Need help diagnosing and repairing diy speakers

Well, you did a great analysis, Callum...
I would add that the input and output areas in that PCB are meant for male faston terminals ( for PCB...) and the vicinity of those stranded wires is alarming.
Abandoning faston is good ( it reduces resistance ) but some rework like 1.2 mm drilling in some place might do
 
Wow thank you so much for your help on this! It's incredible support really! Down to one tweeter on one speaker not working right now. And that's giving a slight sound, not a full sound. I think I'll need to take a break till morning and give it another shot.
 
i was starring at them images for like hour mins just sat there like something ant right here lol.
so i think
re-solder
fix the resistor
I would add that the input and output areas in that PCB are meant for male faston terminals ( for PCB...) and the vicinity of those stranded wires is alarming.
and this too i was looking and imaging the worst
 
was just looking at the eBay listing for theses crossovers and came across this.
1703747328120.png

so who ever put this together had got the old version of the pcb with the new parts.