What is the most dramatic way of increasing a speaker's Bass and Low mid?

Most dramatic way is replace speaker with one that has more frequincy extention while Garry Moore The Loner plays on a distant radio.

Thanks! BTW loving the sound now after upgrading Amps, Preamp, and cables!

The simplest way for bass boost is use your room boundaries.  Using the example of a flat response bookshelf on stand in the middle of a room away from all boundaries, move that stand mounted speaker fully against one wall- this adds +3dB in low end boost.  Then step 2 is move fully into the corner  (2 boundaries) = +6dB bass boost.  Then step 3 is of course 3 boundaries, or the corner on the floor or the ceiling= +9dB in bass boost.  Speaker will sound awful but that is the impact of a corner on a speaker.  

If you do not fully push the speaker against a boundaries, there is still increasing bass response as you get closer and closer.  A good flat speaker will sound very tubby in a corner "area" compared to the middle of the room far away from boundaries. 

Quite often boundaries are the biggest reason why a speaker does not sound good in space. Being aware of the impact boundaries cause on speakers can be helpful.  

(And we haven't even mentioned reflections from boundaries!)    

Brad
Lone Mountain Audio (consumer)
TransAudio Group Inc (pro)
Pro and Consumer Audio Importers

Have you considered doing tests using room eq wizard first

BTW, if doing testing be wary of relying on the mic built into your phone, as they are focused on picking up midrange and won't pick up low frequency with any accuracy. 

Any simple test tone cd and a decent mic will have you on your way to measure the impact of some of the changes suggested(e.g. moving towards the boundary). Cheers,
Spencer