Unfortunately, I don't think you can connect this sub-woofer without the rest of the components of the HTS3440/37 DVD Home Theater System or a related Philips home theater system. The speakers in the system are hard-wired with a colored plug that you connect to the sub-woofer. Then you need connect the inter-connect cable between the sub-woofer to the DVD Player of the system. See the wiring guide in the Quick Start Manual or the User Guide available on the product support page: https://www.usa.philips.com/c-p/HTS3440_37/divx-ultra/support
Sub-woofers that aren't part of a home theater system connect to a receiver with a digital audio RCA cable. One example is here: https://www.amazon.com/Mediabridge-ULTRA-Subwoofer-Cable-Feet/dp/B003FVYXY0
. Then the speakers also connect to the receiver.
Even if you find another Philips Home Theater system that is missing the sub-woofer, I wouldn't rule out a change in the pin arrangement for the inter-connect cable that would cause the system to fail. I can't find any sources for a replacement inter-connect cable; the part number isn't in the manual that I can find.
I wish that I had better news for you.