From Amazon, who have been running a series.

The main reason I'm linking is to explain this, because it struck me that some might wonder why:

Unless you have a high-end receiver and speakers capable of generating a lot of bass, I recommend setting them to "small." This will send their bass to your subwoofer.

Some might ask, "...but what about the stereo for the bass? I thought that stereo required separation. How can you get that if it's all coming from a single speaker?"

Here's the deal. The ability to discriminate the direction of sound is a function of its wavelength. The wavelength of notes in the bass frequency is substantially longer than the distance between your ears, so there's no way for you to tell what direction the sound is coming from at those frequencies. Can you tell where thunder is from the sound? Yes, you can tell how far away it is, if you see the lightning and count the time until you hear it (about five seconds per mile), but absent visual clues, there's no way to tell the direction purely from the sound.

That's why you can not only get away with sending all bass to the subwoofer, but it doesn't even matter where the subwoofer is. So you can place it where it's convenient, or aesthetic (as long as it's at least in the same room). It's the high frequencies where speaker placement matters.

I have Bose cubes, so they're small anyway.

I seem to remember 240 being the magic freq for the crossover.