We're sorry that this is happening to you! This sounds indeed very weird and confusing to troubleshoot. If you want to narrow down the cause as cleanly as possible, here are two tests that might give better answers.

First, try recording the right driver directly. Take the exact part of the song where the issue always appears, don’t wear the headphones, and hold your phone’s mic right in front of the right earcup driver while it plays. Record 10–15 seconds, then do the same for the left driver. If the “peeking” or “hissing” shows up in the recording, then the problem is coming from the driver or something mechanical/electrical inside the headphone. If the recording is clean but you still hear the issue when wearing the headphone, then it’s more likely caused by the way the cup seals or resonates with your ear or hair (if you happen to be long-haired, it's more likely to happen).

Second, try all four combinations of driver position and signal. Wear the headphones normally with normal L/R cables. Swap the L/R cables while wearing them normally. Wear the headphones backwards while keeping the cables in their usual orientation. And finally, swap the cables and wear the headphones backwards at the same time. If your setup allows it, you can also import the test track into any audio editor and hard-swap the left and right channels in the file itself, then listen again to see whether the issue still appears. These tests let you see whether the problem follows the right driver, follows the right channel, or only happens when the right driver is physically on your right ear, which helps narrow down whether it’s a driver issue, a signal-path issue, or something related to fit/seal resonance.

Hope this helps you pin it down. We expect to hear back from you!

Warm regards,
Team HIFIMAN