No need to apologize @theaudiomaniac; just glad for some help.
So I only got to #2 on my list of tests tonight (testing with my 25 year old Arcam CD player as the input instead of the internal DAC) but I may have made a breakthrough of sorts.
First thing is it was surprisingly nostalgic hearing the sound I used to hear when I played music - it sounded terrible, but there was a charm to it. Still enjoyed the sound it made. It doesn’t even sound like you are listening to the same version of the music when playing the same tracks streamed to the Gryphon DAC.
Second thing totally confused me momentarily. I immediately heard the missing frequencies - but on the left side instead of the right! After a very brief moment of confusion as to how this could be, I realized I had mixed up the interconnect inputs to the amp between left and right. I then realized, wait....it is the source material causing the issue! It’s the only explanation as to why the problem would exist on the CD player as well, and that the problem would follow whatever the right channel output of the CD player was plugged into. At this point I’m 95% confident that all of my obsessing over this issue was due to a small number of tracks with the slightest flaws in the recorded stereo image of the vocals, combined with the only aspect of my new speakers which I’m not a fan of: a laser-etched sweet spot, regardless of toe-in and setup. My theory is that these particular speakers are more prone than most others I’ve tried to exposing any flaws in recorded stereo images, in the upper vocal range. On most music is not an issue. It’s just a handful of tracks really where I notice it.
In comparison one of the speakers I had auditioned was the Magico A5’s. These speakers in comparison have a ridiculously large sweet spot. In fact it’s almost like there isn’t a sweet spot with those speakers as position doesn’t matter to a large extent. I doubt I’d have noticed such an issue with those speakers. Having said that, I didn’t take to them and I really do like the sound of my speakers with my system, so I think I can live with this "flaw" for the few tracks that have issues with the stereo image.
The one slightly troubling thing still: When I hear this issue, it’s always the same; missing upper mid frequencies on the right.
For reference, three example tracks where I hear the issue are Keep the Car Running by Arcade Fire (the remainder of the songs on that album sound okay), and Cite Soleil and John the Baptiste by The Afghan Whigs (these two tracks expose the issue to the highest degree).
I’ve lost my CD with those Afghan Whigs tracks so I’m going to purchase it again, and put this issue to rest once and for all. I will confirm that even these tracks when played with the CD player, with the interconnects swapped between left and right, produce the issue on the left side and not the right. If that’s the case I’ll be 100% sure my new speakers are just sensitive to stereo image issues in source material.
Yes, I tend to be on the neurotic side of the audiophile spectrum... I’ve completed my upgrades for now so I should be able to settle down and get back to just relaxing and enjoying the music without thinking too hard!