Car audio at home?

Discussion in 'The Projects Forum' started by LaZyLuke, Sep 27, 2009.

  1. LaZyLuke

    Thread Starter Active Member

    May 10, 2009
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    Hi everyone.
    I have a question on how to properly hook up a car audio system at home. I found many links on google but I don't really trust them since many of them differ with the information provided so i turned to you guys since I found this forum the most reliable source lately ;]. So to start off:

    I have unlimited access to any amount of computer power supplies (most of them will be old from old computers) and I have heard that they can be hooked up in parallel to provide enough amperage for any system- is that correct? And how exactly do i hook them up? (which wires to connect and how to I turn them on etc)

    I will be using a cd deck with a set of stock speakers + one sub woofer (600W rms). And now- I know that this system will be using around 60 amps all together (80 at very most)- now since I have access to many power supplies- Is it safer to provide more amps then I need? or could that will be harmful to the amplifiers and the head unit?

    Also the optimum voltage for the car audio is 13.6-14volts.... Now the power supplies provide 12V max- I read one article on how to mod a powers supplies to get 13.6 volts but the person written it with respect to one particular model with specific references to the circuit elements (labels on the circuit board)- Can anyone guide me through a process of aether modding the power supplies or just a way of connecting them to get a 13.6v?

    Please help me with this project as I am currently on a tight budged since I am at school and all the stuff I will be using are practically free to me- so option of buying a house stereo is really out of question :] and I wont attempt this without a source of information that i can trust (that will be you guys ;]- I got help from you before and it was very helpful and whats important reliable!). Any help will be appreciated. Thank You in advance.
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    A car radio can work fine with the 12V output of a PC power supply.

    What is the wattage of the speakers?

    For the subwoofer you will need a car audio amplifier to run it from 12V.
     
  3. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    A Car radio might work fine from 12 volts from a PC power supply, but an amp to drive a 600W RMS woofer??? (that would have to be at least a 1200watt amp, single channel, or 800W with dual bridgeable channels) Probably not unless you install some stiffening capacitors on your amp power lines to reduce the VD (voltage drop, in vehicles you will see this in the headlights and interior lights, they would dim when deep bass hits.)

    Old PC power supplies wont work that well either, unless they were 500w or more with atleast 16 to 18 amp output capabilities on the 12 volt rail ( the higher the better bass response you will get from it, I have seen some putting out 30 to 32 amps for each rail.), with multiple rail outputs, not just one for all 12 volt leads.

    I tried to power an Xbox360 off of an 450W XT power Supply that only had around 12 amps load on the 12 volt rail, and I have never heard so many things popping like popcorn inside a pc power suplly before!! and the Smoke! The XBox360 requires at least 16 to 18 amps to boot up, I am pretty sure an amplifier requires a lot more constant current when you got the music cranked up!

    Are your power supplies AT or XT ? I ask this so I can tell you how to turn them on, and you did say they were old so I am assuming old out of AT style PC's??

    Just my .02
     
  4. LaZyLuke

    Thread Starter Active Member

    May 10, 2009
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    lol... ok guys..... I have the whole system- meaning head unit, components, 6X9, sub and an amplifier for the sub with the correct amount of power(I know how to run the system thank you :])... basically i was asking how to correctly hook up computer power supplies to get 80amps or more (should i get more?- The reason i am asking is that if I had 70 amps and sometimes i will pull 80- will the power supplies heat up?) And I know it will work fine with 12v- HOWEVER- the optimum output level is achieved at 13.6 volt(or even at 14.4)- is there any way to get that voltage out of power supplies I will be using? .... the power supplies will be old - the scrap I can find at my lab, so not the best quality I guess....

    P.s.- BMorse- If your lights dim in your car you don't need a cap (caps are a huuuge rip off for daily users- only useful for people that pull 5kW+ and that's in competitions since 150dB+ will make you deaf.....er.... lol) all you need is a BIG 3 and maybe upgraded alt if that wont help.

    P.s.2- I dont know whats the difference between At and XT? How to recognize that? and which one is better so I can get "picky" when I go garbage hunting around the lab.

    P.s.3- BMorse - I dont know who told you that you need a 1200W amp for 600W speaker.... NEVER look at Max output... this is useless.... The sub I have is rated at 450rms... however it is a competition driver so you can push it (its actually designed to provide better output when over driven).... so I can run it easily with a jl 500/1 which i got for close to nothing 2 years ago.... it puts out 600rms +.... of pure power (gotta love jl /1 series for that)

    Thanks guys so far for responses.
     
    Last edited: Sep 27, 2009
  5. AdamM

    Active Member

    Mar 7, 2009
    30
    0
    LazyLuke,
    I've never hooked multiple power supplies up in parallel, but here are a few thoughts.

    I don't know for sure, but it seems there is some risk that the supplies would be vulnerable to reverse current. (Someone who knows more about them -- maybe even you -- might be able to answer this question.) If this is the case, you might want to put a diode on the output from each supply to protect it.

    Hooking them up should be fairly simple: determine what the capacity of each supply is, and add supplies until they add up to your desired capacity. Then attach all the supplies' positive 12v outputs together, and all their negative 12v outputs together.

    I think you want your total supply capacity to be well over your expected maximum current draw (I'd go for at least 100A if you're expecting to need 80). This is because 1) if your supplies are old, they may not be operating at their rated capacity and 2) if one supply fails you will be drawing more current out of the other supplies, and they could all get cooked sequentially in very short order.

    For this reason I think you also want to be very certain that all the supplies are powered up successfully before you turn on your amplifier and start putting them under heavy load

    Computer power supplies are typically not very powerful. You might be better off to salvage a supply from a higher current device, like an old audio amplifier or something.

    Another solution (one that I've used before, though not on a system as powerful as yours) is to use an old car battery or two. Old batteries can be had very cheaply (or free) and provide plenty of current to cover the peak draw. Then you just need a power supply/charger to keep up with your average draw.

    Good luck,
    Adam
     
  6. LaZyLuke

    Thread Starter Active Member

    May 10, 2009
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    AdamM - thank you for reply. I have no idea if the power supplies can reverse the current but the diode idea sounds safe (wont that drop the voltage tho? isn't somewhat .7 volt drop for each diode?).... I will be measuring the outputs with the multimeter (so it will be an actual amperage)... the car batteries i can get for $35 a piece so not expensive at all (with a warranty for 5 years too :]) but they usually give out high explosive and harmful fumes so bringing one indoors might not be so much fun without correct ventilation (If i had a basement avaible I could vent it to a dryer vent however I cannot)... So in conclusion to proceed with this project I should know which power supplies to use (AT vs. XT) and how to turn them on .... and if possible - raise the voltage to 13.6-14.4)... And If the re is anything danger sources PLEASE let me know before I actually do it(maybe fuse it in some special manner? - I am going to put fuses before my amplifier and head unit- that is a given i think). Thanks, Luke.
     
  7. BMorse

    Senior Member

    Sep 26, 2009
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    Ps. from personal experience, I think Caps help alot in keeping in my lights from dimming when the bass hits hard, I have a couple of 1600 watt DVC subs wired @ 2 ohms and a 2600 watt amp to drive them in my 04 silverado ext cab.
    When I installed a 3 farad cap (I know 3 farad is overkill since you only need 1 farad for every 1000 watt, but for $49.00 I said what the heck), it helped a lot with the bass response and keeping the music crisp and clean...

    PS. 2 AT power supplies are normally out of those old PC's that use the Large 5 Pin DIN connector for the keyboard, and normally have an actual switch that turns the AC power on or off... and would normally require some kind of load on the +5 volt rail in order to putout the right level voltages (If no load, will only put out a little over 10 volts on the 12 volt rail)

    XT are mostly found in almost all PC's nowadays, they do not have an actual power switch on them and normally have a 20 or 24 pin power connector that goes to the motherboard. If they are XT's, all you have to do is jumper the Green wire on the 20/24 pin MB connector to any of the black ones (Ground), this will switch the power supply on...

    Sometimes there would be a pot inside the power supply that you can tweak to get the 13+ volts.....


    PS. 3 I thought on your first post you said 600W RMS thats why I said 1200W (thats peak) which would be sufficient for a 600W RMS woofer.
    1200W(peak)*.707 = 848.4WRMS
     
  8. LaZyLuke

    Thread Starter Active Member

    May 10, 2009
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    BMorse thanks for advice... this means I will look for the new type of power supply...
    regarding to the cap- cap might help with the dimming lights (for $40 that was worth it- usually they start at $100 for 1.0 farad which is way more expansive then doing the BIG 3- usually that's enough to get rid of any voltage drop... as far as for bass response- if you are listening to hard rock with very quick bass kicks then yes it would help.... but if you listen to techno, house music, hip-hop(old school- not the commercialized junk) then the cap wont do squat since you have many sweeps and bass lines... and for the rms vs peak- if you shop for car audio at wallmart then you can see "1000W amp" when you actually bench test it it will put out 300W(I have seen that myself)... many manufacturers get that "peak" out of the blue.... and its RMS value its not even close to it.... if you go shopping for more sophisticated equipment you will see they don't even list "peak" ..... all I look is RMS and amperage pull of the amp to get the right estimate of the power it will actually put out... same goes for speakers.... just there you look more for efficiency then actual RMS value but that's another story....
    Thanks for the advices... but no one confirmed that connecting the power supplies in parallel is actually safe.... I don't want to put my house on fire so please let me know if anyone did it and if its safe! Thnx again, Luke.
     
  9. BMorse

    Senior Member

    Sep 26, 2009
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    I will try to hook a couple up tomorrow at work and see what happens, I think some "blue smoke" might escape from one or both;)

    I'm pretty sure it would work as long as there is a common ground between power supplies, but then again the regulators in the PS may not like power coming in on their outputs.... but don't take my word on that yet, at least until the morning...
     
  10. LaZyLuke

    Thread Starter Active Member

    May 10, 2009
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    Thanks you BMorse.... I will test it before I attempt to hook up my system but I was afraid of it blowing up all together or getting electrocuted....
     
  11. AdamM

    Active Member

    Mar 7, 2009
    30
    0
    LaZyLuke how were you planning to test the amperage of the power supplies with your multimeter? I'm not an expert, but as far as I know you can't test a power source directly with an ammeter without overloading the ammeter, or the supply, or both. Ammeters (that I'm familiar with) are designed to be used in series with a load. They are essentially a short circuit with a small resistance. The meter measures the voltage drop across that resistance and calculates the amperage based on that. The meter doesn't limit the amount of current going through it, so if you hook it up directly to the supply, the current will go up until it damages (or blows the fuse in) whichever of the meter or the power supply has the lower current rating. Is there another way of testing that you know about?

    Regarding batteries: I have used them indoors often, though at low loads, and equivalently low charging rates (offgassing, as far as I know, mostly occurs when charging). Probably you would want some kind of ventilation -- perhaps out a window? Another option would be a sealed batteries, which are widely available (though more expensive).

    Good luck with your project,
    Adam
     
  12. BMorse

    Senior Member

    Sep 26, 2009
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    Well I connected 2 power supplies together, nothing smoked! and it seemed to work, except for one of the power supplies was making a "whining" noise when I connected the other one to it (I figured it wont like voltage on its outputs...), I guess placing a diode on each 12 volt output would work but you will have to try and tweak the output to compensate for the voltage drop across the diodes, I am not sure if your power supplies would have any pots inside to adjust the output.... these ones I have do have that internally. I opened up one here and it did have a pot and when adjusted I could vary the output of the 12 volt rail from 8 to 18 volts.
     
  13. AdamM

    Active Member

    Mar 7, 2009
    30
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    Here's an article about wiring power supplies in parallel for backup purposes: http://www2.electronicproducts.com/...utputs-article-fapo_Acopian_aug2008-html.aspx .

    Regarding testing, if your PSUs have automatic current limiting or a breaker then you could test them with your multimeter without harm (as long as your meter can handle the current), but the breaker would probably be near their rated current anyhow, so you wouldn't gain much information.
     
  14. LaZyLuke

    Thread Starter Active Member

    May 10, 2009
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    OK.... so everyone seems to be recommending a diode for each PS.... however those diodes are more expensive then the PS itself (I am not sure if im looking at the right places- eBay, some automotive site(battery diode))... im just afraid that if I hook up 5 of them they might just fail (aiming for 100Amps)... anyone know where can i find a fairly cheap diode (I guess the rating should be 12V, 120Amps or more?)
     
  15. AdamM

    Active Member

    Mar 7, 2009
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    The diodes would only need to be rated for the output of the particular supply they are protecting. So if you have five 20A PSUs, you need five 20A diodes.
     
    Last edited: Sep 29, 2009
  16. AdamM

    Active Member

    Mar 7, 2009
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  17. LaZyLuke

    Thread Starter Active Member

    May 10, 2009
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    thanks guys for advices again. So far im working on hooking up my headunit. I will be using one power supply (15amps max) for this. its the one with 24 pin harness. my question is:
    The specs state that its 10A @ +12v1 and 15A @+12v2.... now when i opened the PS both +12v1 and +12v2 are yellow but the +12v2 has black stripes on it and there is only 2 small wires where +12v1 has bunch of them (more then 10) should I use the 2 wires that say 12v2 on them only? or strap them all together (all yellow wires).... Im just concerned that the 2 small wires will have significant resististance when pulling all 15A.... thanks again!
     
  18. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    No.
    Peak Power is exactly double the actual RMS instantaneous power. The RMS voltage is 0.707 times which makes the current also 0.707 times. The power is the voltage times the current so 0.707 x 0.707= 0.5 times the power.

    Many amplifiers are rated in Peak Music Power which is just a bunch of lies.
    PMPO is a power rating with many more lies.
    A little amplified computer speaker is rated 1000W PMPO but its power supply is just 9V/500mA (4.5W) so each speaker gets 1.125W RMS.
     
  19. LaZyLuke

    Thread Starter Active Member

    May 10, 2009
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    thanks for the input but this was already cleared out in this thread.... and its rather unrelated to the OP so.... thanks?...
     
  20. BMorse

    Senior Member

    Sep 26, 2009
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    If you are just powering the head unit and that's it, then the 2 wires (Probably 18 gauge) should be ok, since the 2 wires combined are probably larger than the power wire of the head unit (most likely 16 gauge). But I would still put an inline fuse on it.
     
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