check you have not blown a tweeter.

Thanks for the reply,  all units are playing no problem,  like I said, sometimes they sound OK with very well recorded music, but the majority of the time they sound shrill.

Thanks 

Swap the Loki for one of the MiniDSP units, and *measure* with the UMIK-1 and REW software.  

Their DDRC-24 unit with Dirac Live purports to fix "everything" automagically if you don't have the patience to make the measurements, but one of their standard boxes like the 2x4HD will allow you to fix the likely single frequency range without screwing around with the time domain like Dirac does.  But the important part is the measurement.  "Harsh" often means a divergence from a gently sloping downward curve a la Harman (Toole) in-room.  Measure!  Measure!  Measure!  If the curve looks like a single filter will tame it, you can return the Loki to the chain, adjust it as necessary while measuring(!), then *remove* the MiniDSP box, because it's doing what will then be an unnecessary A/D and D/A conversion.  Depending upon how high volume you listen at, it still might be the drivers failing right at the edge of their performance when other frequencies get added in, whether from total power dissipated or even some unlikely weirdness like the crossover not working.  It could even be your own hearing, if you're accustomed to max volume -- but if so, it's still easy (though time-consuming) to slide a -3dB filter across the frequency range to see if "harsh" goes away.  Good luck!  This will take some time, but surely will be worth it to keep the Beolab 9's.

P.S.  Another method, sacrilegious here I know, is to borrow a different brand of speakers from a friend, adjust them to the same sound level, and see if they too sound harsh.  If so, start looking at your room and weird reflections, for which Dirac Live might be best after all, or back to the source or even the preamp -- which I deemed unlikely else I wouldn't have started off by suggesting the MiniDSP box.  If they do not sound harsh, you know what to do, alas...

P.P.S.  Wait, wait,... 3 years with this equipment and only now it sounds harsh enough to fix?  I'm inclined to agree with Mr. 10Percent: you blew a tweeter, especially if you're listening to EDM.  (Synths make square waves much better than "real" instruments do.)  If "nothing has changed", not your volume (or genre which can amount to the same thing) just borrow & swap, moving down the audio chain, to find your culprit.

Hi Trackbeo, 

Thanks for such a full response!

I'd considered the dsp approach but thought it would be more aimed at the bass end of the spectrum. 

I'll look into it, it would be nice to keep the lab 9s and get the most out of them. I'll also borrow some other speakers like you recommended and see if I get the same problem.

With regards to the 3 years, the tweeters definitely aren't blown, I rarely listen at high volume , I've arranged the room differently a few times, when sat much closer to the speakers they're not quite so harsh, but still not great.   I've also experimented with toeing them in towards the listening position vs facing straight ahead,  straight ahead sounds less harsh in the treble but virtually no bass, toed in better bass but piercing sound.  Perhaps I've just got a phenomenally difficult room for sound, it's kind of slightly triangular in shape, open plan, about 20ft by 17ft, my thinking was an ATL lens would be better in an awkward room but maybe that'snot theecase here.

Thanks again