The N900 is configured to reduce the sound quality when at higher volumes because the speakers simply cannot handle low frequency sounds at high volume. If you try and bypass it you are pretty much guaranteed to break them.

If it was just a matter of the volume being low I wouldn't have said anything, but the fact they are EQing the audio deliberately making it more tinny, that tells you a lot about what the speakers are capable of. It is a shame they aren't better considering how big the N900 is, but they aren't.

You cannot compare it to over-clocking as its a very different matter, you are comparing an analog device vs digital for a start. I HAVE burnt out speakers due to too much bass before, but I have never burnt out a CPU due to over-clocking, there are usually plenty of warning signs well before it starts to fail whereas speakers there are not.

If however you do not mean the loudspeaker then I have no idea what you mean. My N900 has better sound quality than any other device I have heard. Its infinitely better than my iPod, its better than my PC even over SPDIF to a Pioneer receiver. The only negative is the lack of a built-in EQ, but I choose to re-encode my music on the PC with different EQ settings, which is going to be a better quality EQ than a real-time one anyway.