I am thinking about building a guitar cab loaded with a single 15" EV SRO speaker. Cabinet will be used for guitar only and a test bed for everything from my little Blackstar HT1 to my Marshall JTM45. Any tips on determining optimal cab size? I also would like to hear opinions on whether I should go open, or closed back in the design. I'm no speaker engineer, but I'm sure you have to have a certain volume of cabinet space to support the cone that will enhance the frequencies that a guitar will produce.