Need information on car audio

Discussion in 'OT Technology' started by Jaldar, Apr 3, 2005.

  1. Jaldar

    Jaldar X

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    Hello,

    I have a Pioneer headset that is 50 watts x 4. I want to change my stock speakers in my car (4). I'll buy 4 speaker kenwood that are 220 watts.


    1. Now, does that mean that my speakers will only run 1/4.4 of thier power?

    2. What are ohms?

    3. I'd like to buy a ampli and subwoofer too so if I buy a ampli that has:

    - 250 watts x 1 under 2 ohms

    - 125 watts x 1 under 4 ohms

    What does that mean? What specs should I look at when buying my sub and ampli?


    Thank you!!:x:
     
    Last edited: Apr 3, 2005
  2. Ronin

    Ronin Guest

    well for 1 no head unit is actually doing 50 watts, its probably closer to 18
     
  3. veonake

    veonake OnT poster, OT lurker

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    1. Assuming your head unit actually could put out 50Watts RMS (very doubtful), then yes, they would only be running at about a quarter of their max power (assuming that's 220W RMS). RMS (since you don't know what ohms are, I assume you don't know what RMS means either) is an acronym for "root mean squared". Basically, it's a useful measurement that electric engineers use to determine the useful power or voltage, etc. of a device. You get this by taking the peak power/voltage, etc. and dividing by sqrt(2). Blah.

    2. Ohms are a measurement of electrical resistance. Named after the guy that discovered it. You may have heard of ohms law: V=IR (Voltage = Current * Resistance). So, the resistance of a wire, or a resistor, creates a voltage drop along the wire. In car audio, an ohm rating usually represents the nominal impedance (basically resistance in AC) of the speaker. Most speakers are 4 and 8 ohms, subwoofers are usually 2 or 4 ohms, sometimes 3 or 1. When an amp is listed at a certain ohm rating, it means, when driving a load (a resistance, or speaker, is considered a load) it can put out a certain amount of power. As the load becomes more efficient (smaller ohm rating), the more power an amplifier can produce (except for certain designs, like the ones from JL Audio). So, if you have a 4ohm speaker, check the power rating of the amp for that impedance. If the the power is listed for 2ohms though, and you need the power for 4 ohms, just divide the listed power by 2.

    3. I pretty much explained what that means above. They are simply saying the same thing twice. It makes it easier on you to figure out how much power you will get for your particular application (i.e. subwoofer). That amplifier is not very powerful. Unless you get a 2ohm subwoofer, you will only get 125watts out of it.
     
  4. Jaldar

    Jaldar X

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    Thank you veonake. Last question: My headunit is 50watts x 4 (that is 22rms x 4). If my speaker is 220 watts max (that is about 90rms), will my speakers suck? I mean, will it do distortion even if it's not THAT loud... ?
     
  5. 04

    04 Guest

    The speakers wouldnt suck unless you crank them up too loud. Then you'd get distortion. Even with just the headunit you'll have to turn it up rather loud IMO before it starts distorting though.

    But if you plan on driveing down the highway with all the windows down, you'll probably want to get an external (more powerful) amplifier.
     
  6. veonake

    veonake OnT poster, OT lurker

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    Where are you getting your rms calculations? Did you look them up? Cause those figures don't really equate. Anyway...

    Your HU will certainly get them to a level that is audible, whether or not it will get them to produce the volume level you desire is another thing. It very well may not get as loud as you would like without distortion. In this case, as 04 said, you will want an external amplifier. Another benifit to an external amp is it should sound better as well. The sound quality point is debated, but the majority of the hi-fi population believe that a better amplifier does improve sound quality, in addition to making things louder.
     
    Last edited: Apr 5, 2005
  7. 04

    04 Guest

    Whcih Kenwood speakers are you talking about? Technically, a peak rating is twice the rms rating for power, so for 90wrms, that would be 180w peak. Typically the 'peak' power rating used by companies doesnt really correspond though to that rule (as it seems to be in this case).

    For voltage, RMS is the square root of 2 divided by the peak measurement.
     

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