Sometimes a power supply isn't dead, but "latched" in a protection mode due to a power surge.
Understanding the output is essential before attempting any bypass or replacement: Harman Kardon HKTS200 Subwoofers. hys3c210cs power supply free
Look for discarded industrial equipment or high-end LED drivers that output 48V . Many discarded office printers or server-grade networking gear use high-voltage rails that can be repurposed. Sometimes a power supply isn't dead, but "latched"