With the Comply P-Series (longer than the T), I have incredibly good isolation. No IEM will completly isolate you, only attenuate the outside sounds (but I'm sure you know that). I actually only use the T-series when I WANT outside noise to filter in (like running outside).
@ DCofficehack.
I have a few different recordings of the Beethoven 9th. My fave (and my go-to version) is the Solti 1972 London/Decca - Krannert Center recording. I have a MoFi 1/2 Speed master recording and its sonics are amazing. The 4th movement will knock you out of your chair with the right speakers. With headphones, my D7000 are untouchable for this, but for IEM's, the DBA are no slouch. I get better low-end extension with my UM2's, but they don't have the clarity and brilliance of the DBA. The DBA has the speed and resolution, along with the clarity and soundstage presence to render even the more complex passages with aplomb. The DBA do all my music very well.
Your recording(s), rig and other factors will also influence your opinion of the DBA, so obviously... YMMV.