Part 3 Tips of finding your special subwoofer taste: Not all the subs are the same if we took out loudness or spl. Some drivers are different that others. Some driver can reproduce a 16 hz note without any distortion some drivers cant do it. Spl: some specs and information you want to look for spl will be a stiff spider since is what helps the subwoofer move without bottoming out. A flexible surround, a low weight cone to increase efficiency, a big surface area to move some air. If your going with the big boys you will have to look for higher power handling, great cooling option if you are going into high powered systems and a high power coil and a anodized coil for better thermal management. And finally on a spl sub will always be less xmax compared to a sq sub a high efficiency ration ( or spl typically good efficient subs are up to 90 dbs at 1 watt/meter) and a lil bit high Fs rating above 35hz. Sq: some specs to help you find out a good sq woofer is mainly a stiff suspension, a low Fs rating, a high xmax ( is the one of the main things u can see a woofer going lower than the other since to make a tone one octave lower than a specified it needs up to 3 times more xmax to reproduce that tone) an oversized back plate so it can allow the woofer more excursion without bottoming out, a extended pole piece to extend the linear magnetic field for the woofer, Some specs or info can be shared for both applications and are really important like a rigid frame so it can avoid unwanted resonance noise that some cheap frame make, a food Bl rating for good linear and magnetic field. There