Xperia X: Possible speaker destruction by system tone volume?

You do have warranty. If your device is less than 6 months old, it's even up to the seller to prove the defect is your fault - installing third party software does not void warranty. Compare computers, on which you have installed another operating system. You'd of course loose warranty on the OS, and there will be no guarantee the new OS works on your computer, but broken hardware should still be covered. (IANAL, but it's European law.)

If the hardware is properly designed, it should be impossible to break the speaker in any way. Of course, the hardware might not be properly designed (e. g. commercial replaced the speaker designed by the engineers with a cheaper one with lower power rating to save some cents).

Only a hypothesis, but maybe there is an equalizer in android to limit low frequencies on high power output. So Sailfish can kill the speaker and you will have also a warrenty problem when sony get notice of this. By the way this limiter is used in many low cost audio systems nowadays.

Just noticed something similar. Usually I do not set system tones to max loudness. This time I did. And I was having sms conversation, sms app was open. The incoming sms sound (which is default and is rather short and gentle beep, as app is open) seemed to break the loudspeaker. The sound seemed uneven and crackling. I am not an audiophile and expert of sound technique, but as I understood, the incoming to loudspeaker signal was beyond the physical loudspeaker limits. Xperia X with Sailfish X.

Also, checked loudspeakers with CSD tool. Stereo speaker test sound seem too loud for the loudspeaker capacity. Both speakers work, but the voice telling “left speaker right speaker...“ seems too much amplified, as we usually hear some cracklings in loudspeakers, when the volume is too loud for them. The phone system sound volume is 60%, but I guess CSD sound test volume is independent from normal phone sound volume.