Making a 4x12 cab a 5x12

palinilap · Post by **palinilap** » Fri Dec 19, 2014 10:00 am

Let me apologize in advance if this is the dumbest idea ever.... My current setup is a 5150 (120 watts/8ohm) / Marshall 4x12 (200 watts/8ohm). Sounds good but I'd like to experiment with adding a Weber speaker with early break-up. Probably a signature series 12" 25 watt/8ohm. This would just be for occasional recording purposes.

Would it be possible to wire an additional input jack to the cabinet just for plugging in the Weber, or am I looking at possible load issues? I just want to experiment with blending in that early break-up "floppiness" to my existing tone when recording.

EDIT: Thought of another possible scenario... I also have access to a Peavey Valveking 412 (400 watts/16 ohms) with a paralleled output jack for connecting additional speakers. However, again I'm just unclear about the math regarding load and whether this could be harmful to my amp.

Snarl 12/8 · Post by **Snarl 12/8** » Fri Dec 19, 2014 4:17 pm

What Ohms is the paralleled speaker on the Peavey supposed to be? Edit: wait, nevermind, it's just a cab, not a combo? Can you get a 16 Ohm weber? That, in parallel with a sixteen Ohm Valveking would get you to the 8 Ohms your amp wants.

palinilap · Post by **palinilap** » Fri Dec 19, 2014 4:24 pm

Snarl 12/8 wrote:What Ohms is the paralleled speaker on the Peavey supposed to be? Edit: wait, nevermind, it's just a cab, not a combo? Can you get a 16 Ohm weber? That, in parallel with a sixteen Ohm Valveking would get you to the 8 Ohms your amp wants.

The specs say "16 ohms mono, 8 ohms stereo" which confuses me.

Drone · Post by **Drone** » Fri Dec 19, 2014 4:40 pm

Two 8 ohm loads in series make 16 ohms, that makes sense.

I can't think of a good way to add one speaker and maintain the correct impedance.

Do you know the impedance of each individual speaker, could be 16 per, but more likely is 4.

palinilap · Post by **palinilap** » Fri Dec 19, 2014 4:45 pm

Drone wrote:Two 8 ohm loads in series make 16 ohms, that makes sense.

I can't think of a good way to add one speaker and maintain the correct impedance.

Do you know the impedance of each individual speaker, could be 16 per, but more likely is 4.

I believe in the Valveking they're all 16 ohm wired in series/parallel so that the overall load is 16 ohms.

My only thought is to open up the Marshall which is 8 ohm, disconnect one of the speakers, and connect the Weber to those terminals. If I were to do this I would use longer speaker cable to have some separation from the cabinet.

Drone · Post by **Drone** » Fri Dec 19, 2014 4:52 pm

I wouldn't believe that until I measured it, lots of modern cabs use cheaper 4 ohm drivers.

Is there something preventing you just replacing one of the current speakers with the Weber?

As long as you match the impedance of the other speakers in the cab and observe that the power handling is now 4 times the weakest driver it's fine, lots of people mix and match within a cab.

palinilap · Post by **palinilap** » Fri Dec 19, 2014 4:55 pm

Drone wrote:I wouldn't believe that until I measured it, lots of modern cabs use cheaper 4 ohm drivers.

Is there something preventing you just replacing one of the current speakers with the Weber?

As long as you match the impedance of the other speakers in the cab and observe that the power handling is now 4 times the weakest driver it's fine, lots of people mix and match within a cab.

In a live setting I don't want the Weber. I'm the only guitarist in a metal band and we crank it. I don't think the Weber's faster break-up would sound good/be as reliable in a live setting.

Drone · Post by **Drone** » Fri Dec 19, 2014 5:07 pm

The problem is it's power handling. It needs to have 3 other speakers around it to have a chance of survival.

Not knowing your setup, could you use say a Valve Jr. Head or something low wattage for recording, and drive the weber in it's own cab?

The only other way might need some fancy wiring. You'd put the 8 ohm Marshall cab in series with the 8 ohm Weber speaker for 16 ohms, parallel that with the 16 ohm ValveKing cab, and hey presto the little Weber is getting 1/4 power which hopefully it should survive.

Your friendly tech should be able to construct you a breakout box to do this, I had something similar in my setup for a while

- or -

Same friendly tech could wire an extension jack to the Marshall, which like you say disconnects just one driver and lets you run the Weber in a little extension cab, save you opening it and futzing all the time.

palinilap · Post by **palinilap** » Fri Dec 19, 2014 5:19 pm

Yes a jack would be ideal. I think I'll try it the quick and easy method first just to see how it sounds. If the Weber sounds like crap with the 5150 no sense in paying the tech. The curiosity is killing me though!

Drone · Post by **Drone** » Fri Dec 19, 2014 5:31 pm

Well remember to at least mount the Weber on a baffle of some kind. A loose speaker rattling on top of a cab or on the floor will aways sound crappy.

palinilap · Post by **palinilap** » Fri Dec 19, 2014 5:43 pm

Yep I converted an old Princeton '65 into a 112 cabinet. It's a pretty mediocre solid state, so makes good use of it.

ashcat_lt · Post by **ashcat_lt** » Sat Dec 20, 2014 11:24 am

I've heard that you can usually get away with fudging the load impedance by a factor of 2 in either direction without too much worry - especially if you're not cranking everything to 10. It might kinda just be fine...unless something explodes.

Do be careful with jacks and/or switches. Best to make all those connections with the head off (maybe standby?) to avoid potentially fatal open-or-short-circuits.

Drone · Post by **Drone** » Mon Dec 29, 2014 5:55 am

ashcat_lt wrote:I've heard that you can usually get away with fudging the load impedance by a factor of 2 in either direction without too much worry - especially if you're not cranking everything to 10.

I've been waiting for someone else to say it, but nobody else has, so: That's not a good generalisation to make.

Too much depends both on the circuit design, and the tubes being used by the current user. You could maybe make such a claim about a specific amp, and include the tubes you use, but I wouldn't go much further.

GooberNumber9 · Post by **GooberNumber9** » Mon Dec 29, 2014 2:02 pm

Really your best best option is to get a Weber that matches the impedance of one of the drivers in your cabinet, then crack open the cabinet and swap out the driver. You could put terminal lugs on the wires to make it easy to swap drivers back and forth or you could leave the Weber.

I think you can get away with leaving the Weber in full-time because in a live situation you will have three other drivers probably putting out more SPLs than the Weber and so the Weber's influence won't make a huge difference. In the studio (or live wth mics), you just put the mic right up to the Weber and optionally put a mic on another driver so you can mix the sounds.

On the other hand, doesn't Weber have some kind of great customer service or something? You could ask them what they recommend for your setup to incorporate the Weber.

For the Valve King, Peavey should be able to help you determine how you can safely hook it up.

Message Board

Making a 4x12 cab a 5x12

Making a 4x12 cab a 5x12

Who is online