What is it?

[gjpham]

What is Passive Radiator from PartsExpress.com and what does it do ?
It is virtually look like a subwoofer but without the magnet so my guess is:
a, It has no speakerwires hooked to it.
b, It's there to obsorb the moving air from the real sub, by doing so, it's too performing as another "sub".
c,?
d, ???
http://www.partsexpress.com/webpage.cfm?&DID=7&WebPage_ID=3

[MikeyBC]

Its basically a substitute for a bass reflex port as it transmits the rear sound waves from the woofer inside the cabinet and radiates them outward to help re-enforce the bass output. Others here can give a more detailed anwer i think.