I am afraid I don't understand your reply. Specific language is difficult in these matters, I know. Between the two I was wondering if the Er4sr has some improved quality that makes it an upgrade or not. Or whether we are simply talking about the balance. I have yet to come across a post where someone has stated they have both and the one is a little better because of whatever specific thing they heard; something like, sharper focus etc. I certainly appreciate the engineering end of things where if something measures equivalent then they are equivalent, and I can subscribe to that. If that is what you mean.