Conclusion

A planar piston is a relatively simple radiator and may be understood with simple concepts.

A hemispherical radiator requires a more sophisticated approach to explain its behavior.

An axially vibrating spherical cap in a conical waveguide behaves in a simple way provided it’s center coincident with it’s apex and the angle is not too large.

A finite waveguide with dome angle perpendicular to the start of the waveguide behaves in a similar way to a vibrating spherical cap in a conical waveguide; the effect of a carefully designed flared waveguide appears benign in respect to high frequency modal behavior. The response variation within a typical listener window is small and there is a lack of lobing in the audio bandwidth. This type of transducer is an ideal candidate for equalization whether by analogue or digital means.

next>>