I don't know. It might be too loud so the amp become hotter, or wrong speaker connection to the amp such as bi-wiring. Because I always do the bi-wiring, no matter what kind of amp.
My point is, the speakers survive but the amp broken.
I think you are part right, but the diagnosis of a randomly failed voice coil seems the best place to start. What most people get backwards is how clipping often works. You have to look at the power handling of the speakers and match that to your amp choice, but there is then another range of AUDIOPHILIC choices here. Now, if your speakers can handle 100 Watts RMS and your amp RMS's that and handles peaks too, well if you are listening at 50% this will work great: in the amp's typical sweet spot, lots of overhead.
The best configured systems manage to put gentle, ideal RMS into the speaker at normal listening levels, but where the amp also still has a good design and enough on demand response to do the damn cannon's on Tchikovsky's 5th (5th?) too without draining the peak power capicitors, for an example.
But, if you then run the volume full (never a good thing, 90% is a good place to ALWAYS STOP!!!) now this will stress both your amp (more) and your speakers (maybe).
Then, there is another subtle issue here. If you record distortion and play it back with a balanced system, as long as you are not listening to Ryoji Akeda and driving square waves (which is what amp clipping produces) your speakers will seem to be "distorting" but they are fine; the source is simply being accurately revealed as it was recorded. I hate the noise I hear when a stream stutters, it sounds so bad, but it is just what the messed up audio signal is "telling" the speaker to reproduce, and is not likely to cause damage at sane volumes, but it sure sounds like it might (???).
What you need to avoid (beyond Japanese noise music that will make you put a gun in your mouth, some spooky shit, but worth a listen on a system that can deal!!!) is using an amp with way less power than the speakers can handle at high volume levels. Here's why. When your amp exceeds 90% of it's output into a speaker that needs way more power, well, not only will your speakers seriously underperform on transients, bass, etc. at some point this non-ideal speaker load forces your amp to start clipping (making square waves exactly because there is no longer enough overhead to deal with the signal ideally).
This is internally generated distortion, it is not coming from the source or speakers really AT ALL. BAD, BAD, BAD. It may sound the similar to some harmlessly reproduced distorted sound, but it is bad, bad, bad for voice coils. If you use an amp at or beyond its limits at some point this may cause square waves. What this means is the voice coil spends too long in a high DC current situation without relent, and this may melt the very fine wound wires in the coil (not unlike transformer windings), all from heat that can't properly dissipate as the better SINE wave would allow it too.
Here is the kicker example: A 50 watt amp driving 200 watt speakers will clip at 50% of max volume (in theory)!!! And mismatched impedances can make this better, or much, much worse!!!
Amp's need SINUSOIDAL BASED WAVES and matched impedances BY CONVENTIONAL DESIGN, it is a background assumption few understand why, and Ryoji's square waved "masterpieces" come with warnings about not listening at high volumes for this exact reason, seriously!!!
Here is the goal for people who don't need or want to "crank it" (but some can't help themselves no matter how well they choose their componenmts and these FOOLS are the ones that start viral memes about "bad" components, fights for waranties, etc. and they are usually the cause of their own problems, but will never see or admit that).
If you have self control here is the advice I was given, and with my hard science degree it makes sense. Start with the speakers you want FIRST (source matters too, so it is the ends of the signal chain you start with, actually). Take their max power rating and set up your system to put as much as twice that power thru them, but otherwise just try to match power to power reasonably (as new risks enter now). Now you have overhead for anything you'd need it for in your sources and are likely running the amps and speakers ideally and GENTLY (EVEN LOUD AS FUCK, lol), but then if you want to really crank it, well you might get to 60-70% and have to leave the room (When I mono-blocked Energy RC-70's with 300 watts a side, they were rated for 250 watts, they were the loudest CLEAR speakers I had ever heard, I literally had to leave the room at about 70%, lol, but there was NO DISTORTION AT ALL, just ear pain! The soundstage jumped out of the speakers with this bump in power too!!!)
However, when your amp can put more RMS power (peaks and loud or complex transients are easier for coils to handle over their power ratings, but never RMS for very long at high volumes!!!) into those drivers than they were meant to handle, this risks a new kind of "distortion", that of your voice coils or filters or fuses melting and then SILENCE, here your amp will likely be fine, it simply now sees an infinite load, lol (maybe some low probability bad things can happen to amps in such a case, but I am not sure, it seems to me that once the signal path gets cut the amp is basically powered on with no output anymore, but this stuff is complex, and the fancier, the flakier too at times, you seem to experiment and switch up gear a lot, bi-wiring alone is pointless and gives you more ways of doing something ill-advised).
In the first case, underpowered amp, your speakers will sound shittier as you turn them up, but your amp pays the HEAT price, and at some point that may spill back over to speaker damage. In the second case you need to MATCH COMPONENTS WELL and have self control, but will reap HUGE SONIC REWARDS!
ENERGY use and INFORMATION decoding are mathematically correlated. If there is not enough on demand RMS or Peak overhead for a given source, you are leaving actually recorded sounds in the source UNREVEALED!!!
People think power is about more LOUDNESS, no it is about headroom and matching source (lp, CD, hi-res digital, etc.) to sink (your brain!!!). Ideally you want speakers with massive power handling and then put as much as double the power into them (but never go past 50% volume!!!). This is about TIGHT TIGHT driver control, big magnets reduce slop in cycling but they need more power to be controlled due to the added mass and back-induction (the impossible ideal is too have a zero friction cone path, infinite power and power handling). This is about IDEAL coupling of the driver paths to the ideal RMS signal, and still allowing on demand peak resolution of ALL FINE DIFFERENCES, of information..
Any well matched system will go above 105 db, but say good bye to your high frequency hearing and non-distorted reproduction then, lol.
If the problem moves with a FIXED component, start with it.
You had some bad weird luck, maybe self-caused (but you want to learn and that is AWESOME!!!) but now you seem, perhaps, biased towards this always being the next problem too, but your model of the problem may simply be in error. I am sure I said things above that are wrong, I'd value knowing that, as long as the person isn't a JERK about it.
These things are conventionally simple in isolation, but chain a few of them together and the game of complexity really begins!
