How should I tidy up loose speaker wires?
My first concern here is safety and code compliance.  Ordinary speaker wire is not in-wall-rated.  

You need to use CL2 or better, CMR rated cable for in wall use..  

CL2R is short for Class 2 Riser  Site detailing low voltage cable options

  Link to speaker wire

As far as neatness goes, installing a termination panel or a "brush" wall plate would help

  

Decora style insert which would mount to a low voltage old work ring