Here are the steps I took to install the PinballPro Subwoofer into my Medieval Madness. This utilizes the original SW-2 kit.
First off, let me just say that I have NO connection with Pinball Pro. I am just a satisfied customer who is sharing my installation experience with others. I installed the first SW-2 that I purchased in my Theatre of Magic. The new bass response provided by the SW-2 in Medieval Madness is even more impressive!
These are the steps that I took that deviated from the supplied installation instructions. Those instructions do not take into account the clearance problem this game has with the troll assemblies.
The first thing that is necessary is to remove the existing woofer AND the standoff bracket it sits on. You can accomplish this with either a screwdriver or chisel and hammer combination. This is probably the part that die-hard collectors may have a problem with - I have to agree, but believe me, the results are worth it. A couple of hits on the front and back should be enough to break it free. There are four small nails holding the bracket to the cabinet as well as glue.
Next, mount the new subwoofer to the supplied standoff (the thinner one) sandwiching the existing grill between it. You'll have to use some shorter wood screws and you'll have to drill clearance holes for the screws in the grill. Also, remove the network card from the back of the subwoofer. Be careful during this step so you don't crack the circuit board. The newer version has the network mounted to the side of the subwoofer so you won't need to remove it.
Lastly, mount the assembly in the cabinet. I used hot glue. You could probably do the above step and this step as one if you like, using longer screws to screw into the bottom of the cabinet itself. If you do it this way, you could put the grill between the cabinet and the spacer plate.
Here is a picture of the clearance between the subwoofer and the troll assemblies. Just enough!