my experience is that to improve the imaging of large line-source dipoles (ML Monoliths in my case), one needs to carefully manage the rear wave of the speaker.
Just think about it, a dipole speaker generates equal, out-of-phase signals that bounce of the walls behind and to the sides of the speaker, and then mix with the direct sound from the front of the speaker. Not only does this create comb-filtering, it also induces spatial positioning anomalies. it's the latter that are often referred to as the 'spacious' soundstage of dipoles.
If one manages the rear-wave with appropriate absorption, these large line-sources can actually generate really uncanny soundstages where depending on the mix, the engineer places sounds inside or outside the circle of speakers.
On recordings like the
audiophile vocals SACD, the intimate presence of the singer is right there, in the room with you, and large-scale symphonic is as natural as being in the symphony hall. Or heavily layered prog-rock, like Steve Wilsons oeuvres display his mastery at multichannel mixing and careful positioning.
I've heard these same recording on other top-tier systems in dedicated custom rooms, and while good, not quite the match of large line-sources for imaging,
but, the panel speakers are in a carefully set up room and system.
