How is it with no sub?
The sub may be not tracking along with the volume output of the speakers. So the sub gets too loud when you crank it up, but at lower levels it seems good?
The sub may also have room resonances that go crazy when loud.
An alternative' World view is you cannot listen long at loud volumes due to the hatred pouring from others outside your bedroom sending you "DIE NOW!" evil messages through the aether due to noise pollution?
The sub may be not tracking along with the volume output of the speakers. So the sub gets too loud when you crank it up, but at lower levels it seems good?
The sub may also have room resonances that go crazy when loud.
An alternative' World view is you cannot listen long at loud volumes due to the hatred pouring from others outside your bedroom sending you "DIE NOW!" evil messages through the aether due to noise pollution?