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

No I didn't check the schematic, but I know only the most expensive speakers use teflon capacitors. I don't even know if your speakers are among the most expensive speakers; maybe they are.

My speakers were custom built by me. A speaker design engineer designed the crossover, and I took it from there with some help from a place that sold raw drivers. In order not to go over budget, we used electrolytic capacitors; this gave us a general idea of what the speaker would sound like.

After listening for awhile, I decided they were worth much better and more expensive capacitors, such as Jantzen Silver Series Z Caps. The largest capacitor running my 12 inch woofer is a "Solen", 100uf, 400V.

     
          https://solen.ca/product-category/capacitors/ capacitor



These capacitors on the woofer section of the crossover will eliminate "tubbines"; you will have sharp bass lines.

I think you wrong , woofer crossover 1st order use just the coil, no any capacitor, Crossover 2nd order, use capacitors , but 99.99% using teflon
capacitors. the teflons capacitors get different grade and low grade cost
50-100 mkf cost $5-10 , electrolitic cost around $1.  I did not  see electrolits
in mass bestbuy speakers. 

No my friend, you are wrong; this crossover was designed by a crossover engineer who was working for a company that sold speakers. It is a 3-way 4th order crossover, T-type.
92 DB efficient.

What I'm listening to has solid firm bass.


These are the capacitors that are in the bass leg of my crossover.


      https://www.parts-express.com/solen-100uf-400v-poylpropylene-capacitor--027-616

My friend tell---- if so , why he install electrolytic capacitors  in crossovers and
let you change capacitors for teflon. i dont want to explain my degree, i  also design and selling  speakers. i just told you about you  wrong post----only 
very expensive  loudspeakers using teflon capacitors +

bache, polypropylene capacitors are better than teflon capacitors; no one let me do anything, I changed the capacitors because I wanted the best sound; they're my speakers, my crossover.

Here are the ratings in capacitors, and teflon comes in down the list from mine;


        https://www.gearslutz.com/board/geekslutz-forum/434325-what-best-musical-sounding-capacitors-use-rec...