For three years, I have owned a pair of Beyerdynamic 990dt pro 250 ohm, I am happy with them. But since a month or so, I've been having an issue where the sound on the left side starts dimming down for like 5 seconds until it reaches zero - the right side works perfectly all the time.
When I tap with my hand on the left side right after this happens, the sound comes back. If I wait for say a minute and then tap, the sound doesn't come back and the only solution would to unplug and plug the jack into my computer for the sound to come back on the left side.
I have tried the following:
Switching the jack port from my DAC to directly plugging them to my computer.
Wiggling the cable and moving it to see if the problem comes from there, sound remained unaffected and problem doesn't occur when I do this.
I have dismantled the left side and made sure that all the connection are in good condition, everything seemed to be fine.
Trying the headphones on another device, problem persists.
I have read a post on Qora mentioning "gum" and "net", but I don't know what those are, as I am not familiar with speakers and I just chose this model to have a durable and good quality pair.
I do not understand where the problem can be coming from. I do not know if a dead driver behaves like this. If I should replace the driver, the cable, or something else.
If anyone had had this problem before, please let me know what can be done.