you turn off the other 2...
and never turn them back on.
seriously, unless all 3 (or 2 for the matter) have a pretty good location, the sub in the NOT so good location will mess up the aggregate frequency response.
so, Im using the velo DLR-5000R for my PC ...
im thinking of using the axiom EP500 as my center speaker subwoofer OR surround channels subwoofer (setting those channels to large)