...the ER4 is perhaps one of the most underrated, if not the most underrated IEM on the market. The main complaints are usually that it lacks bass and/or sounds too clean. Personally, I completely disagree with both of these views. I don't think ER4 lacks bass at all and I also don't think that sound can be too clean. ... I haven't heard a high end custom like JH13, but in my humble opinion, the ER4 blows away pretty much every IEM I've heard, including Westone ES3X in timbre accuracy and overall sound quality. I am starting to doubt the need for multi driver IEMs.