I do not own this pair of headphones, nor do I use 2-in-1 headphones. But since no one has responded, I'll just throw whatever I can think of at you and see what sticks.
Low Likelihood Solutions
I am listing these to try and give answers. None of these should work, but they're easy to try and don't cost anything
- Are you connected via jack? Try connecting via USB instead. The jack has a TRRS connector and PCs usually only have TRS. This shouldn't cause any problems normally, but idk what JBL or your PC is doing
- Are you using Stereo Mix on your control panel > sound settings? Switch over to the actual mic and disable the Stereo Mix. That could be what's causing your audio doubling
Medium Likelihood Solutions
These might work
- Have you tried this without EQ APO installed? Try fully uninstalling it and ensuring sound devices are set correctly. EQ APO could for whatever reason be mixing your output and input. It's been a while since I've used EQ APO, but I only used it for audio output
- Is the mic not disabling correctly and picking up audio from the headphones' speakers? Try lowering audio output to a minimum and seeing if that changes the volume of your echo. Ask another person to help test
- EDIT If possible, can you try a different cable? The cable could just be faulty. Wherever you got it from might have a spare to try
This requires additional spending to confirm
- Is the USB or are drivers the problem? Get a TRRS splitter (3.5mm, 1 female to 2 male), and split the mic audio from the headphone audio
I hope one of these work, because...
The Nuclear Option
Get new headphones or claim warranty on them (if you have it). My cursory googling showed that this problem has cropped up with a reddit user, and they ended up buying new headphones. If you do end up buying new headphones, I highly recommend buying a solid pair of wired headphones and a mic separately. It'll be more cables, but much easier to swap out if things go wrong, and a good pair of headphones will last you a good 5+ years.
Best of luck, and let me know how it goes!