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2ohm vs 4 ohm

Discussion in 'Car Audio / Security / Electronic Accessories' started by RiCe RoCcEt, Dec 13, 2004.

  1. RiCe RoCcEt

    RiCe RoCcEt Junior Member

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    can someone please give me a explanation on what is the difference between 2ohm and 4ohm. thanks
     
  2. Dustin_m

    Dustin_m Active Member

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    an ohm is a unit of resistance, also called impedence. HIgher ohms=more resistance
    lower ohms=better(as far as bridging the subs down)
     
  3. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Lower resistance also means that you're putting a larger load on the amplifier, so you need an amp that can handle the lower resistance (but higher load) setup.
     
  4. RiCe RoCcEt

    RiCe RoCcEt Junior Member

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  5. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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  6. cheese9988

    cheese9988 Senior Member VIP

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    A larger load will mean higher wattage (depending on the situation). If you take a dual voice coil (dvc) and wire it for a 2 ohm load, it will be slightly louder due to the increased current flow, but put more of a load on the amplifier. If you wire it for say 8 ohm it will not be as loud but have less of a load on the amp. Simple equation w=v^2/r
    w=watts
    v=volts
    r=resistance (ohms)

    You decrease the resistance the wattage goes up. Keep in mind that some amplifiers cannot operate in 2 ohm mode, and there are even less that can do 2 ohm in briged mode. Even on some cheap amps that are labeled for 2ohm will over heat after some time, so keep them in a ventilated spot if possible. So if you amp can do it, and your speaker is set up for it, have fun!
     
  7. CRX-YEM

    CRX-YEM Super Moderator Moderator VIP

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    The perseption of it being louder is what is really due to the amount of power/watts the amp needs to be able to produce. the impeadance load and the speaker sensitivity. Actually presenting a 2 ohm load vs an 8 ohm load to an amplifier does not make a speaker louder it increases the SPL (Sound pressure level)

    Amplifiers have different ratings for different loads, an amplifier that is 2ohm stable will often have a spec stating peak (or rms if it's a quality product) power output w/ a 2ohm load and a different rating for an 8ohm load. It will also specify at what input voltage these specs refer to 12vdc or 14.4vdc.

    e.g
    Amplifier model# @ 12vdc
    100w/ch @ 2ohms
    25w/ch @ 8ohms

    all this is saying is the amp uses more power to run the two different impeadance loads. The amplifier doesn't magically produce any more power than it was rated/designed for.

    also keep in mind that the specs on a speaker in ohms are not true ohms readings they are impeadance measurements.

    To change the loudness the speakers sensitivity needs to be changed.
    expressed in decibels per watt at one meter, or db/Wm. So, with an input of one watt, a speaker with a sensitivity of 90 db/Wm will produce 90 decibels of sound at a distance of one meter.

    So it's a combination of 4 things
    Amplifier power, speaker sensitivity, number of speakers, and distance from speaker
     
  8. cheese9988

    cheese9988 Senior Member VIP

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    The wattage on an amplifier is still based on the load. There is nothing to limit the current, the equation v=v^2/r still holds true. All a class b amplifier is are two power transistor connected directly to a dc voltage. The transistors are biased so they are not all the way on or off. One transistor takes car of the top half of the sine wave, the other takes care of the top half of the sine wave. If any transistor is turned completely on, the transistor will draw as much current as possible through the collector and emmitter (provided the leads are shorted + to ground). The only thing limiting it is the beta of the transistor (resistance between the collector/emitter), and the resistor between the collector and the power source. Simple ohms law still holds true, lowering the resistance increases power, it will draw more current from its power supply, as long as your keeping voltage the same.
    P=v * i
    p=power (watts)
    v=voltage
    i=current
    Its not that it cannot create power from nothing (it can't simple physics), its that there is nothing to limit the current other than a fuse or the transistor blowing out, or the power supply burning up. An amplifier does not create power whatsoever, it just takes the dc source and causes it to oscillate based on the input of the transistor, everything else is ohms law.
    The way they increase the power per speaker is to increase the dc voltage going into the collector on the transistor, and finally the speaker. There is actually a power inverter inside the amplifer, if you look inside there is a large circular coil, thats the transformer. The take the dc voltage, make it oscillate through some mosfet transistors (cheap amps usually use something labled irfzXXXX), step up the voltage through the transformer, and convert it back to dc through a bridge rectifier, (usually a couple of things that look like a transistor but are not (usually have diode symbols on them though). You use this equation w=v^2/r and you will see that per load, ie 4 ohm, increaing the voltage increases wattage.
    An increased load, ie. lower resistance will make more power, BUT keep in mind that your amp might not be able to take it.
     
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