You can only hear the lowest bass leaking through. A small open-back box for the speaker. A large box for the speaker isolation cabinet. A very large box for the 2nd speaker isolation cabinet to mute the first. A single box could mute your sound almost as much as both of my boxes, if you get serious about it.
Portability is a concern.
My inner box is light and more portable. But it's not clear whether you want an iso cab when you're not at home. I made a box with 3 different dimensions, about the usual dimensions of a speaker cabinet. You see a rectangle when viewing it from the end, top, or side. I made it fairly big, to give room for bass waves.