Did you futz with the cables? The change in sound could well be ’out of phase’ caused by the reversal of one set of cables to your speakers. If you return them to the original placement does the sound change back to ’directional?
Another thing to check - put on a recording which has a solo voice. Does the image sit centered between the speakers, or has it spread out to the rooms corners with little voice left dead center? If so you have inadvertently reversed phase in one speaker.