This is me doing stupid stuff. I always try to hook everything up first to make sure it works before putting everything where it is going to live, just to make sure I don’t have a dud component or picked the wrong spot for an earth. In this case the subwoofer was a dud, the voice coil is burned out (shop floor demo unit). Luckily they had an identical one still stinking up their display so we swapped them over. Given the small displacement of the box it isn’t as gut bustingly growly as the big Sony unit in my 300c but it’s good enough. Have another two smaller boxes speakers to fill out the sound a bit as the dashboard factory ones are pretty unimpressive but also impossible to get to without breaking the plastic covers so I will just dial them down a bit in the mix. Usually the step of trialling everything is uneventful but I am very glad I did it this time.