| Re: Alternate idea for 7Pi midhorn enclosure? [message #75408 is a reply to message #75406] |
Fri, 01 February 2013 09:35   |
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Wayne Parham
Messages: 18695
Registered: January 2001
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Illuminati (33rd Degree) |
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| JCDC wrote on Fri, 01 February 2013 08:01 | For some reason I thought I recall you saying that the rear chamber is sized to be "small" and provide a bit of a freq boost near 200Hz. ?!? Is this correct, or am I doing the very thing you mentioned--applying box theory to horns.
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There is some similarity, in that the sealed rear chamber provides some peaking if it's small enough. The electro-mechanical parameters of the driver shift when it's mounted on the horn though. Still, reactance annulling does that, essentially providing a smidge of peaking right below cutoff.
But in the case of the π midhorn, the rear chamber is sized large enough it doesn't do that. You could, I suppose, if you wanted to. But I don't. I want a smooth gradual rolloff with output down into the modal range, to blend with the woofer.
| JCDC wrote on Fri, 01 February 2013 08:01 | So would leaving the driver open backed and then covering it with a few layers of insulation be good? Or is the driver still producing lower freq (<200Hz) so the insulation is less effective?
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That's right. Insulation surrounding an open driver would work fine at higher frequencies but would be almost completely ineffective at lower frequencies where you needed it most. If the rearwave is strong, and then "amplified" by corner loading, you get some weird interference patterns and the lobing that results. So put that driver in a box.
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