Fx stock ldc vs donnyfl

well you might be able to hear the difference but a sound meter will help prove the difference and you can find them for under 20 bucks and if you were to test the factory unit and got in the 82-87 DP level you are do alright

as long as you or anyone else did the testing the same, you could compare notes but just a note don't let the sound meter hear the pellet strike or mechanical noise
 
Don't know if this helps at all. I don't have an Impact or Crown but have an FX Royale 500 (.25 cal.) & an FX Boss (.30 cal.). Both VERY quiet guns but with my Donny Ronin BOTH are markedly quieter than FX factory shroud. Don't see why you shouldn't get similar results. Didn't think they could be quieter than they already were! Hope that helps.