My Event TR-8 speakers are seven years old. Lately I've been noticing there's some weird going on with the left speaker. First, it outputs about 2,5db less than the right speaker. Ok, that's not the big problem. The main phenomena is that when I play back 56hz sine noise from both speakers the left one seems to output some sort of hiss and mellow crackling noise from treble tweeter. The phenomena isn't that obvious when playing back for example 180hz sine noise. Is there something wrong with crossover mechanics? Or what can cause this?
I have seen an issue with the Event ASP-8 that could be similar. You might be at an early stage of the same problem. If so, the speaker will eventually start crackling by itself, and, the back plate will be noticeably hotter than the other speaker. That fault is caused by some SMD resistors going bad. Search around here for the ASP-8 thread for more details.