Running Two Cabinets with Different Impedances?

[Agileguy_101]

I have a Bassman with separate outputs for 4, 8, and 16 ohms. I have a Fender cab that runs only at 8 ohms and a Mesa that runs only at 4 ohms. They both only have inputs, no outputs for chaining a second cab. What do I need to be able to run them together?

 

[MetalManiac]

Re: Running Two Cabinets with Different Impedances?

Doesn't Radial make a cab switching pedal that does that?

 

[Agileguy_101]

Re: Running Two Cabinets with Different Impedances?

What you're thinking of (the cab bone) only lets you switch between different cabinets. I want to be able to run two different impedance cabinets at the same time from a single speaker output from the amp. Basically, it should be something that I plug the amp into and it has two different outputs which can be set to whatever impedance I need them to be. Does such a thing exist?

 

[MetalManiac]

Re: Running Two Cabinets with Different Impedances?

^ No, not to my knowledge come to think of it. I remember looking around for something like that myself, and I couldn't find anything that does that. I even think I checked Weber, but I don't remember. If such a thing exists, you'd think Weber would probably have it.
I think something like that defies the law of physics, but hopefully someone else would know for sure.

 

[Empty Pockets]

Re: Running Two Cabinets with Different Impedances?

Your Bassman's minimum resistence is 4ohms... If you add any cab to that 4ohm cab, you are running less resistence than the amp wants to see and risking damage to your transformers. I've read that vintage Fender transformers were able to handle going to 2ohms but i still wouldnt risk it.

You could run two 8ohm cabs safely, or four 16ohm cabs.

 

[King IzzO)))]

Re: Running Two Cabinets with Different Impedances?

Re-wire your Boogie 2x12 from parallel to series, making it 16 ohm. Then run the 8 ohm Fender cab on the 4 ohm connection and the 16 ohm Boogie cab on the 8 ohm connection. This is the best you'll get without getting 16 ohm speakers in the Boogie or vice versa.

 

[CTN]

Re: Running Two Cabinets with Different Impedances?

it's funny how many times lately i've had to pull this formula out:

Parallel resistances:
1/Rtotal = 1/R1 + 1/R2 + ... 1/Rn

so if you're chaining two cabinets together in parallel (as you would need to do to connect both cabs to the parallel outputs of your amp)... so if you have an 8 ohm cab and a 4 ohm cab, your total impedance is going to be 2.66 ohms, and it would be unsafe to run that load.

Buuuuut, you might want to think about perhaps rewiring one or both of the cabs to give you usable impedances that can be run together.

Like Izzo said, if you rewire the boogie to 16 ohms, then your total impedance between the 8ohm and 16 ohm cabs would be 5.33 ohms, and you can safely run that load from the two 4 ohm taps (albeit with a very very slight loss of power)... it's not a good idea to be mixing transformer taps.

 

[King IzzO)))]

Re: Running Two Cabinets with Different Impedances?

it's not a good idea to be mixing transformer taps.

Based off of Mesa Recommendations to do so in this exact situation I don't think there's really an issue. They wouldn't recommend something that would cause a warranty claim.

 

[King IzzO)))]

Re: Running Two Cabinets with Different Impedances?

Dank deleted his post, but to answer the question, to run two 8 ohm cabs you'd have to run parallel to them out of the 4 ohm tap.

 

[Joe L]

Re: Running Two Cabinets with Different Impedances?

Re-wire your Boogie 2x12 from parallel to series, making it 16 ohm. Then run the 8 ohm Fender cab on the 4 ohm connection and the 16 ohm Boogie cab on the 8 ohm connection. This is the best you'll get without getting 16 ohm speakers in the Boogie or vice versa.

This is absolutely correct and your best option. The amp will have the correct load.

And no, there is no box that you can plug in and match impedances. You could add a large 4 ohm resistor in series with your 4 ohm cabinet to make it 8 ohms and then parallel it with the 8 ohm cab for a total of 4 ohms but this usually doesn't work as well as the option above. The amp would be happy tho.

..Joe L

 

[hydro]

Re: Running Two Cabinets with Different Impedances?

I searched around and found this. Not sure if it would help in this application but it's an external box which is supposed to take a single speaker output and then let you run two cabs off it in either series or parallel.

http://www.palmer-germany.com/mi/en/CAB-M-Passive-Cabinet-Merger-PCABM.htm

 

[CTN]

Re: Running Two Cabinets with Different Impedances?

Based off of Mesa Recommendations to do so in this exact situation I don't think there's really an issue. They wouldn't recommend something that would cause a warranty claim.

interesting... perhaps there is nothing to it.

though the amp is a fender bassman, not a mesa...

 

[ericmeyer4]

Re: Running Two Cabinets with Different Impedances?

Weber makes an impedance matcher if you don't want to rewire one of your cabs.

 

[MetalManiac]

Re: Running Two Cabinets with Different Impedances?

^ welll, theres one speaker out, 4 ohms on the Bassman, so you'd need a splitter, right? There is one company that makes a pro splitter, and another one that makes a decent one, but most of them are cheap, and I wouldn't use one.
I'm also not sure the effect of a impedance matcher on tone.

 

[Agileguy_101]

Re: Running Two Cabinets with Different Impedances?

A few notes:

As I said in the OP, my amp has a single speaker output for four, eight, and sixteen ohms.

I was under the impression that you couldn't use two different outputs of differing impedance simultaneously? If it was two jacks with switchable impedance that would be fine, but that's not the case. I believe that means that the outputs aren't parallel, as they are each for separate impedances?

 

[MetalManiac]

Re: Running Two Cabinets with Different Impedances?

You COULD disable one of the jacks you arent using, and run the two cabinets in paralell 16 Ohm , and as a 12 ohm load,I doubt you would have any troubl;e. I think the deal is to go up in impedance, not down. You'd disable one jack hot wire not being used ( Not sure about excatly how to diable a transformer tap though, or if all you have to do is disconnect the hot wire?... be very careful) Then I think you'd have to run the ground wire , wire tip to tip, and sleeve to sleeve from your 8 ohm tap.
( Or instead of disabling and rewiring a jack out, you could add a hole and a new jack..a jackhole.).

 

[CTN]

Re: Running Two Cabinets with Different Impedances?

think of the taps as indicating minimum impedance.

so plugging an 8 ohm load into a 4 ohm tap is fine, as is plugging a 16 ohm load into an 8 ohm tap.

but you don't want to plug an 8 ohm load into a 16 ohm tap because that 8 ohm load falls below the minimum load rating for that tap.



also, you can't just "disable" a transformer tap. It's akin to saying that you have a 12kohm single coil that's coil-tapped at 4k and again at 8k. Those taps are hardwired into the coil, just like the taps on a transformer winding. You can't just disable them.


PHYSICS, B!TCH!

(please note, I am not actually calling anyone here a b!tch)

 

[MetalManiac]

Re: Running Two Cabinets with Different Impedances?

think of the taps as indicating minimum impedance.

so plugging an 8 ohm load into a 4 ohm tap is fine, as is plugging a 16 ohm load into an 8 ohm tap.

but you don't want to plug an 8 ohm load into a 16 ohm tap because that 8 ohm load falls below the minimum load rating for that tap.



also, you can't just "disable" a transformer tap. It's akin to saying that you have a 12kohm single coil that's coil-tapped at 4k and again at 8k. Those taps are hardwired into the coil, just like the taps on a transformer winding. You can't just disable them.


PHYSICS, B!TCH!

(please note, I am not actually calling anyone here a b!tch)

OIC, yes. So he would have to make another...and it would be his existing 8 OHM Speaker out, wired tip to tip and sleeve to sleeve to the new chassis mount input jack, run in parallel to make 16 Ohms that the new 12 Ohm load that presents to his Bassman amp sees, in which case, all is ostensibly well...
-'Jack Hole'.

BTW...from what I know, you cannot treat solid State circuits in this same manner as detailed above, in case anyone thinks they could.

 

[CTN]

Re: Running Two Cabinets with Different Impedances?

yes, or just tape off the lead wire from one of the taps that he's not using, and use that jack as a 2nd, parallel output for the tap that he needs.

that way, Jordan, you'd be making a set of parallel outputs for a single transformer tap, and as long as your total impedance load (calculated using the formula i posted) is above that, you should be fine.

 

[MetalManiac]

Re: Running Two Cabinets with Different Impedances?

yes, or just tape off the lead wire from one of the taps that he's not using, and use that jack as a 2nd, parallel output for the tap that he needs.

I am confused.I asked about disabling..now you say to "tape off" the the lead wire from one of the taps he isnt using. Isn' that the same sa s disabling the tap?