I recently bought the er4s to p 150ohm adapter from here: http://www.ebay.com/itm/ETYMOTIC-ER4P-TO-ER4S-RESISTOR-ADAPTOR-3-5MM-PLUG-/290372905689
Although from what I've what adding resistance makes the frequency response more linear, I noticed that using the 150ohm adapter with my Westone 4R closes up the 3d sound stage totally. There's also somewhat of a channel imbalance, with one side of the IEM being louder than the other. Does anyone using a resistor experience this too? Or is the resistor I bought just defective?