Subwoofer Popping sound?

[ShouBhebak]

i dont know much about all the technical stuff you wrote but i'm just guessing they can't take really high frequencies produced by some music........they must not be as high quality as u assumed

 

[TaylorMorrison]

All right i asked this a few days ago but didn't get a great answer so im going to try again
i have two Alpine Type S 1223 DVC subs being powered by a Pioneer D8500 Mono Block amp
so 600WRMS at 2 ohms
they are in a sealed box with a net of 2.0 cuft so 1.0 per partition which is perfect
yet whenever i play them above a certain volume and they hit certain low frequencies they sound like they are disconnecting or a noise like that it sounds like a damaged voice coil yet they are BRAND NEW so i dont know how this happened but other than that my wiring is fine and my terminals from the amp are perfect the ground is clean and tight for both the amp and my capacitor and when i put my two Sony Xplod 4ohm subs in it is perfect yet the Pioneer is actually DESIGNED for the Alpines as it has a 2 ohm output
can anybody help me?