Don't shoot the messenger, but here's another positive review from SoundAndVisionMag:
"Because opinions of headphones vary so much, it’s always hard for us to recommend one unconditionally. A tonal balance that’s absurdly bass-heavy for one listener may be perfect for another. But with the Custom One Pro, you’re pretty much assured of getting not only the right tonal balance for your taste, but also the appropriate tonal balance for the music you’re listening to. We hope Beyerdynamic extends the sound slider concept into more models, because it is definitely a winner."
Nice that the reviewer provides wrong info Don't know how the reviewer isn't aware what bass vents are for...