Art Welter wrote on Fri, 06 August 2010 00:34 |
On big boxes, the difference between V(total)and the gross exterior dimensions is not much, but on small cabinets the percentage can be pretty high, on a small mid bass ported cabinet the volume taken by the speaker, wood, port, and handles may exceed Vb.
After having some ports end up tuning the box differently than "the plan" said, I now initially make them longer than the plan says, then test the Fb, and shorten as needed. It is a lot harder to make them longer ...
Art Welter
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The last batch of subs I made were 12 cubic feet external, which for me is small.
I do remember Harris-tech software will take the thickness of the wood, the port, bracing and loudspeaker (if you add the dimensions) into consideration. It will even add the insulation in the equation on the overall response.
I had some bad tuning predictions with WinISD when the non-pro version wasn’t available that differed by 10 Hz. I knew something was wrong when the cabinets sounded lower than WinISD (non-pro) predicted.
With the exception of four, all of my subs are rear-ported to minimise any port noise being propagated to the front. It also ensures the cabinets maintains the proper tuning for those who like to stand in front of the cabinets either by pleasure or no other choice.
Best Regards,