The sub and amp is one of those active enclosures where the amp is built in and 2 12" inch subwoofers, Vibe brand.

Were purchased brand new, and ran in for a week or two at low/medium volume as the manual says to do so to avoid damaging it.

Turned the gain 3/4 of the way round, the frequency is at around halfway, the headunit is set to 0 on bass, 0 on mid, +3 on treble, the LOUD is on, the amp output on the headunit is turned right up, but for some reason the bass isnt loud through the sub as it should be? You can hear it and you know its on, but it doesnt reallly boom, or echo, it more or less bangs? Turning up the bass on the headunit you end up with distorting loud speakers and a little louder on the sub, tried fading it too, im at a loss as what to do, i dont have the headunit manual but looked on kenwoods site manual online and doesnt seem to throw up much joy either.

Tried swapping phonos around to no joy, adjusting the amp on the sub, no joy, played with the headunit, no joy, the higher you set the bass, or the amp, the more it bangs instead of thumps but at lower volume it thumps/punches as normal, ??

Really cannot figure out what is going on, the sub/amp is fine as far as i know as its powering up fine and all the settings on the amp are working, just doesnt seem to as powerful as it should be.

The headunit is a Kenwood flip front KDC-M7024 model. its a fly/vibe 12" twin active inclosure, 800watt RMS

Any ideas?