Ah, thanks for the info. I didn't know it has too much treble, but I knew it had more bass than the ER4. Not sure if any top tier universals would be an upgrade along the same lines than. Some people say the F111 isn't similar either. Maybe the ER-4S is just in its own little world.
They are :) Read this;
and taken from the 'about etymotic' page;
Innovation, education and hearing conservation are central to Etymotic's mission. Etymotic's products are used by scientists, hearing practitioners, hearing-impaired consumers, professional and amateur musicians, and others who insist on superior sound quality. Audio engineers, audiologists and musicians working together have generated over 100 patents issued and pending. A number of Etymotic's 60 employees are accomplished musicians.
What 'standard' are other top IEMs using? This is what makes the ER-4S unique.