4x12 cab in multi config 4, 8, 16 ohm

[angelodp]

Hi, I have a 4x12 cab ( all 16 ohm speakers ). I want to set the cab up to go 4, 8 & 16 ohm. I realize that I can only do this by running the cab in parallel for the 4 ohm setting, and i can achieve the 8 ohm setting by running only two of the speakers in parallel and breaking the 4 ohm connection with a DPDT switch ( prefer to use a 20amp toggle to do this ). I am trying to figure out if, with one additional switch, I can also make the series/ parallel for 16 ohms.

Wondering if anyone has done this. Its a bit of an experimental rig so i am fine with two large DPDT switches on the back of the cab. I do not want to use switching jacks.

Ange

[thetragichero]

not to be a contrarian, but why?
that's more switches you have to worry about being in the right place while setting up for a gig, or you risk blowing your OT

[angelodp]

Yes I realize there is an inherent risk, but I do not play out and this is for my own use at home for the occasions when I jam with friends.

[JohnH]

Are you doing this to provide options for matching a tube amp? I can’t think of any other reason, since solid state amps are happy with cab ohms greater than their rated minimum.

You could do it like this:



The speakers are in two parallel pairs, and the left switch puts the pairs in series for 16 Ohms, or parallel for 4 Ohms. If in series mode, the right switch bypasses the lower pair to give 8 Ohms.

The thing to watch out for though is that the 8Ohm setting will sound different to the other two, since the lower speakers are not running, but will be driven passively out of phase, which may reduce bass response. By bypassing them, instead of disconnecting them, this effect should be minimised since their coils will tend to damp the passive movement. So, treat this as experimental, and consider why normal cabs don’t have this feature – maybe it sounds bad!

If you delete the right switch, the left one is fine for a 16/4 change.

[angelodp]

John, great stuff. I see where this might be problematic. How about a more simple 4 ohm 8 ohm config for the 4x12 ( 16 ohm speakers ).

Yes this is experimental. I have an 8 ohm tube amp and a 4 ohm tube amp that I would like to use on this rig.

So with just one DPDT switch i should be able to run all 4 in parallel for 4 ohms and then switch out two speakers and leave two in parallel for
8 ohms.

What might that look like if you would be so kind.

best Ange

[vonFrenchie]

I did a 16 and 8 stereo set up for my 212. It worked great. I know stereo is "pointless" because sonically everything mixes because the speakers are mounted in the same cabinet. But I say "pointless" because I have two Eminence Man-O-Wars which are 125 watt speakers. My roommate has a Dual Rec and I am picking up a JCA50H as soon as my winter training check comes in. With the whole stereo cab we can both plug our amps into one cab to save space.

Clearly in this model, each speaker represents one pair. As you already know, each pair is wired in parallel achieving 8 ohms per "channel."



In position one it is wired so you have two parallel channels that are wired in series which achieves 16 ohms. In position two it is wired so the two parallel settings are wired in parallel which achieves 4 ohms.

As you can tell, this gets 16 and 4 ohms. I am not sure of any wiring scheme of 4x16 that gets 8 ohms. Sorry man.

[JohnH]

Here's an 8 / 4 version:



As before, I followed a hunch that it may be a bit better to short out the unused pair rather than just disconnect them. I'm sure there's no risk in this, but I don't know if it will actually make an audible diference.
cheers
John

[mrmeaner]

Hey guys Im new here but looks like some good info. Ive got a question for ya. I have a Hughes and Kettner empty 4x12 vortex cab. I just bought 4 Vintage 30s all 8 ohms. I want to use the cab and it has wires already in it but I dont have a clue how to wire it. My Bogner has 4,8 and 16 ohm settings so I figure Ill wire it at 8 ohms. The rear plate has 8 ohms at 100 watts printed on it. It has an input jack with a red and black wire and an out with a black and red also hanging inside. In the bottom are a loose red wire and loose black wire laying in it. Can someone help me out. Thanks Tim

[elderik]

I'm in the opposite boat - I have a 4x12 loaded with 8 ohm Celestions, so I can set it up 8 ohms (4 or 16 ohms in stereo was my original intent), but my H&K Switchblade wants 16 Ohm for an external cab, unless I use ONLY an external and not the built in 2x12 - it would be nice to have a true 3/4 stack if I can get the 4x12 to run at 16 Ohm. The amp screams at 100W all tube so I know it will push them

Is there a clean way to do this with some assistance from a resistor or something? I can do the math, but don't want to ruin the sound. I see A Marshall cab out there that will run at 4/8/16 - how do they do it and still use all four cones?

EME

[JohnH]

Most Marshall cabs use 16Ohm speakers, to get 16 or 4 Ohms in the cab overall using all cones. The only 8 Ohm option that is possible is 2x8Ohms stereo. So with only one channel, you can only use 2 cones at 8 Ohms.

In your case, you can switch out two 8 Ohm speakers and leave just two in series to get the 16 Ohms, but you cant get all 4 running together and adding resistors is regarded as a bad idea.

John

[elderik]

Mar 27, 2011 16:29:02 GMT -5 mrmeaner said:

Hey guys Im new here but looks like some good info. Ive got a question for ya. I have a Hughes and Kettner empty 4x12 vortex cab. I just bought 4 Vintage 30s all 8 ohms. I want to use the cab and it has wires already in it but I dont have a clue how to wire it. My Bogner has 4,8 and 16 ohm settings so I figure Ill wire it at 8 ohms. The rear plate has 8 ohms at 100 watts printed on it. It has an input jack with a red and black wire and an out with a black and red also hanging inside. In the bottom are a loose red wire and loose black wire laying in it. Can someone help me out. Thanks Tim

Four 8 ohm speakers can easily be wired for 8 ohms total:




hope that helps - EME

[elderik]

Sept 19, 2011 4:29:53 GMT -5 JohnH said:

Most Marshall cabs use 16Ohm speakers, to get 16 or 4 Ohms in the cab overall using all cones. The only 8 Ohm option that is possible is 2x8Ohms stereo. So with only one channel, you can only use 2 cones at 8 Ohms.

In your case, you can switch out two 8 Ohm speakers and leave just two in series to get the 16 Ohms, but you cant get all 4 running together and adding resistors is regarded as a bad idea.

John

So I guess I can either swap for 16 ohm speakers, or get a 2x12 cab.

[sumgai]

Sept 19, 2011 5:26:41 GMT -5 elderik said:

So I guess I can either swap for 16 ohm speakers, or get a 2x12 cab.

Or you can ask John to dive into his archive, and dredge up the circuit he devised for newey some time ago. Therein, you will be hooking up your external cabinet in series with the amp's internal speakers.

Go ahead, ask him, he won't bite! ;D




sumgai

[ashcatlt]

This is a bit late, but for the OP you could wire two parallel pairs and then wire these to a DPDT on-on-on exactly the way we do with pickups for the old Series/Single/Parallel config and save a switch.