oldric_naubhoff said:
if you went to see a doctor with pain in your chest seeking expert opinion and the only answer you got was to wait patiently and it would dissapear after some time, what would you think about competences of such a doctor?
I would hope that he knows what he's doing. It wouldn't be the first time a doctor sent someone home with a "keep under the covers for five days before returning" prescription.
don't get me wrong. I believe you are capable of putting together some decent hi-fi's if asked to. in the end you're exposed to different kits of hi-fi on a daily basis. but I think if the problem is beyond one's knowledge it's best to apply this golden rule that speach is silver but silence is gold. especially if one has nothing meaningful to say.
that goes both ways. Your comment actually detracted from the OP's question (and now, so does mine), so your net contribution to the OP's question is negative. On a more direct note, are you suggesting that we do not respond to forum messages before we've paid a visit the poster's house and have done our own measurements?
As for the OP: other people have already pointed out that there are two reasons why you should wait: 1) the speakers may not be fully run-in yet, and 2) your mind is still adjusting to the new sound. That means that even if the speakers don't change, your ears might. In the meantime, you could try some simple things. These changes don't have to be permanent, but they might give you a clue as to what's causing the harshness.
In order of priority for me:
- toe out your speakers. Direct the cones of your speakers away from your listening position. Do not have them fire directly at the wall behind you, but slightly off-axis. They're Kefs, they can handle it.
- place a heavy rug on the floor between you and the speakers. If there's a hard-top table there, place a rug both on and under the table.
- do not sit too close to the back wall (if any), preferably 3ft away
- if there's a window behind you, close the curtain. If it's a wall, place a curtain

- try different volumes; if the harshness disappears at low volume, the problem is in your source or amp (very unlikely).
I have not heard any Naim/Kef pairing so I'm reserving judgement. But it's not a combination that I would pick, especially because of what you're describing now. From my blissful state, I would have recommended Dynaudio or Quad speakers.