I didn’t measure them as my multimeter is on the blink but I think I’ve found the happy ground. Also, I noticed that issue trying to use MIDI notes. Thanks for your help. I found, rather than being an exact science, calibrating it was like setting up/setting the intonation on a guitar - its all about compromises but with a little patience it will sound great
I always think sound is just more pleasent in a warm room, Even solely physiologically!