i don't know what the problem is but when i turn up the power on my subs they start getting popping noices but when there low i don't hear the noise anymore... could this be an underpowered sub or bad wiring
could be anything maybe even your box build i know my friend built a box and he doesnt know what he was doing lol so then his subs popped when he turned it up to loud of course he ported it to w/e he felt like he doesnt know numbers he just made a box and i laughed.