6x12 cabs need advice

[xjbear]

I'm running 2 6x12's loaded with 16 ohm celestions. Total impedance is 12 ohms per cab paralleled to 6 ohms together when plugged into my Model T.
My question is if running at 12 ohms am I better off setting the amp for 8 or 16ohms? And whats the drawbacks? Same with when running both cabs ill have 6 ohms, is it better to set the amp for 8 or 4 ohms? And why?
I would assume to always opt for the higher setting on the amp to stress the ot less but im not sure.
Thanks for any clarification,
Bear

[Chuck H]

You are correct. Running the 16 ohm tap into a 12 ohm load is a tad easier on the OT. Running the 8 ohm tap into a 12 ohm load is a tad easier on the tubes. But at that small mismatch the difference can probably be ignored. Listen both ways. If you actually hear a difference, or even think you do, go with your ears. Your amp will be fine either way.

[Enzo]

Does it really stress the OT? I'd think the tubes were more stressed than the iron. And not much at that. All the impedance thing does is shove the tubes up and down their curves, at least in my mind. This strikes me about like "should I eat my French fries two at a time or three at a time, which would be less stress on my teeth."


I'd make the choice based on what sounds better.

[Chuck H]

Does it really stress the OT? I'd think the tubes were more stressed than the iron. And not much at that. All the impedance thing does is shove the tubes up and down their curves, at least in my mind. This strikes me about like "should I eat my French fries two at a time or three at a time, which would be less stress on my teeth."


I'd make the choice based on what sounds better.

Two at a time! Teeth be damned.

[eschertron]

Does it really stress the OT? I'd think the tubes were more stressed than the iron. And not much at that. All the impedance thing does is shove the tubes up and down their curves, at least in my mind. This strikes me about like "should I eat my French fries two at a time or three at a time, which would be less stress on my teeth."


I'd make the choice based on what sounds better.

Three at a time! It holds the ketchup better!

[Leo_Gnardo]

I was a-wonderin', HOW do you get 12 ohms from 6 x 16 ohm... I can see 10.6 ohms easy enough. Maybe that's close enough to 12. Pass the ketchup please.

[xjbear]

I was a-wonderin', HOW do you get 12 ohms from 6 x 16 ohm... I can see 10.6 ohms easy enough. Maybe that's close enough to 12. Pass the ketchup please.

4@16ohm par=4ohm 2@16ohm=8. Series the two groups for 12. or thereabouts

Thanks for the replies, very interesting that the end resistance still dictates the curve of the power tubes, eventually it will all make more sense to me I guess I thought the effect of the transformers impedance ended at the it's primary.

[Chuck H]

I hadn't thought about it before Leo brought it up. But he's right. The way your wired now doesn't distribute the power evenly among the speakers. If you wired them in parallel threes and then series those you'll get a 10.6R load (that you could run on the 8R tap) and all the speakers would receive the same power.

[xjbear]

So it's an unbalanced load, something about that doesn't seem right. It all terminates into the same reaction, all coils receive the same signal and take up the same slack so how would it matter?

[xjbear]

10ohms is fine with me and I like the idea of it balanced. My experience with electronics is that some of what seems logical to me oftentimes is about 180* off from my normal way of thinking. Lol

[pdf64]

'4@16ohm par=4ohm 2@16ohm=8. Series the two groups for 12.'
'all coils receive the same signal'
No, 2/3 of the power will go to the pair wired for 8 ohms, ie they will each get a 1/3 of the power.
The other 4 will only get 1/12 of the power each.
Pete

[xjbear]

Well great galloping titties that stinks! Thanks for breaking it down like that much appreciated!

[xjbear]

I could probably still run it at 16ohm tap too I bet. Close enough?
Two cabs is 5.3ohms so 8 or 4 I guess

[Chuck H]

Just wire up the cabs for 10.6R each and leave the amp on the 8R tap for 1 or 2 cabinets.

[xjbear]

Sounds like an excellent plan, thanks man