Depends on the plastic.
(Yes, I'm a plastic and glue geek, just like you're into audio)
My father was director of engineering for three plastic companies and owned his own.
DCM (methylyne chloride) will literally fuse (weld) plastics like acrylic '
plexiglas' yup one S...
Rhom & Hass trademark.
PVC, and ABS both have fusion cements common for plumbing.
They also work with DCM and some ketones.
Hard to stick plastics like polyethylene and polypropylene can be bonded (not welded) with specialty epoxies like G-Flex from West System.
Careful prep makes for a strong and tough bond.
This epoxy exccells at many plastics.
If you have the time for it to cure.
Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.