How does MIT vary the impedance of their cables?

I have a pair of MIT 330's that are "medium" (47~100ohms) and I need "low" (10~47ohms).
I was wondering how MIT alters the impedance in their different versions? I'm guessing that it's with the use of a resistor in the network box? I thought that if I could open the box and jumper the resistor... Any opinions?

Unless I'm mistaken, most speaker crossovers are "buried" in epoxy to improve performance by reducing vibrations.

Just a different, non-cynical, view.

Cornfedboy: Such cynicism about those fine professionals who bring us high-end cables. Can you prove that the epoxy resin they use doesn't improve the sound?
Thanks for the info so far guys. I didn't know that the circuits would be potted, but it shouldn't surprise me as it's common practice for any cable mounted circuitry in other non audio applications. The reason that it's done is to protect the circuit from shock, vibration and humidity when components are used on cables. As you can imagine real cables get dropped and banged around a lot and don't enjoy the privileged and pampered life that our "audiophile" cables live. Velvet lined presentation boxes, give me a break...
Despite what others say, I personally like the sound of my MIT IC and speaker cables, especially considering the prices that I have paid for them used. I knew when I bought these used 330's that I needed "low", but I thought for the price I'd try these "mediums" anyway. I can tell that they are better than the T2's that they replace, but the top end is veiled and compressed. MIT says that it's an impedance issue and I though that if I could somehow lower the impedance... Would anyone sell a Zobel circuit pre made for this IC application? I also now think that despite being bought used, they may never have been burned in so I'm working on that...
Thanks again.
Peleon: There may be good reasons why they would pot the circuits, but I do know of one case where someone opened up a network box on a cable and found absolutely nothing but potting compound. The cable just ran right through it. (The box at the other end had a resistor of some sort in it, if memory serves.) So caveat emptor.
Speaking of MIT - I was deeply enthralled in a Clapton blues tune the other night and wham - left speaker goes dead. After some tinkering with everything, especially the speaker cable, I booted back up and it worked but the soundstage was pulling way right - the voice was dead center but drums and rythm were skewed to the right. When I twisted the network box everything centered up..must be a short or something screwed up in the box. Fortunately I have a pair of Kimber's for back up so I know it's definitely the cable. What the hell is that all about? Ever happen to anyone else?