Offhand the bass rattling and going out of control is due to the woofers being worn/tired and the foam surround that acts as the "suspension" to the speaker is dry-rotted (which is common in the 10 year range). That said there are no settings/adjustments that will fix this. These would need to be "re-foamed", or replaced to fix the issue, and since Bose are the only ones with access to replacement parts and schematics, they would need to be contacted directly regarding repairs made to this unit. However, given the age of the system- and the cost of repairs, I would seriously consider whether or not putting much money into this system is cost-effective? Electronics have a finite lifespan and duty cycle- and as such, are not designed for infinite usage. In the 10-12 year range is when we typically have to ask whether or not it's more cost effective to purchase a new system. However if you'd like to have this repaired, then you would need to setup a repair ticket on this system through Bose:
For assistance with your product, please call us toll-free at 1-***-***-****. For help with our aviation headsets, call 1-***-***-****.
For the best possible service, please have your product nearby when you call. Hours of operation: Monday – Friday: 8:30 AM – 8 PM ET
Other than that, I'm sorry for the bad news here and wish there were a quick fix.
If you need further assistance let me know. Before you go, PLEASE DO click at least a 3 STAR RATING, at the top of your screen. That is how I am credited for my efforts by the site. You can follow up any time as needed at no additional cost.