Adding a 'speaker out' jack to a combo amp

I have a GK MB112-II. Essentially, it has an MB200 head directly wired to a 12" driver. While I absolutely love this combo, it would be nice to use the built-in MB200 to power other cabinets. My thought was to install a Neutrik NL4MD-V-S between the power amp and speaker. It's a switching jack, so I can wire it so that the connection of a Speakon cable will break the amp's connection with the 12" driver and route signal to an external cabinet. This is just a conceptual idea at this point. Can anyone find any flaws in this plan or have other suggestions?

 

I'm not sure of the location yet. I need to open up the chassis to see how much room is in there. If there is no room for the new jack, then I may have to look into making a new hole in the back of the wooden cabinet area, creating a mounting plate, and attach the new jack to the plate.

My big concern right now is that Neutrik specifically states that the jack is not air-tight. While the amount of rarefied air traveling back and forth through the new jack would be small, I worry that it could create a weird whistling noise or similar undesirable sound.

 

I like the idea of maybe putting two parallel jacks in, as I may have a need for connecting two 8-ohm cabinets. There is no chance that I would run two 4-ohm cabinets, so series jacks wouldn't be needed.

Edit: Just out of curiosity, how did Acoustic wire the series jacks? If only one jack was used, wouldn't that leave the circuit open? Did Acoustic have a switch on the amp to close the circuit for only one cabinet? Was a jumper plug of the sorts needed to close the circuit for only one cabinet?

 

Some interesting input here. Just to clarify some things:

• The MB112-II does in fact have a complete MB200 as its internal amplifier. This has been verified by GK.
• My mission is not to get more volume. My mission is to gain flexibility.
• All I’m considering is installing a solution that will take the internal 12” out of the circuit and allow me to connect either an 8-ohm or 4-ohm external cabinet instead. Essentially, I would be using my MB112-II just as a head from time to time.

 

Simple. Instead of using the internal 12” driver, I would like to occasionally use a 210 or 115 cabinet. The MB200 is already there. It’s just a matter of accessing it.

 

I like the idea of building a box inside the cabinet area to seal the new jack. However, the addition of the box would decrease the cubic footage used by the internal 12” driver, which may effect its performance (negatively).