Quote Originally Posted by pressorv View Post
I've put many hours into trying to install the Polk MM6501s. I finally got something that I was really happy with, until i did a test run of the speakers. They sound like they are farting instead of solid bass. they aren't bottoming out, I tried sealing the enclosure and held them as tighly against the frame with no improvement. I'm not sure if I have defective speakers or what to do. After putting all this time into it and finding the fit to be insane, I'm deflated. I'm not sure what to do next.

-R
Did you stuff the cabinets with polyfill or other cabinet dampening material? It's the white fluffy stuff you see in speakers. You can get something similar at walmart in the arts and crafts dept.
I notice some notes resonate horribly with the stock speakers.
If you've ever been in a big building and a truck drives by you might hear standing waves, that's when certain frequencies reinforce themselves as they bounce around inside an area.
Then there's resonant frequency. If the plastic enclosure is not rigid enough it will vibrate at frequencies that match its resonant frequency or frequencies.
I plan to stuff mine like crazy to see if it smooths out the response. Every bass note of "Papa was a Rolling Stone" plays at a different volume!
I'm no expert, you can probably find more info here.

If it's not the above issues; the farting noise could be over-extension of the speaker cone, the cone could have a wire too close to it that it's bouncing off when driven, it may be defective and the "spider"(the surround that is underneath and surrounds the voice coil) could have come loose. Maybe you'll hear from another Polk user who went through this. I'm still on the fence as I don't expect much from such small enclosures. May just try better tweeter and stuffed cabs before committing to new speakers.