My room is ca 70sq mtrs and very asymmetric. Nevertheless, with Chesky Records Test File #47, the phantom scene is more than 20ft deep and with precise instrument location, as well in depth as in lateral position.
Speakers are only 8ft apart and cannot be audibly located:
Scroll down here to "setup2021"
http://www.linkwitzlab.com/LX521/Stereo_Sound_System.htm
to see the picture for the Chesky Track #47.
Cheers, Frank