Best position for rear channel.

I have a Home theatre system consisting or Martin Logan CLS11Z front L&R,Theatre centre and depth sub, and CLS11z rear L&R. The null zone for the rear speakers doesn't seem to work. Any suggestions.Room size -22ft X 17 X 9.
i'd place rears close to the wall.
How far away is your seat from side and rear walls?
This should not be a problem really, even with dipole Logans. You simply place the speaker where your head will be in the listening seat, play music and test tones as you walk around room near your placement options, and find were the sound is the best! That's your spot. Now switch speaker from seat to that location. Works everytime.

Can you explain what you mean by the null zone does not work? Are your rear speakers dipoles, or is this something different?

Well I can tell you, when you get that position nailed; you get a rear/center image.---Much like your front/center image. Just move them till you dial in that image.
If the speaker is not made to be close to the wall it will not image right (i will not get into acustices here) You need to fins a spot where it images well just like the frount. ANother trick I have a similar romm and oput them about 8' high and that worked really well for sourounds.
The null spot is to the side of the listening chairs. I have to be closer to the rear speakers than the front so I can't go with a 360 degree arc, me in the middle equi-distant arrangement.Believe me I have tried every spot short of suspending them from the ceiling. I was hoping for a solution from someone with a similar system using CLS for rear speakers. The sound is very detailed and engulfing as it is with the speakers behind me, equally distanced to the side and rear wall as the front speakers are.Thanks to all.

I would recommend trying a 7.1 speaker set up. With two speakers directly to the sides of your primary listening position (+- 90 deg), and another two speakers spread apart in the rear of the room, behind your listening position (about +- 160 deg), you will get much better surround envelopment than using only two surround speakers.

You will need DPLIIx and /or Logic 7 to properly drive a 7.1 speaker system, since there are no 7.1 sources, but in my own experience 7.1 is well worth it.