Resonant coupling can be an issue if you’ve got you speakers placed on a shelf, table and even stands. The phenomenon is caused by the frequencies vibrating the speaker against what it’s sitting on, which in turn can cause comb-filtering causing frequencies to add or cancel with each other when coupled. This resonance can inaccurately color what you are hearing.
How to solve this?
Go out and invest some money in a good monitor isolation product.
Have a look at the Isoacoustics stands, Auralex MoPad and Primacoustic’s Recoil Stabilizers or IsoPads. These products are designed to isolate a monitors from the surface it’s placed on, thus reducing acoustic coupling.