50/50 and matching ohms

[haha]

Let me first start by apologizing in advance for bringing up this topic yet again. I know the question of matching impedance has been done to death, resurrected and done to death again.

I'm confused by this part of the manual:

"If using two 8-ohm speakers (assuming they are wired in parallel) or cabinets on a channel, plug them both into the 4-ohm jacks. (The logic here is that two 8-ohm loads connected in parallel add up to a 4-ohm total load)."

So far I've only been using an 8 ohm 212 with my rack so I haven't bothered about the 4 ohm outputs. Would anyone be so kind to explain how to properly use those? I just can't make sense of that sentence.

Thanks,

Phil

 

[iceman]

Two 8 ohm speakers in parallel equal a total of 4 ohms. Rtotal = 4 = (8*8) / (8+8)

Another example is your 212 is actually 2 16 ohm speakers in parallel, together the load is 8 ohm. 8 = (16*16) / (16+16)

Two speaker in series (not parallel) is just the sum of the loads, most cabs are wired in parallel.


Does this answer your question?

 

[haha]

Sorry man, that's not what I meant. I'm wondering what to actually plug into those outputs. Do I plug in one 4 ohm load or do I have to plug one 4 ohm load into each output on a channel? The wording of that sentence has me very confused..

 

[elvis]

If you have one 8 Ohm load, plug it into the 8 Ohm output.
If you have one 4 Ohm load, plug it into one of the 4 Ohm outputs.
If you have two 8 Ohm loads that you want to run in parallel, plug them both into the 4 Ohm outputs.

The two 4 Ohm outputs are wired in parallel just to make it easy to hook up parallel loads.

 

[crane]

If you have one 8 Ohm load, plug it into the 8 Ohm output.
If you have one 4 Ohm load, plug it into one of the 4 Ohm outputs.
If you have two 8 Ohm loads that you want to run in parallel, plug them both into the 4 Ohm outputs.

The two 4 Ohm outputs are wired in parallel just to make it easy to hook up parallel loads.

+1
I'l just add this is for one channel. I f you have 2 8ohm loads and want to use the 2 channels, plug them into the 8 ohm output of each channel.

 

[haha]

Sounds like a bad idea to label both outputs with 4 ohms then to me. If someone were to plug in two 4 ohm loads into each output that wouldn't be too good now would it?

 

[elvis]

That's why the amps come with a manual.

Also, it won't hurt them to run with a 2 Ohm load (2 4-Ohm cabs in parallel). It will push the tubes pretty hard, though.