Tapestrys, quilts, etc on the wall at 1st reflection points (on sides) Pillows in the upper corners. For cheap bass traps, stack a couple of boxes in the corners, fill up with newpaper about 1/2 way in each box. There are several do it yourself idea's on other sites. email me and I'll point you there.
There may be something in the archives here as well.
There may be something in the archives here as well.