using 2 8 ohm cabs with my Mark IV question

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Depends on the impedance of the 2nd cab. If is an 8 ohm cab, then yes, both combo and 2nd cab plug into the 4 ohm output jacks.

If you look at any of the more recent amp model's user manual on Mesa's website, they began including the pages that had several different combinations of speaker loads and how to make us of them. Some they call a safe miss-match (combination of a 16 ohm speaker and 8 ohm speaker).

For example: If the 2nd cab was 16 ohms, the safe miss-match according to Mesa is to plug that into the 8 ohm jack and the 8 ohm combo speaker plugs into the 4 ohm jack.

I am just stating the basics in general. Tried to look up the Mark IV user manual but Mesa lost their customer support pages, nothing comes up after selecting the manuals button on customer support.
 
there's no combo here it's a head with 2 2X12 cabs , thanks for the 16 ohm tip as I do have a 16 ohm 4X12 as well that I wouldn't mind running along with one of my 2X12's :)
 
I know this is not the Mark IV, but if you look at this manual for the Mark VII, they cover that speaker pairing thing. Mostly boiler plate stuff they stick in all of the manuals now. I wanted to look at the Mark IV manual but the links were broken on Mesa's website. Not sure if that had the speaker thing or not. the Mark V manual also covered that topic. If you have the Mark IV manual, see if there is any references in that about speaker loads.
 

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  • 070655_MarkVII_230113 (1).pdf
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oops, my bad, the Mark VII did not have the blend of the 16 and 8. The speaker thing starts at page 53. I captured an image on the safe miss-match. the Mark V only has 8 and 4 ohm jacks. Same with the Mark VII. Wonder why that was omitted. Best to see what is in the Mark IV manual. I did find another way to see it. Nothing specific on safe miss-match stuff. There was too much contend on bias why Mesa does not do it and the Irishmen and tubes story. Not much useful content.

This was in the Mark V90 manual. The JP2C has the same content. Mark VII and Badlander, they removed it. Wait and see if anyone else responds to your post. You can send Mesa customer service an email on the subject. I get that thought why was it in some manuals and not others or why was it removed? What is up with the flip-flop stuff. In my opinion, best to keep both cabs at the same impedance and run to 8's in the 4 ohm jacks. Most Mesa 212 cabs have 16 ohm speakers wired in parallel. Their 412 cabs run a pair of 8s parallel and then connect it in series internally. As for the save miss-match, it may not have the ideal sound. You may notice a slight drop in upper frequencies when running two 8 ohm loads in the amp with the 4 ohm jacks. Just do not connect them in the 8 ohm jacks as they are wired in parallel and would result in 4 ohm load on the 8 ohm output of the OT.

Mark V safe miss match.JPG
 

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  • 070425-MkV_160928.pdf
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I would send customer service an email and ask if the Mark IV can support a 16 ohm cab in the 8 ohm jack while an 8 ohm cab is in the 4 ohm jack similar to the "safe miss-match" diagrams used in the Mark V manual. See what they say about that. They may just direct you to the FAQ section.

I found this in the customer support, FAQ section on cabinet connections:

https://mesaboogie.zendesk.com/hc/e...-the-best-way-to-connect-speakers-or-cabinets
 
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