Posted by Wayne Parham [ 64.216.176.155 ] on September 24, 2004 at 02:03:17:
In Reply to: Re: 8 Pi Tuning posted by Jeff Aiken on September 24, 2004 at 00:37:18:
I think it's great you are looking into this in such detail. It is a new design, so I welcome the extra examination.
For the front section you've described in part #1, I calculate 26 x 32 x 10.34 = 8602in3. I calculated the rear section you've described in part #2 as two extruded triangles and an extruded rectangle. I combine the triangles to form a rectangle. The two triangular portions are 6 x 6 x 32 = 1152in3. The rectangular portion is 6 x 14 x 32 = 2688in3. Combined, it is 12442in3 or 7.2ft3.
The horn, driver, panel wood thickness, braces and brackets all displace volume inside and so must be removed from this figure. I don't recall the displacements right off hand but I remember they were around two cubic feet, and virtual volume increase from insulation adds some of this back. Fortunately, at this size of cabinet, a few hundred cubic inches difference either way doesn't make any difference.
As for resonant frequency, I don't know about the accuracy of WinISP. I use the Helmoltz formula to calculate resonant frequency:
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