When double-clicking an audio region and thus opening the Sample Editor, it tends to use Track Object 1 for playback. This can be very annoying, as you might have a massive reverb and huge distortion inserted on this track - not nice if you try to edit a sensitive choral passage :). There are 2 solutions for this problem, one better than the other.
At the left hand side of the Sample Editor window is a white box, reading "Cha 1". You can click-scroll there to pick another channel (Track Object) for playback. As long as Logic is running, the newly picked channel will remain the active one. However, as soon as you shut down Logic, the next time Logic will revert to "Cha 1" again. In other words, there's no way to change this default behaviour permanently.
 
A better solution is to not use Track Object 1 at all. In the Audio Mixer, make sure the "Audio 1 " channel strip has no effects inserted, no Sends active, and has volume set to 0 dB (90). Drag this channel strip out of the way, somewhere off-screen. Just forget it exists and never use it. Now the Sample Editor can safely use this object for playback.