Vocalist Height system dependent?

My guess is that given the rack in front of your left speaker that you are disrupting the primary imaging.

This means the most coherent sound you get is from the reflection from both speakers from off the ceiling.

Another factor could be the crossover...when Eva belts out her sustained high notes it is possible that some is from the midrange and some from the tweeter - this can cause beaming or lobes in response with cancellation in some directions (if you sit below the tweeter) and coherence in other directions (such as the sound that hits the halfway point on the ceiling between you and the speakers).

Another possibility is that they used a plate in the studio to record her voice or they added a reverb that makes you think she is standing 10 feet tall. Refected sound off a lively floor (or plate or delayed microphonic feedback from tubes) causes comb filtering of the sound and rightly or wrongly your brain will use this information to judge height as well as the amount of space around a sound.

All or any of the above might be a factor - but you could try by eliminating any obstacles (like a large rack stand) that may affect the sound reaching you.

Good Luck. Frankly I doubt it has anything to do with cables.

I measured my mid range driver is at 40 inches.

Then I would think your tweeter is around 48 inches. If you sit 10 feet back with ear level at 36 inches in your comfy seat then you should have the impression of a vocalist standing at about the right height.

Remember that funny flap of skin around the ear....well it has an uncanny ability to judge the up down direction of where a sound is coming from (it also tends to cue on things in the 4K to 12K Hz range which is why sounds tend to appear to come from tweeters - even on three ways).

Also the more energy from above the plane of your ears (direct and reflected off the ceiling) the more the pinea will be telling your brain that the singer is above you.

Since music can be reverbed and deliberately engineered to give you an impression of space or height you really need to try many recordings (with no added ambience effects) to confirm.

Alternatively;

Try Tom Petty "Last Dance with Mary Jane" - lead guitar from the right and Tom Petty Dead center at tweeter height (not much added ambience on this one).

Try Tower of Power Soul Vaccination "What is Hip" - singer and band should apear to be up on stage (loads of ambience here).

Try George Bensen Weekend in LA Live "On Broadway" - Harvey Mason's drum set appears to be on a stage and you can hear him move around the set.