I've recently ended up with a load of old Sennheisers: HD535, HD545 Ovation, and (another) HD265 Linear. I ruined both drivers in the HD535 trying to clean them; only one driver worked in the H545 and I was unable to repair the other; but the HD265 is fully functional. Therefore suitable drivers need to be found for the open backs.
The housing is the same as HD580 and 6x0 series. The screen differs between models and over years. The HD535 and HD545 appear to have an identical very thin paper screen, like crepe paper. This may be the same as in the contemporary HD580, but I have never owned one of those so don't know. Point is you can do this on any model with this housing.
This is a quick review, with measurement, of my first experiment: Koss KSC75 in the HD535. Total cost was around 30 GBP, so great value if sound is good!
Things are going ok until 4kHz then everything gets massively boosted.
Listening
No surprises, It sounds tinny and lo-fi, really horrible. The treble is boosted way beyond 'bright', not like anything I've heard before, not even Grados with G cushions.
EQ transforms it, however, to something listenable. I only needed 2 filters to bring it closer to the FPC measured response of my HD6XX. I ignored the 4kHz dip for now, just focusing on taking down that horrible treble:
It's still not great though. I think it's ok then I swap to my HD6XX and realise something wasn't quite right. I imagine the filters are flawed due to the measurement being on a flat plate coupler rather than an artificial pinna and ear canal.
In conclusion, I do not recommend unless you just want to mess around like me. I think you'd need to put some moderate effort into the EQ too. As a basis for modding it would be a laborious project I believe (see below).
Postscript theories of what's going wrong:
The housing is the same as HD580 and 6x0 series. The screen differs between models and over years. The HD535 and HD545 appear to have an identical very thin paper screen, like crepe paper. This may be the same as in the contemporary HD580, but I have never owned one of those so don't know. Point is you can do this on any model with this housing.
This is a quick review, with measurement, of my first experiment: Koss KSC75 in the HD535. Total cost was around 30 GBP, so great value if sound is good!
Things are going ok until 4kHz then everything gets massively boosted.
Listening
No surprises, It sounds tinny and lo-fi, really horrible. The treble is boosted way beyond 'bright', not like anything I've heard before, not even Grados with G cushions.
EQ transforms it, however, to something listenable. I only needed 2 filters to bring it closer to the FPC measured response of my HD6XX. I ignored the 4kHz dip for now, just focusing on taking down that horrible treble:
It's still not great though. I think it's ok then I swap to my HD6XX and realise something wasn't quite right. I imagine the filters are flawed due to the measurement being on a flat plate coupler rather than an artificial pinna and ear canal.
In conclusion, I do not recommend unless you just want to mess around like me. I think you'd need to put some moderate effort into the EQ too. As a basis for modding it would be a laborious project I believe (see below).
Postscript theories of what's going wrong:
- The KSC75 housing is too wide so only just pops into the clips. This means the driver sits further away from the paper screen than the stock drivers, leaving lots of space. I wonder if this causes reverberations boosting high frequencies, like what happens with Koss or Grado headphones in Grado G cushions.
- The KSC75 might not be the best choice because it already has an increased treble response compared to non-titanium coated models such as Porta Pro. Perhaps this would be a better candidate, however point 1. above might still apply.
- Sennheiser developed the drivers in this line of headphones to have a very specific response which only works with this screen and pads. Anything else will fail.
- File down the sides until it fits closer to the front of the housing, like the original driver does.
- Try other Koss drivers.
