Yes you only need a line out signal, the volume have to be controlled directly from the source. Their are named studio monitors because normally you use it for mixing musicians records (audio production), the signal response is flat and analytic with a very good resolution and instruments separation.
http://en.wikipedia.org/wiki/Studio_monitor
Personally a feed it with a LittleDot MK3 Tube Pre-Amp to give a touch of warmness for music listening and I can also control the line out volume.