Hi Dan, not sure how we missed your post--my apologies for the late reply. Bass traps in the corners or along the front or back walls of a room works wonders for improving bass impact and clarity, however this cannot be accomplished with bookshelves (bookshelves are at best are only mildly diffractive at high frequencies and would unfortunately not affect the bass). Bass trapping does not actually redirect the frequencies and instead absorbs standing waves ( in fact, redirecting bass would be undesirable since it would muddy up the sound and blunt the impact of bass transients)-- therefore large, absorptive devices, tuned directly for bass frequencies, would be called for, due to the long wavelengths of bass frequencies. Here's a couple of links worth checking:
--more good information on how to treat your room, and some room tuning products as well:
http://www.realtraps.com/facts.htm
--Another option for bass traps:
http://www.gikacoustics.com/gik_monster.html
Hope this info helps, and happy listening.
Regards,
Oliver
Oliver Amnuayphol
Home Theater/Audio Guru
Aperion Audio