The first thing you should look at is the seal. You might want to change the eartips' size or try the foam tip out. s-JAYS is what I consider to have good bass response for an balanced armature based IEM. Obviously you can't get as good a bass response as many dynamic transducer based IEM, but s-JAYS bass isn't too shabby either. If you are just coming from a bass heavy IEM like a pair of Creative EP-630 or Sennheiser CX300 kind of IEM, then it is very likely than you have adapted to bass heavy sound and will need to to adjust and appreciate s-JAYS sound signature. As for burn-in, 20~30 hrs should be more than sufficient - but don't expect any day and night difference.