Based on the Etymotic Research ER4P the Etymotic Research hf2 is unchanged save for a lighter cable and a hands free microphone and control button for the iPhone or 3.5mm Blackberry. Featuring the same balanced driver technology used in their more expensive ER4 design, the hf2 also shares the same unbeatable isolation as the rest of the Etymotic line. At $179, these are a great option for high fidelity travel and on-the-go listening or talking, with unsurpassed background noise isolation, and a small body which gives the hf2 a much lower profile than Etymotic's more expensive options. It is important, however, to be aware of the dangers of such high isolation. Wearing these in public expose an unexperienced wearer to all sorts of common hazards such as traffic. Also, while high sensitivity allows for greater volumes with low powered media players, it also means a greater amount of noise at lower volume levels without the use of a high quality IEM amplifier.
