Open or closed back?

Hi, I've been using a couple of Carvin 2/12 open back speaker cabinets with my 130HD Head. I'm wanting to get some more mid's out of my sound. So, I'm thinking of turning those open backs into closed back cabinets before buying any different speakers to bring the mid's up. Has anybody tried this, did it work out for you?
Thanks, Dave.

So.. I did put backs on my cabinets and also tried the two channel amp connection trick. But no luck, my mids had left the building. Then one stormy Christmas night..
Well actually it was a warm July night, and we were playing a gig when my old guitar chord when out. I put in a fresh guitar chord and ta-da, I had my mids back..
I know this sounds nuts, and I do use high $$$ cords. But I really did noticed a difference when I changed out the cords.
That's my story and I'm stick'in to it, Dave.

I guess I better also say this all happened not to long after my orginal post. Just thought I'd up-date it. Dave.

I go through that at time with all the cords that I've made for my pedal board. I'm not exactly gentle with my stuff, though I'm not rough either. I make it work and crap does break. Went through just what you did a couple of months ago while working an outdoor thing in the town over. Sounded like crap, thin, no balls, not very loud. I'm trying to diagnose while playing (of course) and finally come down to the ONE cord that it COULDN'T be. Guess what. A wild spur was touching the case at times and it would come and go. That was the only cord that I ever bought GOOD ends for so I thought THAT one couldn't be it. Get out the dremel and grind the little sucker off and it's fine but it was wierd how it didn't blank the entire signal out, just some.

Same here, I never would have thought it was the cord being there was a signal going through it. I was lucky it finally went fooey on me and I found the solution.