It is indeed smooth. About 10db up from 110 - 10khz. I use the EQ to actually bring the mids down a touch, the boost the u know what out of the LF. Alsmot 30db in the 20hz region. Freaky eh? Somewhat less up top. Regarding your tubes, have you checked on using cardboard ones? Like the style used in paper towels? I use them for port tubes all the time, they work rather well. Just seal them up with whatever... spray paint, etc. You can calculate your volume then squish them whichever way you want, right? Plug the ends with tapered chunks of MDF using a circle cutter on your drill press... off you go!