Kaney16 if you can PM me the dims of the enclosure I will try to use WinIsd to get close.
1st >>> H x W x D (Overall)
2nd>>> top chamber H x W x D
3rd>>> middle chamber H x W x D
4th>>> bottom chamber H x W x D
5th>>> thickness of material used (3/4 mdf ???)
Here is what my HWK15 looks like with a slot port. I can remove the slot port and return it to original if I want a change.
http://s541.photobucket.com/albums/gg367/HT-EXT/HWK15%20AND%20HW10s/No Smoking are you sure it is motor noise or maybe it is port fart. I would think at that low power neither problem should be occurring but 18" does move alot of air. My guess would be either top or bottom is leaking a little but I am just guessing. You can use a piece of paper laid across any gaps to see if you have a leak. I sometimes use a lighter around the edges to check for leaks but don't set it on fire.
Just my two cents hope it helps.
HT-EXT