# Safe? 4 ohm setting on amp/4 ohm hotplate/8 ohm speakers



## Evilmusician (Apr 13, 2007)

Just wondering if this is safe I searched and found alot double talk,just want a straight answer ,is it safe to do 4ohm setting on Amp Head/4 ohm Hotplate/8 ohm Speakers cheers!


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## Wild Bill (May 3, 2006)

Evilmusician said:


> Just wondering if this is safe I searched and found alot double talk,just want a straight answer ,is it safe to do 4ohm setting on Amp Head/4 ohm Hotplate/8 ohm Speakers cheers!


The short answer is "probably yes".

You didn't say what kind of amp. I'm assuming it's a tube amp. A 4 ohm load from the Hot Plate in parallel with the 8 ohm load from the cab will work out to a bit over 3 ohms. Close enough for a tube amp.

The power will not split equally. The Hot Plate being the lower load will hog the power. That means if the Plate is rated at 50 watts and the speaker cab at 50 watts if you crank a 100 watt head into the system the speakers might see only 25 watts and the Plate would see 75. In such an extreme case the Plate could burn out.

If you're not pushing the envelop in this fashion I wouldn't worry about it.

:food-smiley-004:


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## Evilmusician (Apr 13, 2007)

Sorry Custom JTM 45 Head ,variable @ 4/8/16 ohms ,Tophat Cabinet 212 8 ohm speakers 80watts , Marshall Silver Jubilee 412 8ohm speakers 75 watts each thanks


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## dwagar (Mar 6, 2006)

so, you're plugging 2 8 ohm cabs into the output jacks of the hotplate? that would be 4 ohms.

unless I misunderstand what you're saying.

balancing the different speakers would be a different problem.


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## Wild Bill (May 3, 2006)

Evilmusician said:


> Sorry Custom JTM 45 Head ,variable @ 4/8/16 ohms ,Tophat Cabinet 212 8 ohm speakers 80watts , Marshall Silver Jubilee 412 8ohm speakers 75 watts each thanks


Hmmm...Dwagar is right that it can be a bit more complicated.

How are the cabs wired? Two 8 ohm 12" speakers could be wired in series to total 16 ohms or in parallel to make 4 ohms. Four 8 ohm speakers are usually wired in series/parallel to make a total of 8 ohms.

If you run a 4 ohm Hot Plate with an 8 ohm 4-12 then the previous answers make sense. If you run the Hot Plate with a 4 ohm 2-12 then you have two 4 ohm loads in parallel together. This makes 2 ohms! This is not really very good. It won't likely blow anything up but it might shave some months of the life of those EL34's.

:food-smiley-004:


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## Evilmusician (Apr 13, 2007)

No No just running each cab alone in different situations (either 412 or 212 ) 212 has 2 Celestion G12H 80's 8 ohms each


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## Sneaky (Feb 14, 2006)

Evilmusician said:


> No No just running each cab alone in different situations (either 412 or 212 ) 212 has 2 Celestion G12H 80's 8 ohms each


That cab is wired to 16 ohms I believe (if it's my old one). Two 8 ohm speakers will give you either 16 or 4 total, depending on how it's wired.

Pete


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## Evilmusician (Apr 13, 2007)

Hmmmmmmmmmmmm Sneaky Tophat Scripty 212 Green tolex? and how do you tell how its wired? but if its wired 16 ohms is it ok to use a 4 ohm attenuator and 4ohm amp setting ?


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## SinCron (Mar 2, 2006)

Why do you want to use both? If it's because you like the sound of both speakers, take the speakers out of the 2X12 and put them in your 4X12 so you can enjoy both tonal qualities.


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## Evilmusician (Apr 13, 2007)

Both at different times I keep 412 at jam space and take 212 to gigs :rockon:


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## Sneaky (Feb 14, 2006)

Evilmusician said:


> Hmmmmmmmmmmmm Sneaky Tophat Scripty 212 Green tolex? and how do you tell how its wired? but if its wired 16 ohms is it ok to use a 4 ohm attenuator and 4ohm amp setting ?


Here are the wiring diagrams...

http://www.avatarspeakers.com/wiring%20diagrams.htm

Yeah, I think that is one of my old cabs. :wave:

I don't think it is safe to use a 4 ohm hot plate in this case, but I am not an expert on these things.


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