# Speaker Impedance setting on receivers



## Andre (Feb 15, 2010)

What in the world does this actually do? No speaker in the world that I know of has a flat impedance curve, nominal impendance is "subject to change without notice".


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## Jungle Jack (Jul 28, 2009)

Hello,
The 4 Ohm Setting is a Safety Measure that throttles back the amount of available power. A 4 Ohm Nominal Speaker presents a more challenging load on an AVR. In addition, for an AVR to be UL Certified, a 4 Ohm Setting is almost always required. 

Especially on AVR's with weak Amplifier Sections, a Speaker which dips below 4 Ohms can and often does cause an AVR to go into Protection Mode or worse when the Volume Setting is high.

The thing is most Speakers which go into low impedances are fairly expensive with the expectation that the partnering Components will be expensive as well. With the inverse, most Budget Speakers are 8 Ohm Nominal. The scary thing is the "White Van Speakers" which are sold under a myriad of Audiophile Sounding Brand Names which are absurdly poor Designed and often do have huge Impedance Drops. In the most extreme cases, such as with Electrostatic and Planar Speakers which can drop below 1 Ohm, an outboard Amplifier is all but required.

All I can say is even if your Speakers are 4 Ohm Nominal to first try the 6 Ohm Setting and carefully raise the Volume and if steady, set it and forget it. Only if your AVR is contantly going into Protection when Playback is high would I use the 4 Ohm Setting. And then, I would look for an outboard Amplifier if Preamp Outputs are present or an more powerful AVR as the 4 Ohm Setting causes a major loss of available power.
Cheers,
JJ


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## Andre (Feb 15, 2010)

Are their receiver amplifier sections that can easily take dips below 4ohms? Also what happens to the same amplifier if the impedance spikes at 32ohms? Is that just as bad?

Its sad that most if not all listed specifications for amplifiers on recievers are so vague. I would like to know the rated output 20-20 rather then at 1k, ALL channels driver at the same time rather then individual channels.....etc

Some have said that weight is a nice key, however, the manufactures probably figured that too and jmust add dead weight.


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## Jungle Jack (Jul 28, 2009)

Andre said:


> Are their receiver amplifier sections that can easily take dips below 4ohms? Also what happens to the same amplifier if the impedance spikes at 32ohms? Is that just as bad?
> 
> Its sad that most if not all listed specifications for amplifiers on recievers are so vague. I would like to know the rated output 20-20 rather then at 1k, ALL channels driver at the same time rather then individual channels.....etc
> 
> Some have said that weight is a nice key, however, the manufactures probably figured that too and jmust add dead weight.


Hello,
In the Internet Age, I truly do not believe AVR Manufacturers add dead weight as many Reviews include Pictures of the AVR with the Cover off. Germany's Areadvd.de does excellent Reviews which are quite comprehensive about the Amplifier Stages of AVR's. Also, low Impedance is what I would be more concerned about as opposed to say a Speaker spiking up to 32 Ohms.

And indeed 98% of Manufacturer's quoted Specs do not come anywhere near the Rated Specs of the AVR. This is especially the case with Entry Level AVR's. That being said, most Home Theaters do not need 100 Watts into every Channel to attain Reference Levels. It is predicated on the size of the Room, Speakers used, and so forth.

I truly think the way to go is to get a Mid Range AVR that offers Preamp Outputs and add outboard Amplifiers.
I have been doing this for well over a Decade. There are a myriad of Amplifier choices out there with Amplifiers like many of the Behringers being available for a couple hundred Dollars and outputting some serious power.

I personally prefer Class A/AB Amplifers like the Parasound and Aragon Amplifiers that I use, but almost any outboard Amplifier Topology will be an upgrade over the Amplifier Stage in most AVR's.
Cheers,
JJ


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## Jungle Jack (Jul 28, 2009)

Hello,
Here is a great Article about the Impedance Sector in AVR's:http://www.audioholics.com/education/amplifier-technology/impedance-selector-switch-1

It does an excellent job of explaining why you really should not use the 4 Ohm Setting as it massively reduces available Power in almost all AVR's.
JJ


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## lcaillo (May 2, 2006)

I would not say that one should not use the impedance selector *BECAUSE* it reduces available power. I would suggest that one understand when this mode should be used and when it is needed it *IS PRECISELY BECAUSE* it reduces available power.

The article is a good one, overall, but as in most cases there is almost always more to the story. It suggests that there is no reliablility benefit to using this limitation. While Yamaha may have said that they have noted no changes in failures since beginning the use of the voltage swing limits, I would be very surprised if any vendor would admit that there was a problem with their products that something like this fixed. That is simply the way that these companies answer this kind of question. It is simply the safest answer to limit exposure to both new and old customers. From first hand experience with hundreds of installations and sales of Yamaha receivers over 30 years, what I can say is that using the proper impedance selection does dramatically reduce instances of protection shutdown. The reason that there is not a big change in failures is that the products are well protected, and it take a lot of repeated abuse these days to cause output or power supply failures.

The fact is that many receivers cannot deliver the power to properly drive low impedance speakers, or do not have the cooling system needed to sustain operation at lower impedances for very long at high levels. Reducing the voltage on the rails to keep the system operating within its limits is a reasonable tool that works adequately for many applications. So how do you know when you need to use the low impedance setting?

Well, when in doubt, play it safe and use it. Otherwise, frankly, in most cases it won't hurt much to run the unit into a marginal impedance. Make sure it is well ventilated and if it shuts down you know you are pushing it too hard or it simply won't drive the load. If so, try the switch. Just don't keep pushing an amp into protection. They are far more bulletproof than units of the past but it is still not a good idea.

Voltage limiting the power supply like they do with these switches is one way to limit the power. The other way is to keep the impedance of the load from dropping too low. This is done with a resistor in line with the load, as is found in many switching units with impedance protection. The problem with this method is that you are not only current limiting, but you are dissipating some of the power in the resistor. That means that you are both limiting the output at the speakers AND wasting power, but the amp is delivering the current that is heating up that resistor. The next improvement in stress on the amp is less over the long run than lowering the voltage swing on the power supply rails as is done with the switch in most modern units.


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## Jungle Jack (Jul 28, 2009)

Hello,
That is exactly what I recommended a few Posts back. I should have made the distinction about not using the 4 Ohm Setting unless your Speakers are 4 Ohm Nominal and you are experiencing Shutdowns. That is if ones Speakers are causing the AVR to go into Protection to then use the 4 Ohm Setting. I said this after first attempting to use the 6 Ohm Setting and carefully raising the Volume Control and if there are issues, use the 4 Ohm Setting and seriously consider an Amplifier or in the case of not having Preamp Outputs a new AVR.

Thankfully, most Speakers that are used with Entry to Mid Level AVR's are generally not difficult to drive. It is primarilly with Speakers that cost in the Thousands that Low Impedances are a factor.

However, I was primarily pointing this out as many with 6/8 Ohm Nominal Speakers do presume that the 4 Ohm Setting actually results in more available power when the inverse is true.
Cheers,
JJ


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