Assuming you're referring to a system with a SS amplifier: Slowly increase your listening volume and focus your attention on the middle(especially vocals) and higher frequencies. They will start to sound distorted and very irritating(clipped off/square waves/odd order harmonics). Don't leave the volume there, as most tweeters can't take much of that abuse without voicecoil damage. Crossovers see the high freq distortion as DC and pass it right to the tweeters. Tube amps clip much more gently(rounding off the waveform, rather than chopping it off) and are somewhat harder to gauge, when being overdriven.
