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Microphone Month 3

Sweetwater Forums [Archived]

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a question about impedance, 8 ohm into 16 ohm

dcz702

what up people. i have always played through combo amps, but i recently played through a mesa boogie transatlantic and i am ordering it from sweetwater by the end of next week. today i purchased a Orange ppc112 cab that just sounded so good with the transatlantic!!
so my question is, when i got home and unboxed my new cab i saw that it has a 16 ohm impedance and the mesa transatlantic has a 8 ohm impedance, is this going to be a issue? ive read on other forums it is ok as long as the amps impedance is lower than the speakers, if its the other way around thats bad. then i read some post saying that the impedance must be matched on both the amp and cab, but i have a feeling that the people claiming that are mistakin i dont have a problem taking the cab back and getting a mesa rec 212 but i like the orange alot, and im looking for profesional advice not what people think they know. but like i said if the impedance must match ive got no probs going with the mesa cab.
one more question...
if i am able to run the transatlatic through my orange and im playing with a loud drummer would you suggest that i get one more ppc112 so im running a stack with the tranatlantic+ppc112+ppc112 making a stack? and is this ok with the mesa being 8ohm and the two oranges being 16ohms? wow im confused. and sweetwater techs feel free to call me. and i will be calling next week to order the transatlatic.
thanks guys for checking this post out and thanks for any help i can get
April 2, 2011 @03:13am
yeahforbes

ive read on other forums it is ok as long as the amps impedance is lower than the speakers, if its the other way around thats bad.

This information is correct for solid state amplifiers. But the Mesa is all tube so the opposite is true: you can use an equal or lower impedance.
When you have no cabs connected, you have infinite impedance (the opposite of a short circuit) which by the logic above is an acceptable situation for a solid state amp but horrible for tube amps.
When you have multiple cabs connected, the impedance is calculated by the parallel method which is 1/(1/cabA + 1/cabB + 1/...) or more simply you just cut the number in half every time you double the number of equal-impedance cabs. So 2 16-ohm cabs would yield an 8 ohm load and thus make your tube amp happy. I wouldn't recommend running it with only the single cab.
Matching the source and load impedances exactly also gives the most efficient power transfer (loudest output).
April 7, 2011 @04:30am
kev6string

right on spot...only difference in this case is actual power amp output...higher impedance more resistance...and never go lower than recommend impedance...unless you like buying amps all the time
March 7, 2012 @04:27pm