Post binding for crude tone control

I have a newish pair of ATC SCM40 passive speakers.  They're 3-way, notoriously revealing and have triple binding posts*.  The posts are connected by metal plates (steel?).   The dealer advised, and I believe it's common practice, that I bind my cables to one of the bass driver's posts, and to one of the tweeter's posts.  I expect this setup treats all 3 drivers the same, with an equal amount of plate in each's circuit.

Recently, I've upgraded cables, fuses, USB cables etc, and resolution of the system has increased along with a little digital glare.  Female vocals are too often sibilant.  The probable cause is the ethernet stage and I am working on improving it, but to "tame the treble" I thought I'd try playing around with the binding setup.  It occurred to me by binding across the bass or mid-range posts I might be "favouring" those drivers, and attenuating the others.  I'm assuming the plates have a slightly higher resistance than my TelluriumQ Ultra Black II cable.

So, I unplugged from the tweeter's terminal and moved the cable's plug to the mid-range's.  Each cable is now bound to both the bass and mid-range posts.  The tweeter's posts are connected by only the plates.

And, hey presto, the system is now exhibiting a slightly warmer, darker sound.   I might be wrong, of course;  wouldn't be the first time the Emperor's new clothes are warmer and more musical. 

Has anyone else done the same?  

It did occur to me that strategic use of resistors might attenuate a driver even further, though I doubt this could improve resolution.

* - has anyone ever tri-wired their speakers?