This may be more than what you want to do, but if you have a computer you can easily hook up to your receiver (for sound output), try downloading this test tone CD.

Select some of the tracks in the 20-80hz range and watch the woofers on the M80s. At the lowest frequencies, you should see quite a bit of movement. As you get higher, you'll see less movement but hear more sound. This will at least confirm they're functioning properly and playing all of the frequencies they should be.

Jason

Epic 80-800: HG Cherry