There are two ways to test a sub IMO:
1) Use the RCA left/right connectors (red and white) and play MP3 test tones.
2) Connect the sub (Left/LFE) to a dedicated LFE/subwoofer channel of an AVR.
Refer to Figure 3 of the manual.
To do Method 1 you need 1) Test Tones 2) iPod or any other digital player 3) 3.5mm to RCA jack for the iPod/digital player. You can download Test Tones from the internet, I use Bass Mechanic. CAUTION: Please turn the volume on the sub all the way down, before you hit play on your iPod and slowly raise the volume to a comfortable level.
Method 1 will only show that the sub is working, you will see/feel the cone move. Some test tone have an intro voice that tells you what tone is about to play, you will NOT hear (or it would be very muffled) this when you connect directly to a sub (you will hear it when you play the MP3 file on your computer). The RW-12D is rated on paper for 24-120Hz....so theoretically you would hear/feel 20-30hz tone and beyond but not hear/feel anything from a 10-20hz tone even at max volume.
Method 2 is what you would actually use the sub as, so you either need to beg/borrow an AVR and set it up in your place or haul your 49lb sub to a friend's house who has at least a 5.1 set up and plug in your sub instead of his/her sub and play your favorite demo track like War of the Worlds/Tron etc. CAUTION: Please turn the volume on the sub all the way down, before you hit play on your demo clip.
This is what I have done in the past...others might have more creative solutions.