There is only a handful of info around here on the ES2 so I thought I'd add to it. These impressions are initial as I just received them yesterday and probably only have about 5 hours or so on them. I'm happy to add after I've had a couple weeks with them. I have been listening to them on my iPod using a combo of genres, recordings and lossless as well as 256 AAC VBR. I have been going back and forth from the Audiolineout Cotton Dock > Hornet to directly out of the iPod headphone jack.
I'd like to preface with a quick rundown of the IEM's I've owned. I started out with the E4C which I really liked for their slightly forward and warm midrange as well as the level of detail they offered. I later sold them in my search for more bass and bought the UE Super.fi 5pro's which were returned within a week. I did enjoy the bass but the highs were totally rolled off and the mids sounded a bit muddy to me. I later picked up the UM2's which I had for a while and really enjoyed their strong bass and forward vocal presentation. After hearing the early impressions of the E500 I placed a pre-order and sold my UM2's shortly before they were released. The E500's came and while I did enjoy the soundstage and level of detail they offered I found them somewhat boring. I guess I like color because the E500 were just too neutral. They had nice balance but it came at a cost of bass quantity and vocal presentation (two things I was not willing to sacrifice) as well as overall "fun" factor. I sold the E500's and ordered the ES2.
I have to say the ordering process was much easier and faster than I had expected. Special thanks to Doug and Dale at Westone for putting up with all my calls and questions! Westone recommended a local audiologist that had the least re-fits in my area. Well they nailed it first time around! I had my molds shot on Wed 8/9 and received them yesterday 8/21. They came in a nice Pelican hard case with a wax cleaner, "oto-ease" insertion lube, name tag, and cleaning cloth. I ordered the "candy blue" with the clear cable. I've heard all the praise about the isolation you get with customs but this is just plain crazy! I can see now how custom folks have a hard time going universal, SQ aside the isolation alone is nothing short of amazing!
Build quality is seems very solid, the ES2's have a nice weight and do not feel heavy nor do they feel frightfully fragile. The cable which is braded like the UM2 butslightly thicker also has memory wire at about the last 1-2 inches where the cable connects to the monitor. The cable can also be disconnected from the monitor and is terminated with a right angle 1/8 plug. I would have liked to received a 1/4 adaptor but it's not that big of a deal.
From what I have read the E500's signature has more in common with the UE10 so you and connect the dots of comparison between the ES2 and UE10 that way if you like. The ES2 does not have the level of detail or soundstage that the E500's offer. I would say the detail is slightly better than the E4C. The highs seem to change the most depending on what I am listening to. At times they sound a tad sharp or bright and other times they sound liquid smooth. This seems very dependent on the music as the ES2's are very sensitive to recording quality (among other things!) At all times they maintain a crisp sound with an impressive extension. Cymbals have good decay and nice sparkle. Other instruments (including soprano vocalists) sound exceptionally clear, like you can hear straight through them; I must say it's very intoxicating. Thus far I have detected no sibilance but I will again say that the ES2's are very sensitive and if there are any weaknesses in your source or recordings they will find it and let you know! Newbs - If using these straight out of the headphone jack I highly discourage anything other than a flat EQ
The bass is slightly less in quantity than the UM2 but is also tighter, better controlled and extends much further. The mid bass hump many have complained about with the UM2 has disappeared for the most part, although it does have a slight presence on a couple tracks I've heard but it is very slight. The bass quantity is surely enough to keep even the homeis happy and I am certainly not missing any quantity. This is coming from a guy who listens to the PS-1's with flats so take it FWIW. Listening to Mahler symphony No. 6 (Levi) the bass has a very nice texture and sounds perfectly balanced with the rest of the spectrum. Cello's maintain their texture very well and I detect no bloat whatsoever. Listening to Tool, or Brad Paisley the bass remains tight and controlled, never boomy and the punch is consistently tight on the bass drum while bass guitars really shine in that the ES2 does a fantastic job capturing the true tone of strings. It maintains that solid foundation that can often go underappreciated among audiophiles. Because of the exceptional seal I would guess this level of quantity would remain in air travel or subways. The bass maintains good texture, extension and quantity from one song/genre/recording to the next.
The mids are easily the ES2's forte. Like the UM2 the ES2 has a forward midrange placing the vocalist in the chair next to you. I would say that if you like the PS-1's mids the ES2 is as close as I've heard to that liquid smooth and warm presentation. The ES2 does not favor male or female vocals; it is equally happy doing either with exceptional clarity. Percussion is another strong point in the mid range. Toms and timbales sound tight and maintain excellent separation, never bleeding into each other or other instruments. Even the snap of a rim shot in the upper register maintains quick resolution.
Overall the ES2 is a quick IEM with a fast and accurate attack. They pass the UM2 up in a number of ways as they take the strengths of the UM2 and bring them up a few levels and improve on the UM2's weaknesses. They sound great straight out of the iPod but really shine with the Hornet in the loop adding sonic weight, better depth in the three dimensional sound and mellowing out the top end. These are not neutral and do not have the detail or soundstage of the E500 so if that's your thing these are not for you. If you want something that's going to get your head moving and foot stomping these are for you. The ES2 have strong and tight bass with great extension, a mid range that is liquid smooth with a warm signature and in your face vocal presentation and a top end that is crisp, detailed and also offers very impressive extension. Add it all together and you have one hell of a fun, engaging and altogether musical custom!