Flat isn't possible except under the most ideal conditions in a fairly large room. Placement of speakers too close to the wall behind them is the biggestest contributor to getting an uneven frequency response below, say, 500 hz.
The next biggest contributor is location of the listening chair. Optimize both and you will still have dips and bumps but there are some room dimensional suck outs or humps you just can't get rid of. BTW frequency response much above 500 hz has more to do with your equipment synergy, speaker toe in, and killing first reflection points on the side walls, floor, and ceiling (if possible).
I'd suggest, if you have not alread done so read so set up theories which will give you some god starting points. Cardas for one, Physic's for another, and look up Rives site - last time I was there he has a CARA program which just might even include your speakers. That program works well, but all of these are just starting points.
With a SPL meter (Radio Shack), a test disc with 1/3d octave test tones (Stereophile) you can pretty much do your own set up work. It takes a lot of time and experimentation so patience will be necessary but the initial frequency response flattening isn't very hard. Its the subsequent fine tuning that takes a lot of small moves and time listening to the results.
BTW, if you do this, buy some graph paper and keep careful notes of your set up distances - it can get a little complex trying to keep all of these in your head, as it will also give you some visual clues about what you can change, cannot change, and whether its lspeakers or listening position that is causing the issues you like or dislike.
Hope that helps a bit.
The next biggest contributor is location of the listening chair. Optimize both and you will still have dips and bumps but there are some room dimensional suck outs or humps you just can't get rid of. BTW frequency response much above 500 hz has more to do with your equipment synergy, speaker toe in, and killing first reflection points on the side walls, floor, and ceiling (if possible).
I'd suggest, if you have not alread done so read so set up theories which will give you some god starting points. Cardas for one, Physic's for another, and look up Rives site - last time I was there he has a CARA program which just might even include your speakers. That program works well, but all of these are just starting points.
With a SPL meter (Radio Shack), a test disc with 1/3d octave test tones (Stereophile) you can pretty much do your own set up work. It takes a lot of time and experimentation so patience will be necessary but the initial frequency response flattening isn't very hard. Its the subsequent fine tuning that takes a lot of small moves and time listening to the results.
BTW, if you do this, buy some graph paper and keep careful notes of your set up distances - it can get a little complex trying to keep all of these in your head, as it will also give you some visual clues about what you can change, cannot change, and whether its lspeakers or listening position that is causing the issues you like or dislike.
Hope that helps a bit.