Fender Rumble 60w troubles

[souz...@gmail.com]

Hello brainiacs.

Here is one for you. I have a fender 60w Rumble bass amp. I'm using
a esp/ltd bass with emg active pickups. The amp when cranked up,
especially with the highs turned up, when I come down hard on the
strings, I use a pick, the sounds will cut out and the speaker will
bulge. If I turn down the highs on the guitar as well as the amp I
can play harder but lose some volume. The higher the highs and or
volume the easier I have to stroke it. I slapped another speaker in
it. 150w speaker at that and it does the same thing. Does it have
anything to do with the active pickups? is it the guitar? something
funky in the amp? Does anyone have any knowledge on this?

Thanks

Mike.