i hear more bass with the 1950, but would not say that the cable actually alters the overall flat frequency response of the 18. it's more of a subtle change that seems to make a big difference (kind of an oxymoron, i know, but this is pretty much what cables do.)
the best way i can describe my impression of the a18t with the 1950 cable is as follows:
using the 1950 cable, i can use the m20 module and have nearly all the high-end clarity of the m15 module, more bass, better overall detail, and better overall spatial cues.
when you read the above line, you might think the cable makes a significant difference...and it does...but it also doesn't.
imagine a beautiful piece of art...painted on the head of a pin. it's only noticeable (or, perceptible at all,) if you're really looking [listening] closely. cables 101.