Midrange Waveguides

[thadman]

Waveguides and constant directivity, they are some of the new trends sweeping this forum. Although, the subject of this thread is one not often discussed, midrange waveguides. Their is a plethora of information available online thanks to Earl Geddes' presence on this forum with reference to waveguides designed for treble compression drivers, but little regarding midrange waveguides

Rather than asking specific questions which presuppose certain circumstances which may not apply to all users of this forum, would you care to educate us on the benefits of midrange waveguides and how to properly design them?

Potential subjects to comment on:
According to my research, a spherical wavefront is the best match (least HOMs) for a conical waveguide and a planar wavefront is the best match for a OS (oblate spheroid(sp?)) waveguide and the throat is the most critical region regarding generation of HOMs. Also, conical waveguides begin to narrow in dispersion once the wavelength reproduced approaches the circumference of the throat. You also expressed interest regarding a different type of phase plug that minimizes generation of HOMs in the throat, but felt it was too costly to have them machined solely for your purposes and thus opted for open-cell foam in the Summa.