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Old 11-30-2012, 03:53 PM   #1
User_Name336
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Can I Wire A Cab to be 4, 8 and 16 ohm?

I made a thread a week or two ago about how to wire, and now comes the time to actually figure out if this is possible. My cab is a 412 with all 8ohm speakers. I have learned its possible to get 4, 8 or 16 ohm out of it through how I wire it, but is there any way I could wire it, maybe through some sort of switch(s) that would allow me to have all three? I was hoping to have three individual input jacks, with some sort of toggle switch.

I have a lot of vintage gear come through that has only one of the three outputs so I really need a versatile setup. I was suggested the Weber Z-Matcher, which I will only purchase as a last resort. I have amps in my collection right now that run only one of those (vox thats only 16, traynor thats only 8, etc) so having all three is a must for me. I cant afford, nor do I have space for another cab.

EDIT: would something like this work?

-if i wire it as two separate 212 cabinets in the same box. could i wire the top two speakers with a marshall style switch so that they are 4 and 16 ohm, then the bottom two with the same style switch. from there, connecting the two (just like i would connect two cabs externally with a speaker cable) would give me 8ohm parallel, correct?
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Last edited by User_Name336 : 11-30-2012 at 04:33 PM.
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Old 11-30-2012, 04:43 PM   #2
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Quote:
Originally Posted by User_Name336
I made a thread a week or two ago about how to wire, and now comes the time to actually figure out if this is possible. My cab is a 412 with all 8ohm speakers. I have learned its possible to get 4, 8 or 16 ohm out of it through how I wire it, but is there any way I could wire it, maybe through some sort of switch(s) that would allow me to have all three? I was hoping to have three individual input jacks, with some sort of toggle switch.

I have a lot of vintage gear come through that has only one of the three outputs so I really need a versatile setup. I was suggested the Weber Z-Matcher, which I will only purchase as a last resort. I have amps in my collection right now that run only one of those (vox thats only 16, traynor thats only 8, etc) so having all three is a must for me. I cant afford, nor do I have space for another cab.



usually the way people do this is they use 16 ohm speakers. one setting has all the speaker connected in parallel (for 4 ohms). one setting has the speakers connected in series parallel (for 16 ohms) and one setting has the speaker connected for 'stereo' operation (that is pretty much the two 2x12's in one 4x12 box method you were talking about).

you can buy jack plates to implement this with the switches (DPDT) already there, you just hook up the correct wiring for it to work

Quote:
Originally Posted by User_Name336
EDIT: would something like this work?

-if i wire it as two separate 212 cabinets in the same box. could i wire the top two speakers with a marshall style switch so that they are 4 and 16 ohm, then the bottom two with the same style switch. from there, connecting the two would give me 8ohm parallel, correct?


i have to do the math to figure that out. lets see, make two separate wiring system, two 8 ohms in parallel and one in series for a 4 ohm side and a 16 ohm side respectively...

if you hook those sides together in parallel it'd be:
1/Rtot = 1/4 + 1/16 = 4/16 + 1/16 = 5/16
Rtot = 3.2 ohms

if you hook them in series it'd be
Rtot = 4+16 = 20 ohms

so no, that wouldn't work if you also wanted to be able to use both sides at once. but if instead you just wanted to use one side or the other, then it would work but you'd only have a 4 ohm or 16 ohm available.

another option is to use a series/parallel connection with a stereo option like so:



it'd give you a mono 8 ohm cabinet and a 16 ohms per stereo side (when just using two of the speakers).
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Old 11-30-2012, 04:58 PM   #3
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Quote:
Originally Posted by gumbilicious
usually the way people do this is they use 16 ohm speakers. one setting has all the speaker connected in parallel (for 4 ohms). one setting has the speakers connected in series parallel (for 16 ohms) and one setting has the speaker connected for 'stereo' operation (that is pretty much the two 2x12's in one 4x12 box method you were talking about).

you can buy jack plates to implement this with the switches (DPDT) already there, you just hook up the correct wiring for it to work



i have to do the math to figure that out. lets see, make two separate wiring system, two 8 ohms in parallel and one in series for a 4 ohm side and a 16 ohm side respectively...

if you hook those sides together in parallel it'd be:
1/Rtot = 1/4 + 1/16 = 4/16 + 1/16 = 5/16
Rtot = 3.2 ohms

if you hook them in series it'd be
Rtot = 4+16 = 20 ohms

so no, that wouldn't work if you also wanted to be able to use both sides at once. but if instead you just wanted to use one side or the other, then it would work but you'd only have a 4 ohm or 16 ohm available.

another option is to use a series/parallel connection with a stereo option like so:



it'd give you a mono 8 ohm cabinet and a 16 ohms per stereo side (when just using two of the speakers).


sorry, i may have phrased that wrong. if i hook the top two speakers up with the marshall style jack so its 4/16 ohm, and i did the same to the bottom (4/16 ohm). the marshall jack has an 8ohm stereo option, so couldn't i just simply hook it up on the outside as if it was two different cabs? or am i missing something about how that marshall style jack works

this is what i'm thinking. wire two separate ones of this style


using this style of jack


essentially, i would be using it as a 212 with 4 or 16 ohm most of the time using the top two speakers. if i needed an 8ohm thing, i would just attach the bottom two speakers using that external jack as if it was a second cabinet
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Last edited by User_Name336 : 11-30-2012 at 06:06 PM.
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Old 11-30-2012, 06:01 PM   #4
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Quote:
Originally Posted by User_Name336
sorry, i may have phrased that wrong. if i hook the top two speakers up with the marshall style jack so its 4/16 ohm, and i did the same to the bottom (4/16 ohm). the marshall jack has an 8ohm stereo option, so couldn't i just simply hook it up on the outside as if it was two different cabs? or am i missing something about how that marshall style jack works

this is what i'm thinking. wire two separate ones of this style


using this style of jack



well, it'd depend on how the jackplate is actually wired and how you connect the jackplate to the speakers.

that jackplate is set up for a 2x12 with 8 ohm speakers or a 4x12 with 16 ohm speakers. afaik, that jackplate doesn't have a DPDT so that jackplate doesn't necessarily match the schematic

but lets just say you were going to use two of those jackplates and wire your cab as two 2x12 cabinets in a 4x12 housing.

what you'd effectively have is two 2x12's that can facilitate a 4, 8 or 16 ohm output. but once you try to use the other 2x12 as well (assuming you hook them both to the same amp) then you'd probably connect them in parallel and you'd most likely use it as an 8 ohm 4x12 cab by using the 16 ohm setting on each jackplate and connecting them to the speaker outs on a tube amp set to 8 ohms.

Quote:
Originally Posted by User_Name336
essentially, i would be using it as a 212 with 4 or 16 ohm most of the time using the top two speakers. if i needed an 8ohm thing, i would just attach the bottom two speakers using that external jack as if it was a second cabinet


you could also use two different amp heads to drive the two separate 2x12 setups. i did that for a while.
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Last edited by gumbilicious : 11-30-2012 at 07:02 PM.
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Old 11-30-2012, 06:11 PM   #5
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Quote:
Originally Posted by gumbilicious

but lets just say you were going to use two of those jackplates and wire your cab as two 2x12 cabinets in a 4x12 housing.

what you'd effectively have is two 2x12's that can facilitate a 4, 8 or 16 ohm output. but once you try to use the other 2x12 as well (assuming you hook them both to the same amp) then you'd probably connect them in parallel and you'd most likely use it as an 8 ohm 4x12 cab by using the 16 ohm setting on each jackplate and connecting them to the speaker outs on a tube amp set to 8 ohms.
.

that is exactly what i'm trying to do. but i think i might have had it wrong the first time around. those jacks dont actually have an output, do they...? if not, could i instead use that jack on lets say the top speakers only so its 4/16 ohm. then wire the bottom two speakers in 16ohm in with a 16ohm out. from there, if i needed an 8ohm impedence, i could run an 8ohm impedence from my tube amp head, into the bottom speakers 16ohm input jack, run a cable from the 16ohm out into the top 16ohm input. 16ohm+16ohm=8ohm i believe

EDIT: i might have messed up again. if i wired the bottom two speakers for 16 ohm, then it would be series, so the output would also be series, right? then if i hooked up the two 16s together, i wouldn't actually get 8 but rather 32? this is all very confusing to me. i'm just learning this right now as i'm typing haha!
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Last edited by User_Name336 : 11-30-2012 at 06:43 PM.
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Old 11-30-2012, 07:00 PM   #6
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Quote:
Originally Posted by User_Name336
that is exactly what i'm trying to do. but i think i might have had it wrong the first time around. those jacks dont actually have an output, do they...?

no, they don't. those jackplates generally have the jacks already wired together or they are connected to PCB that connects them. it is possible to get jackplates that are 'blank' and you could wire them up any way you want to. but i assume the one you showed is made to work as the plate is labelled

Quote:
Originally Posted by User_Name336
if not, could i instead use that jack on lets say the top speakers only so its 4/16 ohm. then wire the bottom two speakers in 16ohm in with a 16ohm out. from there, if i needed an 8ohm impedence, i could run an 8ohm impedence from my tube amp head, into the bottom speakers 16ohm input jack, run a cable from the 16ohm out into the top 16ohm input. 16ohm+16ohm=8ohm i believe


yes actually you could. you already have the diagram for the top speakers, so then you'd just connect the bottom speakers as such:



that connects the two 8 ohm speakers in series for a 16 ohm load. the jacks are wired in parallel so you could use either as an input or output. technically the math for wiring resistances/impedances in parallel is

1/Rtot = 1/R1 + 1/R2... +1/Rn
you basically add all the fraction together and take the reciprocal as the answer. there is an example in a previous post.

when connecting in series you simply add:
Rtot = R1 + R2... +Rn

just in case you may need to do some math figure out impedances at sometime. it can come in handy.

Quote:
Originally Posted by User_Name336
EDIT: i might have messed up again. if i wired the bottom two speakers for 16 ohm, then it would be series, so the output would also be series, right? then if i hooked up the two 16s together, i wouldn't actually get 8 but rather 32? this is all very confusing to me. i'm just learning this right now as i'm typing haha!


no, you will be fine. the jacks are wired together in parallel regardless of the speakers being connected in series, this will ensure whatever extra cab you hook up will be run in parallel with bottom 2x12 will be run in parallel with it.

in fact almost all connections like this tend to be parallel connections, you would have to get a series box to hook cabs up in series.
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Last edited by gumbilicious : 11-30-2012 at 07:01 PM.
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Old 12-01-2012, 06:44 PM   #7
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Quote:
Originally Posted by gumbilicious
no, they don't. those jackplates generally have the jacks already wired together or they are connected to PCB that connects them. it is possible to get jackplates that are 'blank' and you could wire them up any way you want to. but i assume the one you showed is made to work as the plate is labelled



yes actually you could. you already have the diagram for the top speakers, so then you'd just connect the bottom speakers as such:



that connects the two 8 ohm speakers in series for a 16 ohm load. the jacks are wired in parallel so you could use either as an input or output. technically the math for wiring resistances/impedances in parallel is

1/Rtot = 1/R1 + 1/R2... +1/Rn
you basically add all the fraction together and take the reciprocal as the answer. there is an example in a previous post.

when connecting in series you simply add:
Rtot = R1 + R2... +Rn

just in case you may need to do some math figure out impedances at sometime. it can come in handy.



no, you will be fine. the jacks are wired together in parallel regardless of the speakers being connected in series, this will ensure whatever extra cab you hook up will be run in parallel with bottom 2x12 will be run in parallel with it.

in fact almost all connections like this tend to be parallel connections, you would have to get a series box to hook cabs up in series.

perfect!! does anybody else want to give a second opinion before i go forward with this?
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Old 12-01-2012, 06:46 PM   #8
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Originally Posted by User_Name336
perfect!! does anybody else want to give a second opinion before i go forward with this?


thats the right attitude right there

it's never bad getting a second opinion.
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Old 12-03-2012, 12:05 PM   #9
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Quote:
Originally Posted by gumbilicious
thats the right attitude right there

it's never bad getting a second opinion.

its just too bad that nobody seems to know enough (or care enough) to help out or give their opinion.

By the way, I really appreciate all the help buddy. Thank you so much

EDIT: I contacted an amp tech (supposed to be one of the better guys in southern ontario) asking him if this will work, and he seems to be avoiding the question. He just keeps answering with things like "the marshall switch works like this" or "i can rewire a cabinet" or "the marshall switch is going to cost you $____". should I be concerned? I've already made up my mind that since he's not being upfront or answering any questions I've asked that he wouldn't be getting any business from me now or in the future again.
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Old 12-03-2012, 12:16 PM   #10
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Gumbi speaks truth. You can switch between 4 and 16 with all four speakers running or 8 ohms if you turn off two speakers.
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Old 12-03-2012, 12:21 PM   #11
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Originally Posted by Cathbard
Gumbi speaks truth. You can switch between 4 and 16 with all four speakers running or 8 ohms if you turn off two speakers.


How's he going to accomplish that when all his speakers are 8 ohm? Did I miss something above?
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Old 12-03-2012, 12:26 PM   #12
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Oh, 8 ohm drivers. Let me reread all that then. I was thinking 16 ohm speakers. That'll learn me not to read properly.



Edit. Yeah. To get 16 you'll have to run just two in series, two in parallel for four. All four in series/parallel for 8.
You could run two in series and two in parallel and series them up for 20 ohms which will work close enough for 16 but you're going to have unequal power distribution across the speakers. It's probably not going to be worth the trouble because two speakers will be doing the lion's share of the work so it's added complexity for little benefit. You may as well just run two speakers in series and call it a day.
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Old 12-03-2012, 10:31 PM   #13
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Quote:
Originally Posted by Cathbard
Oh, 8 ohm drivers. Let me reread all that then. I was thinking 16 ohm speakers. That'll learn me not to read properly.



Edit. Yeah. To get 16 you'll have to run just two in series, two in parallel for four. All four in series/parallel for 8.
You could run two in series and two in parallel and series them up for 20 ohms which will work close enough for 16 but you're going to have unequal power distribution across the speakers. It's probably not going to be worth the trouble because two speakers will be doing the lion's share of the work so it's added complexity for little benefit. You may as well just run two speakers in series and call it a day.

uhhhh... what?

i'm a little confused here. i dont know if you've read everything (i really hope you didnt) but to sum everything up, here's what we have decided upon:

-i'm splitting the cab so its essentially 2 212s in a 412 box
-the top two speakers will be wired series for 16 ohm (16 ohm in, 16 ohm out)
-bottom two speakers will get the marshall style switch so it can run 4 or 16 (4ohm in parallel, 16 for series, and its switchable. check out the marshall 1960 cab if you dont know what we were talking about here)

the thing in question now is:
-will it actually be an 8ohm impedance if i run the cable into the 16 ohm input (top speakers), take a cable from the 16 ohm output and run that into the bottom two spekers (plug it into the marshall style 16ohm input).

we have concluded that it SHOULD be 8 ohm since the other guy said even though the speakers are run in series, the inputs are wired parallel? i'm not sure about that so i wanted a second opinion before i risk blowing my amp.
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Last edited by User_Name336 : 12-04-2012 at 01:13 AM.
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Old 01-06-2013, 08:06 PM   #14
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Don't intend to jack the thread but, what I need to do is use a DPDT in a 2x12 cab to switch between a 2 speaker parallel and a 1 speaker single only setup with only one input jack. Is this even possible? Indendence is not an issue as I know what I need already. BTW, the switch I have is the 2 rows of 3 type. Thanks.
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