Chosen Solution
I have the same problem as described here: How toReplace broken speaker for QC25. In short, the speaker on my right died. The question is where to buy the replacement part. It seems that this part is available on eBay for a range of prices, which warns me for cheap replacement parts. I am looking for a source for a quality replacement part, in order not force me to replace (=downgrade) the other, currently working side at the same time.
@asdmin the only way to get the guaranteed right working speaker is through Bose itself. Contact them and see how much the repair would be. Anything else you’ll take a chance but you may just get a good replacement. You can also purchase a complete set that is broke, other than the speaker, and then harvest the speaker from that.