clipping Possible Clipping?

[MattMatt]

Ok so I have 2 American Bass Elite 1244 running off an AudioPipe APCLE 1800.1. Box is 5 cu.ft. And tuned to 30hz. We thought the box seemed big but that’s what they call for 2.5 cu.ft a piece. Have 0g Skar power and ground. Not OFC just CCA for now. And my ground is ran maybe a foot from the amp to a seatbelt bolt that I cleaned to bare metal and it’s on solid. Just did a Big 3 with 1/0g SkyHigh OFC. I know when I did the Big 3 my battery actually ground to the motor then from there to the firewall. I added a ground from the motor to the frame. Oh and 8g copper welding wire for amp to box. And head unit is a Pioneer Carrozzeria DEH-P760. It’s a Japanese model pioneer. 
 My issue is when turn my volume up to anywhere from 38 -45 I’ll start to get a popping/crackling sound. I’ll immediately turn it down. And it doesn’t always do it. It’s not the subs themselves max out it’s more of a connection or signal interference sound if that makes sense. My volume on the head unit maxes out at 62 so I’m not turning it up to the max. My gain is set to right at a quarter. LPF is only slightly up from the 40hz. Subsonic is maybe a 1/8 turn. Bass boost and bass boost frequency are both all the way down. Now I’ve watched 2 videos on YouTube tryna see what the actual watt output of this amp is so I can try and set my gain with a multimeter sines I don’t have an O-scope. But both videos had different results so I’m not sure which one to go with to do the math of finding voltage. So I guess I’m asking (1) does anyone know what this could be possibly? Am I clipping? If so what could be the issue? Then (2) does anyone know what the actual watt output is of this AudioPipe APCLE 1800.1 at 1 ohm? Also it didn’t do this before I got the new box. Before I had em in just a QBomb ported box. It was way too small for these subs for real.  I know they’re hitting so much harder and deeper with the new box but do you think it could be idk too big? The port is 6”x12.5”x 18”. You think the ports too big? Like if I were to maybe add a piece of 3/4 wood to the inside of the port would do anything? Idk I’m just at a loss right now. I can’t figure out why this is doing this. Amy I under powering the subs? I know they say 1200rms. So 2400 for the pair. The amp puts out, from what I’ve seen either 1325 or 1750 lol. Two videos saying two separate things. Idk. Any help would be much appreciated. Thanks in advance. Bass on mfers lol.