For those of you with the EP600 or 500 is there a small crease type thing where the rubber surround attaches to the aluminum cone?

I brought the EP600 up to my place because I have been wanting to try a sub in my system so I figured what better way to find out if I want one than to try the best. Well I was playing this "thx worlds deepest bass" thing i have on my computer and was able to find out the limits of the sub itself. Heard this unnatural overdriven sound (I didnt think that was possible with this sub and the DSP?!) and some port chuffing, But then When i turned it off I noticed that crease all around the cone and cant remember if it was like that before or if I actually sortof bent the cone... all the way round...