Well, your ER4XR will have a bit more low end than
@EmPathWalker's ER4B. But even so, I think the comment about the unrealistically lean low end is understandable. IEMs like the KSE1500, Xelentos, FLC8S, etc., can all produce a realistic amount of sub-bass without losing anything up top. Now, if I'm walking, or in a really noisy environment, the Etys still win for me, because I get zero occlusion effects and better isolation with an Ety than anything else. But I'm looking forward to Etymotic making that ER5XR with SE846 levels of sub-bass...