Hope everyone will enjoy the Airpods Pro!

Each "port hole" seems to have a particular function (example: for bass or treble), removing only one may give an imbalanced sound.

Warning, once you mod the 439, the headphone us done for, there's no turning back or reversing it. Yes it's true, once the three holes have been opened up by removing the tape cover, it will turn the 439 into a mega super basshead with full high details that after you listen for awhile your ears...

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I have the HD439. When I was researching headphones, I read that the HD449 has a "fun" sound and is very detailed in the treble, they say it is very good for critical listening.