They both function and sound like a single driver.
The actual purpose of this setup is that... if you compare it with other single dynamic-driver IEMs, this setup can sound a little cleaner, a bit more accurate, in the sense that the "rough edges" around the actual sound are dialed down a couple notches. I'm not certain what these are...extraneous vibration or undue resonance perhaps? I'm just making up terms at this point
Of course this will depend on what caliber IEM you're comparing to, but I definitely hear a difference against several IEMs cheaper than the IM50, and I went "wow so that's what the tech is for."
Edited by heatofamatch - 7/28/14 at 6:06pm