When you can hear a difference than it is your result, when you hear nothing it is of equal value.
Todd has described how to perform testing. When I say I have to look to the speaker it was meant to turn the head in that direction.
As said for me it is a very subtle effect. With normal music I do not notice it. For testing I took hiss from left or right. (Telarc 1812 SACD has some tracks.)
As said I do not care as I live with my glasses. Or should I consider to go for a plastic surgery to model my head for ideal refraction whatever this will be?
I think we are living with our heads the way they are.
(It is time for another )
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Peter