Driver pattern, directivity and other confusing issues

[mefistofelez]

1. It is my understanding that a sound pattern emanating from a driver will change with changing frequency, specifically narrowing with increasing frequency. I also seem to recall, that the narrowing is dependent on the driver dimensions.

I was wondering if there are any references, describing how this change in pattern depends on the driver dimensions and frequency. In other words, given a dimension of a sound radiating surface of the driver and a frequency, can one predict the pattern?

2. It is my further understanding that the change in pattern can be controlled by a waveguide; however, the pattern will be controlled only down to a certain frequency [1] according to a formula:

Fc= 10^6/(theta*X)

where: theta is the included angle of the waveguide;
X is the mouth width of the waveguide [in].

I fail to understand how to apply this formula to a waveguide that has several included angles a la MantaRay, or a curved mouth section a la Geddes. Should anyone know an answer, I would appreciate it.

Thank you,

M

[JMB]

http://www.pvconsultants.com/audio/radiation/arpe.htm

This program can assist you in estimation of the effects of frequency and driver radius. You can also find a spreadsheet that does something similar in the Unofficial Speaker Workshop Manual downloadable at www.audiodiycentral.com. I believe it is in section 5 or 6.

Jay

[mefistofelez]

Thank you very much Jay.

M