Passive Subwoofer

Passive Subwoofer

can I use a active (powered) sub woofer on a Home Theater system that has a passive subwoofer?

The active subwoofer has a rca connector and a power cord and the subwoofer output on the stereo has the speaker wire. can you interchange the two?

I have no idea what onegrtch is talking about. Some active (powered) subwoofers have speaker inputs for use with systems that do not have a preamp level sub output such as yours. The impedance of these inputs will be in the K-ohms and it has nothing to do with the impedance capability of your receiver. Your receiver will typically be capable of a few ohms so it will not even know the several thousand ohm input of the active subwoofer is there. These subwoofers will also have speaker outputs which are just a pass through of the speaker inputs. If your sub is like this then you simply connect your receivers sub speaker output to either of the speaker inputs on the sub and you do not use the other speaker connections on the sub.

If your sub has only the preamp output then it gets complicated. It can be done but you will need to build a simple circuit with resistors. Without knowing the gain of your sub the exact resistor values needed are unknown. What you need is a voltage divider with a total impedance of about 8 ohms give or take a couple ohms. An 8 ohm and a 1 ohm might be a good starting point. The two would be in series with the 1 ohm at the ground end. You would tap off the top of the 1 ohm and ground to go to your sub's preamp input. You might have to experiment some to determine the best values. If the signal is too strong you could put another 1 ohm in parallel with the first making your voltage divider become 8 in series with 1/2. If the signal is too weak then replace the 1 ohm with a 2 or larger until you get optimum results. If you have no idea what I'm talking about then don't try this at home. Or at least first study the concept of resistor network voltage dividers by googling it before you try. And then recognize that the voltage coming off your sub speaker output is too strong and that you are trying to reduce it while maintaining an appropriate impedance load on the sub output.