I think a good method is to use a track with a female vocal and fairly deep bass and move the speakers away from the walls to achieve the best balance between bass response and vocal clarity. As you move closer to the walls the bass might increase, but the vocal may get muddy. This will always involve a compromise, so just move around until you get the balance you like. I think Nora Jones' first record (Come Away With Me) works well. A lot of tracks on there fill the bill. Trouble is, in real-world rooms, the traditional formulas for speaker placement don't always work and you need to just tune by ear. IMO of course.