4x12 with a 2x12 ohm question???

[Chadman]

Hello, I have a question about Ohm’s; although I’ve been playing with tube amps for 15 years and have never had a problem sorting out impedance issue’s I just want to pass this one by your guys to make sure my assumption is correct…

What I’m looking to put together is what I refer to as a “Mini Stack” (1) 4x12 and (1) 2x12 (before I start getting the jokes and cracks, I already have (2) 4x12’s… this in strictly for transporting reasons)

So I have an 800 RI which can be set to 4, 8, and 16 ohms (great!) and as we all know the standard Marshall 4x12 can run 4 and 16 ohms mono on that designated jack..(also great!)

Well the 1936 2x12 cab only runs 8 ohms mono! (16 would be awesome!, but that’s not the case)

So after all that…here is my question: If I was to run my head on 4 ohms would it be safe to run to the 4 ohm input on the 4x12 and the 8 ohm input on the 2x12?
From what I always understood, it’s OK to run smaller to larger….not larger to smaller, for example I would never run (head) 16 to an 8 ohm cab…I know that’s wrong for sure, but how about 4 or even 8 ohms from the head to a 16 ohm cab that’s cool…right? If that’s the case then the “Mini Stack” should work…correct?

Thanks!

 

[JohnH]

Sorry no. The idea that its OK to run an amp with cabs of higher Ohms than spec only applies to amps with solid state output stages. With a tube amp, to avoid risk to your output tranny, you need to match Ohms head to total cabs. Theres no good way to run an 8 Ohm cab with a 4 or 16. If you need a smaller rig, isnt one 4x12 enough?

John

 

[Chadman]

That's what I kinda thought...thanks man, and ya one 4x12 is fine but the extra cab just brings the sound up a bit for cutting through..

it's too bad the 1936 is only 8 ohms mono and not 16...that would work killer! Orange makes an awesome 16 ohm 2x12 but it's a ton of cash!!!


Cheers!

 

[JohnH]

You could always change the speakers. Get two 8 Ohm speakers and put them in series to make a 16 Ohm cab. Then Ebay the old ones.

 

[Chadman]

Dude! you read my mind! that was my next question..."is it possible to re-wire the 2x12 to make it 16 ohms...I take it the speakers in the 1936 are 16 ohm speakers..."right? I'm sure some 8 ohm vintage 30's would sound better anyway..

thanks JohnH!

 

[Dickie]

On the JVM forum, the same question was asked and 'Santiago' worked on the JVM project and had this answer on the subject which I thought would shed some light on the subject

"there won't be a mismatch if you plug the 8ohm cabinet into the 1x4ohm output and the 16ohm cabinet into the 1x8ohm output. Everything will be perfectly matched and the power splitted equally into both cabinets.

Santiago"

Of course this is for if you are running an amp that is running at its fully power, and not having any tubes pulled. Hope this helps

 

[JohnH]

On the JVM forum, the same question was asked and 'Santiago' worked on the JVM project and had this answer on the subject which I thought would shed some light on the subject

"there won't be a mismatch if you plug the 8ohm cabinet into the 1x4ohm output and the 16ohm cabinet into the 1x8ohm output. Everything will be perfectly matched and the power splitted equally into both cabinets.

Santiago"

Of course this is for if you are running an amp that is running at its fully power, and not having any tubes pulled. Hope this helps

Well thats quite interesting - Ive not heard that before but I can believe it when you have the various taps on the tranny.

what Santiago says is gold standard info, at least for the JVM since he designed it. You'd expect it would apply to others too though.

Note how with two cabs, the amp sockets used are at 1/2 the cab Ohms, as they are when you plug in two similar cabs. So for this example of a 4x12 and a 2x12, youd set the 4x12 to 16 ohms and plug it into an 8 Ohm socket, and put the 8 Ohm 2x12 into a 4 ohm socket.

I think another tech opinion is warranted however - any takers?

John

 

[Dickie]

I've just emailed Marshall technical team for confirmation of it all, they are probably canceling my warranty now

When I pick up my 1936 later I'll give it a shot anywho

 

[Dickie]

Well I got my reply back from Marshall today and this is what they have to say in the subject

"Hi

Regarding your question you could use both the 1936 and the 1960 into your JVM you would take the speaker lead from the mono socket on the 1936 and from the 16 ohms socket with the switch on mono on the 1960 and plug the two speaker leads into the two sockets on the JVM marked 2/8 or 1/4 ohms. The two cabinets together used in this way will give a combined impedance of 5 ohms which will work with the amp.

Many Thanks"

"will work with the amp." Doesn't sound all that convincing does it?

 

[poeman33]

Well I got my reply back from Marshall today and this is what they have to say in the subject

"Hi

Regarding your question you could use both the 1936 and the 1960 into your JVM you would take the speaker lead from the mono socket on the 1936 and from the 16 ohms socket with the switch on mono on the 1960 and plug the two speaker leads into the two sockets on the JVM marked 2/8 or 1/4 ohms. The two cabinets together used in this way will give a combined impedance of 5 ohms which will work with the amp.

Many Thanks"

"will work with the amp." Doesn't sound all that convincing does it?

Is it just me, or does that not make sense at all? How can plugging in a 16ohm cabinet and an 8 ohm cabinet into sockets marked "2 8ohms" equal 5 ohms?

 

[JohnH]

Its a 4 Ohm socket on the amp, into which you can plug one 4 ohm or two 8 Ohm speakers. A 16 Ohm and an 8 Ohm cab both plugged in, equal a load of 5 Ohms (actually 5.3)

Its a slight mismatch, and its the first time Ive heard of Marshall saying that that is OK. It probably is too!

John