Like many others here, I wanted to try out the higher level iems such as the SE530, W3, UM3X, etc. but opted to try the highly regarded but much more economical ER4P. At first, using the orange sponges, the ER4P sounded exquisite but there was definitely a lack of powerful bass. Then, I remembered comments saying that how you fit the ER4P in your ear greatly determined the amount of low frequency sound. I exchanged the orange sponges with the grey tri-flanges and carefully inserted them in my ears as far as I could. I replayed the same tunes I had just tried and....... O M G !!! Whoever says that the ER4P lacks in bottom end have definitely not used them properly. The bass that I got was simply "awesome". I come from the Ultrasone sound (which is famous for its mind/body rattling quality power bass) and have used the "el-cheapo" Sennheiser CX300 and CX400 for a considerable amount of time, so I am quite knowledgeable when it comes to what high-quality bass and bloated/over-emphasized bass is. This pair of Etys was simply amazing... More than enough bass to satisfy my hunger for deep down lows.
Now, I have also purchased a P-to-S adapter and tried comparing them. Simply put, the amount of bass that you get from both style is almost exactly the same. The difference is in the highs where the S seem to give you further extension to the higher frequencies and, maybe because of this, I get a feeling that I am getting a generally much richer, smoother, silkier sound using the ER4S mode.
FYI, I have used my April Music Stello DP200 DAC/Preamp as fixed DAC and had its signal fed into my Little Dot MKV through pure silver interconnects. I used my Denon DVD-3910 as my redbook CD player and fed its digital signal via coax to my Stello DP200.
I am not used to giving reviews, so excuse my poor vocabulary and ways of expression. In any case, the ER4S/P is an amazing piece of art/technology which made me realize how iems can be great and can replace headphones SQ wise.
