best/most versatile ohms for 4x12 speaker?

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Professor Plum
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best/most versatile ohms for 4x12 speaker?

Post by Professor Plum » Thu Sep 16, 2010 10:35 am

if you were going to order 4 new 12" speakers for a 4x12 and could pick between 8 and 16 ohms, which ohm(s) would you get to have the most options of wiring up different ohms, and what will work with one of those stereo/mono 8/16 ohm selectors? is there a way to do mono/stereo and 4/8/16?

thanks guys.
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Re: best/most versatile ohms for 4x12 speaker?

Post by null.fuzz » Thu Sep 16, 2010 10:49 am

With 4 16-ohm speakers you could easily get (A) 4-ohms (all 4 in parallel) or (B) 16-ohms (2 parallel branches of 2 in series). For a stereo combo, the option A would turn into 2 8-ohm channels and option (B) other would turn into 2 32-ohm channels. If you go with 8-ohm speakers, all the numbers in the above post would be halved.

As for what's more versatile, I don't know. If the stereo option would work with 2 8-ohm channels and you could handle 4 ohms for mono then I'd go with 16 ohm speakers. Is there any amp in particular you're going to use this with?

Or just wait for the amp ninja to chime in with a characteristically informative and helpful post.
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Re: best/most versatile ohms for 4x12 speaker?

Post by Professor Plum » Thu Sep 16, 2010 11:14 am

thanks for the info! there is no specific amp that this is gunna go with, actually pretty much the opposite. in the revolving circus of amps in and out of the stately plum manor, my old beat nothing-special marshall 4x12 has been a staple, and i wanted to try to treat it to speakers i love, and make it be able to be use with the greatest number of amps.

in an ideal world i could hook it up to be 8 ohms as a 4x12 and split have a 4 and 16 ohm 2x12. i dont know if thats possible though. defintaly not with all the same ohms i think right?

i too was hoping to get this thread amp-ninja'd :ph34r:
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Re: best/most versatile ohms for 4x12 speaker?

Post by null.fuzz » Thu Sep 16, 2010 11:33 am

Professor Plum wrote:in an ideal world i could hook it up to be 8 ohms as a 4x12 and split have a 4 and 16 ohm 2x12. i dont know if thats possible though. defintaly not with all the same ohms i think right?
That's possible with 8-ohm speakers. For a 4x12 you'd want them wired in the series/parallel combo to get 8 ohms. Then the individual 2x12's would work if one was 2 in parallel (4 ohm) and the other was 2 in series (16 ohm) - which could be accomplished with a switch of some sort. I don't have the wiring in my head right now but it shouldn't be hard at all.
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Re: best/most versatile ohms for 4x12 speaker?

Post by øøøøøøø » Thu Sep 16, 2010 11:49 am

null.fuzz to the rescue!

Let's see if we can put together an actual scheme...

OK so you get four 8 ohm speakers.

Wire two up in series, and then the other two also in series. Then you wire the two series-pairs up in parallel to get 8 ohms.

Then, you can defeat one series pair in order to use the other series pair alone--this gives you 16 ohms.

Then you could defeat one speaker from each series pair to leave you with a parallel pair for 4 ohms.

This might require two switches, or a complicated switch. I can't really wrap my head around implementing that right now with a single switch. With two switches it could be easy, but then you run a high risk of having it set wrong.

It would probably have to be a multi-pole rotary switch of some sort.

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Re: best/most versatile ohms for 4x12 speaker?

Post by null.fuzz » Thu Sep 16, 2010 1:16 pm

øøøøøøø wrote:null.fuzz to the rescue!

...

This might require two switches, or a complicated switch. I can't really wrap my head around implementing that right now with a single switch. With two switches it could be easy, but then you run a high risk of having it set wrong.

It would probably have to be a multi-pole rotary switch of some sort.
With 2 input jacks and a 4PDT switch it would work - and you can get those in heavy duty toggle versions that would handle any power you'd throw at it, and would be very easy to wire (a lot have screw lugs). Basically:
A) use 1/2 of the switch as a DPDT that does the series/parallel thing for a pair of the speakers. Series for a mono cab, parallel for one half of the stereo cab.
B) The other half would be used to switch the s/p combo from being across the terminals of input #1 (the use-in-mono/16-ohm stereo side) to being across the terminals of input #2 (the unused in mono/4-ohm stereo side)

I'm sure there's also a rotary switch that would work if you'd prefer that. I can come up with a diagram tonight.
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Re: best/most versatile ohms for 4x12 speaker?

Post by Professor Plum » Thu Sep 16, 2010 6:12 pm

thanks guys! that exactly what i was hoping to hear...

null, a diagram would be rad beyond words. id owe you a beer or something if you were ever in brooklyn.

actually, speaking of which, i should buy brad a beer on behalf of all of us someday, since he IS in broooklyn. :D lol
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Re: best/most versatile ohms for 4x12 speaker?

Post by null.fuzz » Fri Sep 17, 2010 6:54 am

So here are 2 schematics showing my interpretation of the options we discussed:
Image
Image

And here is how I would wire it, 2 jacks, 1 4PDT switch:
Image

Dotted lines are supposed to connect to the "-" terminal of the speakers connected to the ground/return/sleeve part of the speaker cable and the solid wires are supposed to connect to the "+" terminal of the speakers and the signal/tip of the speaker cable.

Also, I like beer. :)
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Re: best/most versatile ohms for 4x12 speaker?

Post by øøøøøøø » Fri Sep 17, 2010 7:15 am

beautiful!

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Re: best/most versatile ohms for 4x12 speaker?

Post by Professor Plum » Fri Sep 17, 2010 9:46 am

wow man, thats sooooooooooooooooooooooooooooooooooo cool of you. many many many thanks!!!!! :w00t:

on a beer note, i had some of these at the practice space last night, and it was most awesome.
Image

null, seriously- if you make it to brooklyn, hit me up and ill have some of that ready to wash down a tasty jam at our practice spot. :D
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Re: best/most versatile ohms for 4x12 speaker?

Post by null.fuzz » Fri Sep 17, 2010 10:58 am

Professor Plum wrote:null, seriously- if you make it to brooklyn, hit me up and ill have some of that ready to wash down a tasty jam at our practice spot. :D
You live at most 4.5 hours me from. If I didn't have a child and a pregnant wife I'd be there tonight!
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Re: best/most versatile ohms for 4x12 speaker?

Post by Professor Plum » Fri Sep 17, 2010 6:50 pm

null.fuzz wrote:
Professor Plum wrote:null, seriously- if you make it to brooklyn, hit me up and ill have some of that ready to wash down a tasty jam at our practice spot. :D
You live at most 4.5 hours me from. If I didn't have a child and a pregnant wife I'd be there tonight!
yo if/when you get a day or two to escape, hit me up! 8)
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Re: best/most versatile ohms for 4x12 speaker?

Post by raoulduke » Wed Jan 22, 2020 2:05 pm

NECRO THREAD.

I have an older marshall 4x10 with 8 ohm speakers wired to 8 ohms.

I'd like to add a switch to disable the top two speakers and run the bottom ones at 4 ohm. It appears I have to add a jack to do this (and the switch)

I don't need 16ohm or stereo. Is there a diff diagram i should be following or will this give me what im after plus a little extra?

Sorry for the dead thread thing. Just digging into this project and came across this :-)

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Re: best/most versatile ohms for 4x12 speaker?

Post by somanytoys » Mon Feb 17, 2020 9:06 pm

Wish I was better at this and could help.

But hey, at least it’s a cool thread to revive - I enjoyed reading it.
-David

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