Posted by David McBean [ 144.138.221.145 ] on July 24, 2008 at 04:01:11:
In Reply to: Re: Woofer directivity posted by Wayne Parham on July 13, 2008 at 19:58:37:
Hi Everyone,
"You can expect a rigid flat piston radiator to generate a 90° pattern (-6dB) at the frequency where diameter equals wavelength."
Just out of interest, the effect described by Wayne in his statement above can be readily demonstrated in Hornresp.
A circular piston with an area of 929.41 cm^2 has a diameter of one wavelength at 1000 hertz. To simulate in Hornresp, set Ang = 2.0 x Pi (for infinite baffle), S1 = 929.41, S2 = 929.41 and L12 (Exp) = 0.01. Calculate the results, then run the Directivity Beam Width tool from the SPL Response chart, and Sample at 1000 hertz. The -6dB beam width is calculated to be 89.5006 degrees (which rounds to 90 degrees, as indicated by Wayne).
Kind regards,
David
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