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Thread: How do the speakers work as far as ohm ratings go.

  1. #1
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    How do the speakers work as far as ohm ratings go.

    I have a non HK sysyetm in my E46 sedan. I have a blown mid range or atleast I think so because its buzzy/ rattly and was looking at a few diys. I read that my car is an 8 ohm set up for the tweeeters/ midrange and 2 ohm for the mid bass,

    I found a few diy's where people use 4 ohm Vifa speakers for a good alternative but would that work on my 8 ohm car? I think all those diy's were on HK set ups but idk how much a difference they are to mine.

    I tryed to ask in the audio section but they were no help.
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    Does anyone know how the keyless ignition is meant to operate? The current system could be very dangerous if someone drove to an unsafe area, and then could not start the car.
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    ask in the car audio section they should know
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    I did they were no help so far.
    Quote Originally Posted by softwarehawk View Post
    Does anyone know how the keyless ignition is meant to operate? The current system could be very dangerous if someone drove to an unsafe area, and then could not start the car.
    Quote Originally Posted by deathwarden5 View Post
    What?
    Quote Originally Posted by Sidewayzracer View Post
    The poors might get him...

  4. #4
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    PM BennyZ...he should know...and while you're at it, tell him to get his ass back to our section...
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    BennyZ knows for sure, but its not a good idea to change to speakers with different impedance (ohms).

    If you put a 4 ohm speaker on a circuit that was designed to drive a 2 ohm speaker, the speaker will be 1/2 as loud as before. You'll need to turn the volume button up on the amp which will likely start clipping sound and that won't sound good. If you listen to it low, its OK, but if you want to increase volume output, its likely to clip (distort).
    Stick to the right 2 ohms for mid range bass.

    These are pricey : http://www.bavariansoundwerks.com/ca...Speaker-Pairs/

    Any right impedance speaker with approximate frequencies to the original will do.

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    Yea I looked at the BSW kit, ill pm Benny and see what he has to say/ offer. I can get the BSW kit if I want but just want to see what else I can do.
    Quote Originally Posted by softwarehawk View Post
    Does anyone know how the keyless ignition is meant to operate? The current system could be very dangerous if someone drove to an unsafe area, and then could not start the car.
    Quote Originally Posted by deathwarden5 View Post
    What?
    Quote Originally Posted by Sidewayzracer View Post
    The poors might get him...

  7. #7
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    You're best of staying with the same resistance (in ohms) speakers if you're driving them with the same factory stereo.

    At a constant voltage (as we have in our cars, 14.4v), the current demands of the speakers increase proportional to a decrease in speaker resistance:
    I=V/R (Current = Voltage / Resistance)

    The power output of a speaker is defined by:
    P = I*V (Power = Current * Voltage)
    so at a constant voltage the power output increases proportional to the current (which increased inversely proportional to the speaker resistance)

    Whether you can run the 4ohm speakers depends on whether your head unit can handle them (unlikely) and whether the speaker wires running along the car can cope with double the current capacity if you change a 8ohm speaker for a 4ohm (also unlikely)

    As Oli77 said, increasing the resistance of a speaker from stock will decrease the volume of that speaker (it decreases the power to the speaker). Stick with stock resistances if you're using the stock head unit. If you have an aftermarket amp that can handle a variety of speaker types, that's a whole nother story.

  8. #8
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    Its all stock audio, I will probably just get the BSW kit then, thanks for the info.
    Quote Originally Posted by softwarehawk View Post
    Does anyone know how the keyless ignition is meant to operate? The current system could be very dangerous if someone drove to an unsafe area, and then could not start the car.
    Quote Originally Posted by deathwarden5 View Post
    What?
    Quote Originally Posted by Sidewayzracer View Post
    The poors might get him...

  9. #9
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    Waehrik's post is correct with his summary. However, the audio signal from the amp is an A/C output where speaker ohm values are measured in impedance not resistance. Impedance = A/C resistance. I see where he uses P=IE (P=I*V) to demonstrate amp load. This is where it gets interesting as other variables come into play when you add frequency.

    If you load the amp with a higher value speaker than it was designed for, you may have to adjust volume to get "unity gain" to achieve the same db output as the original speaker. In that you can't control just the mid-bass level for example, you may have undesirable results. Should you change out all speakers to let's say 8 ohm where the factory installed 4 ohm, you may find the volume knob has to be driven harder (1/4 turn) to get the same level as original. The amp can handle the load but is closer to clipping meaning there's less headroom and it won't go as loud. This is only noticeable with frequencies that suck power - Mid-bass and subs. Mid range and tweeters are barely noticeable (if at all) when substituting 4 ohm units into factory 2 ohm locations you will find they work fine. There are many variables with speaker design where a replacement unit may have better efficiency than the factory flavor where even though it may have a higher ohm value, it may produce better, even louder sound due to its efficiency.

    Basically, there is considerable voo-doo going on here and no one is wrong with their contributions. But it's frequency dependant. Amps shouldn't be loaded with higher ohm speakers with demanding frequencies - mid-bass and subs. You will take away overall headroom and gain. But mid and high freq. speaker impedance is more forgiving to the amp because it's not "working" hard to drive them. Therefore, substituting a 4 ohm mid or tweeter will not be audibly noticeable or damage anything. Size and depth are more of a concern.

    Note: installing a 4 ohm mid-range into an 8 ohm location will work and not be twice as loud as thought. I didn't mention this above as the thread was talking about going from a lower to higher value. The 4 ohm speakers, in this case, will be less working load on the amp but again, due to the cone material, voice coil winding and magnet pull, efficiency may be more responsive. Trust me, they won't suddenly seem punchy because of the lower impedance.

    Speaker sizes are exactly the same in both the Standard and HK audio systems. The main difference between the two systems are the speakers impedance rating.

    6.25" Midbass
    HK : 3 ohms
    Standard : 2 ohms

    2.5" Midrange
    HK: 4 ohms
    Standard : 8 ohms

    .75" Tweeter
    Hk : 3 ohm
    Standard : 8 ohm
    Last edited by White Knuckles2; 02-07-2011 at 12:43 AM. Reason: Automerged Doublepost
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