Which speaker companies are honest when rating their impedance, and which companies lie?

[Pyrrho]

...
Speaker manufacturers lying about the impedance of their speakers encourages amplifier manufacturers to make amplifiers that are not rated for less than 8 ohms. First, even if it can honestly deal with 4 ohms, the lying speaker manufacturers will put out a speaker that is 2 ohms with a higher rating and risk damage to the amp. Second, if every speaker is rated high, then amplifier manufacturers can sell a product that is only rated for high impedances, because it will then seem to be compatible with everything. The motive to make an amplifier capable for low impedances comes from having speakers of low impedances, and if the makers of speakers choose to rate them too high, then there is no need for amplifier makers to bother with anything better to make a sale.

So in fact, you have it exactly backwards.

That statement is no near right.
Manufacturers who insist on building $300 5~7 channel AVRs with NO pre outs are just being as cheap as cheap can get. Build it cheaper = more profit.
Why is it that the AVRs with pre outs are always the ones with the highest power output, and the highest price?
When in fact, the AVRs with low power are the ones that need to have pre outs. Because adding 5~7 pre outs would increase their cost.
But what is that added cost? It can not be much.

The explanation of the statement in bold are the statements immediately following it.

Think of it this way: If all speakers were rated as being 8 ohms, then there is little incentive for an amplifier manufacturer to make an amplifier rated for less than 8 ohms. After all, according to the speaker maker, it isn't necessary, and the average person buying an amplifier can see that an amplifier rated for 8 ohms should be compatible with a speaker rated as being 8 ohms. So the lies that speaker makers tell encourages amplifier makers to take shortcuts on amplifiers.

If every speaker were rated as being 4 ohms, then an amplifier maker whose amplifiers are rated as being for 8 ohms minimum would not sell very many amplifiers, as everyone could see that such an amplifier would not be compatible with the speakers available. Imagine a car amp that is rated for 8 ohms minimum, and you can imagine a product that would not sell very well, given the fact that car speakers are mostly rated as being 4 ohms. So what the speaker makers claim about their speakers is a significant factor in what amplifier makers will make.


Now, it is true enough that many amplifier manufacturers cut corners with low end products. It would be impossible for them not to at such prices. But they are not rating them as being suitable for driving low impedance speakers, so they are not lying about what the amplifier can do.

You see the difference? In one case, we have manufacturers lying about their products, and in another case, we have manufacturers making cheap products but not lying about them.

 

[Pyrrho]

That statement is very sensible. It sounds as if they know there are hardly any 8 ohm speakers.

To sum it up the speaker manufacturers try and hide the true impedance so as to not loose sales. [emphasis added]

The receiver manufacturers only give an 8 ohm rating, to conceal how much current their amps will actually deliver, so as to not loose sales.

Marketers are a perfect curse!

There is a difference between omitting information (and they all will necessarily do that, as there are countless things that can be said of any piece of gear), and actively saying something false. In the case of many (though obviously not all) speaker manufacturers, they simply lie about the electrical characteristics of their speakers in order to make a sale. I am no lawyer, but that sounds like fraud to me.

I would guess that it does not legally constitute fraud in this case because there appears to be no legal definition of nominal impedance, even though, as I have demonstrated already, there is such an idea among electronics experts.

Like with other businesses, there needs to be a legal requirement in order to get a change in such fraudulent practices. Just like the changes in the laws regarding power output specifications; before the standard RMS ratings, they were quite crazy and generally worthless. Now one can compare, as long as one is smart enough to look at the details (such as impedance and distortion and frequencies). But before standardization of power ratings, the numbers were virtually meaningless, and one could not compare the numbers from one manufacturer to another in any straightforward way. Just like the impedance claims of many speaker makers today.

Regarding your statement I have highlighted in bold, why don't you have a problem with manufacturers lying about their products? Why don't you care that they willfully mislead people about what they are selling? Do you think there should be no rules and regulations, and that fraud should be legal?


************


For those who have wondered if a low impedance can harm an amplifier, you can try this experiment: Short out the output of your amplifier (that is, hook a wire from the plus to the minus on each channel), and turn it on and try to play some music. That will be giving the amplifier a nearly 0 ohm load. If it has adequate protection circuitry, it may not damage the amplifier, and it may simply cut out. Otherwise, it is likely to destroy it.


No manufacturer should lie about their products. I am frankly amazed that anyone disagrees with that concept. And yet many have expressed the idea that it is fine for manufacturers to lie and willfully mislead people about their products!

 

[DD66000]

A speaker's impedance is NOT a finite, hard number. It changes as the frequency changes. The JBL L890, for example is rated 8Ω.
And for most of the FR, it is or close to it. Its only from about 250 ~ 80 htz it dips to around 4Ω. But the HK AVR635 I had at the time could drive them with no problem. But when connected to a 220w amp via the 635 pre outs, the L890 certainly played with more authority from 250~80.

 

[TLS Guy]

There is a difference between omitting information (and they all will necessarily do that, as there are countless things that can be said of any piece of gear), and actively saying something false. In the case of many (though obviously not all) speaker manufacturers, they simply lie about the electrical characteristics of their speakers in order to make a sale. I am no lawyer, but that sounds like fraud to me.

I would guess that it does not legally constitute fraud in this case because there appears to be no legal definition of nominal impedance, even though, as I have demonstrated already, there is such an idea among electronics experts.

Like with other businesses, there needs to be a legal requirement in order to get a change in such fraudulent practices. Just like the changes in the laws regarding power output specifications; before the standard RMS ratings, they were quite crazy and generally worthless. Now one can compare, as long as one is smart enough to look at the details (such as impedance and distortion and frequencies). But before standardization of power ratings, the numbers were virtually meaningless, and one could not compare the numbers from one manufacturer to another in any straightforward way. Just like the impedance claims of many speaker makers today.

Regarding your statement I have highlighted in bold, why don't you have a problem with manufacturers lying about their products? Why don't you care that they willfully mislead people about what they are selling? Do you think there should be no rules and regulations, and that fraud should be legal?


************


For those who have wondered if a low impedance can harm an amplifier, you can try this experiment: Short out the output of your amplifier (that is, hook a wire from the plus to the minus on each channel), and turn it on and try to play some music. That will be giving the amplifier a nearly 0 ohm load. If it has adequate protection circuitry, it may not damage the amplifier, and it may simply cut out. Otherwise, it is likely to destroy it.


No manufacturer should lie about their products. I am frankly amazed that anyone disagrees with that concept. And yet many have expressed the idea that it is fine for manufacturers to lie and willfully mislead people about their products!

A short circuit is hardly a fair test!

But with respect I think you a flogging a dead horse. You are not going to find an 8 ohm speaker these days and you would not want one if you could.

To really estimate a the load of a speaker, requires the curve and phase angle and then you need cosine tables to actually see what the impedance of the speaker is at a given frequency.

Despite your previous post, nominal impedance is a useless term, and of no value in deciding the difficulty or other wise of a load. The average consumer is not going to be able to do that.

There was a paper a few years ago, that had the math and an index of load difficulty. The originator called it the amplifier torture test index. Industry showed no interest as you might expect.

Now lets put this in perspective. Her is is one of my three way designs, form three 8 ohm drivers. I used all known techniques to get the load as resistive as possible. Component count for each crossover ended up being 27. This is the result.

Now a budget speaker will not have a 27 part count. So having a go at speaker manufacturer's is tossing at windmills.

The receiver manufacturers could solve this easily, by quoting the power into 8 and 4 ohm. It is easy math then for most consumers to work out the current limitations of the receiver's amplifiers. They choose not to and that speaks volumes. So as Irvrobinson said in a previous post if you buy one of those cheap receivers: - caveat emptor.

There really is no more to be said. It's flogging a dead horse beyond this point.

 

[Pyrrho]

A short circuit is hardly a fair test!

But with respect I think you a flogging a dead horse. You are not going to find an 8 ohm speaker these days and you would not want one if you could.

To really estimate a the load of a speaker, requires the curve and phase angle and then you need cosine tables to actually see what the impedance of the speaker is at a given frequency.

Despite your previous post, nominal impedance is a useless term, and of no value in deciding the difficulty or other wise of a load. The average consumer is not going to be able to do that.

There was a paper a few years ago, that had the math and an index of load difficulty. The originator called it the amplifier torture test index. Industry showed no interest as you might expect.

Now lets put this in perspective. Her is is one of my three way designs, form three 8 ohm drivers. I used all known techniques to get the load as resistive as possible. Component count for each crossover ended up being 27. This is the result.

Now a budget speaker will not have a 27 part count. So having a go at speaker manufacturer's is tossing at windmills.

The receiver manufacturers could solve this easily, by quoting the power into 8 and 4 ohm. It is easy math then for most consumers to work out the current limitations of the receiver's amplifiers. They choose not to and that speaks volumes. So as Irvrobinson said in a previous post if you buy one of those cheap receivers: - caveat emptor.

There really is no more to be said. It's flogging a dead horse beyond this point.

You are again writing nonsense, and are also ignoring the issue of dishonesty entirely. You have, however, made it very easy to prove that you do not know what you are writing about. Here you go for a cheap speaker that is 8 ohms; the Pioneer SP-FS52:

Pioneer SP-PK52FS 5.1 Speaker System Measurements and Analysis | Audioholics

Ironically, the speaker manufacturer rates it as 6 ohms, which might be due to the other speakers in the set being actually 6 ohms.

For a more expensive speaker that is 8 ohms:

Aurum cantus

Notice the minimum impedance. Those are very definitely worth owning.

Those are two that I found quite quickly, and undoubtedly many more could be found if one were to bother searching for them. But their existence proves beyond all doubt that you are simply wrong.


As for "nominal impedance" being a useless term, that is the result of it evidently having no legal definition. (Anything without a legal definition is useless in the description of a product.) If it were legally defined as the minimum impedance times 1.15, then it would be useful for determining whether a particular speaker would be suitable for use with a particular amplifier. Or if the IEC method were used ("The IEC method of specifying nominal loudspeaker impedance is set such that minimum impedance must not fall below 80% of nominal, so for an 8 ohm speaker this would be 6.4 ohms minimum, and for 4 ohms would be 3.2 ohms."), as for the above determinations, it would be useful for matching speakers with amplifiers. The fact that many manufacturers choose to mislead people with bogus nominal impedance ratings is precisely the problem that this thread is about.

Blaming amplifier makers for this is absurd and ridiculous. Knowing that a particular amplifier can deliver more current than another will still not tell you whether either is suitable for use with a particular speaker if one does not know what the impedance of the speaker actually is. It could well be that neither amplifier would work, or either one might work, or it might be that one would work better for one speaker, and another might work better for another speaker. But in order to make such determinations, one would have to have reliable data on the speaker impedance, not some random number that is basically meaningless.

It is interesting that you regard dishonesty in business as not a problem. At least, not when it is the dishonesty of speaker manufacturers. You don't make speakers for a living, do you?

 

[DD66000]

Notice the minimum impedance. Those are very definitely worth owning.

So in your mind if an 8Ω speaker's lowest impedance is 6.4Ω its a good buy.
But if an 8Ω speaker's lowest impedance is 4Ω its a bad speaker. BS!

If that is your criteria for determining if a speaker is good/bad, I suspect there are many very good speakers you would pass on. Your loss.

 

[Irvrobinson]

for 90% of the people that buy them

I agree, and 90% is probably low.

 

[gene]

I don't think dishonest is the word. I think it is don't discourage sales. There is no definition of impedance rating. In other words a manufacturer is free to quote an impedance from any part of the curve he wants to.

Frankly any speaker that does not drop it impedance below 500 Hz to the tuning peak or peaks, you likely don't want.

The only devices that I know of that are inclined to go into reset, over heat and or blow up when confronted with four ohm loads or difficult phase angles are receivers. Most have lousy power amp sections that are not worth the time of day.

I don't blame the speaker manufacturers for this. The receiver manufacturers are squarely in my sites for producing units not fit for purpose.

I have been in the field a long time and I never remember this being an issue, until some lunatics got the ideal of cramming a radio, HDMI boards, Internet streaming, preamp, Dacs, bass management, and five or seven power amps is a box and charging $300 or less for it.

That's the problem, not the speaker manufacturers. I don't know of a speaker, where the speaker manufacturer should expect a device connected to it should blow up. Complain to the guys that make the junk that blows up. They are the villains.

The IEC standard is pretty set for speaker impedance.

Loudspeaker Measurements Standard: Our Procedure for Objectively Analyzing Speaker Performance | Audioholics

Honestly people beat up receiver manufacturers about power ratings when those companies are giving you every technology under the sun for dirt cheap and essentially throwing in a decent amp section for free. Meanwhile, there are some subwoofer companies claiming a 2400 watt amp will do 8kwatts and nobody really gives them and grief.

While fudged specs are part of the game in any industry, since this topic deals with speakers, I'd say that many speaker companies like to play around with impedance and sensitivity ratings to give their products a marketing edge. This is why 3rd party verification is such a necessary asset when choosing between speakers.

 

[Irvrobinson]

You are again writing nonsense, and are also ignoring the issue of dishonesty entirely. You have, however, made it very easy to prove that you do not know what you are writing about. Here you go for a cheap speaker that is 8 ohms; the Pioneer SP-FS52:

Pioneer SP-PK52FS 5.1 Speaker System Measurements and Analysis | Audioholics

Ironically, the speaker manufacturer rates it as 6 ohms, which might be due to the other speakers in the set being actually 6 ohms.

For a more expensive speaker that is 8 ohms:

Aurum cantus

Notice the minimum impedance. Those are very definitely worth owning.

Those are two that I found quite quickly, and undoubtedly many more could be found if one were to bother searching for them. But their existence proves beyond all doubt that you are simply wrong.


As for "nominal impedance" being a useless term, that is the result of it evidently having no legal definition. (Anything without a legal definition is useless in the description of a product.) If it were legally defined as the minimum impedance times 1.15, then it would be useful for determining whether a particular speaker would be suitable for use with a particular amplifier. Or if the IEC method were used ("The IEC method of specifying nominal loudspeaker impedance is set such that minimum impedance must not fall below 80% of nominal, so for an 8 ohm speaker this would be 6.4 ohms minimum, and for 4 ohms would be 3.2 ohms."), as for the above determinations, it would be useful for matching speakers with amplifiers. The fact that many manufacturers choose to mislead people with bogus nominal impedance ratings is precisely the problem that this thread is about.

Blaming amplifier makers for this is absurd and ridiculous. Knowing that a particular amplifier can deliver more current than another will still not tell you whether either is suitable for use with a particular speaker if one does not know what the impedance of the speaker actually is. It could well be that neither amplifier would work, or either one might work, or it might be that one would work better for one speaker, and another might work better for another speaker. But in order to make such determinations, one would have to have reliable data on the speaker impedance, not some random number that is basically meaningless.

It is interesting that you regard dishonesty in business as not a problem. At least, not when it is the dishonesty of speaker manufacturers. You don't make speakers for a living, do you?

First of all, I think you're being needlessly rude.

While more information is always welcome, having another statute about it is not necessarily the perfect answer. Are you also going to mandate a discussion of electrical phase? Will amplifier manufacturers have to specify that their products are capable of driving rated output into highly capacitive loads, while not affecting frequency response by more than some specified number of decibels? And somehow this is useful by the public, where at least 90% of the population probably couldn't tell you the difference between resistance and impedance?

While I agree philosophically with TLS Guy that many AVR amplifiers are just so much under-engineered junk, I do continue to wonder, is there a problem for the large majority of consumers? Are you making a mountain out of a molehill, as fmw asks? My sense is that you are. How many people are really damaging amplifiers because some speaker manufacturer forgets to tell anyone that their impedance curve drops to three ohms at 50Hz, because that was the only way to get reasonable 50Hz output from a too-small woofer that needed a highly-damped cone to lower the resonance frequency, which lowered efficiency, so the driver designer lowered the voice coil impedance to draw more current in an attempt to even things up?

Is there documentation of amplifiers being damaged?

 

[DD66000]

Since we are talking about dishonesty, I find it much more dishonest of amp manufacturers that label a multi-channel amp 250w, but that is only one channel driven.
And then in small print, 180w all channels driven.

If I have an 8Ω rated speaker that drops to 4Ω around 80 htz, I don't have a problem with that. Because, the impedance is always fluctuating.

 

[Irvrobinson]

Honestly people beat up receiver manufacturers about power ratings when those companies are giving you every technology under the sun for dirt cheap and essentially throwing in a decent amp section for free.

If only they were marketed with that sort of honesty. Actually, if I were running surrounds, and not 2.1 as I do, I would use an AVR with pre-outs, because rightly or wrongly I've always considered surround speakers a waste of a great amplifier.

 

[PENG]

If only they were marketed with that sort of honesty. Actually, if I were running surrounds, and not 2.1 as I do, I would use an AVR with pre-outs, because rightly or wrongly I've always considered surround speakers a waste of a great amplifier.

Only 2 years ago I was using a 4308+amps for the LCR, now I am running 7.1 separates with 5 unused amp channels. I found absolutely no gain in my HT enjoyment and would have no trouble going back to something like a X4000+amp for the LCR so yes preouts are important to me but I am not interested in entry level AVRs regardless, not even for HT. However, if for some reason I have to downgrade my life style some day, I wouldn't have problem accepting a near entry level AVR but then I wouldn't need external amp or preouts in those scenarios.

I cannot understand why people have such trouble with the way most major brands (Denon,Marantz,NAD,Anthem,Yamaha,Pioneer etc.) specify their features and power output. They keep flocking the horse about their non ACD power rating, when AH, and respectable manufacturers such as Yamaha have previously explain why they would rather focus on dynamic power capability then ACD capability, even HK has apparently waken up.

 

[PENG]

So in your mind if an 8Ω speaker's lowest impedance is 6.4Ω its a good buy.
But if an 8Ω speaker's lowest impedance is 4Ω its a bad speaker. BS!

If that is your criteria for determining if a speaker is good/bad, I suspect there are many very good speakers you would pass on. Your loss.

I don't think he is saying that at all. He is simply saying there are 8/6.4 ohm speakers can be good speakers, that does not mean 8/4 ohm speakers are bad.

 

[PENG]

Since we are talking about dishonesty, I find it much more dishonest of amp manufacturers that label a multi-channel amp 250w, but that is only one channel driven.
And then in small print, 180w all channels driven.

So they focus and emphasize their strong points, not much wrong (not saying its totally right either) with that and is a far cry from being dishonest. Just to be off topic one more time, the design/manufacturing teams don't have an unlimited budget so they have to make some tough choices. it may actually be wise to invest on maximizing dynamic power and 2 channel power output capability than ACD and continuous duty. For real world HT and music applications higher dynamic power and 1,2,&3 channel driven power output are better for SQ and overall enjoyment than lower overall but ACD power rating. If you want to see an example, you can compare the HTM lab measurements of the Denon AVR-3805 and HK AVR-630 that are in the same price range. Actually that example is not the best because even though the Denon's ACD drops quite a bit below their 2 channel output, their ACD output still beat the HK's. That being the case, it still demonstrates the principles of optimizing for real world applications where music and HT contents don't benefit a lot from ACD capability.

 

[TLS Guy]

Only 2 years ago I was using a 4308+amps for the LCR, now I am running 7.1 separates with 5 unused amp channels. I found absolutely no gain in my HT enjoyment and would have no trouble going back to something like a X4000+amp for the LCR so yes preouts are important to me but I am not interested in entry level AVRs regardless, not even for HT. However, if for some reason I have to downgrade my life style some day, I wouldn't have problem accepting a near entry level AVR but then I wouldn't need external amp or preouts in those scenarios.

I cannot understand why people have such trouble with the way most major brands (Denon,Marantz,NAD,Anthem,Yamaha,Pioneer etc.) specify their features and power output. They keep flocking the horse about their non ACD power rating, when AH, and respectable manufacturers such as Yamaha have previously explain why they would rather focus on dynamic power capability then ACD capability, even HK has apparently waken up.

I agree and don't care about ACD for the reasons you state. However I think they should give an 8 and 4 ohm power rating, and only one channel driven would be acceptable to me. Then I would know how robust the output stage was.

 

[TLS Guy]

You are again writing nonsense, and are also ignoring the issue of dishonesty entirely. You have, however, made it very easy to prove that you do not know what you are writing about. Here you go for a cheap speaker that is 8 ohms; the Pioneer SP-FS52:

Pioneer SP-PK52FS 5.1 Speaker System Measurements and Analysis | Audioholics

Ironically, the speaker manufacturer rates it as 6 ohms, which might be due to the other speakers in the set being actually 6 ohms.

For a more expensive speaker that is 8 ohms:

Aurum cantus

Notice the minimum impedance. Those are very definitely worth owning.

Those are two that I found quite quickly, and undoubtedly many more could be found if one were to bother searching for them. But their existence proves beyond all doubt that you are simply wrong.


As for "nominal impedance" being a useless term, that is the result of it evidently having no legal definition. (Anything without a legal definition is useless in the description of a product.) If it were legally defined as the minimum impedance times 1.15, then it would be useful for determining whether a particular speaker would be suitable for use with a particular amplifier. Or if the IEC method were used ("The IEC method of specifying nominal loudspeaker impedance is set such that minimum impedance must not fall below 80% of nominal, so for an 8 ohm speaker this would be 6.4 ohms minimum, and for 4 ohms would be 3.2 ohms."), as for the above determinations, it would be useful for matching speakers with amplifiers. The fact that many manufacturers choose to mislead people with bogus nominal impedance ratings is precisely the problem that this thread is about.

Blaming amplifier makers for this is absurd and ridiculous. Knowing that a particular amplifier can deliver more current than another will still not tell you whether either is suitable for use with a particular speaker if one does not know what the impedance of the speaker actually is. It could well be that neither amplifier would work, or either one might work, or it might be that one would work better for one speaker, and another might work better for another speaker. But in order to make such determinations, one would have to have reliable data on the speaker impedance, not some random number that is basically meaningless.

It is interesting that you regard dishonesty in business as not a problem. At least, not when it is the dishonesty of speaker manufacturers. You don't make speakers for a living, do you?

Clearly the Pioneer has used 16 ohm bass mids. These are not common at all with practically none on the OEM market.

I doubt the Aurum Cantus is fully BSC compensated. They are made by a Chinese OEM company and sold pretty cheap in China as Haihuang and given a fancy name in the west.

You have never designed a speaker. I can tell you that you have no or little control over the impedance. You have to take what you get when you are done.

My speaker I referenced would be 6 ohm nominal at least. I equalized the impedance as I was doffing the hat to Raymond Cooke who felt this was a good thing and used these techniques extensively in his later designs. However I gave up a lot of sensitivity and still need a big amp.

As I speaker designer I would expect amps out there to drive any speaker without blowing up. But as others have stated, I'm not sure if speakers are blowing up amps. If as you suggest they are, then the receiver manufacturers need to address it, as it is virtually impossible for the speaker designer to do so.

 

[DD66000]

I agree and don't care about ACD for the reasons you state. However I think they should give an 8 and 4 ohm power rating, and only one channel driven would be acceptable to me. Then I would know how robust the output stage was.

Most certainly having 8Ω and 4Ω power ratings is what is best. My old Citation 19 clearly shows both and when bridged.
But unless we are talking a mono amp or one that can be bridged, I do not want to see "one channel driven" spec used to describe a multi-channel amp.
It should always be 2 channels driven. With the exception of a center channel, speakers are always used in pairs.

 

[PENG]

Most certainly having 8Ω and 4Ω power ratings is what is best. My old Citation 19 clearly shows both and when bridged.
But unless we are talking a mono amp or one that can be bridged, I do not want to see "one channel driven" spec used to describe a multi-channel amp.
It should always be 2 channels driven. With the exception of a center channel, speakers are always used in pairs.

I fully agree with you on this, but I think TLSG just want to see how robust the amp section is, not the power supply.

 

[DD66000]

There is something to be said for how much reserve power an amp has. My Citation 19 stereo amp is much heavier than the 7 channel HK AVR.
The transformers, and 4 caps are huge in the 19. At only 100w rated, that amp never comes close to breaking a sweat.

 

[PENG]

I agree and don't care about ACD for the reasons you state. However I think they should give an 8 and 4 ohm power rating, and only one channel driven would be acceptable to me. Then I would know how robust the output stage was.

If you trust some of the lab measurements published by HTM, S&V, HCC etc., you would know the output stages of most AVRs may be more robust than you think they are. Take a look of the figures from the following link for outputs into 8/4 ohms at 1% THD.

http://forums.audioholics.com/forums/amps-pre-pros-receivers/85615-avr-power-output-comparison.html

and to see the numbers at 0.1% THD you can visit the HTM site http://www.hometheater.com/equipment-reviews

I also found another UK site that has more measurements. I pasted some test results below to show how well a couple of older AVRs compared to some power amps.

HK 630
2 ch driven continuous: 121W/196.6W/8/4 ohms @ 0.5%, Dynamic output: 289.5W @ 0.3% into 2 ohms

Denon 3805
2 ch driven continuous: 164.4W/260.2W/8/4 ohms/0.9%/0.5%, Dynamic output: 299.9 @ 0.9% into 2 ohms, 160.3W @ 0.8% into 1 ohm

Onkyo 5007
2 ch driven continuous: 172.2W/282.6W/8/4 ohms/0.5%/0.7%

Quad 909
2 ch driven continuous: 157.5W/258.0W/8/4 ohms/1.0%/0.7%

Halo A21
2 ch driven continuous: 290.8W/477.7W/8/4 ohms/0.5%/0.1%
Dynamic output into 1 ohm (Failed) Note: not sure what they meant by "failed".

Bryston 4B SST2
2 ch driven continuous: 356.9W/569.1W/8/4 ohms/0.5%/0.6%
Dynamic output into 1 ohm: 1828.9W @ 0.004%

Note that the AVRs 8/4 ohm output ratios are quite comparable to those of the power amps. I think their limits are the power supplies, but the amp sections are actually quite robust.