How can I get 20-25Hz boost?

My system lacks deep bass response—below approximately 65Hz—while the speakers have dual 10” woofers per cabinet; Braun LS200. The amplifier is an integrated amplifier Braun atelier A2. I normally don’t use Loudness button and tone controls (both bass and treble knobs).

In fact, the Braun LS200 were launched with their own amplifiers which would be attached to the recess at the back of the cabinets modeled Braun PA1. The PA1 literally has a deep bass adjustment knob which allows user to boost or cut deep bass output by +/-3dB. The deep bass is referred to 25Hz frequency according to the user manual. Nevertheless, there’s an alternative choice for amplifying these speakers. It’s a separated component launched for them as well which are Braun CC4 and PA4, preamplifier and power amplifier, respectively. The CC4 also has deep bass boost adjustment where deep bass is referred to 20Hz and level is 0-6dB range.

As you can see, it’s likely that the LS200 speakers were designed to have deep bass assistance by electronic. And, I couldn’t agree more with this idea. As mentioned earlier, I use an integrated amplifier, A2, with linear mode operation—never use Loudness and tone controls.

I’d like to ask how can I get deep bass assistance with the lowest cost, except using anything cosmetics the signal such as Loudness, EQ, and Tone Controls?

Actually, I also have the answer in my mind that is using a subwoofer. However, the question was initiated because my subwoofer is now being repaired, Lol. And I thought I already have four 10” bass drivers in my hands, so is there any way to maximize outcomes from them?

I would love to hear everyone’s thoughts.