I have two identical crest LQ-12p monitor speakers. They are the ones with the built in amplifier.

Each box consists of a 4 inch tweeter and 12 inch sub.
Randomly while I am listening to music the sub on one of them shuts off. The tweeter still works. But what even gets me more is that it only happens to the same speaker everytime. By shutting off the speaker and turning it back on about 5 minutes later it is usually fixed.

What is wrong with it?

Although I don't know anything about these monitors it sounds to me like the protection circuit (if they have one) is kicking in on the sub. This usually means your driving it too hard or the input level on it is up too high. I dont know if these speakers have seperate internal amps for the LF and HF driver but if they do it could mean the LF amp is on its way out. Check to make sure its not overheating too.

Not sure if that helps but its a few things to keep in mind with active speakers.

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I checked for heat but the sink feels quite cool when touched. I don't think overheating is the problem.

It has a light that comes on when the speaker is experiencing clipping. The light doesn't even go on and the sub will go off. I don't think the speaker has any levels to adjust on it itself. If the source is too loud wouldn't both of the speakers shut off together?

It's a strange problem indeed.

well, I guess this depends on two things:
a) are they under warranty
-and-
b) do you have any electronics experience?

if no and yes...

then you need to disassemble the amplifier section of the speaker and check:

a) that the final amplifier transistors are properly mounted to the heatsink and have heat transfer compound between them and the sink
b) that no single component on the board (not just the transistors mounted to the heatsink) is running too hot (check EVERY component on the board just after it shuts down)
c) check for voltage from the power supply just after shutdown -- if the power supply is not providing voltage anymore the protection circuit kicked in, or the power supply is overheating or otherwise dying.

regardless, it sounds like a heating issue... or something otherwise tripping the protection circuitry. there may be known problems with these puppies, but im not familiar with the crest internal amps... you might give crest a call and talk to a tech, see if they can advise you on common malfunctions on these models.

for shits n grins, is there a vent, or a fan? maybe the fan has stopped spinning or a vent is clogged up with dust/debris/other junk ?

this is why i cant stand powered speakers. it doesnt take long before the amps act up and then the whole cabinet is just useless. so much nicer to just switch to a backup amp and troubleshoot the standalone amp at your leisure! 9 out of 10 times the failure is the amp, not the a passive crossover or driver unless you really rag on your speakers and dont have a limiter

good luck

I guess I will have to give crest a call.

Thanks for all your help.