The ER-4P has slightly more forward bass response, and are easier to drive making them suitable for use with portable devices that don't have amplification. 'Stereophile' Magazine summed it up best when they said: "The Etymotic ER4P provides sound quality equal to that of the best loudspeakers money can buy", a big call indeed, but one which is not out of line.

“Properly seated in the canal, the ER-4Ses are capable of bass response better than many loudspeakers. The coupling is crucial; if not properly seated, their sound will be anemic. Get it right and the bass is full—flat to 40Hz, and probably only down about 3dB at 20Hz!”
- Stereophile Magazine - Read Full Review

RRP: $495 - Buy Now and SAVE!