It is possible to do series piggyback. Normally wired sockets and speaker leads however don't work for these purposes.

The majority of those pictures show the 'standard' set up where you switch STEREO and use both inputs (one for each channel L&R) OR you switch to MONO and use EITHER the 4 ohm or the 16 ohm input. You DO NOT use the second input. (eg) if you use the 4 ohm one you don't use the 16 ohm one for anything at all. These sorts of set ups mean you CAN NOT piggyback the cabinets.

In your pictures the one with three sockets has been wired specifically to allow for piggybacking when in mono. If you have this sort then all is well.

A splitter box is a 'box' that has three sockets in it all wired in parallel. You plug the amplifier output into one and then have two places to plug in speaker boxes.

Yes I was suggesting that you use the 1x15 and when you wire it up put in two parrallel wired sockets so you can go amp->1x15->4x12 assumming the Randall had the "standard" STEREO/MONO setup.

__________________
My Gear , please wack with the side of your hand for normal service.
Bringing you EVIL VOODOO WAX MAGIC since 2009

Well I think maybe a splitter box might be the best thing even if I do add a second parallel jack in the 1x15. Can a splitter box be built easily? Sounds like there wouldn't be much to it.

The cabinet I posted a pic of the panel that had XLR outs and a 3 position EQ switch is from one of their most expensive cabinets. I think the George Lynch and Kirk Hammett signature series are their most expensive cabinets they sell. Just seems odd to blow over a grand on a cabinet and you can't piggyback from it...

Welcome to the new millenium! Our way or the highway.

Splitter boxes are ridiculously simple just remember to isolate the mounts from the chassis. It is just three sockets with a wire between the relative lugs (ie) all tips joined, all shields joined.

The only down side is it is another item to remember to bring and check is connected properly.

__________________
My Gear , please wack with the side of your hand for normal service.
Bringing you EVIL VOODOO WAX MAGIC since 2009

Explain the isolate the mounts. Why is this necessary and are there schematics of what is going on?

Don't have the chassis of the box connected to the outer of the jack socket. Speakers can run at ~100V and you don't want that being randomly grounding on all and sundry. Either use a plastic chassis box or plastic surround jack sockets. If you ~really~ need a schematic use google.

__________________
My Gear , please wack with the side of your hand for normal service.
Bringing you EVIL VOODOO WAX MAGIC since 2009

So i'm just wanting to make sure I'm getting the right kind of hotplate.. i just bought the reissue twin... the amp is the 4ohm w/ the two speakers at 8 each (equaling 4ohm) just wondering do i need to get the hotplate as a 8ohm to accommodate for the speakers or do i get the 4ohm hotplate..