What factors determine good isolation in an IEM?

[colonelclaypool]

hey all,
 
I have been pondering the question what gives an IEM good isolation.
the most obvious factor is the tip and seal. however, is there more? can the materials used, the driver, the way the IEM is built influence the isilation? as well?
 
I have shure se215's and the rockit R50 and with the same tips it seems the shure isolates way better.
 
what's your experience?

 

[bubsdaddy]

Personally, I have found that tips and a lack of ports is the largest factor in isolation. After that, material may play a role - metal vs. plastic. I'm sure someone more knowledgeable can give you a better answer. For most IEMs, I achieve the greatest isolation and best sound from the Super Small (red) Sony hybrids. These allow me to get a very deep insertion with comfort.