CS1000P Sub drivers blown?

My CS1000P sub drivers (MW7015) seem to be blown. I purchased the center a few months ago. When I turn up the volume on the sub control on the speaker itself they sound horrible like something is broken/loose inside. I pulled them out I didn't see any damage. When pressing in the cones move freely with no sign of any imperfections. Put a voltmeter on and readings came out good. I can only put the volume close to less than half way on the sub volume control and at that point I don't get the noise. Any thoughts? Thanks for the help.

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