Rick, you really don't get seating placement from mode calculators. They simply divide twice the dimensions of a symmetrical rectangular or square room into the speed of sound(about 1130 feet per second)to get the various room modes that result from sound traveling back and forth(that's why twice the distance is used)on each dimension. For example, your 25' length dimension results in the first length mode at about 1130/50, or 22.6Hz, with the next mode at 45.2Hz, then 67.8Hz, etc. The same is done for width and height. Problem frequencies where the various modes pile up are evident from this and possibly can be attacked by use of electronic room equalization and/or bass traps.
