Results of mini-testI normally listen to ER-4S and not ER-4P, but I did a mini-experiment to see what I could tell you. Just one track, Massive Attack's Protection, from iPod 4G into ER-4P, unamped and via Go-Vibe V5.
There's no question that amplification helps. The intro to this song features strong bass, some hard drum hits, and a little bit of tricky cymbal work in the background. With the amp it sounds great. Without the amp, here's what happens:
- the strong bass notes sound "pooped out" -- the way you might sound if you tried to sing a few notes when you were out of breath from running: maybe you'd hit the notes, but the the diaphragmatic support, the clarity, and the power aren't there.
- the hard drum hits have no sharp strike; they're there, but without exclamation points or emphasis. It's like the drum version of Ben Stein saying "Bueller...Bueller..."
- the cymbal work moves from the background into more of a front-and-center role, since it has so much less to compete with.
Don't get me wrong, the ER-4P really does sound good unamped. But it's very much worth adding an amp to if you have one handy.