According to my boxmodel program, if i use a 35l box tuned @ 35hz, the -3db point is just under 35hz. That is slightly smaller than the box shown in the kit. If I model the box in the kit, the -3db point is even lower, but the driver xmax gets a little much. I know that the drivers are expensive, but after hearing a friends diy pair of speaks with Scanspeak 18w/8546 midbass's in an mtm design, I've just gotta have that midrange sound!