I purchased the Challenger portable sound system. One day the sound became very low and I could not figure out why. I called the AV sound support and they told me that the "speaker blew out" and advised to take to the local sound system store or to ship to the supplier. I called AV sound again and just spoke with the AV sound representative about how to ship it to the supplier and explained what was going on. He advised to check if the "voice over" button was accidentally turned on. And it was!!! I turned it off and my speaker was fixed!!! It made me happy!!!