I had the same thing happen with an HSU Research VTF2 MK2. It really sounded like the thing was bottoming out. Or like it was working too hard to keep up with the rest of my system. So I exchanged it for a VTF3 MK2. (Larger driver and more powerful amp.) Now I am able to keep the volume on the sub turned down (trim on my 950 at 0) and it appears to be working seamlesly with the rest of my system. Since the exchange, it has not "botomed out" once.

My dealer hooked up th VTF2 to one of their systems and it seemed to work just fine on the same passages that bottomed it out on in my setup. So the only conclusion that we could come up with is that it was not properly sized for my setup / and theater environment.


Later,
Simp