Speakers that disappear

Bose comes to mind, but only if there's at least one Synergistic Research fuse in the system.

No highs no lows, must be Bose.  

I am pretty sure that there are stand mounted speakers that do a better job at the disappearing act than Bose 901s.  (And I had never heard Bose 901s referred to as "stand mounted" before, but who knows.)

Anthony Gallo ref 3.1 or 3.5s or their current stand mounts Strada II. I obviously a fan boy for Gallo. The cdt tweeters are among my favorites in all the speakers I’ve ever heard. 
 

I’ve also been drawn to most open baffle designs for the disappearance act. Depending on budget, Nola makes some really special sounding speakers. All disappear without much fuss.

My Magnepan LRS+ does a pretty good job disappearing even though I sit close to the LEFT speaker in my small office. However, I cheat by using ROON's digital speaker placement option. That thing is like an analog balance control in a preamp, but on steroids.

The best speaker that I know to totally disappear and also have an incredible soundstage is the KEF Blade 2.

It really begins upsteam...if you can hear you amplifier grilling, then your speakers no matter what they are will not disappear...it is the whole chain.