Problem with a certain frequency in a mix translation

The wavelength of a 100 Hz cycle is quite long (about 11 ft.), long enough so that is would pass your ears by before it would fully develop, especially if you're close to the monitors. If your room has large parallel surfaces this far apart, it's possible a standing wave has developed (perhaps this is why you noticed more bass when you moved back?). I suggest treating your room with bass traps, so that you get a decent "picture" of lower frequencies throughout your room. Use PTs signal generator to judge the difference. But this is also a problem when recording bass amps. The player says "I like lots of low end" and dials down all the mids and highs, and then when he plays a higher note, you can't hear him at all in the mix. It was discussed recently here, but suffice it to say that a small boombox can't reproduce these low frequencies, only the overtones (which reside further up the spectrum). Nonetheless, we "hear" bass on boomboxes because our brains psychoactively fill in the fundamental tones, even though all we're hearing are overtones.

Foam is ineffective at lower frequencies which is unfortunate since that's where most of the problems lie in a small room. EQ cannot adequately compensate for room acoustic problems. I often walk around the room or even into other rooms while checking for low frequency problems in my mixes.

Amazing what a bit of position tweaking will do eh? Being on the east coast you should be able to find compressed fiberglass pretty easily, and at a decent price. Wrap the sheets with some muslin, and put 'em in the corners. Instant budget bass traps. Out here on the left coast when you talk about compressed glass most just look at you funny. The few that do carry it charge accordingly.