What are the smallest speakers that are clean and flat down to 20hz?

I've managed to achieve fairly flat/clean response in my 15.5ft x 10.1ft room down to 22Hz, but I'm using four 12" woofers and lots of power to do that at greater than 90dB.

What I've found is that interesting musical content below 40Hz is uncommon. Most of what I hear is stage/studio vibrations, an HVAC switching on, a truck driving by, or other low, rumbly noises that were picked up by the mics during recording and not filtered out. While these sonic artifacts are occasionally interesting, they rarely contribute to the musical performance in any helpful way, so I'd probably be better off rolling things off sharply below about 32Hz. Here's a graph of actual measured response at the listening position before and after correction:

http://www.dsnyder.ws-e.com/photos/potn/Loft_Before_After_and_Target.png

Here's a photo of the actual room from the listening position:

http://www.dsnyder.ws-e.com/photos/potn/loft_wide.jpg

I'm confident that I could achieve similar response with somewhat smaller loudspeakers, but I estimate that minimally four 10" woofers or two 12" woofers would be required in total to achieve this level of bass extension without a separate subwoofer.

I had these loudspeakers before the room...they are obviously a bit large for the space, . If I was buying loudspeakers specifically for this room, I would probably have chosen Harbeth 30.1 or Legacy Audio Calibre and would have been quite happy.

I'll need to find a way to download that Phil Collins track as a WAV or MP3 to test since I'm using digital room correction. Might be able to get the audio from Youtube to stream over DLNA as well, but I have not looked into it.

In my case, the loudspeakers are close to the walls (18.5" away on-center) for soundstage reasons more than for bass...which I have too much of in this room without correction.

I still maintain that this is a silly exercise for several reasons:

• LF extension without distortion figures is kind-of meaningless
• Most sounds below ~32Hz are from environmental noise rather than music
• Room size and in-room response is a huge factor. It’s one thing to achieve flat response to 20Hz in a closet or Honda Civic vs. a 5,000 cu. ft. listening room
• We have not very clearly defined "speaker". For example, the DuNu DN2000J is a lot smaller than the Triton II+ and are fairly flat down to 5Hz with low distortion. It can do this because the "room size" is only a few cubic mm.

I suppose the fancy way is to use something like this.

http://www.digitalaudioreview.net/2016/09/waiting-for-the-bass-to-drop-with-devialets-samlab/