[audiocrazy]

Something's compromised with one or both drivers as Jim suggests. My ST's can play 90DB with 100DB peaks with no sense of strain. I normally listen in the mid 80's with peaks in the low to mid 90's however. Pull the drivers and inspect. If a spider or spiders are detached, it'll be obvious.

I was avoiding taking out the drivers but I guess I'll have to do it to ensure the spiders are not loose.
Will report back

I see you have a JTR S2, nice sub!  Just an FYI, as I have dual S1's.  I was also hearing a "flapping" type noise on heavy bass passages here recently and thought I had issues.  The issue was one of my JTR S1's.  I actually had to send it back to Jeff.  Luckily it was just the hardware that came loose under pressure.  Sounded like a spider broke loose as you're describing.

I've already experimented without the Sub by running ST full range. The flapping occurs without the sub as well.

[MikeC78]

I figured it wasn't the sub in your case, it was just something to keep an eye on.  The drivers in the Cap's are quite heavy and place a serious strain on the cabinets, especially when driven to high SPL's.  Jeff does use heavy duty locking hardware, but anything can fail at any moment. 

Hope you get this resolved soon...

[audiocrazy]

I took out the driver and took some pics to show the spider. I inspected the driver and spider from all angles and nothing is loose anywhere. I think the driver and spider is in perfect shape and that shows real Salk craftsmanship. I'm really impressed by the quality and level of service after many years of ownership.






I think there is nothing wrong with the driver and I believe its a mixing issue with Migra-Supernatural track. All other track plays fine. Normally I don't listen at 90 to 95db.
Thanks everybody for your valuable help and opinions and sorry for a false alarm.