I always measure from the driver face/cabinet face. 5’ is no man’s land though. You will want to be no more than 39” or more than 7’ for smooth bass due to 1/4th wave rear wall cancelation. It is of course more complicated than that as all boundaries sum.
If you run subs with a highpass you can place the mains at five feet and the subs 39” or less and get flat sound assuming phase is correct.