I would ask for a full refund, including shipping costs. It is very good of you to try to make the best of this, but why should you have to bear the burden of this headache when you clearly did not get what you paid for?
Short of a full refund, if you were fortunate enough to pay through PayPal or a credit card, pursue a remedy that way. I had to do it once when a dealer failed to make good on a defective CD player. Those protections are there for a reason. If the dealer will not work with you, use them to get your money back and then let him arrange shipping of the defective speakers back to him. This should be his problem, not yours.
Just my two cents.