No Consensus on Poweramp/Cab Impedance mismatch

RackAddict

Previous handle "Djenter"
I have a very serious issue here and am afraid to plug in either of these two poweramps I have here into higher impedance cabs as I need to make a decision on which I will keep for running the afx 3 because I need a serious poweramp rack.

And that is trying to research impedance if you can plug a lower impedance poweramp output into a higher impedance cabinet.

So far, the internet is loaded with people who are claiming to be professionals and they say that on solid state amps its safe but on tube amps you can go the opposite direction. Others say its safe on tube amps but on solid state you have to go the opposite direction.

The outputs on the back of the EV CP1800 say 4 ohm per channel with a third output that says 8 ohm bridged but thats too much power for one cab and im trying to run 2 cabinets. (One 8ohm on one channel and the other 16ohm on the other channel).

and a QSC rmx2450. The back outputs don't say anything.

not an ideal situation to not know for sure.
 
Solid state amps are generally ok with a higher impedance load, so go ahead and use the 8 ohm cabs in 4 ohm outputs without fear. Going the other way can cause (possibly expen$ive) problems, however.
 
Solid state amps are generally ok with a higher impedance load, so go ahead and use the 8 ohm cabs in 4 ohm outputs without fear. Going the other way can cause (possibly expen$ive) problems, however.
Ok. Thanks. But this is very uncomfortable to do when the speaker impedance is narrower and you are firing in a rushed stream of electricity from a widened 4 ohm path. How is that not overload? Since unixguy above refers to the manual which allows up to 8, why doesn't it say this on the back like all amps usually do? Marshalls, peaveys, randalls, etc.. All have all the ohm options and from what ive seen its usually with a switch.
Im just going by that plumbing analogy everyone uses to teach electrical stuff. How will it not break the 'dam' so to speak since there is no switch on the back of the amp?
 
The concern with power amps is going below the amp rating. Doing so will generate excess heat and shut down or burn out components in the amp. You simply get less available power in watts as the resistance goes higher. I didn’t see a 16 ohm rating on either one, but I’d assume it would be way low. The EV is already down to 350 watts at 8 ohms.

I‘m not sure about mismatched speaker loads (8 on one side, 16 on the other). You’d need to check the manual on that.

On a note to your plumbing analogy, the load (speaker) would act as a valve in your piping, limiting what output the amp can generate... impeding it more as impedance goes up. Lower impedance allows the amp to push out more power unimpeded than it is designed to make, overstressing the components doing the amplifying. In other words, the amp needs the load to control output.
 
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Gotcha.
I may err on the side of caution by avoiding the combined 16/8 stereo mix.
But one can only assume that,sound quality goes up tremendously by using the 16ohm per channel as,well as efficiency.
I know this from experience in car subwoofers. Making the 4ohm final load always sounded exponentially better than using a 2 ohm final load on whatever sub(s). 4ohm had a very accurate clean and tighter bass. It simply had a much finer quality.
 
I think you're overthinking this. Either amp is fine with 8 ohms on one side and 16 on the other, the left and right sides are independent so they don't care what the other side is doing. You'll have less power available on the 16 ohm side. :)
 
But one can only assume that,sound quality goes up tremendously by using the 16ohm per channel as,well as efficiency.
I know this from experience in car subwoofers. Making the 4ohm final load always sounded exponentially better than using a 2 ohm final load on whatever sub(s). 4ohm had a very accurate clean and tighter bass. It simply had a much finer quality.
The 2 ohms speaker load was probably pushing the amp's (or the power supply's, or the power cable feeding it's) current-delivering capability, which would limit the amp's ability to control the LF resonance(s) of the speaker, while 4 ohms speaker load was more easily controlled by the amplifier, delivering tighter, cleaner, more controlled bass. Some use a huge capacitor at the amp to give it the ability to handle current spikes better, given many amps are buried in the trunk somewhere, and powered by a wire running from the engine bay. It takes a FAT wire to deliver current without too much voltage drop along the wire. My MINI Cooper has the battery in the boot, and a battery cable going forward to the engine bay that's as big around as my thumb so it can reliably crank the starter motor. Ideally, your amp in the trunk would like a wire at least that fat, but a lot of folks don't want to spend that much $$$$ on a "stupid wire", so they cheap out and sort-of fix it with a big capacitor. :)

In any case, at middle-ish frequencies and above, resonances have less torque and the result of mismatching the lower ohm output on the amp to a higher ohm load are generally limited to pulling less power out of the amp than it should.
 
Have you considered other power amps? I believe both the Matrix and the Fryette LXII have the ability to run mis-matched loads.
Fryette LXII back.jpg
 
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