dbg@ihldt.UUCP (dbg) (12/22/83)
y Low frequency drivers have historically been cone shaped for obvious reasons. A wide open (flat) stiff paper driver would break into concentric resonances at very low frequencies. As the angle (forming a cone) is increased, the resistance to concentric breakup is increased (the frequency at which the first concentric resonance appears is higher) because the axial stiffness is increased. Too steep of a cone causes great irregularities in the higher frequencies. Other resonances occur in circumferential modes where the cone sections itself off into quarters, thirds, etc of standing waves. These are made less dominant by the use of contoured cones thus providing smoother coupling to the motor (voice coil) and rim. There have been many attempts at finding a good, light, stiff material with which to engineer a diaphragm out of. In many cases the downfall was the fact that the rigid diaphragms acted nicely until they reached their breakup point. Then they went crazy. Usually the more gentle breakup of the normal paper cone was preferred. New materials have been quite successful however. KEF uses a polystyrene wedge in some of their units. The BBC pioneered the use of bextrene with good results. A light weight honeycomb material might offer some improvements. In the final analysis let your ears decide. This may just be a marketing gimmick. Everybody has a gimmick. My favorite is a good combination of price and performance. ihldt!dbg