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What gauge wire should I use from AMP to Subwoofer?

Discussion in 'General Electronics Chat' started by Peter_wadley, Feb 15, 2010.

  1. Peter_wadley

    Peter_wadley New Member

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    Hey Hey,

    I just bought the 500W RMS Alpine sub amp from Futureshop that is on sale this week

    It's marked down $100!! from 299.99 to 199.99 .. I highly recommend it!

    My question:

    From the 12 v car Battery I am using 8 AWG for the + and - Leads.. since the voltage is so low and amperage is so high 500W / 12 V = 42 AMPS

    What I am wondering is what gauge I should use from the AMP to the Subwoofer ... does the amp step the voltage up and thus reduce the current so that I can use something smaller than 8 AWG??

    Thanks,
    Peter
     
  2. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The Alpine sub-woofer amplifier has a maximum power of 500 Whats (maximum power is peak power which is double the real power) into 2 ohms when the battery is over-charging at 14.4V and the distortion is awful at 10% because the volume control is turned up too high.
    Its output is 180 Watts RMS into 2 ohms when the battery is normal at 13.8V and the amplifier is not clipping.
    Its output is about 100 Watts RMS into a 4 ohm sub-woofer.

    It is class-D so it heats with about 20 Watts when its load is 4 ohms.
    The total power is 120W and at 13.8V the current is only 8.7A.

    You cannot calculate power or wire size properly without knowing the impedance of your subwoofer speaker.

    EDIT:
    The power ratings are just a bunch of lies.
    I found what appears to be this amplifier's owner's Manual. It's power rating conflicts with what Future Shops says.
    Maybe Future Shop are selling an old amplifier that is not on alpine's website.
     
    Last edited: Feb 15, 2010
  3. Peter_wadley

    Peter_wadley New Member

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    Hey guru,

    The Alpine site states:

    RMS Power (at 14.4V THD+N, 20-200Hz)

    Per channel into 4 ohms: 300W x 1 (0.08% THD)
    Per channel into 2 ohms: 500W x 1

    OK I am using one 4 OHM sub

    So the RMS power is 300W not the peak ... 300 is the RMS from their site. This thing really is pounding yes I know the whole deal with dealers saying boosting the PEAK when in reality the real beans is the RMS wattage with a low THD.

    And they say 300W at 0.08 THD... correct me if I'm wrong but isn't 0.08% THD a pretty low distortion level?

    so now we have 300W / 14.4V = 20 AMP ...

    Either way the sound is to my liking as to me it has a good quality pound (i'm no audiophile)

    I have to Subs so I could always wire them as a 2OHM load I guess.

    Back to the question...:

    What gauge would you recommend from AMP to SUB?

    I'd rather just go over-kill on the gauge then under and potentially be unsafe..
     
  4. dave

    Dave New Member

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  5. Peter_wadley

    Peter_wadley New Member

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    Also, what does THD + N mean (the N part)
     
  6. Peter_wadley

    Peter_wadley New Member

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    The CEA-2006 Power Rating is (40hm@14.4V = 1%THD+N), S/N 75dBA (Ref. 1W into 4Ohm):300W x 1

    so it has been officially auditied correct?

    Why on earth would they use 40 ohm? or is that 4ohm?
     
  7. crutschow

    crutschow Well-Known Member Most Helpful Member

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    Total Harmonic Distortion plus Noise.

    Edit: The gauge wire you need depends upon the length of the wire as well as the current through it.
     
    Last edited: Feb 15, 2010
  8. Hero999

    Hero999 Banned

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    You should only use oxygen-free, silver cable insulated with premium grade low dielectric absorption silicone rubber for a crystal clear, super smooth sound. I can sell you a roll for £100 per meter. :rolleyes:
     
  9. audioguru

    audioguru Well-Known Member Most Helpful Member

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    I never heard of the standard CEA-2006. It is for sale but I won't buy it.
    It might be the new way to state a phoney power rating. Maybe it is what used to be called "music-power" which is the power produced only for a moment before the power supply voltage dropped due to the high current.

    Their sales sheet and owner's manual are full of misprinting. The power into 40 ohms would be very low.
     
  10. Peter_wadley

    Peter_wadley New Member

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    Like I said I'm no audiophile.. My ears are pretty daft to the difference between OK and GREEEEEEEAT (tony the tiger)

    Is anyone able to tell me what Gauge I should use from the AMP to the SUB?

    I tried to use volt meter on the AMP outputs but got only order of millivolts
     
  11. Hero999

    Hero999 Banned

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    I was being sarcastic, don't bother with overpriced cable, it's a waste of money.

    The cable doesn't have to be rated to the maximum current draw because the speakers won't be drawing that current all the time.

    I'd probably use 1.5mm² cable (I don't know what that is in AWG) even ordinary twin core mains cable will do.
     
  12. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Alpine used to have fairly honest ratings years ago so if they are still being honest a 500 watt sub would need 14 - 12 gauge unless you are 100's of feet away from the amplifier.

    I would recommend a middle grade of copper speaker wire. The high end stuff is for idiots with money and the low end stuff has weak low grade plastic insulation that doesn't strip well or take cold temps without cracking or falling apart plus it usually has low grade copper that is brittle and higher Resistance.
     
  13. Peter_wadley

    Peter_wadley New Member

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    So it looks like 14 AWG it is then, thanks!
     
  14. mneary

    mneary New Member

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    I try to keep the speaker wire resistance to less than 5% of the impedance (reasonable efficiency and damping factor). So I would shoot for 0.1 ohms on a 2 ohm speaker. Since 14AWG is 0.0025 ohms per foot, 40 feet is 0.1 ohms (20 feet each way).
     

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