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Hi Wayne. We are starting on the 4pi's today, and Since we are going to modify the cabinet dimensions, I put the T/S parameters for the Delta 15" into Winisd, a free enclosure design program. Unfortunatly, the box size it gave me is incorrect. It said that for an 8cuft enclosure with a 4" diameter port 4" long, the tuning frequency would be ~25hz. That is way too low, and as we discussed the other night, it would be in effect acting like a leaky sealed enclosure right? My guess is, the T/S parameters are inccorect. Or the Winisd software does not calculate very well? At any rate, what is the actual tuning frequency for the enclosure? Why would Winisd tell me such an inaccurate spec? Thanks!
You're right that a bass-reflex cabinet tuned too low doesn't do much. If the Helmholtz frequency is tuned low, it forms an EBS alignment. But if it is tuned lower than that, it begins to become ineffective. It's tuning is sort of "out of bounds" and it begins to more like a leak than a tuned port. But this cabinet is designed to be tuned to 25Hz. The response curve is similar to an EBS alignment. It begins to rolloff slightly around 50Hz, but has a lot of energy all the way down to 20Hz.