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Old 05-05-2009
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ohms?????

what does 60 watts at 4 ohms mean? whats the difference between 60 watts at 4 ohms nd 75 watts at 2 ohms? nd what are "bridged" ohms?
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Old 05-06-2009
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and Ohm is just a unit of electrical resistance.


a watt is just a unit of power.





images courtesy of Wikipedia.org

The measure of resistance determines how much current (amperes) will pass through a load with a given voltage.

The difference between 60w at 4ohm and 75w at 2ohm is:

60w @ 4ohm requires 15.5v and that voltage moves 3.8a of current.

75w @ 2ohm requires 12.2v and that voltage moves 6.14a of current.

The difference? 75w is more power. Some argue that high voltage, low current is the best way to transfer power, which it is, but in our case it is such a short distance that it really doesn't matter.
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Old 05-06-2009
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so which is better?
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Old 05-06-2009
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Ohms is resistance. So less is better. Not all amps can run low ohms. A typical car stereo system is 4 ohms while a home system runs at 8 ohms. You can't run a 8 ohm speaker on a amp designed to power a 4 ohm speaker. Running the higher ohms stresses the amp.

Bridged means you took two channels and combined them. My amp in my truck is bridged. So the amp has two channels but only one speaker connected to both which increases the power to the sub. Usually when you bridge you double the output. So if you bridge a 100x2 watt amp you will end up with 200x1.

More info: http://www.crutchfield.com/App/Learn...egory.aspx?c=3

Last edited by whippersnapper02; 05-06-2009 at 11:48 PM.
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Old 05-07-2009
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Quote:
Originally Posted by fddriver02 View Post
Ohms is resistance. So less is better. Not all amps can run low ohms. A typical car stereo system is 4 ohms while a home system runs at 8 ohms. You can't run a 8 ohm speaker on a amp designed to power a 4 ohm speaker. Running the higher ohms stresses the amp.

Bridged means you took two channels and combined them. My amp in my truck is bridged. So the amp has two channels but only one speaker connected to both which increases the power to the sub. Usually when you bridge you double the output. So if you bridge a 100x2 watt amp you will end up with 200x1.

More info: http://www.crutchfield.com/App/Learn...egory.aspx?c=3
What?

No, neither is better.

In the question you (OP) asked I *guess* some would say 75w is better because it is more power. However, there is more to good/loud sound than power. When transferring power over long distances or when you want less electrical interference, high voltage low current (which means high resistance) is the better way to transfer power. In most car audio applications this doesn't matter.

And no, you wont damage an amp for running it at a higher load than its minimum. A speaker is not a constant load. a "4ohm impedance" speaker means that free air, the average impedance for the driver's practical working frequency range is 4ohm when the coil is at room temperature. Put that speaker in a box and have it react with something besides an anecho environment and give it enough power to start heating up the coil and your impedance is way WAY higher than 4ohm.

This is the anecho/freeair graph of an "8ohm" driver resistance vs frequency


www.BCAE1.com is something everyone interested in car audio should read front to back.

Last edited by CBFranger; 05-07-2009 at 07:39 AM.
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Old 05-07-2009
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^^^From your own link: Note:
In car audio, resistance plays a vital role. When wiring speakers, you must have a safe load resistance to avoid destroying your amplifier. Read on to learn more on proper wiring of speakers, head units and amplifiers.

Last edited by whippersnapper02; 05-07-2009 at 11:55 AM.
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Old 05-07-2009
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Originally Posted by fddriver02 View Post
^^^From your own link: Note:
In car audio, resistance plays a vital role. When wiring speakers, you must have a safe load resistance to avoid destroying your amplifier. Read on to learn more on proper wiring of speakers, head units and amplifiers.
Sorry Christian, you are WRONG, it's only an impedance TOO low that will damage an amp, NOT too high.
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Old 05-07-2009
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Originally Posted by Takeda View Post
Sorry Christian, you are WRONG, it's only an impedance TOO low that will damage an amp, NOT too high.
Hmmm. I was told different. All well. Guess I was WRONG.

^^^See. I CAN admit when I'm wrong.

Last edited by whippersnapper02; 05-07-2009 at 12:34 PM.
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