# Car Amplifier Hooked Up To Computer PSU To Power Car Subwoofers In Your House!



## xD3aDPooLx

Just some minor FYI..... on the extension cable, the black is always hot, white is the neutral and green is ground.


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## Fremish

Quote:


> Originally Posted by *xD3aDPooLx*
> 
> Just some minor FYI..... on the extension cable, the black is always hot, white is the neutral and green is ground.


Thank you for the information. The cable has no practical use, you are using it for the thick 8 guage wiring that is within to transfer the power from power supply to amp.


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## hermitmaster

That size wiring (all of it) is not sufficient for a 1000w amplifier. You need 4 gauge wire for power and ground to provide sufficient current. You also need 14 gauge minimum for speaker wire, 12 gauge would be better. PSU size in irrelevant to what size amp you hook up, the current on the rails is what you need to consider. I wouldn't try to run an amp larger than 350w off of a PC power supply.

*edit*
I mean not to offend or discredit you, but this is a potential fire hazard if you don't know what you're doing. If you draw too much current through a wire not able to support it, it can easily start a fire.


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## Fremish

Quote:


> Originally Posted by *hermitmaster*
> 
> That size wiring (all of it) is not sufficient for a 1000w amplifier. You need 4 gauge wire for power and ground to provide sufficient current. You also need 14 gauge minimum for speaker wire, 12 gauge would be better. PSU size in irrelevant to what size amp you hook up, the current on the rails is what you need to consider. I wouldn't try to run an amp larger than 350w off of a PC power supply.


You are correct that however is in the situation that you are in a car. I am running a 1000w Corsair HX to power my 1000w Kenwood amp, i've had this for about a year now and it's still going great. The rails are most the time always 12v if not 14v is the max that most amps can handle. Considering that your only using a molex connector takes out the factor of multiple rails. The wiring is plenty fine for the amp, I've never had an issue where it runs out of power or shuts off because their isn't enough.


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## hermitmaster

Quote:


> Originally Posted by *Fremish*
> 
> You are correct that however is in the situation that you are in a car. I am running a 1000w Corsair HX to power my 1000w Kenwood amp, i've had this for about a year now and it's still going great. The rails are most the time always 12v if not 14v is the max that most amps can handle. Considering that your only using a molex connector takes out the factor of multiple rails. The wiring is plenty fine for the amp, I've never had an issue where it runs out of power or shuts off because their isn't enough.


Semantics, power works the same everywhere. You've had good luck, and that's great. If you were fully loading that amp at it's rated impedance, it would be going into protection or melting wires regularly.


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## Fremish

Quote:


> Originally Posted by *hermitmaster*
> 
> Semantics, power works the same everywhere. You've had good luck, and that's great. If you were fully loading that amp at it's rated impedance, it would be going into protection or melting wires regularly.


First of all, it bottoms out the amp to max often. If it has anything with luck then my buddies are fairly lucky too. Multiple people have a setup similar to mine. Worst case scenario put another wire, but it isn't needed it works perfectly fine, It works and it's stable.


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## Fremish

Quote:


> Originally Posted by *hermitmaster*
> 
> *edit*
> I mean not to offend or discredit you, but this is a potential fire hazard if you don't know what you're doing. If you draw too much current through a wire not able to support it, it can easily start a fire.


Personally, If I thought that it would harm someones home or them I wouldn't have posted it. I have confidence that people use their brain and not do something that is considered dangerous. I have not encountered a report of an amp burning (let alone a house) from this method.


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## hermitmaster

Just out of curiosity, what model is that amp?


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## Gualichu04

Thank you for this guide.


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## Fremish

It's in my build below, but it's a Kenwood KAC-8103D


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## hermitmaster

Quote:


> Originally Posted by *Fremish*
> 
> It's in my build below, but it's a Kenwood KAC-8103D


That amp is only rated at 500w RMS at 2 ohms. 1000 watts is a peak rating. I assumed you were running an amp that was 1000w RMS. I can see a 500w amp working okay in that setup, as they generally only require 8 gauge wiring. A amp that pushes 1000w RMS will draw up 120 amps of current, where yours maxes out at around 40 amps.


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## Fremish

Quote:


> Originally Posted by *hermitmaster*
> 
> That amp is only rated at 500w RMS at 2 ohms. 1000 watts is a peak rating. I assumed you were running an amp that was 1000w RMS. I can see a 500w amp working okay in that setup, as they generally only require 8 gauge wiring. A amp that pushes 1000w RMS will draw up 120 amps of current, where yours maxes out at around 40 amps.


You are correct. But the chances of someone trying to power a 1000w (RMS) amp with a computer PSU are very low. I've ran a 2500 watt (700w RMS) on this power supply, it didn't even flinch. If people are going to go above 700w RMS (Tested) then they should know enough about subwoofers to know that they are going to need thicker wiring (The lower the gauge the thicker the wire). It is all possible to do with the correct wiring. My subwoofers are shaking my neighbors house which is 3 houses away (approx. 3,000 sq/f houses), so 500w is plenty for any in house subwoofer....


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## Fremish

Quote:


> Originally Posted by *hermitmaster*
> 
> That amp is only rated at *300*w RMS at 2 ohms. 1000 watts is a peak rating. I assumed you were running an amp that was 1000w RMS. I can see a 500w amp working okay in that setup, as they generally only require 8 gauge wiring. A amp that pushes 1000w RMS will draw up 120 amps of current, where yours maxes out at around 40 amps.


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## Overkill

This isn't worth it for the sound quality on top of numerous fire hazards you deliberately endorse.


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## hc_416

Not to be a dick but this is just not smart. In the pictures you dont have any connector, any heat warp, and elecrical tape, etc.... DOES not seem safe. You PSU WILL NOT have enougth power to power anything woth while. Why not just go online and get a real home audio amp, more than likely it will cost less. Look for adcom carver, they are not great but will suffice, I had a caver until I steped up to a sunfire 5*425 it is a five channl amp I use two for the fronts and two for the two 15 i have. Works great and all is safe. I just hope you consider you can but a home audio amp for about 100 bucks. Would be a lot easier and a lot safer.


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## Fremish

Quote:


> Originally Posted by *Overkill*
> 
> This isn't worth it for the sound quality on top of numerous fire hazards you deliberately endorse.


First of all, the sound quality is dependent on the amplifier you use and the subwoofers you are using. Fire hazards are only if you don't think about what you are doing. I've done multiple setups for people and not one person has ever had a fire issue. If you feel uncomfortable with something then don't attempt it. But sitting there making comments on something you have no experience on is mind blowing.


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## Fremish

I have electrical tape, I have all the precautions. I took them off for the photos. It's common sense to put those things on. No home amplifier could throw what the car amp puts out. I've been running it all for almost a year now and not once have I thought about something different.


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## Fremish

Quote:


> Originally Posted by *hc_416*
> 
> Not to be a dick but this is just not smart. In the pictures you dont have any connector, any heat warp, and elecrical tape, etc.... DOES not seem safe. You PSU WILL NOT have enougth power to power anything woth while. Why not just go online and get a real home audio amp, more than likely it will cost less. Look for adcom carver, they are not great but will suffice, I had a caver until I steped up to a sunfire 5*425 it is a five channl amp I use two for the fronts and two for the two 15 i have. Works great and all is safe. I just hope you consider you can but a home audio amp for about 100 bucks. Would be a lot easier and a lot safer.


In total I put $25 bucks into this system. I can probably crank my system much louder then any home amp could ever do. Not once have I ran into a fire issue. I wouldn't make a guide on something that doesn't seem safe. People who would use this guide would use their brain and think about ways to keep it safe. Fire hazard? Nah, the approprite wiring and precautions have been placed in consideration of them.


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## Overkill

Quit double and tripple posting; there is an edit button for a reason.


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## xD3aDPooLx

Quote:


> Originally Posted by *Fremish*
> 
> In total I put $25 bucks into this system. I can probably crank my system much louder then any home amp could ever do. Not once have I ran into a fire issue. I wouldn't make a guide on something that doesn't seem safe. People who would use this guide would use their brain and think about ways to keep it safe. Fire hazard? Nah, the approprite wiring and precautions have been placed in consideration of them.


Its still a fire hazard regardless of what you think. The fact that the CAR amp should be run by a battery is one factor and second your running it off a psu. If that amp or psu starts to fail, your computer, amp and speakers might or will go. The fact that you think its safe is redundant.

Putting 25 bucks into isn't worth it. invest in the proper equipment is worth it. Who cares if its louder then what some home amps and speakers do. Have you ever thought about what all the "extra" bass does to your HDD's?


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## Fremish

Quote:


> Originally Posted by *xD3aDPooLx*
> 
> Its still a fire hazard regardless of what you think. The fact that the CAR amp should be run by a battery is one factor and second your running it off a psu. If that amp or psu starts to fail, your computer, amp and speakers might or will go. The fact that you think its safe is redundant.
> Putting 25 bucks into isn't worth it. invest in the proper equipment is worth it. *Who cares if its louder then what some home amps and speakers do.* Have you ever thought about what all the "extra" bass does to your HDD's?


Honestly, if you don't think it's safe then don't do it. It's a modification to a system. If I experience complications with the setup or someone else reports an issue the post will be taken down. But until then, i'll keep the post up.

People who like bass and who find meaning in it's physical attributes think it's totally worth it.


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## OcN13

Thanks for the write up man. I have been researching this for a little bit but keep finding conflicting reports like in this thread. I have a JL 1000/1 Slash amp and a JL 13.5 W7 AE Sub. Would it be possible to power that off of a psu? Also to the people saying by a home audio amp do you have any good links? I'm just wondering b/c I can't find any for a good price. Thanks for any help.


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## Fremish

Quote:


> Originally Posted by *OcN13*
> 
> Thanks for the write up man. I have been researching this for a little bit but keep finding conflicting reports like in this thread. I have a JL 1000/1 Slash amp and a JL 13.5 W7 AE Sub. Would it be possible to power that off of a psu? Also to the people saying by a home audio amp do you have any good links? I'm just wondering b/c I can't find any for a good price. Thanks for any help.


You won't be able to power all 1000w all the time, probably around 500-700w as a peak. This is plenty for in home use. If you have a receiver you could use this plate amp if you don't want to use a car amp. Although it won't be as crips and clear as the car amp. But none the less it will still do the job.

If you do decide to use your car amp use this PSU. It's a single rail 12v that will max at 750w (75% volume on your amp) about.


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## kevmatic

I don't think there is anything unsafe at all with using a car PSU to power a car amp... However, due to the high currents involved the rewiring must be approached carefully. Any connection that's not very good will turn into a mess quickly.

The issue here is that you are likely way overestimating the power levels you, personally, are generating. Remember that your amplifier isn't really able to produce 1000w except under certain, extreme instances and even then only for a moment. That 500 watt measurement is only at 2 ohms. What Ohms are your speakers presenting to your amp?

If its 4 ohms, then your power is only going to be about 250W.... _at most._ Which, yes, is more than enough to wake neighbors with moderately efficient speakers. But then the average current is only 20 amps... in which case 16 gauge is fine. Even then, Molex connectors are only rated to 11 amps, which means to me that your average power is probably under 200 watt if you haven't cooked it. Which, again, means 16 gauge is safe.

Also remember that music is a sine wave - while instantaneous power may be high at the peaks of the sine, the average power will be much lower. Cables only really car about average power.

If your were drawing 1000W through 10 foot of 16 gauge wire, your 16 gauge wire would be dissipating over 500 watt _in the wire_. Which means it would glow. (do the math yourself: 10 foot of copper 16 gauge wire is .04 ohms... ). The issue is that your little how-to implies that its suitable for power levels it simply isn't capable of.

As for your average car amp having more power than any home receiver... it simply isn't true. Its actually easier and cheaper to make audio power with 120V than it is 12V, as a car amp has to step up the voltage, which is tougher than stepping down. The difference is that home receivers are:

A) more conservatively rated (remember your '1000W' car amp is only good for 500W.... With 2 ohm (AKA inefficient) speakers),
B) rated for 8 ohm speakers
C) usually have a lot more channels.
D) Depending on the amp, aren't designed to be subwoofer amps, which means that things like noise and THD are more important.

Thanks to modern ("PMPO") BS ratings on amplifiers, most people GROSSLY overestimate the amount of power needed to remove pictures from walls. Sub-90db sensitivity speakers don't make things better: a more efficient speaker is almost always goes further than a more powerful amp. Rumor is that the original Woodstock had 2 1800W Mackintoshs for the whole thing!


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## Fremish

Quote:


> Originally Posted by *kevmatic*
> 
> I don't think there is anything unsafe at all with using a car PSU to power a car amp... However, due to the high currents involved the rewiring must be approached carefully. Any connection that's not very good will turn into a mess quickly.
> The issue here is that you are likely way overestimating the power levels you, personally, are generating. Remember that your amplifier isn't really able to produce 1000w except under certain, extreme instances and even then only for a moment. That 500 watt measurement is only at 2 ohms. What Ohms are your speakers presenting to your amp?
> If its 4 ohms, then your power is only going to be about 250W.... _at most._ Which, yes, is more than enough to wake neighbors with moderately efficient speakers. But then the average current is only 20 amps... in which case 16 gauge is fine. Even then, Molex connectors are only rated to 11 amps, which means to me that your average power is probably under 200 watt if you haven't cooked it. Which, again, means 16 gauge is safe.
> Also remember that music is a sine wave - while instantaneous power may be high at the peaks of the sine, the average power will be much lower. Cables only really car about average power.
> If your were drawing 1000W through 10 foot of 16 gauge wire, your 16 gauge wire would be dissipating over 500 watt _in the wire_. Which means it would glow. (do the math yourself: 10 foot of copper 16 gauge wire is .04 ohms... ). The issue is that your little how-to implies that its suitable for power levels it simply isn't capable of.
> As for your average car amp having more power than any home receiver... it simply isn't true. Its actually easier and cheaper to make audio power with 120V than it is 12V, as a car amp has to step up the voltage, which is tougher than stepping down. The difference is that home receivers are:
> A) more conservatively rated (remember your '1000W' car amp is only good for 500W.... With 2 ohm (AKA inefficient) speakers),
> B) rated for 8 ohm speakers
> C) usually have a lot more channels.
> D) Depending on the amp, aren't designed to be subwoofer amps, which means that things like noise and THD are more important.
> Thanks to modern ("PMPO") BS ratings on amplifiers, most people GROSSLY overestimate the amount of power needed to remove pictures from walls. Sub-90db sensitivity speakers don't make things better: a more efficient speaker is almost always goes further than a more powerful amp. Rumor is that the original Woodstock had 2 1800W Mackintoshs for the whole thing!


So? Are you supporting or shooting down? I'm confused ;3


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## kevmatic

Not everything is so black and white! I was hoping I was helping each side understand the other's point of view. What you are recommending is safe if done right.

I actually had a 12v PSU car audio amplifier for a while in my home, and it was fine. There's absolutely no reason why it can't work and work... OK.... But you seem to have some misconceptions that others are jumping on. Rightfully so, to an extent: Trying to draw 1000W, or any more than 130W, in the way you described is not a good idea. To do more, you need to use more wires off the PSU and a heavier extension cord. You're probably not drawing more than 130, honestly. Its tough to know for sure without an ammeter. You're PROBABLY OK, but if you really run at max power for an extended period of time, something will likely get hot. You don't have a lot of safety margin. Throw a 20 or 25A, slow-blow fuse in line with your hookup near the PSU and then you're good to go.

Really, you should read up and _understand_ electricity basics before you deal with such large currents. Experimenting with stuff is fine, but a 1000W PSU will generate about as much current as your house uses. If that doesn't make sense then you really should read up!

Say you hook a single rail 1000W PSU up to something 12v with a 15 foot, 16 gauge cord. If the far end of it is shorted, it will turn into a pile of goo before the PSU will trip off, likely starting a fire. Its simple math with Ohm's law! That's why its important to add warnings for stuff like this. If you want me to explain the math, I suppose I can.

Bottom line, again, *The issue is that your little how-to implies that its suitable for power levels it simply isn't capable of.*


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## Fremish

Quote:


> Originally Posted by *kevmatic*
> 
> Not everything is so black and white! I was hoping I was helping each side understand the other's point of view. What you are recommending is safe if done right.
> I actually had a 12v PSU car audio amplifier for a while in my home, and it was fine. There's absolutely no reason why it can't work and work... OK.... But you seem to have some misconceptions that others are jumping on. Rightfully so, to an extent: Trying to draw 1000W, or any more than 130W, in the way you described is not a good idea. To do more, you need to use more wires off the PSU and a heavier extension cord. You're probably not drawing more than 130, honestly. Its tough to know for sure without an ammeter. You're PROBABLY OK, but if you really run at max power for an extended period of time, something will likely get hot. You don't have a lot of safety margin. Throw a 20 or 25A, slow-blow fuse in line with your hookup near the PSU and then you're good to go.
> Really, you should read up and _understand_ electricity basics before you deal with such large currents. Experimenting with stuff is fine, but a 1000W PSU will generate about as much current as your house uses. If that doesn't make sense then you really should read up!
> Say you hook a single rail 1000W PSU up to something 12v with a 15 foot, 16 gauge cord. If the far end of it is shorted, it will turn into a pile of goo before the PSU will trip off, likely starting a fire. Its simple math with Ohm's law! That's why its important to add warnings for stuff like this. If you want me to explain the math, I suppose I can.
> Bottom line, again, *The issue is that your little how-to implies that its suitable for power levels it simply isn't capable of.*


I see what you mean... So correct me if i'm wrong. But I could run a 1000w amp off a 500w PSU with the correct wiring for the wattage that's going through. my amplifier is only 300w (RMS) So it's not that much power it's pulling. 1000w is peak. But yeah...


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## ZoomThruPoom

Did something like this back in my teenage years, (18/19), when I was really into the car audio.

A system in my car wasn't enough. Needed alot of boom in my home system, too. Or so I thought at the time.

Used two 12" Orion XTR DVC (500 watts RMS) with Fosgate amp. Powered by a deep cycle marine battery on a charger.

Grounded the amp on the house piping. Used mostly 12 gauge wiring all around. Except 4 gauge on the battery I think.

Never had issues with anything heating up, or fires, and I ran this setup for about two years.

Although I don't think I ever used the system more than three hours at a time.

Not saying it is totally safe. Use care all the time.

Two Infinity 15" 4way loudspeakers, two Infinity bookshelves for rear channel, a center channel, and the two 12" Orion's with Fosgate amp on a Pioneer receiver.

Needless to say I had too much boom. But my friends and neighbors loved it. Had wires hidden all over my room. Along with a hidden battery and charger.

The thing is after spending on a deep cycle battery, switches ( so I didn't have to unplug anything when not in use), wiring and connectors and fuses, I was not that far off from affording a plate amp.

Build your own box, insulate it, then add your sub (car sub will work great for this), and a properly matched plate amp.

It will take up less space, look better overall, be faster to assemble, easier to handle and move, be safer, and take less materials to put together.

And might even sound better.

Check out Dayton Audio.


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## Fremish

Quote:


> Originally Posted by *ZoomThruPoom*
> 
> *Check out Dayton Audio*.


That's a pitty, your telling people to go out and spend money on something that sounds like crap they have a loud hiss that turns into a rubbing noise (Not the sub, checked it already). Dayton can't make products for the life of them...they work but to my needs they don't sound good.. The products they sell are not recommended by Audiophiles EVERYWHERE.


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## ZoomThruPoom

Funny, coming from someone who has that rigged of a setup and suggesting others to do it as well, would really know what crap is.


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## Fremish

Quote:


> Originally Posted by *ZoomThruPoom*
> 
> Funny, coming from someone who has that rigged of a setup and suggesting others to do it as well, would really know what crap is.


157 S Blackcrater ave.
Sisters, Oregon

Come here and sit in my chair. You sit there and tell me that solid bass hit isn't perfect. I would like you to sit in my chair.


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## ZoomThruPoom

Ahh, that box you have sure looks audiophile. How many types of wood is that?

I'm sure your sound is fine for your ears.

And that is what matters most. Not what I think it should sound like.

I'm also not saying what you recommend is unsafe, or WOULDN'T sound good.

I'm saying it is not practical, and it is also not the best way to go about powering car sub woofers inside a home.

Not a bad method I guess if you are broke.


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## Fremish

Quote:


> Originally Posted by *ZoomThruPoom*
> 
> Ahh, that box you have sure looks audiophile. How many types of wood is that?
> I'm sure your sound is fine for your ears.
> And that is what matters most. Not what I think it should sound like.
> I'm also not saying what you recommend is unsafe, or WOULDN'T sound good.
> I'm saying it is not practical, and it is also not the best way to go about powering car sub woofers inside a home.
> Not a bad method I guess if you are broke.


Lol...Money is no object...The box is made out of cedar and pressboard...Cear back front and bottom. What do you mean the sound is fine for my ears? subwoofer's generate too low of a nose to make you go deaf. and The sound is perfect.


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## OcN13

If you have quality amp then they don't bs the wattage.







Yes you need thicker wiring than posted for RMS ratings and not PEAK.


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## d3vour3r

Quote:


> Originally Posted by *Fremish*
> 
> Lol...Money is no object...The box is made out of cedar and pressboard...Cear back front and bottom. What do you mean the sound is fine for my ears? *subwoofer's generate too low of a nose to make you go deaf*. and The sound is perfect.


wut? low freq noise can and will damage ur ear drums if the amplitude aka volume/power is large enough. its the pressure it creates (*dB).

your method is a great one for people with audio gear lying around as well as an old psu that is half decent.

alot of very valid points are made in this thread by people who obviously know more about basic electronics then you so dont shut them down and maybe take their info on board to refine your method. Yeh sure your method works, but the sound quality is based on what you think is good quality, which may be a different opinion to what others think. Sure these subs kick ur ass and are powerful, but thats not what its all about.

As long as people understand that it is not wise to strap a high powered amp to a mediocre PSU this is a great way to get more life and functionality out of old stereo gear. Just make sure you practice good and safe wiring and understand the risks.


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## Face76

Or just sell everything on Craigslist, buy a decent PA amp(Crown, etc...) for a few hundred dollars, and not worry about burning your parent's house down. http://www.zzounds.com/item--CWNXLS1500


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## kevmatic

Quote:


> Originally Posted by *Fremish*
> 
> I see what you mean... So correct me if i'm wrong. But I could run a 1000w amp off a 500w PSU with the correct wiring for the wattage that's going through. my amplifier is only 300w (RMS) So it's not that much power it's pulling. 1000w is peak. But yeah...


Well, you can't run a 1000w RMS amp off of a 500W PSU. no matter what wiring you have. If the amplifier is actually capable of 1000W, that is: A watt is a unit of power, can you can't just "conjure" that extra 500W from the wiring! If you did actually get use a 1000W amp and a corresponding speaker array for it (no single cone can handle that, don't care about marketing BS), you'd be shocked at the size and power. It's almost 1.5 horsepower, and is an IMMENSE amount of heat. Imagine sticking a 900W heater in your sub box (speakers are almost never more than 10% efficient).... It would roast the speaker and the box!

Chances are, your amplifier has never produced 1000W, even for a second.

Peak ratings are completely useless marketing numbers that can't be used to compare anything to anything, even within a manufacturer. Even the RMS value amplifiers give can have quite a bit of "fudge" to it, actually. Such is deceptive marketing today... But RMS is certainly better than peak.

I still recommend adding a fuse to your setup. For 16 gauge wire, I recommend a 25 amp fuse or so, right after the molex. Then, keep an eye on that molex. If it looks brown or charred (and it very well might!) quit using it and ask for help here. Remember that its only rated for 132W (11A), and often times, THAT's generous. They're obsolete for a reason.

Also, your method is only cheaper if you have the stuff.... To get 1000W like that crown above is rated, you'd need a $200 PSU and at least a $400 car amp... And even then, you'd only get that wattage into 2 ohms, which sucks. I can't even find a car amp that'll do 1000W into 8 ohms!


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## CL3P20

How do you properly ground the AMP .. when indoors?









**Are you actually grounding through the PSU? If so.. that seems to me it would be a bad source of noise. I would test for actual voltage and current draw using a ground through the PSU, and then a separate one to actual ground [that is of proper dimension]. Maybe this grounding is not an issue with your low power... but grounding through the PSU seems like a 'red flag' to me from previous experience with car audio gear.


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## kevmatic

Quote:


> Originally Posted by *CL3P20*
> 
> How do you properly ground the AMP .. when indoors?
> 
> 
> 
> 
> 
> 
> 
> 
> 
> **Are you actually grounding through the PSU? If so.. that seems to me it would be a bad source of noise. I would test for actual voltage and current draw using a ground through the PSU, and then a separate one to actual ground [that is of proper dimension]. Maybe this grounding is not an issue with your low power... but grounding through the PSU seems like a 'red flag' to me from previous experience with car audio gear.


Tons of electricity misconceptions around...

How do you ground your car amp.... When the car its in is sitting on rubber tires?







Not to mention, asphalt isn't electrically conductive....

"Electrical Ground" means "the reference 0 voltage." On a vehicle, its the leg of the battery that's connected to the car body, establishing a car-wide zero point. If you look at the battery cables, the negative on in your car will run to the engine block, so its negative ground. That's why "grounding" on a car means "hook a wire to a metal surface on the car body." You're basically using the car itself as a giant negative wire.

Same thing for a computer: the case is the ground, but it also happens to be connected to earth ground via house wiring ("_Earth Ground Referenced_"). You could omit the negative wire on your hard drive and ground it car-style.

Grounding the amp through an earth ground would actually make the noise worse because you'd form a very long return path and probably a ground loop...And you'd have to pound a peg into the ground or put a wire on your water pipes or something lame like that.

http://en.wikipedia.org/wiki/Ground_(electricity)


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## ma8ashl

Hey I have something like this set up to my amp powering 2 12's i have a 400 watt power suppy i was wondering if i could hook both psu's up to the amp would that work and how would i do it works off of one but i can turn the amp up much it draws to much power and distors it..


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## givmedew

This is just a plain bad idea... there will be a lot of wasted energy in heat. I would recommend that if you really plan on keeping these in your home that you just sell the car amplifier and the capacitor and you purchase a d-class home amplifier.

As for hooking them up together... I am going to guess it needs to be a parallel connection but I am no electrical engineer and I do not know what could happen if you do this. I am guessing it will be fine but that is a guess.

Another thing to keep in mind is does your PSU(s) have single or multiple 12v rails... The reason I ask is it is my understanding that with multiple rails you will not be able to get 100% of the 12v power off of just one rail therefore your 400w PSU may be much less than that.


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## kevmatic

You won't loose as much power to heat as you'd think....

Hooking up 2 PSUs in parallel will almost certainly not work, however. There's quite a bit of variance between power supply voltages, so the one with the higher voltage (even if its only .1v higher) will bear most or all of the load. You'd need load balancing resistors, and since the power supplies are regulated, they'd have to be pretty high resistance....


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## givmedew

You loose whatever energy the PSU looses (efficiency) plus whatever the amplifier normally looses. If the amp is D-Class it isn't going to be that big of a loss if it is not a D-Class amp then there is no way he can power it with a small PSU.

You can probably google the average efficiency for a specific amplifier technology.

Either way the power supply inside a descent amplifier is usually the size of a small computer supply.

I don't think I agree with what is said about mixing the 2 power supplies...

Although I don't recommend doing it I don't think the reason you offer is the reason you don't want to do it.

But I have to say I am not an electrical engineer so I would not know for sure.

Either way I'd recommend against this.

I have some (a lot) of experience with car audio and I have a lot of experience setting up a display system that ran several head units and could switch between several sources, amplifiers, speakers, and subwoofers. The power supply we used was HUGE and I do mean huge and most likely cost close to or possibly well over $1000. We used 2 of them one (smaller one) to run all of the head units (they always stayed on) and 1 (the huge one) to run only the 2 selected amplifiers (speaker and sub) and even when running the speakers off the head unit (smaller power supply) the bigger sub amps could really dip the voltage down.

Also your car amplifier is designed to run at 14.4v not 12v and it will create less power at 12v and when it hits it will drop the voltage which a computer supply may not be able to handle.

Hook a multimeter up to the supply and see how low it drops. If you are getting to 11v or lower I would probably abandon this venture. The larger amplifies would dip a 50-80LB 12V only power supply down to 11-11.5 the PSU would shut down somewhere below that.

You can buy a used home audio amplifier for a decent price by the way.

I am def no know it all especially when it comes down to the real rules. I do know that when we needed to use 2 power supplies together to power one display (the lucky stores did this) we had to use a very large very expensive diode on each supply which in my understanding would keep the power from one power supply to enter into the other power supply.

A diode has nothing to do with a "load balancing resistor".

Alas I was only trained in the basics plus what I learned in school which again was the basics.

My guess is diodes would allow you to do this but the higher current ones cost more. Again I don't recommend any of this... It isn't even cost effective and won't save you a lot compared to selling what you have and getting the correct gear. Plus if you have multiple 12v rails in the PSU you will not be able to get all the power from the PSU... If I am correct about the diodes and you had multiple rails you would need multiple diodes for one PSU to get all of the rails.

I use a Infinity Kapa Perfect DVQ for my home sub I have (2) Alpine V12 M500 D-Class amplifiers that used to run that sub when it was in my car. I wouldn't dare use them in my home unless I built my own PSU based off a large transformer. Even then you are better off just selling the car stuff and buying home stuff.

*If you really want to pursue this just say so and I do have someone I can ask that can definitively answer the question.*


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## kevmatic

Well, remember that the efficiency of the power supply isn't factored into its rating- a 400W, 80% efficient power supply will still supply 400W. I doubt the heat matters much.

I obviously don't know the specifics of the power supplies you were using, but linear power supplies have an easier time sharing loads. This is even more true if the supplies aren't regulated or have an adjust so that they could be matched more closely.

If they were "Bench" power supplies (typically ones that have voltmeters on the face), they could have current limiters, where they automatically drop the voltage after the current gets too high. This would allow the power supplies to work together very very well- as the load on one gets too high, its voltage comes down and the other one kicks in. Now that I reflect on it, this is probably what you were using.

But computer PSUs don't have any of that. What do they have is a LOT of variance between models in output voltage, so I feel my point stands.

All the diode does is prevent one power supply from "dumping" power into the other. Diode voltage drop is fixed, so they are useless as load balancers. Since, as you mentioned, the voltage of a computer PSU is so low to begin with, load balancing resistors and diodes would only make things worse.

tl;dr: ganging multiple computer PSUs is still a bad idea.


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## ma8ashl

Well Im running the punchs the other one are not hooked up. and i keep the amp most of the way down and use my eq to tune. there DVC i have them wired at 1 ohm and briged. and it hit nice it actualy gets distored because its only a 400 watt psu but i tryed both and everything is fine so far. my efx's are mint so i just beat on the punchs. no problems use it everyday.


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## ma8ashl

If i feel like hooked them both up ill go get 2 more recivers and put 2 on 1 and 2 on the other. ive always just used recivers and eqs. and my **** bangggg. ether way if it works i aint complaining.


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## ramicio

I don't get the negativity and people saying crap about burning down a house.


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## kevmatic

Who said that?

I'm not even sure what his last post is saying, though- I can't quite figure it out.


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## hatrix216

Quote:


> Originally Posted by *kevmatic*
> 
> Well, you can't run a 1000w RMS amp off of a 500W PSU. no matter what wiring you have. If the amplifier is actually capable of 1000W, that is: A watt is a unit of power, can you can't just "conjure" that extra 500W from the wiring! If you did actually get use a 1000W amp and a corresponding speaker array for it (no single cone can handle that, don't care about marketing BS), you'd be shocked at the size and power. It's almost 1.5 horsepower, and is an IMMENSE amount of heat. Imagine sticking a 900W heater in your sub box (speakers are almost never more than 10% efficient).... It would roast the speaker and the box!
> 
> Chances are, your amplifier has never produced 1000W, even for a second.


While you seem to know good info on electricity, I don't think you're super knowledgeable in car audio.

I could list of tons of subs that easily handle over 1000 watts. And a true 1000 watts of power.

My Fi SSD 18", 2 ohm DVC, is rated at 800 watts and sees 1200+watts every day. The amplifier supplying the power is a Sundown Audio SAX-1200D. Their numbers are typically underrated, as proven by tons of benches.

Wired at 1 ohm, it's definitely seeing 1200 watts + when it calls for it. Of course I'm not saying it's constantly seeing 1200 watts every second its playing, but it definitely does at times.

Current model of the SSD, specs:


Spoiler: Warning: Spoiler!



Fs: 27.6 Hz | 27.6 Hz
Re: 0.7 Ohms/coil | 1.4 Ohms/coil
Qms: 9.56 | 9.56
Qes: .47 | .47
Qts: .45 | .45
Mms:338g | 338g
Cms: 0.098mm/N | 0.098mm/N
Sd: 1210cm^2 | 1210cm^2
Vas: 201.4 l | 201.4 l
Spl: 91.4dB 1W/1m | 91.4dB 1W/1m
Bl: 13.1 N/A | 18.7 N/A
Xmax: 20mm
Rms: 1000W



The SSD isn't even their best sub. The Fi SP4 can see 3000watts easy. No these aren't BS ratings, nor are the amps "peak" power (which is a nonsense term that is used by ****ty amp manufacturers).

Old thread I know, but I felt some people should know that there is real quality car audio out their plenty capable of high power.


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## givmedew

EDIT

I misunderstood the above!

MY bad


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## hatrix216

I really can't even tell if you are addressing me, cause just about all of your post seems to be directed at someone else.

I wasn't bragging about anything, nor did I post a picture of anything. I was stating an example of a subwoofer more than capable of high power, and an amp that pushes out said power.

I had multiple reasons why I necrod this thread. It came up on the first page of a search and needed to be corrected. Anyways, the guy who posted the actual picture necrod the thread when it was 1 year old or something.

This thread is full of misinformation. There is nothing wrong with using an ATX power supply to power a car audio amp, as long as the necessary precautions are taken.

All 12v lines should be fused with the appropriate amperage. Any exposed wires should be cleaned up. Never use a PSU incapable of delivering the amount of amperage draw required by the amplifier. Use come common sense when dealing with electrical.

If all of that is followed, you won't have any problems. Your friends 12 years ago are no comparison, as any PSU 12 years ago wasn't near the specifications of today's higher end PSUs.

Yes, obviously combining two different PSUs is a dump idea (even the same PSU model would be bad). I'm not recommending that or saying it's safe. A single PSU is fine.

And of course efficiency varies on amplifiers. However, anybody stating most amplifiers are only 10-20% (someone back in the beginning of the thread I believe) is pretty wrong. Both amplifiers I have are >85% @ 4 ohms. Yes, efficiency reduces with lest resistance, but that should be expected.

EDIT:

Ok, thank you for the edit. Glad you understand. I'm still gonna leave this post as I addressed a bit more of the misinformation in this thread anyways. Nothing against you.


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## givmedew

Those amps that you have that are 85% efficient are D-Class... the other person is correct about a/b class amplifiers although not for sure but on an a/b probably a little better than just 10-20 but my non digital class amplifiers doubled as heaters so it isn't necessarily incorrect... but nearly all sub amplifiers have been D-Class since the early 2000s. So you are correct in saying that the other person is incorrect.

12 years ago the my friends where using 12V PSUs. I think one person did try a computer PSU but yes it was horrible. Efficiency has gone up and so has the size of computer PSUs. Quality 12v dedicated PSUs still cost hundreds of dollars BUT they don't have to be as big as they used to because the amount of heat per watt of audio that the amplifier puts out is lower. If you look up 12v power supply and look at the ones that can put out 500-1000w they are multiple hundreds of dollars. They essentially have a non audio oriented crappy version of what an AC home amplifier would have in them. They can also only power 1 or 2 amplifiers. They do not use a high end toroidal transformer and the capacitors are not designed for such huge spikes.

Want to power car subwoofers in your home? Sell the car amp and buy a d-class subwoofer amplifier that is designed for home use. Want to use a car deck... go ahead a cheap $50 12V PSU will be fine in most cases.

Nothing wrong with putting a car subwoofer in a home. I use an Infinity Kappa Perfect DVQ that I have had for almost 10yrs. Only difference is it is hooked up to a rack mount B+K Amplifier not some crazy contraption.

Also I totaled misread your post and kind of mixed it in with someone else's and also for some reason I thought this thread was about the guy who was trying to join 2 power supplies together because it has been so long since I received an update about it. I totally forgot the actual OP wasn't even doing that.

I am sorry and I really didn't mean to offend you... I tried to ninja edit the post as fast as I could and I truly feel ashamed for misunderstanding what was being written so badly and then on top of it complained about necroing a post. I really thought you where necroing a thread started by the guy who tried to join 2 PSUs together and I was already like REALLY!

So I want to make it clear... I do not disagree with anything that YOU said...


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## hatrix216

Yea as I said, all good man. I figured you had me mixed up with someone else in the thread.

And yes, I'm speaking strictly class D amplifiers for subwoofer use.

The easiest way to power any subwoofer in a home audio application is to simply by a good plate amp or rack mount amplifier (or even a non rack mount, but something meant to handle low ohm loads).

I have a Sundown Audio E8v3 in my room in a customer ported box. It's rated at 300 watts RMS, however my old plate amp took a **** so I now have to buy a new one. Great thing is the plate amp I want is $120 and produces exactly the 300 watts I need. Just haven't got the money to spend on it yet lol.

In the mean time I've temporarily used a Rockford Fosgate P500-2 amp to power it. Works as needed. And is my solution for powering my 18" at a party in a few days since I no longer have a working plate amp.

Doesn't get much cleaner than fitting a nice plate amp inside your sub box (accounting for any displacement of course) and plugging it right into the wall.


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## givmedew

The huge huge benefit to a plate amp over a rack mount is the plate amps usually have cross-overs and high level inputs... I am having a nightmare of a time with my UMC-200. The room correction testing plays full range audio out of the sub. Then it sets the x-over to 200HZ!!!! sounds like POOOH.

Then I can go in fix it and what not but still POOH...

Also there are some issues with playing 2CH sources and having the UMC-200 send audio to the subwoofer... which is why typically I hook the LFE to the subwoofer and then run high level inputs from the left and right. That way the sub gets the lows form the left and right and the LFE.

Unfortunately with a full range rack mount I have neither a x-over nor high level inputs. It ends up being fine in the end but a pain at first... the firmware update to the UMC-200 fixed it where the audio can be easily sent to the subwoofer in 2CH mode without turning on a high-pass x-over on the fronts.

I will end up buying a plate amp someday (when I rebuild the enclosure) but until then...

Promise not to laugh but this is my enclosure LOL









If you wonder why on earth the sub is inverted believe me it needs to be. That enclosure was "re-purposed" and once you add the displacement of the subwoofer it is nowhere near big enough. When I make a new enclosure I will do a better job but I don't exactly have a workshop in my condo nor a basement!


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## kevmatic

Quote:


> Originally Posted by *hatrix216*
> 
> The SSD isn't even their best sub. The Fi SP4 can see 3000watts easy. No these aren't BS ratings, nor are the amps "peak" power (which is a nonsense term that is used by ****ty amp manufacturers).


For a second or two, sure. That Fi SP4 also has a beyond awful sensitivity rating. 86db! That's about .7-1% efficient. I challenge you to put 55V, 55A into that thing in an enclosure and see what happens over a minute or two. Where does that 2900+ watts of heat the speaker is generating go?

If you were to get 93db (which is decent, but still not great) speakers, you could make the same amount of sound with 750 watt, which a LOT more manageable.

So, I fail to understand all those ultra-low resistance speaker coils. Seems like a waste. Wait, no. Not 'seems.' Is a waste. I've personally shaken pictures off of walls with a 2x47W Pioneer SX-780. Right now my homemade LM1875 chipamp makes enough racket for me (been itchin' to build an LM3886 one, though).

Anyway, I wonder where the post that says that amplifiers are only 10-20% efficient is. I can't find it. Who said that? I think you might have been misreading one of my earlier posts where I said _speakers_ are almost never more than 10% efficient.


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## lovecat48519

You know it is easier to simply buy a cheap power supplie on ebay? I got 1 for my amp on ebay for $20 (free shipping) It's just a simple Chinese power supplie but it runs my amp with no issues.


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## FlailScHLAMP

I applaud the attempt.

however, this seems to be an out of the way DIY. if you have the parts and don't need to put anything into it.. COOL..

coming from a career in Pro Audio, i know there are easier and safer ways of doing this. This is not something i would let
a friend use, at-least in the way it looks in the OP.

Build a dedicated box for this.. keep all the splices and wire contained. much safer that way.

I just don't understand the need for so much power for your bass. Low wattage Class A amp and a single middle sensitivity bass driver, or even a bridged 100W stereo referance amp, with a pair of 10 drivers.
is more then anyone should need by their computer. These configs will give you enough bass that if you use a mouse with DPI/cpi greater then 1800
you cursor never sits still.. flying all over your screen when the bass gets intense.


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## ramicio

Power like that is just absurd and pointless. Why purposely create a inefficient speaker? Something of only a few watts can deliver all of the sound you need, at much lower distortion (transparently). That kind of power is only useful for squeezing out every last bit of decibel. A sound system shouldn't even need 10 watts RMS per speaker. Why we have 100+ watts per channel, I don't know. A surround sound receiver could be the size of a modem or router, but instead, they're gigantic, bulky pieces of heat-generating crap.

You don't need to put a few between an ATX power supply and a subwoofer amplifier. The power supply has its own protections, and the amplifier has a fuse in it. You only fuse car wiring because it runs from the from battery to the back, so there is a chance the wire insulation could be pierced and cause a short. If you cause a short on a computer power supply, it will shut off. All you need to do is disconnect its power, by either unplugging it or turning off its switch, and it will work again.


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