Dual Rec and cabs impedance

[tomprs]

Hello!

I usually connect my dual rec to an Orange PPC212 (2x12 V30, 16 Ohm cab) for rehearsals or small gigs but I'd like to connect another cab also for bigger venues (a 4x12 JCM800 lead 1960 cab with G12 T75 speakers). The idea is to keep the Orange cab for micing and to use the Marshall cab to hear myself better. The thing is that I don't know the impedance of the JCM cab...connections on the back have been replaced over the years (it's from 1984) and there's nothing written on it. Can someone help me with this? Is this two cabs - one head a good idea? How should I connect those to the head?

Thanks!

Tom.

 

[screamingdaisy]

A Marshall cab is typically 16?, but that assumes it still has the original speakers in it. The easiest way to know for sure is by testing it with an ohm meter or multi-meter. A 16? cab will actually read around 14.7?. If you don't have one I suggest borrowing one off a friend.

The next way is to pull the back off and verify the speakers (it's usually written on them somewhere) and that the cab is still wired series/parallel and hasn't been converted to something goofy along the way.

If both cabs turn out to be 16? you can run both of them in parallel by using the two 8? jacks on the back of your Recto.

 

[tomprs]

Thanks screamingdaisy!

The cab has still the original speakers yes, I will anyway open it and check the wiring. I've got one more (maybe dumb) question: as there's a 16ohm input and two 8ohm inputs on the dual rec, why not connecting one of the two cabs in the 16ohm input and the other cab in one of the 8ohm connections?

Thanks for your help!

Tom.

 

[screamingdaisy]

When you connect two loads (in this case cabs) in series you double the impedance (8? becomes 16?)

When you connect two loads in parallel you halve the impedance (8? becomes 4?).

The connections on the back of the amp are in parallel, so when you hook up two 16? cabs you're halving the total impedance, which results in a 8? load.

 

[tomprs]

Clear! Thanks!