It seems people say the ER-4B are even more neutral than the S but say the B has more treble, it doesn't go well with what Etymotic explain on the accuracy of their phones. It seems like all they need to do to achieve totally flat line is less treble and realy little bit less mids-higher mids.
Etymotic Research, Inc. - How we measure response accuracy
Etymotic Research, Inc. - How we measure response accuracy
