4-8ohm? - AVS Forum
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post #1 of 5 Old 01-26-2013, 02:05 AM - Thread Starter
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Hey People, I've been looking around at speakers and I've noticed some Magnat Quantum 1009 towers that have rated impedance of 4-8 ohms. What does this mean as most speaker I've found are rated at a straight 8 ohm? Is it selectable? The receiver I'm considering is a Denon 2313 is only rated down to 6 ohms, does that mean I can't run speakers rated with this 4-8 rating?
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post #2 of 5 Old 01-26-2013, 04:38 AM
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this somewhat means that some 8 ohm speakers will dip into the the 4 ohm realm and should have no effect on your reciever

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post #3 of 5 Old 01-26-2013, 06:57 AM
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Quote:
Originally Posted by smasher50 View Post

this somewhat means that some 8 ohm speakers will dip into the the 4 ohm realm and should have no effect on your reciever
More likely it means that they're 6 ohm speakers and the manufacturer is playing fast and loose with the specs.
Technically a speakers nominal impedance is based on the measured DC resistance, with the DCR averaging 0.7 times the impedance. For a 4 ohm speaker it should be no less than 2.5 ohms, for an 8 ohm speaker no less than 5 ohms. A receiver rated for 6 ohms will not be happy with a speaker DCR of less than 4 ohms, so if in doubt you need to get that DCR figure. If you can't get it look at a different speaker.

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post #4 of 5 Old 01-26-2013, 07:22 AM
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You need to realize that every speaker system has a different impedance at each frequency.

To really see what the impedance of a particular speaker system looks like, you need to find a published graph of their impedance vs frequency.

It is very common for speakers to have an impedance between 3 and 5 ohms at some frequency below 100 Hz, and then go up to as high as 20 ohms or so at some higher frequency.

Your receiver will no doubt handle TWO speakers that go down to 4 ohms, but if you try to run 5 speakers with impedance that low, the receiver power supply will not be able to supply enough current to drive them all at higher volumes.

The speaker manufacturer should be able to supply you with a graph of impedance vs frequency for your speaker system model.
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post #5 of 5 Old 01-27-2013, 07:02 PM - Thread Starter
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Thanks people, I'll try to get my hands on that graph!
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