I was going to add one thing to this. There is another speaker that is supposed to have a similar characteristic to the EVM12L. I bring this up since the MC90 is rear baffle mounted. The EVM12L (including the Mesa EVM12L Black Shadow) will not fit properly in a combo due to the oversized basket and ceramic magnet if rear baffle mounted. I can only speak with experience when I tried to mount one in the Mark IVB combo and when I converted the Mark V90 head to a combo. Obviously, the layout was different with the Mark IVB than the Mark V90. There was still little room to gain access for the preamp tubes. Tube shields do stick out far enough. My only option was to sand down the speaker opening with a round drum sander using an air compressor tool to prevent any divots on the round surface so that the speaker could be front baffle mounted the way the Mark III was made. This also required modification to the speaker grill as there was not enough room for clearance the way the frame itself was made.
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The speaker in the image is an Organic Timber Rapsody G12 which is a reverse engineered EVM12L speaker from the early 90's. It does not have a flat response curve like an Electro Voice speaker. The basket is a lot larger too. Note, I did not use the T-nuts as that requires drilling the holes larger where there is not enough wood to do so. I use washers and locking nuts. Hex cap screws if into the holes on the speaker just right. I took these pictures when I changed from the OTR to the EVM12L classic.
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Considering that Mesa had no plans to bring back the EVM12L black shadow, either due to cost or what ever else was the issue with that as an offering, trying to get an EV speaker to fit into the new Mark VII combo may be more of a hassle. So the alternate speaker that is a new product from Celestion is the Copper back. Much lighter in weight as it uses a neo driver. 2.5" voice coil and supposedly has a flat response curve. It should work as a direct replacement for the MC90 if you decide to go that route. I have not tired one out yet. I was waiting for reviews of the speaker.
https://celestion.com/product/neo-copperback/
I copied the frequency response of the copper back
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Here is the frequency response of the EVM12L classic (same for the black label). As for the Mesa Black Shadow version, it would probably be similar.
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I am sure there are differences between the two. I only bring it up as the Celestion copper back should fit without having to modify the cabinet.