By installing bass traps in a room you will immediately reduce the low frequency build up which can occur. This will then make controlling your sound much easier by tightening up the sound and giving you more control.
Lower frequencies are much harder to deal with than high and mid frequencies as they have long wavelengths. This makes them more powerful. In order to deal with this much more acoustic foam is needed the thicker the foam the better it deals with low frequency issues. However placement also plays a large part particularly in the corners of a room which are most prone to low end frequency build up.
The most common placement for bass traps is the corners of a room. This is because low end frequencies tend to congregate in the corners.