I recently upgraded my JL Audio 12W3 to a JL Audio 12W6. The 12W3 was in a ported box built by a local shop. The dimensions are 17.5"x13"x16" (WxHxD) and the port is 2.5" wide 11.5" high and 11.75" deep. With my amplifier settings all set at stock still and my head unit at 0 for subwoofer EQ it was producing great bass. When I purchased the 12W6 I decided I would make my own box and build it to the JL recomended specs which is 26.25"x14"x13" (WxHxD), and the port dimensions are 1.5" wide, 12.5" high, and 10.75" deep with a 16" extension. With this sub I am using factory settings on the amplifier, but to produce the same bass as the 12W3 did I have to turn the subwoofer EQ up to +15 on the head unit. I do not see why this is, seeing as it is a better subwoofer in a box built to JL's specs, but many people say it is the port width and I somewhat agree. Can anyone out there confirm this for me and possibly help me design a box that brings the 12W6 to its full potential. I have been searching the internet for a program that will design a box for me, but I have had no luck.