Saying they were working before shipment is complete BS. They didn’t magically die during shipping. I would demand my money back including shipping. If you are willing to keep waiting for the replacement tweeters I would be demanding some compensation for you sitting there speakerless for half a year when none of this was your fault.
if it gets nasty you can pull the social media card. I got into it with a not to be named company and after I talked with their corporate and explaining I would dedicate all my free time to tenaciously MFing them on social media they changed their tune.
If mentioned I missed it, did they give you an eta when your tweets would finally be delivered?