My first obsevation... maxells Black Magnetite tapes have changed over time. XLII got darker after 1995 and the later tape is also almost opaque.
Never saw a FeCo tape that is that kind of opque, you will not see anything coming through he tape unless you use a masked light source directly behind the tape, so you don't see any direct light. The tape of my 1996 UDCDII is showing this behaviour too and also the 353 CRII Focus!
The XLII-S BM from 91, 93 and 1995 I checked are far more translucend, not like some TDK SA but no comparision to the late XLII and UDIICD tapes.
In fact the XLII-S tape looks somewhat identical to the CRII Sudio tape, so I started a quick measuring between a 1993 XLII-S and the Studio...
Noise is exactly the same: -59,75dbA
But Sens. 400Hz is around -0,9db for the Studio and -0.4db for the XLII-S
MOL400 is only +4.2db for Studio and +5.5db for XLII-S....
Ic checked 4 different Studio from different batches 40062, 54032, 54041 and 54071.
All were cleaned by me some time ago, because they all were slightly affected by the yellow stuff.
The tape looks very good flat and without signs of Railroads or other defects.
I got MOL numbers from +3.8 up to +4.4db... very unusual!
I did send one Studio to WernerO some years ago, I choosed the one with the visible yellow spots on the J-Card.
At that time I thought it was just a spot of glue or something else, only after Werner informed me about the bad performance I learned the stuff is from the shell.
https://tonbandforum.de/showthread.php?tid=23420
https://audiochrome.blogspot.com/2020/07...pe-ii.html
His numbers are far worse than mine and so it's possible that even my tapes are affected from the yellow stuff.
Also the 1995 Sereo Review had all of them (Studio, Focus, XLII, XXLII-S) in one Test and there were performing identical, without lower MOL and sens...
Same HF LF Dynamic numbers and the Same FQ plot for XLII and Focus and XLII-S and Studio...
https://drive.google.com/file/d/1KtkHCL_...sp04r/view
...so I tend to believe the CRFocus is loaded with the later XL-II tape and the Studio is loaded with the XLII-S BM* tape and the Studio Cassettes are somewhat affected by the "yellow stuff".
(* second version, also found in the first series of BASF TPII, the first Version of Maxell BM from 1991 is slightly different with approx 1db lower MOL)
I also checked CRII-Live and it is clearly loaded with the Chrome Plus Version of the BASF Chrome Extra.
Note: BASF not always used Chrome Plus at that time, I found both Versions the old pure CrO2 tape and the newer CR+ wildly mixed in Chrome Extra Cassettes from 1994, 1995.
So there are Chrome Extra 1995 loaded with pure Chrome and 1994 versions loaded with Chrome Plus.
Never saw a FeCo tape that is that kind of opque, you will not see anything coming through he tape unless you use a masked light source directly behind the tape, so you don't see any direct light. The tape of my 1996 UDCDII is showing this behaviour too and also the 353 CRII Focus!
The XLII-S BM from 91, 93 and 1995 I checked are far more translucend, not like some TDK SA but no comparision to the late XLII and UDIICD tapes.
In fact the XLII-S tape looks somewhat identical to the CRII Sudio tape, so I started a quick measuring between a 1993 XLII-S and the Studio...
Noise is exactly the same: -59,75dbA
But Sens. 400Hz is around -0,9db for the Studio and -0.4db for the XLII-S
MOL400 is only +4.2db for Studio and +5.5db for XLII-S....
Ic checked 4 different Studio from different batches 40062, 54032, 54041 and 54071.
All were cleaned by me some time ago, because they all were slightly affected by the yellow stuff.
The tape looks very good flat and without signs of Railroads or other defects.
I got MOL numbers from +3.8 up to +4.4db... very unusual!
I did send one Studio to WernerO some years ago, I choosed the one with the visible yellow spots on the J-Card.
At that time I thought it was just a spot of glue or something else, only after Werner informed me about the bad performance I learned the stuff is from the shell.
https://tonbandforum.de/showthread.php?tid=23420
https://audiochrome.blogspot.com/2020/07...pe-ii.html
His numbers are far worse than mine and so it's possible that even my tapes are affected from the yellow stuff.
Also the 1995 Sereo Review had all of them (Studio, Focus, XLII, XXLII-S) in one Test and there were performing identical, without lower MOL and sens...
Same HF LF Dynamic numbers and the Same FQ plot for XLII and Focus and XLII-S and Studio...
https://drive.google.com/file/d/1KtkHCL_...sp04r/view
...so I tend to believe the CRFocus is loaded with the later XL-II tape and the Studio is loaded with the XLII-S BM* tape and the Studio Cassettes are somewhat affected by the "yellow stuff".
(* second version, also found in the first series of BASF TPII, the first Version of Maxell BM from 1991 is slightly different with approx 1db lower MOL)
I also checked CRII-Live and it is clearly loaded with the Chrome Plus Version of the BASF Chrome Extra.
Note: BASF not always used Chrome Plus at that time, I found both Versions the old pure CrO2 tape and the newer CR+ wildly mixed in Chrome Extra Cassettes from 1994, 1995.
So there are Chrome Extra 1995 loaded with pure Chrome and 1994 versions loaded with Chrome Plus.