I've been playing with the WinISD to tune the L200 cabinet to the 130A and have a couple questions of those far more knowledegable then myself.
Assuming 150 liters, the two 4" diameter, 7.5 inch-long ports tune the cabinet down to about 34.8 Hz and this is way too long for the 130A. To cut the ports to tune the cabinet to between 45 and 50 Hz, I could cut each port to approximately 3.3 to 2.1 inches in length.
This is not really an easy task to do to get the lengths just right and get a nice finish trying to reach the ports through the woofer hole.
However, if I close off one port, and cut the other port flush with the inside of the cabinet, I would tune the cabinet to 46.3 Hz, which is acceptable. The caveat is that the Mach hits 0.16 and is not recommended above 0.15. The Mach 0.15 is attained at a tuned frequency of 48.5 Hz.
The beauty of this solution would be the simplicity of cutting the ports flush and sealing one with an block-off which would probably be easier when reaching into the cabinet.
I guess I'm asking how sensitive is the Mach rating and would there really be a difference in sound between one flush port or two short ports?
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