| Dealing with internal standing waves [message #64321 is a reply to message #64316] |
Wed, 13 October 2010 13:09   |
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Wayne Parham
Messages: 18723
Registered: January 2001
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Illuminati (33rd Degree) |
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It's hard to say, really. The port is 10" long, so you'll have to bend it if you make the box any shallower than it already is. But that's OK, just make the port like the seven π cabinet. Beyond that, built it, test it and see.
My suggestion is to make a sacrificial cabinet out of MDF. It's cheap enough and the box is easy to build. Make it the depth you want and with a port like what's used in the seven π loudspeaker. That will tune the Helmholtz frequency right, so you'll know what you have there. What you won't know is what the internal standing waves do to response. So build the cabinet and make some acoustic measurements. You can even do an impedance sweep if acoustic measurements are hard to do.
If you see any noticable blips, then the box isn't good enough and you'll need to move something, port position, woofer position and/or cabinet geometry. And don't forget to use insulation - three sides and often a sheet spannning the cross-section, somewhere in the middle of the box. That will damp internal standing waves in the lower midrange better than just lining the walls inside.
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