The room itself will contribute to the sound with speakers placed well, or not. Standing waves don't care about placement or EQ- they persist and are difficult to prevent in that way, especially with such large wavelengths. Once the wavelength matches the room's dimensions, the interference (constructive/destructive) causes problems but the distribution of the waves is why the ratios of the distances is so important during design. After the place has been built, it's more difficult to prevent the standing waves.