Loudspeakers

Only the second metal in the periodic table after lithium, beryllium is a remarkable, if rare, expensive and very toxic element. So why, since Yamaha introduced the metal in the treble and midrange domes of its NS1000 speakers [HFN Oct 18] in 1974, has it subsequently achieved 'cult status' as the high-end driver material? It all boils down to beryllium's vital statistics – it has a higher modulus of elasticity than titanium or steel, a lower density than other 'light' metals like aluminium (comparable with magnesium) plus a velocity of sound several times that of any of these metals. Indeed, in this regard it is comparable only to boron carbide or, if we are talking 'exotic domes', vapour-deposited diamond.

These properties allow cones and domes fashioned from very thin sheets of beryllium to operate in a very linear fashion way beyond the passband of more 'ordinary' driver materials, pushing their primary breakup mode from the 20kHz+ of standard alloy domes up to high ultrasonic frequencies. In this instance, Paradigm's 25mm treble unit finally lets rip at an exceptionally high 51kHz, approached only by the carbon and diamond domes featured in B&W's 700 and 800-series speakers and other beryllium tweeters fashioned by Magico and TAD. PM