That is a really...um...really solid low-end response...that curve...it must drop off really steep after 32.5Hz...
I'm not
as concerned about the HF drop, especially not knowing what condition your heads are in.
Does it look like the wrap is correct (the centerline of the head is perpendicular to the tape path)?
Does the 22 have reproduce eq trimmers for low and hi frequency? I'm betting it is hi frequency only, but if you increase that so that you are -2 ~ -3 in the 16 ~ 20kHz range that may actually pull your level up at the 1kHz mark, and then when you drop the repro level trimmer to pull the 1kHz tone back to 0VU it will also drop your low-end head bump a bit essentially flattening things out across the spectrum.
Leddy, can you find the part number for your amp card?
I agree that you have some HF loss there, at least according to my experience...more importantly,
you heard it before you saw it. And I still maintain that you have an unsavory head bump there.
Your 22 is the 2-track model right? Looking again at the factory response spec it shous +/- 3dB from 40Hz ~ 22kHz...you are running about +/- 4dB in that range, but that is not telling the full picture, because usually the response is dropping off at both ends of the spectrum...yours looks like its still headed uphill at the low end, unless, like I said, it drops off
steeply after 32.5Hz...which it might very well do.
Check your manual...there should be a picture of a rec/play amp card in the maintenance section that shows what each trimmer does. If you can find that, can you list what trimmers you have?
And tell us more about what the tape path looks like, wear patterns etc....better yet, put up some pictures...1000 words and all that.