Ihcho,
There is no exact answer, If the speakers had an ever so slight tilt downward, you might get away with 5 ft to 5 1/2 ft, but in general I agree with Audioblazer. A boundry must be considered. Again, in general I would say 4 1/2 foot max. Depending on dispersion patterns of the speaker you choose and even how far your seating position is and how loud you listen, this could change.
There is no exact answer, If the speakers had an ever so slight tilt downward, you might get away with 5 ft to 5 1/2 ft, but in general I agree with Audioblazer. A boundry must be considered. Again, in general I would say 4 1/2 foot max. Depending on dispersion patterns of the speaker you choose and even how far your seating position is and how loud you listen, this could change.