why my speaker can not play louder

I have a pair of Triangle Celius 202 speakers. They sound wounderful, but if I play the speaker very lound, one of the speakers will shut off, and if I turn down the volume, the sound is back again? can anyone tell me what is wrong? I tried different amps, they showed the same phenomena.
Should I have them fixed, is it a easy fix?
Unless there is a thermal protection circuit for the tweeter then you must be cooking them too much. Basically speaker voice coils get VERY VERY hot - 200 deg Celius!! ( sorry ....Celsius ) is not unheard of.

See this

Apart from the obvious problems that most consumer designs compress (distort) badly at high SPL levels (sounds awful and perceptively very loud even if it is not) there is a risk that you melt something. If you want something that plays really loud then get a pro speaker.

What may be happening? My guess it is getting so hot that something begins to distort or flex and one of the voice coil shorts out - then you suddenly have no output. Another possibility is that the cone gets pushed too far out against the rubber surround and then loses alignment (twists slightly) and the coil shorts out against the gap.

The fact that your amp is not blown up may be because it is only one of the two drivers connected in parallel or behind a crossover circuit. Perhaps both your amps have a protection circuit that kicks in...may be you are just lucky?

Nevertheless - the speaker will probably begin to fail progressively more often with use - now that something has gone wrong...

Don't worry - blowing up speakers is quite common and it will probably cost you the price of replacement woofer or tweeter. The above uis of course speculation - it is hard to be sure what is happeneing.