I had to change rooms a little while back and am now stuck with a room that seems to cause some very large drops in output at certain frequencies, most notably between 97hz-113hz and 178hz-183hz (tested using a test tone generator and my ears, no access to an SPL meter right now). These drops (and overall bass response) improve greatly as you get closer to the walls. From what I've read I think I have an issue with standing waves, but havent seen any practical solution to fixing it. Does anyone have any suggestions, or am I just stuck with it?

Diagram of the room:


Moving the sub out of the corner results in a *massive* output reduction across its entire spectrum in the listening area.