Martin 115 problem

Hey guys , recently acquired some Martin 115 as love them! Just need some cosmetic care!

But there is a annoying noise as if it's distorting and can't find what it is!

I have orberton 15b450 which are a decent match for them , cabs are solid! Only running 200w+ through them when noise starts and gets worse as I drive them more , can hear it when stand at back of cab , driver is moving but barely , it stops completely when I remove rear panel? Could it be that even though it's very secure?

Thanks

It could bethe rear panel, or something else that is released from pressure, when the back panel is removed, like another panel, an air leak or even the driver itself. The best way to solve this is more testing, pressing the back panel forcefully by hand during playback, checking for air leaks and if possible swapping the driver for another one, to rule everything out one step at a time..