What the hell, is one of my subs broken or am I just tripping?

[hispls 5,000+ posts]

They are all the same from first to newest runs.
Depending on where your vehicle peaks the fresher sub may be noticeably louder around the typical vehicle peak frequencies. The response is going to shift downward as the suspension breaks in -- in the case of the VVX the Fs gets very low. I wouldn't expect the kind of difference you are describing, though.

Most likely it has something to do with the connections or how well the woofer was seated to the box. It's not 100% applicable but in our single 8" woofer testing we gained over a dB by trimming the speaker wires to fit better in the terminals and variance in screw tightness has changed it nearly a dB as well.

That's a super easy way to find 2db!

 

[SPLaudio 5,000+ posts]

what i was thinking the stiffer sub is gonna peak higher but shouldnt even be a db in a nonspl setup.

 

[tf3090 10+ year member]

Just got home and put the old sub back in the box, and it is just as loud as the new sub. I have no idea what I changed, but the system is definitely louder than it was before. I'm thinking it might have been due to box placement. I experimented with different placements (e.g. front of the trunk, in the back, as far back as it can go without hitting anything, etc.) and noticed moving the box even just a tiny bit could cause a big difference. Maybe I just now found the sweet spot for my car, with the box a few inches away from the back of the trunk