Avolon Eidolon and Radian (sp?) speakers are all kinds of trapezoidal shapes. Reference Da Capo monitors are trapezoids too--or maybe they are rhombi? [can't really remember what a rhombus is] How about Thor amps, which I think are circular? Some models of Gallo speakers are spheres. Bass traps are tall cylinders. The Ringmat is a circle. And look at all the vibration-contolling "cones" around.
