Rockford fosgate t1500-1bd

Hello! please tell me the permeability and characteristics of L2000. Hello, in general, the situation is that the frequency at which the driver operates is drifting away, why this is happening is not clear, I double-checked all the small details, everything is ok, there is a suspicion that the ring on the output choke has lost its induction due to time and heating.
 
Please don't post in a repair thread that was started by someone else unless you are trying to help them.

Start a new thread if you need help with a repair of your own.

If you think this thread is relevant, include a link to it in the original post of your new thread.

Side note: You're unlikely to find permeability or value published. Someone will likely have to measure value and from that you could calculate initial permeability.