OK..couple things.
You got the speakers in perfect condition, you sent them back in bad condition.
You didn't send them back in the original box, which I bet you was written in fine print as part of the warranty for return, and this is not uncommon.
You used superglue instead of the silicone that you were instructed to use
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Now, you expect a 50% refund? For what, the broken used product you sent back in the incorrect box and installed incorrectly (superglue vs silicone)?
And most speakers, in fact nearly all subs components, require break in time and tell you up front not to use at full frequency for a certain duration. (when I installed components we'd tell people, just like tire and brakes..let them break in).
Frankly, you should take the money and go. Move on to someone else if you weren't happy. Since this is "your first speaker purchase" you have nothing to compare to. I'd really like to see a pic of the speakers
But I'd almost guarantee from whats been written, they were NOT installed correctly...I have NEVER heard of using superglue on a speaker. Why would anyone install them with an adhesive with no give
that is why they said silicone.