I put the D123 in an open back cabinet.It sounds much better than in a ducted port cabinet. No boxy muddy sound. It has the open airy sound of an open baffle system, but with more bass. You still loose some extreme low end, but can always equalize. Also the peaky range of the D123( 1to5khz) is smoother. Harvey Gerst always thought the D123 was one of the best speakers JBL ever made. I wonder if he ever tryed it in an open back cabinet for HiFi use ( not guitar) He said 4 cubic ft was the best for it. I wonder what the best size is for it in an open back cabinet? It goes out to 7 khz where the GREAT JBL 077 takes over = GREAT SOUND!- RUDY