First off, i dont know the correct spelling for defuser, but anywho, i ride in some places where sound is a big concern, and in others where its not. So the root of the question is how much of a difference in db rating can one get with a disk system and changing the number of disks? Note: also in performance mods/project quads but seems to be dead lately

 

my WB's with all discs was 105db, with a quiet core and 6 discs it was 96db. so the quesion you are looking for is sometimes, it depends on the pipe, if you want a quiet pipe go with the FMF one with discs, those are i think 89db with all discs!
hope i helped!

kc

 

I have the FMF on the utility bikes and 250EX. With 12 discs, it is wickedly loud. More discs favor top end power, and fewer favors low end power. I run 6 as a nice compromise. I think I can pass the 96dB rule for public land that we have here in CA??? I don't want to run the quiet core unless absolutely necessary.

One thing to consider is that you are changing the number of discs all the time, you are changing the amount of air into the engine. So, you are going to need to rejet each time! What a pain!