could someone explain this for me?

[sheppard]

i just bought a set of yamaha msp5's.on the rear of the speaker
are 2 trim switches,one for low and one for high.
it is my understanding that these are used to match the speaker to the room.but how.any rules of thumb.

 

[TexRoadkill]

In general you might cut the highs a touch in a really live room. You might cut the bass in a small room. Whatever you turn down on your monitors will be emphasized in the final mix as you boost to compensate.

I would just leave them where they are doing nothing and wait and see if you have any problems with your mixes. If your mixes are consistantly dull or bass shy on other systems then might try messing with those settings.