Even in world-class rooms with the most esoteric systems, providing the most accurate playback requires lots of expertise and time spent adjusting speaker placement, acoustic treatments, and possibly room EQ. For most of us, however, there are practical limitations to the type of monitors we use and the amount of room treatment we can employ. Once our speakers have been chosen and the room has been acoustically treated, we listen, adjust, tune, equalize, re-treat, and repeat until our mixes translate (reasonably) well to other playback environments. Recently, the technologies of speaker system design and advanced materials have allowed manufacturers to produce accurate monitors at every price-point.
It goes without saying that our studio monitors, be they speakers or headphones, influence the sound of our productions more than any other processor, instrument, or device.