How to hook up a car subwoofer to your computer or home theater system

By Contributor

Updated September 28, 2017

Items you will need

  • computer power supply

  • subwoofer (in box)

  • speaker wire

  • paperclip

  • wire stripper

  • screwdriver

  • electrical tape

  • scissors

Have you taken your subwoofer out for the winter or just have a spare one and want to hook it up to your computer or home theater? Well no problem, it's really simple and surprisingly inexpensive.

First you need 12V power like in your car to power the amp so you need a cheap computer power supply (aka PSU). You could buy a 12 volt power source that's built just to output 12V power but they're about $150 on up. Ironically you can find cheap, used computer power supplies on Ebay or other sites for incredibly cheap like around $10-20 with shipping and they can supply just as much power at 12V. The only thing you have to worry about is if it provides enough power for your particular amp. See the next step for those details.

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Luckily every PSU has a large sticker on the side listing its max current ratings in amps for each voltage rail. See the attached image for an example. You're concerned with the +12V section. First find the max wattage rating of your amp. Let's say it's a 300 Watt amp. Now divide that by 12 as in 12 volts and you get 25 amps. So at 12 volts it needs 25 amps to reach max power. The example attached to this step wouldn't be sufficient with its pathetic 18 amp peak power. It's so low because they split the normal 12 volt rail into two. Most modern power supplies can supply 20+ amps at 12 volts. If you have a 600 watt amp, you're probably not going to find a power supply that can supply 50 amps for it for under $150 so just get a slightly less powerful one for a reasonable price instead. Chances are you won't be blasting your amp/sub at full volume if it's that powerful or you'll damage your house so you won't need that many amps anyway. Older power supplies tend to fail a lot and ebay sellers don't always list the max current ratings so if you want to be sure, get a cheap, brand new power supply from newegg.com. For example, the Sunbeam BKS580 is a 580 watt power supply that can push 25 amps through its 12V circuit and it's only about $40 with shipping. There are slightly weaker PSUs there too for about $25.

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Now that you have your PSU, you may have discovered that it won't turn on if it's not inside a computer. Well all you have to do is trick it. Fold out the paperclip so it's like one big arc like a narrow C shape. Or if you have wire cutters, cut it into a shorter U shape. Now stick one end in the main power connector's green wire hole and stick the other end into any black wire's hole. Then tape it in with masking tape or some other tape that will hold it in. See the attached image for an example. Once you have the paperclip in place, it thinks you've installed it in a computer and will turn on when you plug it in and flip the switch.

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MAKE SURE THE POWER SUPPLY IS UNPLUGGED AND TURNED OFF FOR THIS NEXT STEP OR YOU WILL GET SHOCKED AND POSSIBLY LIGHT SOMETHING ON FIRE! Find one of the lines with four pin, white molex connectors and then find the last connector on the chain. Cut all four wires with a scissors just before the white connector so it's just four bare wires. See the attached picture for an example of the correct connector.

Now strip the yellow wire and the black wire next to it so there's about a quarter inch of metal exposed. Wrap electrical tape around the end of the red wire and do not strip it. It won't be used and you don't want it shorting out so wrap it with several layers of electrical tape. As for the black wire next to the red one, cut about two inches of that wire off and strip both ends to make a short with the red wire even less likely and also because you need a spare 2 inch wire later. Then cover the end of the shorter black wire with electrical tape also.

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Now loosen the three power screws on your amp. They should be +, -, and REM. They are likely labeled as REM, 12V+, and GND. 12V+ is the positive terminal and GND is ground aka the negative terminal. Screw the yellow wire from the PSU into the + terminal and the black wire into the GND terminal. Then take your 2 inch spare wire you cut before and screw it into the + terminal and the REM terminal. See the attached diagram. The blue wire is actually the spare 2 inch black one you cut before, I just made it blue to distinguish it better.

After that simple setup your amp will now turn on as soon as you plug the power supply in and switch it on. The REM terminal normally receives a signal through your car's ignition so it only turns on while your car is on. But now with the REM attached to the amp's own + terminal, it will turn on whenever the power supply sends power to it. Now you need to attach the amp to the sub. You'll want to do it exactly like it was in your car. If you're bridging two channels, make sure they're bridged the same way. If you're running two subs from one amp, hook each up separately. Either way, you need some speaker cable to do it. If yours is buried under the carpet or run nicely under your back seat because your amp is far from your sub, don't rip it out. Just go to any car audio shop and buy some speaker cable. You only need to get from the amp to the sub which is like 2 feet if you put it really close and it's about $0.50/foot at most places for 18 gauge so just spend the dollar to buy some short speaker cabling. Then strip it and screw it into the audio terminals, attach it to the sub's terminals, make sure you have the + to the + and the - to the -, and that's about it for the audio hookup.

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Now your amp can power up and send the audio signals to the sub so all you need is some audio input for it. Almost all subs have red and white RCA inputs and luckily your home theater system probably has RCA outputs. So just get a two in one red and white RCA cable at walmart and plug it in and you're set. If you want to hook your sub up to your computer, you need an 1/8" headphone/speaker jack to RCA adapter. They're only a few dollars at most stores. Make sure it's long enough to reach from your computer to your amp though. See the attached picture if you don't know what the adapter looks like.

No matter what your audio source is, it's likely sending at a weak speaker level instead of line level like your car's CD player was and your amp wasn't designed to handle that. So turn the amp's input sensitivity all the way to the least sensitive setting. Now that the higher number means it's less sensitive if the knob has numbering on the outside. If your amp didn't come with a knob for that, it's a really crappy amp but there's still hope. Just turn the volume way down on whatever is sending the signal. A typical PC will need to be at about 5-10% volume to not overload the amp if it doesn't have an adjustable input sensitivity.

Now you're all set. Plug the power supply into the wall and switch it on. The amp should turn on. Then try playing a song with some bass and you should hear it coming out the sub. Make sure you start playing the song really quietly and turn it up from there until the sub is at a nice level. Play around with the equalizer and multiple channel volumes if your computer/home theater has those options until the sub is at a good volume level. Then sit back and enjoy some nice, indoor bass.

Tips

You can hook your sub up to anything that outputs sound like an ipod or a decent radio/stereo.

Warnings

Make sure that the power wires don't touch the terminal next to them on the amp or you'll create a massive short that can spark and start fires.

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