Don Pearce wrote:

I just want to hear how balanced the tweeters are.


Not the slightest chance of doing it that way. Why do you suspect they
may be unbalanced? Play something in mono, something with plenty of
top end to it, and position the speakers equidistant from you, with
the tweeters facing you. Does the sound appear to come from a point
midway between the speakers? Yes? They are balanced. If not, nudge the
balance control slightly to put the image in the middle, then leave it
there. You won't need to do this, though - they will be just fine.

I think this one pair of speakers of mine had a tweeter fried long ago
and I want to check if I can hear a difference between the original one
in the one speaker and the replacement in the other.