[DougofTheAbaci]

Comply tips in themselves don't really boost the bass as such. From what I understand, it's more accurate to say they provide a better seal which in itself helps enhance the sound, giving you what the headphones were made to do. That includes the bass.

 

[LizardKing1]

A tip can't exactly boost the bass. A better seal can improve the vibration which makes bass sound louder and usually deeper. What also happens is that the foam acts as a sound trap and attenuates the higher frequencies. This usually makes them darker, which isn't something I'd give away, but I can understand how some might.

 

[Softdrink 117]

I'm just gonna hop on the bandwagon of Comply recommendations and say that they've always worked well for me. I don't have any experience with the S4s, but I've been using Comply tips on my RE-ZERO for the last few months and had nothing but great experiences with them.
 
They do wear out, which is annoying beyond belief. If you keep good care of your headphones, in general, the wear will be decreased. I usually store my IEMs in an old Altoids tin I padded with high density acoustic foam stuff, and that's really done wonders to extend the life of my tips.
 
For reference, I use the spherical ones, but am probably going to try the normal T- series when I get through this pack.