From my experience I agree with Baylinor. When setting up my room (using the long wall for placement) I was not able to overcome the reflections. Heavy speaker toe in made things somewhat listenable at low volumes but everything fell apart afterwards. I have no direct experience with using a turntable in this regard.
Rotating to the short wall, applying heavy window treatments and moving the speakers further into the room made all the difference. Ultimately I added diffuser panels, one on each side wall and one on the ceiling to tighten everything up. Since making these changes the only improvements have been with my adjusting seating position forward/backward but I only do this when auditioning new equipment.