Moving the sweet spot

Yup lowrider57 has got it. Adjust one speaker for one ear. Set the camber, caster and toe in/out THEN closer or further for DB gain or loss for your ailing ear.

I found the biggest thing about the seated position is height in relation to the Bass roll off and the HF being there but not beaming and boiling your ears to death...

Painters tape a square and a tape measure. You want to get real picky laser line placement or string lines to your head in the seated position..

You can get REAL picky...

A mic stand and some tape to hold the string lines at the speaker and stand.

You know Master M has two different spots he listens to. I can't remember the reason but both have their strengths and weaknesses for listening.

Maybe he'll chime in..

Regards

You may want to experiment with different chairs, too?
And when you identify each chair's respective strengths and
weaknesses, you can adjust for effect.

This is tech talk. Map out your room modes and it will be obvious that cancellation only happens at certain locations that vary by frequency. What happens is the waves reflect off the walls, come back and where they meet they either cancel or reinforce.

This happens all the time everywhere, but really is only audible in rooms with almost all smooth unbroken walls. Because otherwise the waves hit uneven surfaces, bounce off in different directions, and the result is the reflections become diffuse. Which is why surfaces deliberately designed to do this are called diffusers.   

This never happens in as you say "an open space". So we can cross that one off the list and we are left with, "and my left ear is not as good as I was young."

millercarbon,  I think you are right, it happens for most every one of us... with the age.  Thank you