Bad news (Patreon)

Here some measurements of the HD600 before and after my ear cleaning together with my old measurements I did some months ago. Although the peaks have shifted and align better to what I had measured some months ago, there is a significant loss of high frequenices now, which must be a result of the microphone capsules having "aged"? I have no other explanation for this, but as I have another backup unit with the same capsules, I noticed the same issue with those as well, although I haven't used that unit at all. One of those capsules obviously lost sensitivity for high frequenices to the same degree like this unit here, the other capsule remained more constant. 

What does this mean? I have no microphones to record sound samples. The loss of high frequencies would require a stronger boost afterwards which would also result in a much higher amount of hiss, as the capsules are already quite hissy to begin with. I will post a video I did some days ago and tried to compensate for the treble loss, but despite applying some noise reduction it still appears pretty hissy to me.

I can still use these capsules for measurements, because I can simply apply a high-shelf boost to correct for the loss, but I cannot do any headphone or speaker recordings with these anymore. Unfortunately I have no other really decent microphone pair left. I still have Mike the artificial head, which I will try to use for the Sony SRS-XG500 video, and I have one pair of my old binaural mics, that I could use for speakers etc, the other better pair I had died during our holidays in Italy. But I have no inear mics which would allow realistic headphone recordings.