Is the buyer responsible to cover the cost of a return?

What shipping service what was used?
Fedex or UPS are the worst for any speaker shipment using original boxes or not.  If retail dealers use those companies they are shipped using pallets to avoid problems.

  low buzz does not + blown speaker. Probably never the case. It's much more likely he's hearing some sort of AC hum or noise from an upstream component, grounding issue. He should use a cheater plug on his component's and or run them temporarily off of an extension  cord connected to a different circuit- 99% the hum will go away and the speakers won't need to be shipped back. This one screams "user error"...

I’ve had a couple of instances with buyers and when I told them that if the unit returned to me was the exact item (serial numbers matched for example), then I would refund their money. None of them came back after that.How do you know if he received the speakers and he didn’t like the sound, he could be making up an excuse to get his money back especially when he claims only certain music has a problem. I would tell the buyer that if you get the speakers back and you test them out using the exact piece of music and there are no issues, then there would be no refund. If indeed there is a problem, you then have to determine if the problem is with the speaker or shipping caused this, not the buyer.This is exactly why my last 2 high budget sales, I listed them as local sales only so the buyer can make sure everything was as stated correctly in the ad, then a cash only transaction occurred. Both guys drove over 600 miles to pick them up (Hanns T-60 turntable and Usher speakers) and I had all the original boxes.  Wood crates won’t protect a piece of equipment if it’s dropped, something could become loose or damaged inside the unit

The dealer is reputable. They sell the brand of the speaker ( HARBETH ) to be checked out!

what dealer? you could select who he takes it too, or, at least talk to his dealer choice before they mess with it, make sure you think they are qualified.

it may be best to just pay the return shipping, these things can get out of hand, cabinet finish messed up by ___?

They take a good beating in shipping. 

Things do happen in shipping. It's happened to me, as a seller, and it does put you in a terrible position.

The coil assembly may have got knocked out of alignment during shipping.

The buyer has all positive feedback. He just contacted me and said that one speaker has a low buzz that is not noticeable on most music. He would like to take them to a dealer to find out what the problem is. I told him that I will pay if there is a problem. These were shipped 3000 miles maybe it is a simple fix like a loose connection.
Thanks

He should pay return shipping. I’m curios as to what sort of feedback this buyer has.

Hi,
I was using these speakers and there was no problem. I would never have sold them with a blown woofer! I told the buyer to ship them back and I will give him a full refund. When he bought them he asked for free shipping and I did that for him!
Thanks