This is almost how I picture it too. Default would be centered, rotating the knob CCW would delay the left side, rotating CW would delay the right side instead. Or bring it back to center for 0/0 All values could be negative, since you are delaying things. Only one speaker would need it at a time, too, since it's a relative deal between them. I think milliseconds is sufficient, and even 0-10 is about all you'd need in the car, if even that much.

Positive delays, is that kind of like going into the future? I could have a few uses for that

Oh, this is sweet! I was excited about possible GPS someday, but this is the highest wish on my list, I suppose you've read that already in the Wish List forum.