They’re not rear speakers, they’re surround-channel speakers. For film sound, the ideal surround-channel speaker placement in a 5.1-channel system — what most people have — is roughly lateral to the prime listening area, well above head-level, and aimed or positioned so the direct sound bounces off the side and/or rear wall before reaching listeners. If your couch is positioned against your room’s back wall, surround speakers should be placed firing somewhat forward so the sound washes along the side walls. (Note that this advice doesn’t apply to the back surround speakers used for 7.1-channel setups, which get properly positioned at the rear of the room, roughly mirroring the front left/right speaker array.)
