as a general rule I go 2 ways

1st use a mounting bracket that attaches to the television mounting bracket like the [Link: sanus.com]. I snug the bar close to the tv and zip tie all the wires up behind the television.

2nd is to cut a horizontal old work box with the back cut off. Stuff most of the wiring into the box and finish it with a blank plate with a hole drilled into it or a reverse nose plate that can be painted to match the wall. Then mount the speaker so it covers the box and plate.

I use channel as a last resort