Unable to hear back of the head sound effects

With two properly placed speakers, sounds can appear to come from behind you if they are recorded out-of-phase with the rest of the music.  The effect is used relatively rarely, mostly on a few rock and ambient-music recordings.  I used it on my first Dr. Muso album, Music for Picking Your Nose.  Listen especially to the slide guitar solo on "Brilliant Sky" (which is an over-the-head circular-panned effect), but you may hear it on other tracks as well.

Sometimes out-of-phase sounds can sound like they're right next to your ear or even on the floor right in front of you.  Room reflections can interfere with hearing such sounds.  My dipole speakers minimize side reflections which could affect such sounds.

Listen to “When I need you “ by Leo Sayer for such an effect 

The song "The Temple of I & I" on Thievery Corporations' album "The Temple of I & I", at around the 30 sec mark, throws a VERY VIVID image that passes back and forth directly behind my head.  So vivid I feel like I can reach behind me and swat it!

Also, as mentioned, Amused to Death has some 360 deg effects that are cool.

I'm sure this effect is not the result of reflections (for me), but rather of very deliberate mixing, and my brain playing tricks on me.  I surely don't understand everything that is involved in creating this effect, but it's very cool.  

I've had visitors hear it and they say they assumed I had speakers in the back.

My rig: speakers are full Volti/Klipschorns, 300B SE amp, Counterpoint SA-5.1 pre, Innous Zenith Mk3, and Yggdrasil "Singular" DAC.   Good recordings throw a very wide, floor to ceiling soundstage.....but the Thievery Corporation recording is extra fun!

If it's just with headphones, it might be the shape or size of the cups.

I used to think the people who said they heard sounds from behind them on two channel stereo were delusional. I have read that on the Qsound recording Amused to Death by Roger Waters you can hear dogs barking behind you. On my system they are far right and left but even with my ears. Well, just recently on another CD, I heard it. It wasn't directly behind me, but it was to my right and clearly behind my listening position. After the song finished, I started it again to verify it did happen. It did!  I'm a believer!