Yeah, most subs will loosen a bit after a few hours of playing time. The surround and spider are a bit stiff when new. You can either play music for a few hours or play a 45-60Hz test tone through it for a little while. It also depends on the suspension material and temperature. Rubber surrounds in cold will obviously be stiffer than when it is warm.
The box size plays a big part as well. Manufacturers usually recommend a range of box sizes, but I find most recommendations to be a bit on the small side. Smaller boxes will play tighter and fit more easily, but you may want a larger box for more output. Plus, each sub's specs can help determine whether it is more suited for a ported or sealed box. A good program for box building is WinISD. Once you enter the driver's T/S parameters, it will recommend a box type and size. You can tweak it for the sound you want from there. The basic program is free: http://www.linearteam.dk/default.aspx?pageid=winisd
The box size plays a big part as well. Manufacturers usually recommend a range of box sizes, but I find most recommendations to be a bit on the small side. Smaller boxes will play tighter and fit more easily, but you may want a larger box for more output. Plus, each sub's specs can help determine whether it is more suited for a ported or sealed box. A good program for box building is WinISD. Once you enter the driver's T/S parameters, it will recommend a box type and size. You can tweak it for the sound you want from there. The basic program is free: http://www.linearteam.dk/default.aspx?pageid=winisd
