Try a google on EQ Room Wizard.
Note that when you play a test tone from a CD with a simple Rat Shack meter then the meter is seeing all the energy including harmonic distortion effects...a spectrum analyzer will allow you to see harmonic distortion from a pure test sine wave. (For example a 20 Hz test tone played with 50% harmonic distortion at the first fundamental of 40Hz with a 12 db room mode boost also at 40 Hz will give you a misleading impression of oodles of bass at 20 Hz..but what you have is a 40 Hz partial tone dominating the sound!)
A spectrum analyzer is the only way to go if you are serious about this...but it will disappoint you in the ultra LF (when you find out all what you thought is music is more a mixture of speaker harmonic distortion and room mode effects)
Note that when you play a test tone from a CD with a simple Rat Shack meter then the meter is seeing all the energy including harmonic distortion effects...a spectrum analyzer will allow you to see harmonic distortion from a pure test sine wave. (For example a 20 Hz test tone played with 50% harmonic distortion at the first fundamental of 40Hz with a 12 db room mode boost also at 40 Hz will give you a misleading impression of oodles of bass at 20 Hz..but what you have is a 40 Hz partial tone dominating the sound!)
A spectrum analyzer is the only way to go if you are serious about this...but it will disappoint you in the ultra LF (when you find out all what you thought is music is more a mixture of speaker harmonic distortion and room mode effects)