hey Joe. Sorry let me clarify. What i meant was that i was considering purchasing a JH13 still in a the JH Audio shell. But since the reshell would be done by a different company like unique melody, would there be some level of difference in the sound?
also there doesnt happen to be a UM office in North america is there...
I think average_joe was exactly spot on. There's no way you might know - you cannot cram the original earpieces into your ears without reshelling, and because of that you cannot get an idea of what the original sound signature is like, thus no base for comparison with the sound signature of the pair after reshelling.
To my knowledge, the company doing the reshelling does not merely take out the drivers and put them in the moulds and call that a day. They do measure the frequencies pre and post and do try to match them as closely as possible. Of course, frequencies alone do not tell the whole story, but at least there's something for them to work with. UM and JHA both use acrylic shells on their CIEMs, so my 2 cent is that normally the sonic difference would be negligible.