sbo6, I would suggest you read up more on modes/nodes. They aren't caused by loading problems like you suggested in another post (corner loading). They occur from reflections in a room that causes overlapping or cancellation. That is why we can fairly easily calculate them, for a given frequency size and for given room size.
Also, yes I get how room modes occur, thanks. If I made an earlier statement, especially last night that may have been a bit tilted off, that's the bourbon talking. ;-)