Smallest room dimensions for good bass to 20hz


Woundering how small of a room can you build and still get good bass responce to 20 hz.
sarcher30
20 HZ is 56.6 feet long, so I guess the perfect room would be that long or longer. I doubt there are many homes with a stereo room that length, so maybe all of us are compromised?

Maybe Rives or some other acoustics persons has a formula that determine how much less than that still works fine for our needs.
Is there a formula for figuring out how long (in footage) a given frequency is?
I thought a frequency of 20 hertz would be a wave 20 feet long between peaks.
So what does it mean if your SPL gets a good rolled off read when you play that frequency?