Is a phase plug required to minimize/eliminate cancellation if the throat size of the horn/waveguide is the same as the diameter of the diaphragm of the [compression] tweeter?
Also,
Is there a function with which one can determine the necessity of a phase plug whose variables are diaphragm size, throat size, and frequency? i.e. a 2" compression driver with a 1" throat will require a phase plug at x kHz.
Let's say necessity is defined as when cancellation causes over 2-3 dB drops on an otherwise perfectly flat frequency response.
Also,
Is there a function with which one can determine the necessity of a phase plug whose variables are diaphragm size, throat size, and frequency? i.e. a 2" compression driver with a 1" throat will require a phase plug at x kHz.
Let's say necessity is defined as when cancellation causes over 2-3 dB drops on an otherwise perfectly flat frequency response.
In one specific case I've been playing with, a center exit from the compression chamber gives a nocth around c/d where d is the outer diameter of the compression chamber (this is all round, axisymmetric). In my case I'm 3dB down a bit above c/d/2, though. How you tune your front chamber will also effect this, as will the breakup of the diaphragm, and maybe your compression ratio (I'm using a high compression ratio). In my example, I pushed the notch higher by using a single slot phase plug, and even higher to ~2*c/d by going to a 2 slot phase plug. Beyond that, you are probably into diminishing returns, as the diaphragm will be breaking up unless you have an exotic material.
In the case of a direct-radiating tweeter with a horn, there is no compression chamber, correct? (You could use one... but I don't see why)
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