you wont get many 4inch subwoofers as they usually start at about 8inches due to them needing size to shift air
ok i just wanted to replce the subwoofer that came with my creative p580 speakers cant i just get a woofer than
You'l have a tough time finding a 4" sub driver and even then it may not be suitable for the enclosure as mentioned, most subs start around 8" so 4" drivers are mostly used for midbass but even then their quite small its likeley that creative have comissioned a company to make 4" long throw drivers specifically for their subwoofers so finding them aftermarket may be next to impossible.
Look into the company Tang Band, the're pretty much the place to go for small speakers. I believe they had a 4" sub, although Parts Express doesn't have it.
