Hello, It is so hard to find the extreme limit of the Tumult woofer because it sounds so clean!!! I have for it a QSC PLX2402 amp and it seems to me that the amp clip before the woofer can bottom out (I measured the woofer excursion with a ruler). So now Im confused... when I begin to see the red LEDS flashing on the QSC amp (indicate clipping), I hear a kind of very noticable "TICKK" noise. I wonder if this is really the voice coil hiting the back plate or this is the sound you hear when the amp clip. Im so confused with that wonderfull woofer :b , how do you know if the voice coil hit the back plate? How different is the sound (clipping/voice coil hit)? Thanx for any explanations! Im sure that some users such as Brian know how to differentiate the sound of a voice coil clacking or an amp clipping in the case of the Tumult.