restorer-john
Grand Contributor
Beryllium is an outlier in specific stiffness for metals, along with Boron. Most metals have the same specific stiffness, for example steel, titanium and aluminium are 3:2:1 in both density and modulus so making a titanium dome the same weight as an aluminium dome is necessary to make it as stiff (not strictly true since stiffness is geometrically proportional to thickness cubed so the aluminium will be stiffer than the titanium due to being a bit thicker.
Beryllium OTOH is a special case and its specific stiffness is much higher than other metals.
So if you want a pistonic tweeter Beryllium is the best metal since I am not sure one could make a boron dome (boron is usually built up as fibres on a thin iron wire core.
Or you can use 99.9% pure crystal ceramic alumina.
These tweeters are (NOS spares) for my Sony SSG-333es loudspeakers. Rare as the proverbial hen's teeth as they were only made for the one speaker and only for less than one year. Had Sony Japan find me a pair back in 1993 and have had them as spares "just in case" ever since. Ironically, it was the woofers that failed and now need new rubber surrounds...
Fully die-cast, spun aluminium, champagne anodized basket, finished all the way down the rim, even though they are flush rebated. Rubber trim between mesh and outer. Screw fit diffuser ring/magnet assembly and magnetically shielded (2nd magnet). Approx 1.2kg all up weight per tweeter.
They go in these:
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