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Post by chuck on Jul 6, 2010 18:48:42 GMT -5
Howdy guys ,
i have a speaker wiring question for ya ....
i have two old Peavey 2x12 cabs with 16ohm Celestion G12K85s.
is it possible to rig an external " adapter " to in effect make one series / parallel 16ohm 4x12 out of the pair ?
each cab has two input jacks ...
you can use each speaker alone ( 16ohms )
or both ( 8 ohms )
if i use 2 speaker cables ( plugged into the 8ohm jack ) and wire them into a Y with neg to pos , and pos to neg would that achieve my desired 16ohm load ?
i know this is simple , but my poor old brain is acting like a PC and keeps crashing on me.
i need an Apple brain .....
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Post by newey on Jul 6, 2010 21:21:06 GMT -5
No. To wire 2 16Ω speakers together in parallel gives you 8Ω combined, in series they give 32Ω. Switching the pos and neg wires just puts one speaker out of phase with the other- one cone is going in when the other is going out. The impedance is unchanged.
But if you're wiring 4 together, from 2 separate cabs, you could wire each cab in parallel at 8, then wire the 2 cabs together in series for 16&Omega total.
Now, if the ability to switch from one mode to the other is required (i.e., joined cabs in series or individual cabs separately) that could get complicated. We've had some discussions along these lines in the past- let me see what I can dig up in the basement here.
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Post by chuck on Jul 6, 2010 21:53:23 GMT -5
ok ...
each cabs 2 speakers are wired parallel already ( 2 16ohm speakers @ 8ohms )
if i have a speaker cable plugged into each cab ( 8 ohms each ) and wire the 2 cables together pos-pos , neg - neg it will give me a 16ohm load ?
i just want a simple plug in patch cable doohickey to connect the pair of 2x12s ... yes , i AM awesome at using fancy technical terms arent i ;D
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Post by newey on Jul 6, 2010 22:30:56 GMT -5
No, that's still in parallel, you've got 4 Ohms.
If the means to switch around is not required, a "box" is not required, it can be done with a specially-wired cable, and some added jacks for the series connection alone, leaving your existing jacks for their current uses. Other schemes are possible as well- you can use jacks with switching capabilities to keep the number of output jacks down, for example.
JohnH and I had a PM discussion a while ago for a means to add an extension speaker to my Fender combo(8 Ohm ext cab and 8 Ohm internal speaker), so that the 2 were on together when a cab was plugged in, running in series at 16 Ohms, and then unplugging the ext cab left just the internal speaker at 8 ohms. JohnH calculated a -3dB drop with the 16 Ohm load, not enough to matter for practice use. He gave me a diagram, which I'll repost as soon as I find it . . .
A lot of thought went into making it "newey-proof" such that there was no possibility of leaving the amp without a speaker load regardless of the state of the ambient lighting, my sobriety, etc.
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Post by chuck on Jul 6, 2010 23:22:31 GMT -5
OK ... i FINALLY get it ... DUH you explained it right there in black and white ... told ya , i am a bit on the slow side  parallel is + + , - - .... correct ? so if i use the + from one cab , and the - from the other to the jack , and connect the left over + and - to each other ... THAT should give me a 16ohm series / parallel wiring like a Marshall , Peavey , etc 4x12. ? or am i still suffering from FBS ( fuzzy Brain Syndrome ) ? |
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Post by ashcatlt on Jul 6, 2010 23:32:21 GMT -5
Was just about to jump in here, but I think you've got it.
I'd be inclined to use brown extension cord (some folks call it zip cord), though it might take an extra large barrel on the plug where they come together.
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Post by chuck on Jul 6, 2010 23:36:33 GMT -5
why would you use zip cord instead of good speaker cable ? i like to know WHY stuff works thanks for the heads up  |
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Post by ashcatlt on Jul 7, 2010 0:00:01 GMT -5
why would you use zip cord instead of good speaker cable ? $$$ |
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Post by chuck on Jul 7, 2010 0:06:42 GMT -5
oh ... i was going to use one of my George L's speaker cables .
no soldering required ...
but its a simple thing to fire up the ol iron if necessary
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Post by sumgai on Jul 7, 2010 2:34:57 GMT -5
why would you use zip cord instead of good speaker cable ? Because zip cord is good speaker cable, pure and simple. Since we've been down this road a few times, I'll just hit the highlights here. Copper wire, stranded or solid, can carry only so much amperage. Voltage doesn't count, it can be high or low (which will affect some safety aspects), but in general, only so many electrons can flow through a piece of wire at some instant in time. It should be obvious that the larger the wire, the more electrons that can flow, for that same time span. What's not obvious at first, but I'm about to make so, is that when the wire gets large enough, then the resistance is so low that it makes no difference to the circuit (amp to speakers and back). Above a certain size, there's more than enough electron flow to keep the speakers working happily, and for the wire to not overheat. What size is that, you ask? Glad you asked. I'll cut to the chase with some rules of thumb: For anything at 100 watts or less (and I mean tube or solid-state... a watt is a watt), 18ga. wire will work for up to 25 or 30 feet. Much longer, and you should probably use 16ga. instead. For 100 - 300 watts, at cable runs of up to 25 or 30 feet, 16ga. will do you just fine. Longer runs, step up to 14ga. For 300 watts and up, just go with 14ga. and be done with it. There are places, of course, where even these guidelines will fall short, but I'm talking about the average guitar/bass player with the average amps and speaker cabs. Now, the magic question: Should you get the high-priced spread, where you pay a very hefty premium that goes to make the mortgage payments on someone's vacation home in the Bahamas; or do you take the standard zip cord found in the aisles of Lowes/Home Depot/Menards/etc. - your choice. Like ash said, it all boils down to $$$$. HTH sumgai |
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Post by chuck on Jul 7, 2010 4:06:50 GMT -5
ahhh ... that makes a lot of sense !
even I can understand $$$$
thank you fine gentlemen for the informative words .
i do believe a trip to the Home Depot is in order ...
and here is a real sanity saver ... if you try to find Home Depot in the phone book , look under T not H .
it is listed as THE Home Depot.
drove me NUTZ trying to find it one day ;D
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