Series/Parallel switch for cab...

Sundogue · #1 05-23-2010, 11:48 AM

I know the Accuswitch is bogus, but that's because it's "supposed to" switch between 4 and 8 ohms. What kind of switch would I need to be able to switch between 8 ohm and 2 ohms? It would effectively switch the speaker wiring from series to parallel or back again.

I built a 210/6 cab that when used by itself I wired up to be 2 ohms. I use a Carvin BX1200 amp and bi-amp the two BP102's in it on one side with a dedicated 6" mid on the other side.

By itself it sounds great and I get plenty of volume out of it for smaller gigs. The reason I wired it up as a 2ohm cab is that it is very similar to an Acme in that it really shines when given enough power. My Carvin puts out 600 watts into this 2 ohm 400 watt cab (obviously not the full 600, but you get the idea here).

But, for larger gigs I built a duplicate 210/6. But to use them together I had to wire them both as 8 ohm cabs giving me a 4 ohm load on the one side of my Carvin amp (the other side going to both mid drivers). Until I put in an 800Hz crossover in each cab, I can't run my amp bridged into both 8 ohm cabs (which would give me 1200 watts into the combined 800 watt cabs). Running all four tens on one side of my amp (with each cab being 8 ohm) is only giving me 400 watts total for both, which is fine for now but a tad wimpy.

Any idea on a switch to go between 2 and 8 ohms for the single cab and how to wire it up? It will be a while until I can get the internal crossovers for both cabs so I wanted to be able to switch the single cab to 2 ohms when it's run alone. I have some idea on what to do, but I want to be sure.

bobcruz · #2 05-23-2010, 01:57 PM

You need a double pole-double throw switch that's rated to handle the current that you'll push through it. I don't have a diagram for wiring up two speakers but here's one for wiring four speakers that could get you started:

Sundogue · #3 05-23-2010, 02:23 PM

Thanks. That's about what I had in mind.

Couple of questions.

What should the actual ohms read on an ohmmeter if the wiring is either 2 ohms or 8 ohms?

Would a 10 amp DPDT switch be enough?

BassmanPaul · #4 05-23-2010, 02:27 PM

Use the same schematic but ignore the bottom pair of drivers. You'll get 16Ω and 4Ω. You cannot wire a pair of 8Ω drivers to give 2Ω.

Paul

Sundogue · #5 05-23-2010, 02:30 PM

Quote:

Originally Posted by BassmanPaul

Use the same schematic but ignore the bottom pair of drivers. You'll get 16Ω and 4Ω. You cannot wire a pair of 8Ω drivers to give 2Ω.

Paul

I'm aware of that. My single cab is made up of two 4 ohm BP102's. So I want to switch it between 2 ohm or 8 ohm depending on whether or not I run it alone or with another 8 ohm cab.

dose · #6 05-23-2010, 03:59 PM

What size switch would you guys recommend for a Eden 410xlt 8ohm cab? i have it rewired at 2ohms but it would be nice to be able to switch it on the fly to use more cabs

BassmanPaul · #7 05-23-2010, 04:48 PM

Quote:

Originally Posted by Sundogue

I'm aware of that. My single cab is made up of two 4 ohm BP102's. So I want to switch it between 2 ohm or 8 ohm depending on whether or not I run it alone or with another 8 ohm cab.

Then that is what you will get.

Paul

BassmanPaul · #8 05-23-2010, 04:52 PM

Quote:

Originally Posted by dose

What size switch would you guys recommend for a Eden 410xlt 8ohm cab? i have it rewired at 2ohms but it would be nice to be able to switch it on the fly to use more cabs

A 10-15A switch will do the job. It's not something that I'd recommend doing at all. Sure as eggs are eggs you'll use the switch in the wrong position or it'll get flipped accidentally and your amp will be toast!

We DO play with drummers you know!

Paul

Sundogue · #9 05-23-2010, 05:00 PM

Quote:

Originally Posted by BassmanPaul

A 10-15A switch will do the job. It's not something that I'd recommend doing at all. Sure as eggs are eggs you'll use the switch in the wrong position or it'll get flipped accidentally and your amp will be toast!

We DO play with drummers you know!

Paul

I doubt it. I'm very conscious of my setup, especially now that I'm bi-amping. If I forget to flip (or check) that the X-Over switch on my amp is engaged, I'll fry my mid drivers.

The Series/Parallel switch is worth it to me and I have no worries about using it properly.

walterw · #10 05-23-2010, 05:08 PM

my 4x12 guitar cab is wired to switch between 16 and 4, and I did it with no moving parts to go bad. using those thick black plastic stereo jacks, I just have a 16ohm Jack and a 4ohm Jack on the cab, and it switches depending upon which one I plug into.

Marshall might have some cab schematics online.

BassmanPaul · #11 05-23-2010, 05:14 PM

The switches in those jacks are not rated for the service. Anything more than a hundred or two watts can lead to problems. There's enough people having problems with similar jacks in effects loops and they are running at a couple of hundred millivolts.

Paul

Sundogue · #12 05-24-2010, 12:22 PM

OK. I found a 20 amp DPDT On/On switch at my local hardware store (Radio Shack only had 3 amp). Yeah, 20 amp might be overkill but it has to be rated equal or higher than what I'm putting into it, so this one is heavy duty, so no worries there.

Now, just to be clear...I found another diagram and I want to be sure this is how it needs to be wired, so if anyone cares to chime in, I'd appreciate it. Thanks.

I modified the diagram below (using the lettering of the switch lugs from the pic above), so in the diagram from bobcruz, which ones are A, B, C, D, E, F? Is it like the image below? Because between the two diagrams, the one above is marked that B and F go together, but from the one below it seems like C and F should go together. I'm a bit confused on just those connections. I think C and F should go together so when the switch is in the "1" position, the positive of one speaker connects to the negative of the other (but only when the switch is in that position). B and F soldered together makes it a permanent connection doesn't it?

Sundogue · #13 05-25-2010, 05:03 AM

Just a bump. I know it's hardly a compelling thread, but can anyone confirm the above diagram(s).

Thanks.

Jason P Bass · #14 05-25-2010, 07:27 AM

I can't help you with the letters, but with a digital multimeter you should be able to figure out which terminals need which connections. In other words, you know that "position 1" needs to have a connection between certain terminals, and "position 2" needs to have a connection between certain terminals. It won't take more than a few minutes to figure it out.

Sundogue · #15 05-25-2010, 07:53 AM

Quote:

Originally Posted by Jason P Bass

I can't help you with the letters, but with a digital multimeter you should be able to figure out which terminals need which connections. In other words, you know that "position 1" needs to have a connection between certain terminals, and "position 2" needs to have a connection between certain terminals. It won't take more than a few minutes to figure it out.

Yeah, I've got a few extra speakers lying about and I'm going to wire up the switch, speakers and an input jack outside a cab on my bench. I'll just test it out there.

Anyone else want to save me the hassle?

jsbarber · #16 05-25-2010, 08:32 AM

Why not just build a special cable to connect the two cabs in series. Wouldn't this be easier?

Sundogue · #17 05-25-2010, 09:26 AM

Quote:

Originally Posted by jsbarber

Why not just build a special cable to connect the two cabs in series. Wouldn't this be easier?

My issue is when using the single cab on it's own. When by itself I want to push more watts through it. I'm not going to be putting the switch on both cabs. Just the one.

At some point I'm going to install internal crossovers in both 210/6 cabs. Then I can run my amp in bridged mode rather than mono and bi-amping with it. But that won't be for a while, so I want the switch as most of the time I use only the single cab and prefer to run it at 2 ohms. There are a few times when I'll use two cabs, so I can't just wire the one up as a 2 ohm and still use it with the other without the hassle of removing the speakers and re-wiring as 8 ohm again.

This is for my use, not as a commercial endeavor. I built these cabs and have no intention of selling them so it's just a personal desire.

Sundogue · #18 05-28-2010, 01:59 PM

I tested out the switch wiring on my bench with two other speakers outside my cab.

My wiring diagrams are both correct. Connecting either C and F, or B and F yields the same result. Using 8 ohm speakers I get 16 ohms with the switch one way, and 4 ohms the other way. The speakers in my cabs are 4 ohm speakers which will give me an 8 ohm or 2 ohm cab. The other cab will remain only an 8 ohm to use when I need both cabs.

Now I just need to put it in my cab and I'll have a nice ball buster 210/6 - 2 ohm cab or two 210/6 - 8 ohm cabs for larger gigs.

rockstarbassist · #19 05-28-2010, 03:30 PM

Get the EpifaniSwitch cabs. They claim they work.

will33 · #20 05-28-2010, 04:18 PM

Quote:

Originally Posted by Sundogue

I tested out the switch wiring on my bench with two other speakers outside my cab.

My wiring diagrams are both correct. Connecting either C and F, or B and F yields the same result. Using 8 ohm speakers I get 16 ohms with the switch one way, and 4 ohms the other way. The speakers in my cabs are 4 ohm speakers which will give me an 8 ohm or 2 ohm cab. The other cab will remain only an 8 ohm to use when I need both cabs.

Now I just need to put it in my cab and I'll have a nice ball buster 210/6 - 2 ohm cab or two 210/6 - 8 ohm cabs for larger gigs.

Hey, cool idea and it actually works....you should work for Accugroove and charge people out the a$$ for it.

Just for future reference an 8ohm speaker can read as low as 5.something ohms, a 4ohm can read 3.something. If you're testing it at the other end of the speaker cable, resistance can increase some depending on the cable run. If you're trying to test something that has a built-in passive crossover you won't get a good reading, the caps and coils will screw with the meter, then you have to remove a woofer and go from there.