This could be two issues, either your device is set to Mono, or your adapter may be damaged. I would like to remind you that these headphones are Apple Product friendly, so use in other devices may leave you with less than perfect results.
When a speaker gets blown out, the cone is generally coming loose from its moorings, until eventually, it can be completely broken and fail to provide the sounds that it did when it was brand new. Blown speakers are often bass speakers, though they can control other ranges. When they are fully blown, the thudding bass sound is replaced by a rattling sound, or no sound at all.