Also true that a sub, no matter how good is it, does not fix issues created by speaker placement and setup. For music, the L112 can be set up to be near perfect but does still lack in the under-40Hz range. It does tend to the thumping sound especially if not well placed. I like them at lower volume but think they need a LOT of space around them for the best sound especially if pushed.

IOW, if there are issues created by placement and lack of EQ, adding a sub will not remove them. I think I'd round up some good sweep tones and sine wave tones and isolate exactly where the peaks and valleys are, then proceed with placement adjustments before looking at a sub. That's not to say that a sub won't be a nice addition. But doing the above first will give you the info you need to set up a sub too.