I think the search for the Holy Grail of tone is an individual one and I don't think any two setups of guitar and amp are going to be the same. For me, the overrall sound was fuller. My Vintage 30's were breaking up real fast and I was looking for a little cleaner sound out of them as I play a Tele HH and had way more distortion than I needed or wanted and opening up the back definately helped with that. Moving the opening around produced slight changes in tone also. The first time I used it at practice, I didn't say anything and right away the guys asked me what I did to my amp.What do you like about the sound with the back closed as opposed to open with that cab?