Running 2 cabs out of one amp, different ohm cabs

[bryan_kilco]

My band is playing a show without me as I'm out of town.
Setup would be Dual Recto in a recto cab and also a 5150 cab. The Mesa is rated 8 ohms and the peavey rated 16.

Can someone clarify the correct way to set this up? Ohms always confuse me in these types of situations. He was talking about daisy chaining the cabs but I'm not certain that's the best method.

From my understanding, he should run out of the (2) 4 ohm jacks on the amp to each cab. But I know the Mesa cab has more than 1 input and the peavey cab only 1.

 

[Empathy]

Disregard that, I'm retarded.

 

[53Crëw]

Huh?

Bryan, Look at the mesa manual. Page 25 figure number 7 answers your question exactly.

http://www.mesaboogie.com/manuals/2chRecto.pdf

They show all types of combinations. Some are a mismatch, but considered safe to do per Mesa Boogie.

Personally, I'd just run the Mesa cab.

 

[bryan_kilco]

Do not do this. A tube amp's resistance output must be HIGHER than the cabinet. Common mistake. 8ohm amp into a 16ohm cab = bad. 16ohm amp into an 8ohm cab = fine. Use the two 8ohm parallel outputs, not the 4ohm ones. Or better yet, play it safe and just don't do it at all. If he wants to run a stereo setup, just do it through the mesa.

Huh? Pretty sure you got that backwards man. I always thought it was like this:

You can fit 8 people (amp) into a car that can hold 16 people (cab), but you can't fit 16 people (amp) into a car that can only fit 8 (cab).

So I guess it's "safe" to do? 4 ohm out into 8 ohm cab, 8 ohm out into 16 ohm cab.....

 

[53Crëw]

+1. Empathy, you have it backwards.

 

[bryan_kilco]

BUT - should you run 4 ohm out to Mesa cabs 8 ohm input? Doesnt Mesa cab have a 4 ohm input as well?

Or match the 4 ohm out of head to Mesas 4 ohm input?

Sorry guis!!!

 

[SethTheGreat]

I believe "daisy chaining" is the same as running from the head to each cab. Either way, they are wired in parallel.

Running the 8 ohm cab and the 16 ohm cab at the same time would result in an average 5.3 ohm resistance (http://www.sengpielaudio.com/calculator-paralresist.htm). 4 ohms is your minimum, so it would be safe to do this.

Long story short, the 4 ohm output depends on at least 4 ohms of resistance. Any less and you are over-working the amp (basically, the lower the resistance in the circuit, the more similar you are getting to cutting the cable and pressing the wires together... which would be bad for your amp...)

http://www.prestonelectronics.com/audio/Impedance.htm

Someone correct me if I'm wrong! (It's been a while since I've dealt with any of this stuff)

 

[bryan_kilco]

So, let me try to get this straight.

AMP -> 8 ohm -> Peavey cab (only 1 input @ 16 ohms)
AMP -> 4 ohm -> Mesa cab 8 ohm input?

OR

AMP -> 8 ohm -> Peavey cab (only 1 input @ 16 ohms)
AMP -> 4 ohm -> Mesa cab 4 ohm input?

 

[SethTheGreat]

BUT - should you run 4 ohm out to Mesa cabs 8 ohm input? Doesnt Mesa cab have a 4 ohm input as well?

Or match the 4 ohm out of head to Mesas 4 ohm input?

Sorry guis!!!

If you're running just the Mesa cab, you can plug into either, it will only affect the sound coming out of the speakers, one is not really "safer" than the other as far as I know.

I believe most people would suggest using the 4 ohm input.


From Dual & Triple Rec manual:

"You can always have a higher resistance ( 16 ohms,
for example ) without damaging results, but too low of a resistance will likely cause problems."

"When running a higher resistance ( for example: 8 ohm output into 16 ohm cabinet ), a slightly different feel and
response will be eminent. A slight mismatch can provide a darker smoother tone with a little less output and attack. This response is
a result of the amplifier running a bit cooler. Sometimes when using more than one cabinet a mismatch will be the only option."

 

[bryan_kilco]

If you're running just the Mesa cab, you can plug into either, it will only affect the sound coming out of the speakers, one is not really "safer" than the other as far as I know.

Understood, but he wants to run 2 cabs, one on each side of the stage, to fill out the sound, since I (other guitarist)won't be able to make it to the show.

 

[Empathy]

Oh fuck me sideways, I need more coffee.

 

[SethTheGreat]

So, let me try to get this straight.

AMP -> 8 ohm -> Peavey cab (only 1 input @ 16 ohms)
AMP -> 4 ohm -> Mesa cab 8 ohm input?

OR

AMP -> 8 ohm -> Peavey cab (only 1 input @ 16 ohms)
AMP -> 4 ohm -> Mesa cab 4 ohm input?

The first one.



16ohm cab + 8ohm cab = 5.3 ohm load = More than your 4 ohm minimum = You're in the clear

16ohm cab + 4ohm cab = 3.2 ohm load = Less than your 4 ohm minimum = You just blew your output transformer.

 

[JeffTD]

never wanna blow your tranny.

 

[SethTheGreat]

never wanna blow your tranny.

 

[bryan_kilco]

What'ts even worse is the fact that you may already have a tranny..... o.0

Thanks for the help guys, much appreciated!