Re: Mesa 12" black shadow
All Mesa speakers carry the name "Black Shadow". So, there are several "Black Shadow" speakers: The "Black Shadow"/Celestion C90; the Black Shadow/EVM 12; the Black Shadow MS-12 (by Eminence); as well as a 50-watt Black Shadow found in some of the Caliber amps (I don't know this one's mfg., sorry.)
I think the Black Shadow/C90 is a re-worked Celestion Lead 80. They have used these for a a long time, at least since the early 1980's. They used them in a lot of amps, like the Heartbreaker, and now the Lonestar--they can be found in various configurations in most of the old Mesa 412 Half-Back cabs.
The 412 Half-Back cabs are often found in the open-back top half of this 412, with either the 150-watt MS-12s OR the 200-watt EVMs in the bottom. The C-90 does not come AFTER the EVM as one poster claims above--it is a contemporary.
EVMs weigh a ton, as you can imagine and they are very expensive; and being capable of handling 200 watts--they don't break up. Highs, mids, lows--its all there. They are great in the high-power combos, like the Mark IIIs and Mark IVs. In the 112 Theile cabs, they add tremendous punch and projection to these rigs--enough to rival and put to shame most 412s! My fave speaker in a Boogie combo. Mesa used up the last of their EVMs about 2 years ago. Theile cabs are still available, but now come standard with the C-90. The C-90 was a lower-cost option for the Theile 112 for many years.
The MS-12 is a good sounding speaker, though it is very heavy in the lower mids, giving it a really thick tone. I had a set of these speakers with a Dean Markley brand in an old Fender Bandmaster 212, and they killed with my 50-watt JCM 800--really smoothed out the edgy highs. Mesa used up the last of these in the mid-1980s, as I recall. They also weigh a TON.
The little 50-watt Vintage 12s used in the Calibers, were pretty good sounding in those amps, as I recall--but they too disappeared in the 80's. Pretty rare, I think. These might also be a Celestion, now that I think about it.
The C90 and Celestion's Vintage 30 have now become Mesa's standard speakers. In combos like Mesa's Wide-Body Mark IV, the C90 gives a more "vintage" tone with more breakup. My impression is that compared to the Vintage 30, is that it has a little more highs and lows, with a little less mids--giving it a nice amount of "cut". I think the 412 C90/EVM halfback cab might be the best sounding 412 of all time, IMHO. I love mine, and with my 200-watt Mark III Coliseum head it is a devastating, toneful rig.
That's about all I can tell you about the Mesa Black Shadow Speakers. Your Number ONe task is going to be determining WHICH Black Shadow you are referring to. I hope this information helps, but you can always give the guys at Mesa Boogie a call if you need more info--they are happy to help.
Good Luck!
Bill