I mentioned this information related to wharfedale 220 speakers.
First of all, most widely available consumer speakers have a lot less deep bass than they seem to have: What they have is lots of mid-bass; it is easy to be fooled into thinking one is actually hearing really deep bass when all one is hearing is lots of inarticulate booming. Mass market speakers (entry level) reproducing unpleasant mid bass (50-80hz) and fuzzy boom bass, these speaker's cabinet design is also not good. Hence the output sound signature may be unpleasant or lack in mid and high frequency areas.
If you connect a home theater sub along with this wharfedale 220 speakers, boom sound increase in high level. The ultimate result will be ''you can't hear the correct stereo image, and also mid, high frequencies''. Bcoz entry level speaker producing less detailed sound, if adding a sub to an entry level bookshelf spkr, musical details were hiding very large level...
You can connect high end speaker with musical sub woofers with crossover settings of 80Hz.