Well, sorry for the slow reply. Had to work and it's been waaaay too hot outside to go mess with a car I don't drive every day lol. Anyway, you guys were right. One sub was wired out of phase. Many thanks
I don't understand why that made such a huge difference though. Years ago I had a seventh order sub box where two subs were bolted to a separation board facing each other. One was wired out of phase on purpose so they would move together. When one moved forward, the other moved backward. That was the loudest sub box I've ever had. Maybe something to do with mounting, I don't know. Anyway sounds awesome now! Again. Many thanks