To Doug Schneider,
I recently purchased a pair of KEF R500 speakers and am in the process of selecting an optimal placement in the listening room of 18’ 10” long and 12’ 5” wide. I would like to know how you set up the R500s when you reviewed them. The manual gave a minimum of 39" from the side walls, which makes the distance between the speakers 1” less than 6’ in my room. I would also like to know about the height relative to ear level (mine 39”), considering the tweeter is about 31” from the floor. Right now (two days after receiving them) I have placed them 37" from side walls and 42" from the back wall. The sound balance is slightly tilted towards the high frequencies. Before experimenting I thought of asking you for some pointers.
Great, great speakers -- I hope I can help.
The R500 is quite a bit different than most speakers because of the way the Uni-Q driver disperses its sound -- essentially, all the frequencies from about 500Hz and up (the range that the Uni-Q driver in that speaker reproduces) radiate equally in all directions, which is quite unlike a speaker with the tweeter placed above or below a midrange driver. To me, this makes the speakers easier to set up.
Insofar as the high frequencies go, because you’re hearing a top end that you perceive as slightly tilted up, the last thing you want to do is have the tweeter at ear level because with the tweeters firing directly at you, they'll sound even more prominent. What you want to do is listen to each R500 off axis from its tweeter, vertically and/or horizontally, because that is where the response drops off (our measurements show that the R500's 45-degree off-axis response is down about 5dB compared to the on-axis response, and the 60-degree off-axis response is down about 10dB). Obviously, you can’t get the speakers lower to get further off the tweeter axis height-wise (the 39" ear height you mentioned is about average), so you have to look to the sides (i.e., horizontal response).
You haven’t mentioned toeing in the speakers, but if you have them toed in, try to position the pair so they fire straight out in the room), which, in most setups, puts the listener about 30-60 degrees off the tweeter axis, depending on the listening distance from the speakers. That alone might be enough to help to tame those highs. You might also want to spread the speakers a little wider, despite what the manual says -- about one foot. Doing so will put you further off axis from the tweeter, although putting them closer to the side walls will increase reflections from those surfaces, which is likely why the manual stipulates a certain distance. Still, it's worth a try.
If none of that helps, I recommend looking at the acoustics of the room, which you haven’t mentioned much but they do play a strong role. Does your room have hardwood floors or bare walls? Flat, hard surfaces reflect the high frequencies rather than absorb them, so that can contribute to brightness. A large throw rug on the floor in front of the speakers can make a world of difference to the sound because it will absorb some of the highs. Likewise, absorptive material on the side walls can help as well.
Let me know if this helps. If not, please write back and I can give you more suggestions. . . . Doug Schneider