Lithium batteries (subject to size limits) that are installed in devices are NOT prohibited in checked luggage. The speaker is fine.

TSA source: https://www.tsa.gov/travel/security-...or-less-device

Official (FAA) source: https://www.faa.gov/hazmat/packsafe/more_info/?hazmat=7

100Wh is a HUGE battery by electronic device standards--a 'normal' laptop battery is less than half that size; even a cordless Dyson vacuum cleaner battery is well within the limits.