Speaker driver beaming frequency formula

[617]

FWIW, with horns beamwidth is usually quoted as -6dB re on-axis. I'm not sure such a standard exists for cone drivers.

I think practically there is no standard, but 3db contours are pretty common. If you think about it , -6db isn't much, it certainly isn't like going from 'full output' to 'no output'. It's just significantly quieter.

I think it's important to keep some perspective about the magnitude of off axis sound irregularities. If you look at the frequency response of a speaker off axis, it's going to be a bit darker, and possibly have a null due to crossover effects, but it's not going to sound dramatically, suddenly different; apart from anything else, the 'correct' axial sound becomes the indirect sound when you move off axis, and it will probably beautify the overall reverberant field.

This why I never liked the term 'beaming', directional effects are quite subtle and smoothly changing, and you never hear them in isolation.

 

[DualTriode]

Hello All,

Beaming is a broad generic term that is fuzzy on the edges, used to describe driver coverage angle.

Many of the posts here borrow from the work of Clifford Hendrickson of Altec without giving him credit.


I much prefer to think of -6dB off axis coverage angle. Controlled Dispersion horns/wave guides are identified this way.


http://alteclansingunofficial.nlenet.net/publications/techletters/TL_237.pdf


For maximizing the smoothness of a speaker’s DI curve and selecting a crossover frequency I plot the Directivity of the two speakers on a single sheet of Log Scale graph paper. If the speakers are a cone driver and a Controlled Directivity Horn/waveguide I place the crossover at the frequency where the directivity plots cross each other, the point where the off axis -6dB coverage angles are equal.

For two cone speakers like a woofer and mid-range the Directivity plots will not cross (without waveguides). The larger speaker’s directivity plot will begin to steepen with increasing frequency and will dogleg the speaker’s DI curve if the crossover frequency is too high.



Thanks DT