speakers and wire size

Discussion in 'Audio' started by EFIMAV, Aug 11, 2013.

  1. EFIMAV

    EFIMAV Member

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    I need a little help with installing 6x9 rear speakers. According to some you can't use low impedance speakers (4ohm or less?) with stock AM/FM radios as the amplifier may suffer damage. Others say this is only a problem if playing the radio loudly. Also, I can't seem to find any 6x9s with higher impedance (all are 4ohms). Also, what size wire should I use?
     
  2. bmcdaniel

    bmcdaniel Senile Member

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    The stock speakers used to be 8 or 16 ohms, I think. The speaker may have it stamped on the rear. You need to match the speaker impedance to the amplifier or the power won't be transferred efficiently causing the amplifier to overheat. They make audio matching transformers that install between the radio and the speakers to do this.

    Edit: Forgot to ask, is the stock radio stereo or mono? Does it have balance and/or fader controls?
     
    Last edited: Aug 11, 2013
  3. EFIMAV

    EFIMAV Member

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    the radio is mono with no fade or balance! What difference would mono or stereo make in this application? I'll likely upgrade to a newer unit in the future but would like to get some sound in the meantime. I'm thinking a simple head unit with two speakers. I'd like to run large enough speaker wire to accommodate this in the future. Not sure what size to use. I'll look into the transformer, any idea where to get one?
     
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  4. bmcdaniel

    bmcdaniel Senile Member

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    Faders and balance controls add impedance to the output. Siince you don't have these controls you might be able to just wire the speakers in series so that you have 8 ohms impedance.

    Here's a transformer on ePay:
    http://www.ebay.com/itm/New-Unused-...ultDomain_0&hash=item5659cc681c#ht_441wt_1062

    Speaker wire gauge depends on what power levels you'll end up running later. Digital stuff, which is pretty much all you find nowadays, doesn't need as heavy wiring as the older analog equipment.
     
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  5. FordsForever

    FordsForever Member

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    Years ago radios were 8 and 16 ohms impedance. There were some even more. some mid-70's fords were only 4 ohms. I have a 74 Mav radio and it is rated for 8 ohm speakers. It is mono and has a built in fader. Some mid 60's ford radios are rated for 4 ohm speakers.

    Generally it's a good idea to try and keep any combined output load at the rated impedance. It keeps the output transistors loaded properly so they don't overheat. And keeps distortion to a minimum.

    If the radio needs 8 ohm speakers and you want two speakers on the output, wire two 4 ohm speakers in series to equal 8 ohms. Or wire two 16 ohm speakers in parallel which still equals 8 ohms. Could still be a slight increase in distortion from each individual speaker but the radio will be happy.

    Some dealers try to tell you to use only the Super conductor speaker wires. And they make a lot of money selling something you don't really need. Even with big amps I don't believe anything more than standard speaker wire is unnecessary. Just a lot of hogwash as far as I'm concerned. You're dealing with dynamic power not resistive power as in a heating element. Save your money and just use good quality standard wire and connections and you'll be alright.
    Ron
     
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  6. EFIMAV

    EFIMAV Member

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    Thanks for the replies. Wiring the 4ohm speakers in series should solve the problem. I have 22ga speaker wire.
     
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  7. EFIMAV

    EFIMAV Member

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    Need a bit more help. The original AM radio with center speaker is 3.2ohm! I have an AM/FM radio from 1980 that has no information about impedance for the amplifier (all of the stickers are gone). Does anyone know where I can access ford part number information? E0EF 19A171 AA is the number on the radio itself. Also, I understand that running lower impedance speakers on a higher impedance amp will cause it to run hot but I'm wondering if this applies in reverse (lower impedance amp vs higher impedance speakers). If not, I could run the two 4ohm speakers in series for 8ohms and should be okay. Thanks.

    Update: I should be okay running a solid state amp rated lower than the speakers (8ohm amp with 16 ohm speakers for example). bmc, the radio has only one connection for a speaker but I think I was incorrect regarding balance or fade. I think it has balance on the left knob (also has volume on that side).
     
    Last edited: Aug 12, 2013
  8. EFIMAV

    EFIMAV Member

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    I need somebody to confirm a few things. First, the speaker wires from the mono radio are black and black/white hash. I did the old 9V battery trick and hooked up the + side to the black wire and the - side to the black/white wire. When I do this the speaker "pops" upward meaning I have the polarity correct? So, the black wire is the positive and the B/W is the negative. Second, to wire speakers in series, + wire goes to + on first speaker, run a second wire from - first speaker to + of second speaker and return negative wire to source. Correct?
     
  9. bmcdaniel

    bmcdaniel Senile Member

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    yes & yes.
     
  10. FordsForever

    FordsForever Member

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    I'm pretty sure you have identified the wires polarity correctly. And you have it right on how to connect them, To wire them in series the + of one speaker should connect to the - of the next speaker. That keeps them 'in phase'. Otherwise they cancel each others sound output. In other words they are 'pushing together'.
    One of those wires may be common with the body of the radio. that would be the - wire.
    Ron
     
  11. EFIMAV

    EFIMAV Member

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    Thanks for the replies, it sounds like it is wired correctly. I was under the dash yesterday while the radio was playing and there was a slight hot "electrical" odor and I wanted to be sure I had it hooked up correctly. It is either a 4ohm or 8ohm radio amp and I have two 4ohm speakers in series for 8ohms so I should be okay. Learn something new everyday!
     

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