4 Ohm Speakers with 8 Ohm System

Discussion in 'General Electronics Chat' started by Rusty Axle, Oct 31, 2013.

  1. Rusty Axle

    Thread Starter New Member

    Oct 31, 2013
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    I do not have a background in electronics. I do understand that Ohm is a measurement of resistance, the higher the Ohm rating the higher the electrical resistance.

    I have a specific set of speakers that I want to replace the stock speakers in my car with. The factory system is 8 Ohm. My speakers are 4 Ohm.

    It has been suggested that I place resistors in front of (on the positive terminal) the 4 Ohm speakers to match the impedance. My concern is that adding anything in the path of the signal may alter or color the signal, resulting in a loss of fidelity.

    Why can I not place the resistor after (on the negative terminal) the speaker? That way (it seems) the speaker would see the full, unmodified signal. I have no fear of speaker damage.

    Thank you for explaining this in laymen's terms.
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    Putting a 4Ω resistor on the positive side will have the same effect as putting it on the negative side.

    Wire two 4Ω speakers in series if you want 8Ω impedance.
     
  3. #12

    Expert

    Nov 30, 2010
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    Adding a resistor will not "color" the sound, except a bit on the low frequency end (due to changing the damping factor), and you might not be able to detect it with your ears. The resistor will use up some of the power. Try to read the labels on the amplifier to see if it is designed to survive 4 ohm speakers. If that is true, you need nothing to modify the circuit.
     
  4. Art

    Distinguished Member

    Sep 10, 2007
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    You could series the door and rear speakers with each other.
    Otherwise you only get half output power as well,
    and end up turning the thing up until you ruin the speakers with clipping.
     
  5. Rusty Axle

    Thread Starter New Member

    Oct 31, 2013
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    Thanks everyone for your assistance.

    The vehicle has a factory signal processor that includes not only fade and balance but also a presence adjustment that relies on all speakers having a separate lead from the amp, so the only option (aside from somehow adding 4 Ohm amps) appears to be the resistors.

    I wish that I could grasp what is happening with the resistors. It is interesting to learn that no matter where they are placed the result is the same. With no background in electronics, it seems that if the resistors are on the negative terminal of the speaker, the additional power (and unfettered signal) would first pass through the 4 Ohm speakers and then be converted to heat by the resistors after the speaker to make the 8 Ohm impedance match.

    Sort of like having a high pressure water hose driving a device, with a "Y" junction following it in the circuit which would reduce the pressure of the water by bleeding some of it off before returning to the original source (bad analogy, but is all I could come up with).

    Looks like the physics of electricity clearly has it own realm of behavior. Pretty fascinating.
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    Electricity does not work the way you described it.

    Think of it as message passing from one agent to another. It doesn't matter who gets the message first or last, they all receive the same message.

    Most modern amplifiers can handle both 8-ohm and 4-ohm speakers. It is quite possible that this is true with your amplifier. It is possible that you can connect 4-ohm speakers to the output of the amplifier with no ill effect.
     
  7. #12

    Expert

    Nov 30, 2010
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    It isn't like a "Y" connection, it's more like the shut-off valve for your house and the hose bib on the back wall of your house. Either one of them can limit the amount of flow, and it doesn't matter which one is first. Partially shut either one, and the flow decreases.
     
  8. wayneh

    Expert

    Sep 9, 2010
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    I think it's also useful to remember that current flows in a loop, not just from A to B like water or information. A pinch in any part of the loop cuts the flow.
     
    #12 likes this.
  9. Rusty Axle

    Thread Starter New Member

    Oct 31, 2013
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    Thanks eveyone for your patience - I think that I am catching on. Please tell me if I have this right:

    It doesn't matter whether the resistor is in front of the speaker (+ terminal) or behind the speaker (- terminal). If the audio signal is going to be affected by the resistor (and only the lower frequencies are, apparently) and there is a resultant impact to audio fidelity, the impact is across the entire circuit. Put the resistor in the circuit anywhere - it doesn't matter.
     
  10. MrChips

    Moderator

    Oct 2, 2009
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    Who said that the resistor will affect only the lower frequencies?

    That is definitely incorrect.
     
  11. #12

    Expert

    Nov 30, 2010
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    Read post #3. I said it will change the damping factor.
    Rusty phrased his interpretation badly.
     
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