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2 ohms speakers

Discussion in 'Audio & Video' started by machman, Sep 3, 2009.

  1. Sep 3, 2009 at 4:28 AM
    #1
    machman

    machman [OP] Well-Known Member

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    I am looking at some Infinity components for my 03's doors. They are 2 ohm speakers and I thought that this low impedence would run the amp in my receiver hotter and therefor run the risk of burning up the amp.

    I did some searching but only came up with things relating to subs.
     
  2. Sep 3, 2009 at 11:32 AM
    #2
    rutherk1

    rutherk1 ElPhantasmo&TheChickenRunBlastarama

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    Lower impedance (ohm) = more resistance.

    I dont think any head unit out there will support a 2 ohm load.
     
  3. Sep 3, 2009 at 11:32 AM
    #3
    PrezidentRedz

    PrezidentRedz Uncivilized Creations Prez

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    All head units are 4ohm compatible, if you have a component system you should have a small box that splits it between the tweeter and the mid range. there for making the 2 speakers 4ohms.
     
  4. Sep 3, 2009 at 11:33 AM
    #4
    PrezidentRedz

    PrezidentRedz Uncivilized Creations Prez

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    thats backwards. the lower the Impedance the less resistance. EX: that's why sub amps that cannot handle 2ohms over heat....
     
  5. Sep 3, 2009 at 11:56 AM
    #5
    rutherk1

    rutherk1 ElPhantasmo&TheChickenRunBlastarama

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    No.

    I = V/R
     
  6. Sep 3, 2009 at 12:56 PM
    #6
    PrezidentRedz

    PrezidentRedz Uncivilized Creations Prez

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    Custom Everything! WHAT º¿º
    No...
    P/I2 = R
    E2/P = R
    E/I = R

    Impedance (Z) is the opposition to alternating current, measured in ohms. (so there for Less Ohms less Resistance)

    Most loudspeakers are 4 or 8 ohms nominal. Actually the impedance varies with frequency. A speaker rated at 8 ohms impedance might range between 4 and 50 ohms, depending on the frequency of the signal. If you connect two identical speakers in parallel, the total impedance is half. For example, two 8-ohm speakers in parallel present a 4-ohm load to a power amplifier. If you connect two identical speakers in series, the total impedance is doubled. Two 8-ohm speakers in series present a 16-ohm load to a power amplifier.
    Suppose you have a speaker connected to a power amplifier. Generally, the lower the speaker impedance, the more power you get from the power amp. Some amps can handle a 2-ohm load, but many will overheat. Try to keep the load 4 ohms or higher.
     
  7. Sep 3, 2009 at 1:01 PM
    #7
    rutherk1

    rutherk1 ElPhantasmo&TheChickenRunBlastarama

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    I think we are talking about the same thing. I was speaking nominally. Low as in (1 ohm) will have a higher resistance than a 2,4,8,16... speaker.

    So yeah. 1 ohm (low number) has a higher resistance than 8 ohm (higher number) lower resistance. I can see how that was misinterpreted.
     
  8. Sep 3, 2009 at 1:02 PM
    #8
    chris4x4

    chris4x4 With sufficient thrust, pigs fly just fine. Moderator

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    PR is correct.
     
  9. Sep 3, 2009 at 1:10 PM
    #9
    PrezidentRedz

    PrezidentRedz Uncivilized Creations Prez

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    Thanks Chris. I wasn't trying to argue. I just happen to be an Audio Freak, and Also have my Degree in Electronics.
     
  10. Sep 3, 2009 at 1:10 PM
    #10
    rutherk1

    rutherk1 ElPhantasmo&TheChickenRunBlastarama

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    Georg Ohm wrote Ohms law I = V/R, V = IR or R = V/I
     
  11. Sep 3, 2009 at 1:13 PM
    #11
    PrezidentRedz

    PrezidentRedz Uncivilized Creations Prez

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    Custom Everything! WHAT º¿º
    "When the electricity passes into the speaker, some of it is resisted. The ohms rating of the speaker is a measure of how much electricity is resisted by the speaker, and an indication of how much energy it takes to drive it - the higher the ohms rating, the more difficult it is to drive."
     
  12. Sep 3, 2009 at 1:15 PM
    #12
    PrezidentRedz

    PrezidentRedz Uncivilized Creations Prez

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    How To calculate Ohms - Series Wiring
    If you connect your amp to one speaker, the ohms rating is equal to that speaker's ohms rating. An 8 ohms speaker would have a rating of 8 ohms.
    If you wire two or more speakers in series, you add the ohms rating together to get the total ohms. I know what series & parallel wiring is from grade school science. It's hard to describe without diagrams, so I'll keep my description minimal. You can refer to the diagrams in the articles from my bibliography if you need more help.
    My grade school science book had the example of christmas lights. When you wire the lights in series, you connect the + terminal of one light to the - terminal of the next light. The electricity flows through one light, and then on to the next. If any of the lights goes out, or any of the connections breaks, all of the lights go out. The connection is broken.
    This increases the total resistance, reducing the total acoustical output. That is, because the electricity has to flow through each speaker one at a time, each speaker adds it's resistance to the whole. The formula is as follows:
    Speaker A + Speaker B = Total Ohms Rating
    8 Ohms + 8 Ohms = 16 Ohms
    Two 8 Ohms speakers wired in series will have a total rating of 16 ohms.

    How To calculate Ohms - Parallel Wiring

    Parallel wiring is something entirely different. If one of the Christmas lights goes out, none of the others goes out. Visually, this looks like a ladder, with each light in the center of a rung. Remove one of the rungs, and the electricity still flows to the next rung via the sides of the ladder.
    This reduces the total resistance increasing the total output. That is, because electricity flows through all of the speakers simultaneously, each speaker added reduces the resistance of the chain. If you visualize all of the negative electrons on one side trying to get to the other, they'll have an easier time because there are so many possible paths for them to go by.
    Resistance = (Speaker A x Speaker B) / (Speaker A + Speaker B)
    Resistance = (8 Ohms x 8 Ohms) / (8 Ohms + 8 Ohms)
    Resistance = 64 / 16
    Resistance = 4 Ohms
    Another calculation I've seen, which may be the same formula stated a different way, or may be more accurate or less accurate is:
    Resistance = 1 / (1/Speaker A + 1/Speaker B)
    Resistance = 1 / (1 / 8 Ohms + 1 / 8 Ohms)
    Resistance = 1 / (2/8)
    Resistance = 1 / .25
    Resistance = 4 Ohms
     
  13. Sep 3, 2009 at 1:16 PM
    #13
    chris4x4

    chris4x4 With sufficient thrust, pigs fly just fine. Moderator

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    X2. And if hooking up 2, 8 ohm speakers in paralel, you get a 4 ohm load.
     
  14. Sep 3, 2009 at 1:18 PM
    #14
    PrezidentRedz

    PrezidentRedz Uncivilized Creations Prez

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    How To calculate Amplifier Output?
    The calculation for figuring out how much is fairly straightforward, and pretty much what I would expect it to be. Since ohms measure resistance, the more ohms, the less output from the amplifier. Conversely, the less ohms, the more output from the amplifier.
    Since the amp is rated at a specific amount of ohms (i.e. 100 watts @ 4 ohms), a different amount of ohms will produce a different output. Two 8 ohms speakers wire in series (16 ohms total) would cause the amp to produce 25 watts to each speaker.
    Amplifier Output = Amplifier Watts x (Amplifier Rated at Ohms / Speaker Chain Ohms)
    Amplifier Output = 100 watts x (4 ohms / 16 ohms)
    Amplifier Output = 100 watts x 1/4
    Amplifier Output = 25 watts
    An amplifier designed to put out 100 watts into 8 ohms will put out 200 watts into 4 ohms. Two 8 ohms speakers wired in parallel (4 ohms total) would cause the amplifier to produce 200 watts.
    200 watts = 100 watts x (8 ohms / 4 ohms)
    The amp produces 100 watts at 4 ohms. When the resistance is increased to 16 ohms, four times what it was rated, the amplifier produces one fourth as many watts.
    You must be careful when wiring multiple speakers together in a series or parallel chain because the amplifier may have trouble dealing with certain Ohms chain ratings, especially below 4 and above 16, and you must be sure that your speakers are capable of handling the wattage that they're receiving. Be sure to check the manual for all of your equipment before doing any of this.
    The limiting factor, from what I hear, is the power supply. If the power supply isn't designed to handle a 2 Ohm load, you may fry your amp. In fact, it takes a very special amp to work below 4 Ohms. Again, check the manual, call the manufacturer, don't just start wiring things into a 1 Ohm load hoping to get 4 times the power out of your amp.
    Mike Faithfull informs me of another possible problem: You could also destroy a transistor in the output stage by demanding it to supply more current (into the extra-low resistance load) than it is rated for (this is probably a more common failure than the power supply!)
    Conclusion
    When combining speakers in a chain, you can do it in Series, Parallel, or even mix the two methods to ensure that the resistance is what you want it to be. With the right equipment you can use this to increase or reduce the output of any element in your chain.
    In reading the calculations from various sources, I sort of skimmed over the complex math, but I know that there is complex math and these calculations are only approximations. Real World conditions may yield actual results that are somewhat different from these simplistic mathematical models. Speaker cabinets can even affect the Ohms rating of the speaker! Also, don't mix speakers, make sure all of the speakers in your chain have the same ohms rating. It would probably be a good idea to be sure they all have similar wattage ratings.
    In other words, try this at home, but be extremely careful with the calculations and read the manual. Don't try anything too extreme like hooking up 18 speakers in a row, even if your speakers and amp say that they can handle what your calculations say because these calculations are only approximates and you could do serious damage to, well, a lot of things.
     
  15. Sep 3, 2009 at 1:20 PM
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    Evil Monkey

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    You're wrong. Prezidentredz is correct. Impedance is measured using ohms (resistance). If impedance is lower, ohms (resistance) must be lower as ohms is the measure.

    Using the formula, voltage is constant (12 volts) so current must be inversely proportionate to resistance. As resistance goes down, current must increase, meaning power draw on the source increases (P=IE), which is why the amp may overheat under a 2 ohm load.

    If resistance increased, the power draw would be less meaning the amp could handle it better.

    Look at any speaker spec or amp spec. The power outputs are measured based on ohms (e.g. 1000 watts at 2 ohms, 500 watts at 4 ohms). Less resistance, more current, therefore more power and more likely to overheat the amp's circuitry.
     
  16. Sep 3, 2009 at 1:28 PM
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    Evil Monkey

    Evil Monkey There's an evil monkey in my truck

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    Just the opposite. Ohms IS the resistance measure. 1 ohm is less resistance than 2,4 or 8 ohms by definition.
     
  17. Sep 3, 2009 at 1:29 PM
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    nad

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    i would not recommend running two ohms on stock deck/amp
     
  18. Sep 3, 2009 at 1:36 PM
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    PrezidentRedz

    PrezidentRedz Uncivilized Creations Prez

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    Thats what I tried to tell him, if its a Component speaker Set., It should have a Cross Over to Join the Set of speakers together making it 4Ohms as well as blocking signals that could blow the Tweeter.
     
  19. Sep 3, 2009 at 2:07 PM
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    Evil Monkey

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    It's the same for two resistors. Using a little algerbra:

    for readability I'll use a = r1 and b = r2

    RT = 1/(1/a + 1/b) = a*b/(a+b)

    Invert both gives => (1/a + 1/b) = (a+b)/ab

    Multiply both sides by ab which cancels the ab on the right formula:
    (1/a*ab + 1/b*ab) = (a + b)
    (ab/a + ab/b) = (a + b)

    a's cancel in first fraction and b's cancel in second fraction:
    b + a = a + b

    The main reason for using the first formula is if you have more than two resistors e.g. 1/(1/r1 + 1/r2 +...+ 1/rn)
     
  20. Sep 3, 2009 at 2:13 PM
    #20
    sooner07

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    It does not matter if the speakers are coax, component, tweeters or subs, cones or magnaplanar, or whatever, most amplifiers in HU's are not stable at two ohms.

    Do not connect a two ohm load to your headunit, you will destroy it in a matter of time. That is to say, unless your HU is stable at 2 ohms (which I'd like to see, as I don't know of any that are).
     
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