I fixed the notorious HiFiMAN HE-R9
As some of you might know the Hifiman HE-R9s sound... bad. You either like them for the stupid amounts of bass or hate them. I paid 60€ for them, which is 10% of the initial price, I guess it was a good purchase? I liked the bass but they sounded like tin cans everywhere else. So I started experimenting;
I first got rid of the hideous red cup thingies and 3D printed plates with gyroid infill and no top or bottom layers. It basically makes them "open back" and the gyroid infill acts like an insulator without closing the back. They sounded better but it didn't open up as much since the plate the driver is attached to is almost completely sealed against the ear cups.
For the second version I made the "grills" deeper to have more infill and a bit more space without the infill. I also made holes through the plate that holds the driver so it is more open.
The result is... better. I would say it sounds like a Beyer DT990. The bass is pretty mild compared to what it was previously and it feels brighter like a happy feeling sound. The highs sound detailed, they are forward like you hear them seperately. Female vocals sound especially good, but the sound stage is not great, it wasn't great before. If I paid like around 200€ for this, I would be happy with my purchase. I don't understand how hifiman can fumble it this much and ask for 600€ originally.
the last pic is there for jumpscare purposes
EDIT: If anyone wants to try the 3d printed grills, I can share the cad or print some for free.