Sub's output randomly spiking

Summary of my setup I've got a HD600/4 amp with 2 channels bridged to a Mr. Marv setup (Arc Audio 10) and it's hooked up to a Pioneer DVD HU.

The issue, and I hate to call it that, is that while listening to music (oddly usually rock music) I'll notice the sub randomly spike from it's normal background volume (I don't like my cab shaking) to what I would consider full output if I turned it up to max gain in the HU. I'm really not sure what to look at but I initially thought it was my bass control knob I bought for the JL Audio amp...but the past weekend I disconnected it and the sub was still randomly spiking (booming) every 30 seconds or so.

Has anyone seen a problem like that before? The next thing I might try is to turn the gain on the amp itself down just to see if that does anything but I already had to turn it up past the JL manual's setup "gain" because I couldn't even tell the sub was there. I honestly didn't pay much attention to it when I first installed it because I drove everywhere with my windows down but now that it's hot / AC running the sub is significantly louder with the windows up started to make my head hurt the other day.

 

You are running two channels bridged for the sub and the other two channel for your mid and high? Have you checked for loose connections inside the sub? Not sure if that will cause a spike or not. And is the amp set to 4 channel or two?

 

Amp is set for 4 channel - 2 channels bridged for the sub and the other two power the Hybrid Audio components up front through the crossovers.

I haven't opened up the sub yet and maybe I should, that doesn't sound like a terrible idea.

Here's another question....I drilled a hole big enough for the speaker wire to run to the sub and did the Marv method of putting a zip tie on the inside of the box on the wire and used hot glue to try to seal the wire to the box on either side of the drilled hole. How well sealed does that need to be if the wire fit pretty tightly into the hole? If there's any air escaping at all would that cause any issues? Just tossing out possible issues.

This whole thing is making me paranoid about the wire gauge running to the sub also so I might dig around and see what I used...been about six months since I built it so I don't remember what I ran to the subwoofer.

*Edit* After digging through my Amazon purchases it looks like I'm running 16 gauge stinger wire to the sub...so that shouldn't be too big of an issue. I might open it up when I get home anyway.

 

All my boxes are just holes drilled with wire through it and hot glue. No issues. Just open the sub and take a look at the wiring and voice coil and make sure everything is attached correctly. When (years ago) I was running Rockhard Prostate amp and sub the cause of my spike was a faulty bass knob and bass knob plug on the amp. But it didn't cause like you. Mine only did that when I touch the knob in a certain angle but what was to blame was the guy I bought the amp from used a phone cord as a replacement cord for the bass knob.