Can I Safely Run These Simultaneously???

Inspector #20

Inspector #20

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My main cab is a 2x12 wired parallel with a stereo/mono switch. In the mono input it is 8ohms. With the switch flipped, the other input is 16ohms.

Here's the diagram I used to wire it:

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My 1984 Jackson 4x12 cabinet has two sets of jacks. They are labeled 4 ohm mono and 8 ohm stereo.

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My question is, how can I run both of these simultaneously (and safely) with my Marshall Origin 50H???

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First cab can be 16 ohms. Second is 8. That adds up to 5.33 ohms. As you have no 4 ohm setting on the Origin I would not do ot. No,other way to do it. If ypu run 8 for first amd 8 for second you are at 4 ohms, making the issue worse.
Unless you rewire
Jackson cab is 8 ohm stereo meaning each pair is wired to 8 ohms making ut extremely likely they are 16 ohm speakers. Obviously check impedance first.
You 2x12 has 16 ohm speakers as well. If you wired each PAIR of speakers in Jackson in parallel, each pair would be 8 ohms. Then wire each pair in series for 16 ohm total impedance.
Run the first in 16 ohm amd second would be 16 ohm using the 2x 16 ohm jacks.
 
Nope...no can do...not safely. Looks like the Origin only accommodates 8 or 16Ohm loads. If you had a series/parallel box, you’d still have a mismatch on your hands. If your 2x12 was wired as a 16Ohm load, you could run the 4x12 in stereo mode to a series/parallel box to be seen as a 16Ohm load...but the 2x12 speakers are each 16Ohm speakers...nope. Two 8Ohm speakers would open the possibility...
 
I posted above. Wire 2 speakers together in parallel. Do the same with the other. Each pair would then be 8 ohms, if each speaker is indeed 16.
Then wire each pair in series for a total load of 16 ohms. Run first cab at 16, Jackson at 16
 
Thatbastarddon said:
What about the 2x12 loaded with 16ohm speakers? Leave it at 8Ohms and run a mismatch? Like a 12-ish Ohm load?
Click to expand...
It has a switch for 16 ohms. I think it only runs 1 speaker but hey! You can run it at 16 at least. That 8 ohm load minimum on the origin is a bit of a pain.
The 16 Jackson rewired and the 8 ohm 2 speaker 2x12 would be a 5.3 ohm load, no can do. Parallel oits on amp
 
I'll have to pay a lot closer attention to things because its easy to hook it up wrong. I was running the 16ohm output into my 8ohm cabinet for a while tonight without realizing it...and playing with the master volume at 7-8 and controlling volume in the FX loop.

Not sure if this Origin is Class A or A/B, but it seems to be a pretty forgiving amp...
 
I also performed an ohm test on the Jackson and it is indeed 4ohms in the inputs marked 'mono' and 8ohms in each of the stereo inputs.
 
There IS another way. Like mentioned earlier: rewire the speakers to series. However as also mentioned, you still have an incompatible impedance because your two 8ohm inputs would need a total of 16 ohms to work both and you will come up short.

However, if you rewire the speakers in series and use just the single input jack ( 8ohm most likely) and buy a speaker cabinet combiner ( like a Palmer PCABM or Radial Cab Link) it should work. It will take one jack, spilt the single into two series or two parallel configurations, allowing you to safely power both cabs.

As long as your total speaker impedance is equal to or greater than the amps input, you are safe. You can always go more of a load but NEVER lesser. More of a load will actually boost the mids of the speakers
 
Amp Mad Scientist said:
I think you can rewire each pair of speakers to series instead of parallel.
That will make the mono input 8 ohms and the stereo inputs 16 each.

Are the speakers in the jackson cab 8 ohms each?
Click to expand...
They have to be 16 ohm each. Stereo uses 2 speakers at 8 ohms per pair.
Either wire as above and use 5 speakers outta 6 or buy tne combiner!
No other way witn the 8 ohm minimum on that amp and that spekaer combination.
 
Clockworkmike said:
You can always go more of a load but NEVER lesser. More of a load will actually boost the mids of the speakers
Click to expand...

Running into a higher impedance is fine for solid state amps, but it can cause problems in tube amps if the mismatch is too high. The problem is the output transformer on the amp. If you run the amp into too high of an impedance, it can create flyback voltages in the output transformer that can shorten its life. Usually, a 1:2 mismatch (i.e., 8 ohm output into a 16 ohm speaker) is fine. But, too much beyond that can be hard on the output transformer.
 
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