs afterwards with subtle adjustments of 1/10th of a turn, either way, until you achieve the quality of reproduction for the type of record you wish to tune for as a default setting…
Some soundboxes allow you to pack a gap between the mating surfaces of the housing, allowing the soundbox to become even more sensitive, with more of the diaphragm being free to move. You can try this by undoing each screw securing the two parts an equal number of turns until the seals leak (when blowing gently into the gland - you could try using Cuban cigar smoke in a mirror, can be quite enjoyable for some!). Take each screw out and insert an appropriately slim rubber washer and tighten up to a turn tighter than the number of turns at which it started to leak. I make my own washers using the small and large punches on a rotary head hole punch, with a bicycle inner tube…
NB. For more on the subtleties of tuning a 4-spring or 2-spring soundbox see EXPERT two-spring v four-spring soundboxes and subsequent pages in that thread.
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