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Rewiring a 5150 Cab

2413 Views 10 Replies 3 Participants Last post by  Stateless, 
7deadlysins
I've got a 5150 Cab that I need to rewire to be 8 Ohms. It may not be possible, though I think it is, and I just haven't found the right diagram to change it. Its currently 16 ohms and has 4 16 Ohm Sheffield speakers in it. Its strange because when I look up the specific speaker, they all come up as 8 Ohms, but the ones i've got are 16 ohm.

I could also wire it at 4 Ohms, but the problem is I have a Marshall cab with 1x12, that his an 8 Ohm Celestion, and I want to use this and the 5150 cab together, So I rewire at 4 ohms, but the Mesa only has one 4 ohm output, and I can't run a 16 And 8, just like I can't run a 4 and 8. :(
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I think you're only going to be able to do 4 Ohm or 16 Ohm. Or 2 sets of 8 Ohm.
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7deadlysins
Excuse me, I have 2 4 ohm spots, and one 8 ohm spot. So basically, I really need 2 8 ohm cabs. :noway:
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7deadlysins
What if I were to daisy chain them? How do you do the Ohm math for daisy chaining?
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I think you're safe running a 8 ohm output into a 16 ohm speaker cab, just not a 16 ohm output into a 8 ohm speaker cab.
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It's been a while, but I think you'd get (16+8)/2 = 12.
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7deadlysins
Matt Crooks said:
It's been a while, but I think you'd get (16+8)/2 = 12.
Click to expand...
Hmm, I know parallel would be (16 * 8) / (16 + 8), so that seems right for daisy chaining (I think). Still nothing usable. :noway:
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Read the manual for your recto. I don't think you actually have a problem.

You can use both cabs as is, as the recto (per the manual) says that ohm mismatching won't damage the amp (it will cause the tubes to wear a little faster, that's it).

http://www.mesaboogie.com/manuals/singleRec_v1.pdf
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Stateless
Ok, so you have a 16 Ohm cab and an 8 Ohm cab and you want to power them both, right?

If you do the calculations, those combined make 5.33 Ohms, so if you plug them both into the 4 Ohm outputs you'll be fine.
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7deadlysins
Matt Crooks said:
Read the manual for your recto. I don't think you actually have a problem.

You can use both cabs as is, as the recto (per the manual) says that ohm mismatching won't damage the amp (it will cause the tubes to wear a little faster, that's it).

http://www.mesaboogie.com/manuals/singleRec_v1.pdf
Click to expand...
:metal: "Sensitivity to speaker mismatching in regards to ohmage differences is low, hence no damage to the amplifier will occur. However,
very low ohmage loads will cause the power tubes to wear faster."

And If I do the math (16 * 8) / (16 + 8) I get 5.33 Ohms each, So I just plug both into the 4 ohm slot i'm guessing, since its just 1.33 ohms over 4 ohms each.

Double Ninja'd! :lol:
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Stateless
For daisy chaining you actually just add them together. So it would be a 24 Ohm load, so don't do that.
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