When I used to work with PA systems we had this really cool old-school looking impedance meter. We used to check the continuity of the PA like you do with a resistance meter in an electrical circuit.

I dont know much about analog audio but if I am remembering correctly, the device could inject a 1Khz tone that was only heard on speakers with impedance problems.

https://toa.co.id/product/zm-104a-impedance-meter