2x12 series/parallel wiring.

[mikeyphys]

I'm converting a 2x12 marshall combo for use as a speaker cab, i've already removed the marshall chassis and I plan on disconnecting the short speaker cable and fitting a jack socket on the back instead, I also want to add a dpdt switch that would allow me to switch between 4ohm and 16ohm. This would allow me to use the amp head I currently have and also allow me to use the marshall (if I ever get it repaired).

I realise the shortcut would be to just make the fitted speaker cable a little longer which would allow me to sit my amp head on top but I'd rather just change a switch position rather than have to open up the back everytime I wanted to swap from series to parallel.

I was just wondering if anyone has a diagram or wouldn't mind drawing me up a diagram, i've tried searching online but can't seem to come up with any decent websites that provide speaker cab wiring diagrams. There's plenty for pickups though. I understand how to wire the speakers in series and parallel but when I introduce the switch into the circuit i'm just lost.

 

[kmcguitars]

Re: 2x12 series/parallel wiring.

This might help? I have a 2x12 cab (Not at my disposal right now) w/t a 4 & 16 switch. I can't remember exactly how it's wired physically? I have a idea how it's done,But not being 100% sure. I don't wanna draw you a bad diagram. Just take a step back and look, It's a common sense issue, Not rocket surgery.

 

[mikeyphys]

Re: 2x12 series/parallel wiring.

I got a diagram for it, it's on my laptop though, i'll post it tomorrow and let you have a look. When I follow the signal path for when in 16ohm mode it all adds up and same goes for 4ohm mode but there's just that though in my head - 'i didn't draw the diagram so best double-check it before I kill my bassman!'
Like you said though, it isn't exactly advanced, just need to follow the signal path etc etc, treat it the same as when re-wiring a guitar for example.

 

[ratherdashing]

Re: 2x12 series/parallel wiring.

I strongly recommend against using a toggle switch. For one thing, it will not be cheap to buy one that can handle the current and voltage your amp will be putting out (no, you can't use the same kind you'd use on your guitar). I personally would also be concerned about the switch getting bumped while the amp was on, dramatically dropping or raising the impedance. That's a disaster waiting to happen. Maybe one of those sliding switches you need to push with a screwdriver would be a safer bet.

Post the diagram and I'll let you know if its correct or not.

 

[mikeyphys]

Re: 2x12 series/parallel wiring.

The parts I have were given to me by a guy who previously had them in a 2x12. I have a heavy duty on-on dpdt rated 10A 250VAC and 15A 125VAC. I'm in the uk were it's 230v.

The switch position being changed during use had crossed my mind, I did find this though:http://www.maplin.co.uk/Module.aspx?ModuleNo=37319 That would probably do the trick for protecting the switch from being touched while the amp is on.

I have also considered scrapping the switch altogether and maybe going with 2 mono 1/4" jacks one in series(16ohm) and one parallel(8ohm). But i'd probably need another diagram for that.

Here's the diagram.

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[ratherdashing]

Re: 2x12 series/parallel wiring.

I am confused by the diagram. If each line is a wire, then it is definitely wrong. I will draw a new one for you tomorrow.

 

[kevlar3000]

Re: 2x12 series/parallel wiring.

I did the same thing with one of my cabs, and love the versatility of it. Let me see if I can track down the diagram I used....

 

[mikeyphys]

Re: 2x12 series/parallel wiring.

I found a diagram at shavano music online, the only problem is the way the dpdt has been drawn, he does have a key further down on the actual page:

Shavano diagram

My dpdt is 2 rows of 3 terminals, I'm guessing I can just rearrange the connections as long as they're connected to the correct numbered terminal?
I redrew it and got this:

Thanks again for the help!

 

[ratherdashing]

Re: 2x12 series/parallel wiring.

I don't have time to draw a diagram, but I do know the Shavano diagram is correct.

Just to make it simple for you, I'll equate the terminals in the Shavano diagram's switch to your switch's terminals.

Shavano diagram:

1 3 4 6
2 5

Your switch:
1 2 3
4 5 6

Does that help?

 

[mikeyphys]

Re: 2x12 series/parallel wiring.

so use the shavano diagram but re-arrange accordingly for my switch, I tried to draw that in paint but i'm a bit **** with it.

One other question, in the shavano diagram there is an arrow pointing to the right marked A for series mode and a left arrow marked B for parallel. should I take that as the position of the swtich? how will that equate to mine, I need to know which position the switch needs to be in for which mode.

 

[ratherdashing]

Re: 2x12 series/parallel wiring.

I think I see the problem here. The Shavano diagram is confusing you because it's showing the inside of the switch. Those red wires between 1 and 2, and 5 and 6 are the switch throws, and not actual wires. You need to remove those from your diagram.

Here's how your switch works. A DPDT is actually two switches that share one toggle. Terminals 1, 2, and 3 are one switch, and 4, 5, and 6 are another.

When the toggle is on the 1 and 4 side, the opposite poles are "on". Here's a better illustration of what that means:

Toggle on the 1 and 4 side:

1 2-3
4 5-6

Toggle on the 3 and 6 side:

1-2 3
4-5 6

Your diagram also seems to ignore the fact that there are two jacks. This is a critical difference. Do you intend to have a parallel out jack on your cab, like in the Shavano diagram?

 

[mikeyphys]

Re: 2x12 series/parallel wiring.

The in and out on the shavano diagram confused me aswell.

I really only want one input socket and one switch for 4/16ohm.
I only really need 4 though cos i'm using a bassman, but if I ever get my marshall repaired I'll still want to be able to use that at 16ohm so I wanted the flexibility in the speaker cab.

 

[ratherdashing]

Re: 2x12 series/parallel wiring.

The in and out on the shavano diagram confused me aswell.

I really only want one input socket and one switch for 4/16ohm.
I only really need 4 though cos i'm using a bassman, but if I ever get my marshall repaired I'll still want to be able to use that at 16ohm so I wanted the flexibility in the speaker cab.

If you're not doing two jacks, you should probably just disregard that diagram completely.

I will be very busy this weekend, but if I have time I will draw up a proper diagram for you.

 

[mikeyphys]

Re: 2x12 series/parallel wiring.

I understand, I do appreciate you taking your time out as you have done already. I got a hold of this diagram from someone else.

I've followed the signal path for both position and it seems to make sense to me, but if you have the time to give it a quick glance that'd be great.

 

[zzmoore]

Re: 2x12 series/parallel wiring.

I found a diagram at shavano music online, the only problem is the way the dpdt has been drawn, he does have a key further down on the actual page:

Shavano diagram

My dpdt is 2 rows of 3 terminals, I'm guessing I can just rearrange the connections as long as they're connected to the correct numbered terminal?
I redrew it and got this:

Thanks again for the help!

For a single jack your speakers are wired correctly to Pins 2 & 5.
You need to delete the connection between Pins 1 & 6.
Delete the negative connection from the input to Pin 4, and establish it on Pin 6. So in phase would be positive of jack to Pin 3, and negative of jack to Pin 6.
Make a connection between Pins 1 & 4.
Then establish an in phase connection (- to - and + to +) from the speakers to your single jack.
Draw that on a piece of paper and see if it gives you what you are after.
Good Luck


Sorry.
Looks like you already had it, just flipped around.
Good Luck

 

[ratherdashing]

Re: 2x12 series/parallel wiring.

I understand, I do appreciate you taking your time out as you have done already. I got a hold of this diagram from someone else.

I've followed the signal path for both position and it seems to make sense to me, but if you have the time to give it a quick glance that'd be great.

This diagram is perfect.

Best of luck with the assembly.

 

[Sludgenutz]

Re: 2x12 series/parallel wiring.

Mikeyphys, whatever you do with any cab mod, test the resistance at the cabs input jack before you actually hook the amp up to it.

Good Luck!

 

[ratherdashing]

Re: 2x12 series/parallel wiring.

Mikeyphys, whatever you do with any cab mod, test the resistance at the cabs input jack before you actually hook the amp up to it.

Good Luck!

As previously stated, resistance does not necessarily equal impedance.

 

[mikeyphys]

Re: 2x12 series/parallel wiring.

That's good news about the diagram, I shall be doing that tomorrow and no longer shall I have to position the amp head behind the cab and have to go behind it adjust how it sounds.

I think the soldering and wiring up will be the easiest part of the whole thing, the hardest part was cutting the holes for the plate for the socket and the plate for the switch! I don't have any fancy tools, i've got a massive saw which was useless for this. So I had to use a power drill and a stanley knife...oh yeah and a deodorant can wrapped in sandpaper. I don't think i'd have enjoyed doing it as much if it was easier though.

I was going to take pictures but I don't think they'd have been of any interest to anyone hah.