Superb cheap speaker placement, finding the "sweet spot" tool.

The XLO Test CD is an old stand-by setup tool. After the standard L channel/R channel stuff there's tracks of him walking around a room, just talking and hitting a clavis (wood block) with two microphones. You hear his voice saying, "The room is 23 feet by 34 feet, I'm standing between the microphones..." and that is what you hear- exactly! Then as he walks around you hear him walk around, until he's standing BEHIND you, and damned if it doesn't sound like he's behind you! 

Then there's a number of tracks, just really good examples of different quality recordings- drum set, classical, etc. Besides recording technique like microphone placement (what you were talking about, what determines sound staging placement) there's also the whole recording chain which can be tube, solid state, and all different kinds of wire, mixing, mastering, etc. A lot of things to listen for.

As far as setting up speakers though nothing beats a tape measure and framing square.

Yes, I agree the XLO CD is excellent.
In combination with the completely phase coherent recordings, mentioned in my first post, you have all the tools necessary for a great set up session.
..... new DXD sampler recording engineer Frans de Rond is proving once again that his knowledge of mic placement and use of equipment is in a class of his own.
He is able to create a sound stage, that projects an almost visual image of the musicians.
A sound stage which is intimate but also has depth and space.
The sound on the recordings presented here are like a three dimensional Van Gogh painting, where you can step in and take a look around.
https://www.soundliaison.com/index.php/536-sound-liaison-dxd-music-sampler

Is this the xlo test CD https://www.youtube.com/watch?v=v0TssXw2zhw&loop=0  ?

The cool thing about the XLO Test CD speaker set-up track is that it’s the only (rpt only) way to find the absolute best locations for ANY speakers in ANY room. All other methods are bound to fall short. The best you can do with other methods is find reasonably good locations, we call those LOCAL MAXIMUMS.

It’s like trying to solve x simultaneous equations in x+n unknowns. As you improve room acoustics with room treatments and add tweaks, lo and behold! You need to find the new optimum speaker locations. It’s a fluid situation on the ground. That’s why lasers and other measurement methods don’t work as well. Oh, you thought you only had to do it once? 😳 “You should hear the sound coming from all around you, from no particular direction.” That’s using the out of phase track, speaker set up track. “The better you can make my voice coming at you from all around when the system is out of phase, the better the sound will be when it’s in phase.”

By the way, it’s not easy at all, especially the first time, to get the guy’s voice to sound like it’s coming at you from all around the room, no matter how hard you try. There is a number of reasons why, you will find out as you go. It’s called coming to grips with reality. A journey of a thousand miles starts with one step. 😬