Audio Science Review = "The better the measurement, the better the sound" philosophy

@fair

Thus, while testing on 2 ohm has its merit, it appears from the discussion that testing on non-purely-resistive loads is of more interest to people with practical experience in designing and repairing amps.

 

It is not in my review charter to help either camp in that.  That aside, I did build an emulator of a 2-way speaker per stereophile.  And used it for a bit of testing.  It didn't reveal anything useful so I retired it.

I have used real headphones for headphone amps.  That too was a useless exercise as the back EMF combined with the impedance of the amp produced completely erroneous and misleading THD measurements. Similar situation exists with testing amplifiers with speakers.

Even if something useful popped out, who is to say that speaker is representative of any other?  It may be a corner case, an easy case, or a difficult case. Who knows.

I do vary the resistive load to test for load sensitivity and report on that (usually a problem with low-end class D amps although some high-end ones suffer the same).

Finally, keep in mind that any speaker or emulated load of one would have to be at very low power.  There, distortion may not be material at all (swamped by noise).  This is why JA at stereophile only uses is load emulation for frequency response test.

Yes, there is a $15,000+ load cube that provides a couple of reactive loads (NOT representing any real speaker).  Audio critic had one but I think it blew up on them and they no longer used it.  I would spend the money if I thought it would add value but it simply doesn't.

Making sure this point is understood: there is a very high bar for adding more tests to the suite that I run.  Every test suggestion must come with strong justification which I have not seen in any of your posts.  Folks on ASR routinely make such suggestions.  You want a new test?  Come back with real data that shows usefulness.  "Would be nice" isn't going to work.  A lot of things would be nice but not when it clutters existing measurements and take time and resources form testing other products.

@crymeanaudioriver - 

Please state for us what other names you've used on Audiogon. 

 

Tammy-

This guy is like a tick that burrows into Audiogon until he causes enough irritation to get booted out... Then comes back under another name and starts the process all over again. 

@henry99  Requoting you:

There has been NO ONE who says that measurements, ASR measurements or any measurements are useless!

Most seem to be like my (and Henry's) view. They aid in the evaluation of equipment, but I do not rely on them alone.

What has been the issue from the 1st page (of this forum) is the CULTURE of ASR!

And that to that, you keep reiterating their point again and again, ad nauseam.

For a man who flaunts his education, I would think you’d get it by now. (@crymeanaudioriver).  

Someone stumbling onto this thread might feel like this:

 

All the best,
Nonoise

@crymeanaudioriver 

 

if you didn't have only 9 posts, all in this topic, all effectively band-handed attacks on ASR, then I may take your post seriously. However, as you do have only 9 posts, all in this topic, I see no need to take you seriously. That would create an account, solely for the purpose of attacking ASR is definitely a point of interest. Education is important if you want to understand certain topics.

Yea, your right! 9 posts in 2 1/2 years.

You have what 72 posts in 1 week?

Silence is NOT a weakness, now matter how you want to spin it.

I am educated my friend, unlike you, I dont need to flaunt it.

Your still making my point however.

@crymeanaudioriver

 

The Infinity IRS wasn’t the amp killer, the kappa 8 and Kappa 9 were the amp killers.

@henry99 , if you didn't have only 9 posts, all in this topic, all effectively band-handed attacks on ASR, then I may take your post seriously. However, as you do have only 9 posts, all in this topic, I see no need to take you seriously. That would create an account, solely for the purpose of attacking ASR is definitely a point of interest. Education is important if you want to understand certain topics.

@crymeanaudioriver

You have neither proven the uselessness of ASR testing, nor have you provided alternatives

Sir you have been here rambling on for awhile now.

There has been NO ONE who says that measurements, ASR measurements or any measurements are useless!

Most seem to be like my view. They aid in the evaluation of equipment, but I do not rely on them alone.

What has been the issue from the 1st page is the culture of ASR!

And that to that, you keep reiterating their point again and again..ad nauseam.

For a man who flaunts his education, I would think you’d get it by now.

 

Amir don’t need a fanboy, fighting his battles.

Audio Science Review. Haha, I love that name. It's funny.

 

[START BOOK]

I see it differently. Sure, we learned quite a bit since these articles were written. Yet, the time during which they were published marked presence of many amplifiers designers and manufacturers in North America. They knew what they were talking about.

It was a comment about how amplifier design and speaker design has progressed. To your point, we have learned a lot.

 

A typical “moving the goalposts” / “straw-man” rhetorical manipulation. That discussion of IM correlation with THD is still conducted in the context of the amp’s linearity under best conditions, not in the context of the linearity of system comprised of amp+speaker.

Pointing out that this whole discussion (not you specifically) seems to be about picking your facts, or what you think they are. I spent more time learning about the math today. One of the joys of being somewhat retired. I don't have the engineering chops, but I took more than a few nasty math courses on the way to my PhD. By testing down to 2 ohms, where only the rare speaker reaches, there is significant exploration of the vast majority of speakers impact on stability.

 

Current limiting occurs in amps without specific current limiting circuits too. As an example, a heating up power transformer coil may in effect serve as a current limiter. Another example is insufficiently sized capacitive power bank.

The article, nor I differentiated what was current limiting, however, I believe the two examples you gave are not. This comes back to the math above.  Some EE's could probably jump in on that.

 

Look at the curves of THD vs output power characteristics of amplifiers, and you’ll see that typically, there is a rise in THD (and by extension in IM) long before the amp clips. The degree of such deterioration is typically frequency-dependent too.

 

Even I know that is about how the amplifier is designed and feedback. The feedback goes down as the frequency goes up. Going back to the math I learned today, as the feedback goes down, the stability will improve.

 

This is indeed one of the mechanisms explaining the phenomenon of some of the amps distorting significantly more while they are connected to a speaker compared to when they are connected to a dummy resistive load.

 

I think you made that up. That does not make sense.

 

Yes, occurrences when a commercially sold amplifier becomes unstable and turns into a generator while connected to a specific speaker are rare. Even though, the thread referred below has a description of a surprisingly common-case instance of that.

If you mean tube amps, I noted that, and that ASR rarely tests them.

 

However, just like with the discussion of THD and IM, we need to take into account that the amp-speaker system can “ring” for some time, instead of turning into a self-supporting generator. Some of the replies in the thread below describe precisely such occurrences.

Which brings us back to the 99.9% of the time it does not happen. "Ring for some time"? You mean unstable. Again, even I know that. Perhaps you should not be the person trying to lecture me on this.

 

However, some of the replies highlight the fact that in some other  market segments, including that of affluent audiophiles, larger speakers employing exotic transducers and much more sophisticated crossovers are more prevalent, and thus the events of ringing and self-generation are much more probable.

 

This is conjecture on your part. Fortunately, we can test this theory as Stereophile tests a lot of expensive speakers. Wilson Alexx5? No issue. Sabrina? No problem. Sasha, Alexia? No problem. Magico, 4 models, worst was 3 ohm, -60 degrees, not extreme by PowerCube article. B&W 801 - no issues. Big Magnepan? Child's play.  Soundlab?  Normally fine, but you can make the Brightness control nasty. Infinity IRS, etc. not as bad as many make out to be. Saw a note that tube amplifiers were considered in their design.

I will stick with my 99.99% and that seems to extend well into audiophile speakers. The corollary is no amp vendor provides any detailed measurements and you are hoping you detect this fault in a listening test.

 

There is no such consensus in that discussion. Interested readers can go there and see for themselves. I would roughly split the multitude of members posted there onto three categories:

1. Designers and restorers of amps from Western countries. They are for comprehensive testing with non-purely-resistive loads.

Restorer John is the only "restorer" and he does not come across as technical as others. More a tinkerer.  As the conversation progressed as noted, the consensus (always detractors) was low resistance for sufficient for goals.

 

1. Designers of amps from China. They are for limited testing with non-purely-resistive loads.

All 1 of them?

 

1. Vendors selling amps made from pre-built blocks, Amir, and some of Amir’s followers. They maintain that testing on purely-resistive load is not ideal, yet good enough for predicting amp’s performance in 99.99% of cases.

By far the most popular being Bruno Putzey designs and B&O. Nice thing given these are modules, they only need to be tested once to cover all units that will use them. 

 

Behavior of most amplifiers, including tube ones, does depend on the value of purely-resistive load, yet the change in behavior is much more predictable with the change in just the resistance value.

That is not a logical sentence.

 

Thus, while testing on 2 ohm has its merit, it appears from the discussion that testing on non-purely-resistive loads is of more interest to people with practical experience in designing and repairing amps.

 

I went back and saw that only one designer felt very strongly about it and he designed car audio amplifiers. That is not surprising given what car audio people will connect.  Going back to the math I learned today, if the designer knows the transfer function, they can estimate with high probability if the amp will be unstable.  You may want to read this:

https://d1.amobbs.com/bbs_upload782111/files_28/ourdev_548669.pdf

I had to read it 3 times, but this is very interesting too.
https://linearaudio.net/sites/linearaudio.net/files/volume1bp.pdf     That pokes holes in all the so called arguments about feedback.

 

Unless a member is an unscrupulous dealer pushing some version of snake oil, most of the “banter” deserves consideration, in my opinion. I give full credit to Amir for filtering out vast majority of such snake oil salesmen. However, the story doesn’t end there.

No it does not, no more than the banter on "medicine" by people with limited knowledge of what they are talking about. It is akin to people here talking about feedback, even a 100 of them, compared to Bruno and his article.

 

Similarly to doctors giving zero credence to patients describing their symptoms, and only relying on the results of locally available objective tests, amp designers and restorers only relying on simple measurements aren’t likely to keep their clientele for long.

Good marketing often wins over good product, and audio is no different. The first thing doctors often, if not normally do after hearing about the symptoms is to run tests. However, unlike audio, where only the external presentation matters, the patient describing symptoms are often the only measurements we may have of what is happening internally.  The issue presents not when the patient describes their symptoms, but when the patient tries to force their diagnosis on the doctor, even when the tests indicate otherwise. The test is almost always correct. The listening part criticality is to ensure there are not multiple issues at play. The communication part is letting the patient think they had influence when they had none.

 

Ignoring your not so subtle attempt of slighting me, a person whom you obviously don’t know much about.

Once again, interested readers can go there and see for themselves. They’ll find the traces of reductions exactly as I described them.

I will use this definition of redacted as I think it is appropriate:

to edit (text) so as to remove or hide confidential or sensitive information:

There is no evidence of this. When someone quotes another poster, it is normal, as one would also do here, to cut out what the replyer considers extraneous content w.r.t. their reply. That is not redacting, that is editing.  I have not seen nor experienced ASR "redact" anything, though they will suggest less harsh language.

 

Indeed, ASR runs on a more modern discussion platform than Audiogon. The “reply system” in practice also includes so-called moderation subsystem, or, in simpler terms, censorship features.

All forums, with few exceptions, have moderation, including this one. If you label ASR censorship, then you have to label all others.

 

Yet a discussion site with overreaching moderation generates its share of issues, both for regular members and site owners. I maintain that the ASR moderation has been such since about 2021.

I only passively use ASR these days, so I will not comment on this. That was not my experience as of 2 years ago when I was still active, though I did find it at times toxic. I think alternate means, i.e. a sand-box for people who don't fit in would be more appropriate. However, I go back to my comment, that many of the commenters here would effectively be flat earth followers on a science site given what they write. Hence, I am not surprised by how ASR treated them and I don't think it is unwarranted.

 

Nope, topic at hand is relevance of the testing Amir does on specifically power amplifiers to the subjective perception of audible distortions contributed by amp A vs amp B when connected to a specific speaker.

Except we come back to 99.9% or more of amplifier / speaker combinations will not have stability problems, ASR does not test tube amplifiers often, and based on my research, however, limited, that even audiophile speakers do not commonly have extreme characteristics, then there will be no change, at the amplifier level, with almost all speakers.

 

My position, as is the position of majority of ASR members with practical experience in designing and repairing power amplifiers who cared to express their opinions, is that the testing Amir has been conducting is marketed as more definitive than it shall be based on scientific understanding of the limited nature of the tests.

I will only state that you have no provided any concrete examples of where this is the case, not even strong potential examples, though I have accepted tube amplifiers could be most at risk here.

 

OK, let me give you another analogy. Imagine if we assigned championship titles in boxing based on tests involving a boxer and a punching bag.

The geometry of the bag and the rope it is suspended on would now influence the system dynamics stronger. An audiophile analogy would be thermally induced deviations of the load resistance value, and parasitic capacitance of the cable leading to the resistive load.

Thermally induced variations in the load have no impact on the amplifier performance as you admitted it is effectively time invariant. Cable capacitance is very low, and with the rare exception, far in the past (was that Naim) has not been a real issue. One could argue there is no reason to have that low of capacitance.

 

The goal of the boxer remains the same: the center of the mass of the bag he is punching must exhibit a specific pattern of acceleration. Only now the bag is also pushed and pulled by other swinging bags via the springs and the ropes threaded through friction pads and pulleys. This is analogous to how an amp must work when attached to a practical speaker.

 

You are pushing me out of my comfort zone, but I will respond with what I know, what I read, and my newfound knowledge of the math of stability and feedback. Looks like those math courses were not single minded!  I read in one technical article that the electrical simulation models using resistors, inductors, and capacitors are both realistic and valid models of real speakers including the movement of the cones.  As these are all linear elements, at least for the purposes of our discussion, then they can be simplified to magnitude and phase.  Hence we are right back to our stability discussion and 99.9% it does not matter. Audiophiles may be interested. It does not mean their interest is relevant.

 

Indeed, thermal drift of a transducer coil resistance value due, to ,say, a loud music passage, is a factor that a good amplifier must somehow compensate for. Yet even if we remove the friction pads in the system of bags described above, its behavior will remain pretty sophisticated, and very different from a behavior of a single heavy punching bag.

This is not the purpose of the amplifier. How would it know it was the transducer coil, and not some other element.  This would be the job of the speaker designer to compensate for.

 

One of the cases is simply running our of amp’s power supply current capacity. A music passage may be such that at some point all the bags will be moving towards the boxer, overwhelming him with the combined impulse.

Testing power output at different frequencies and 8,4,2 ohms would cover your argument. Again, even I know what. Using a reactive load that is not the same as your speaker is not going to provide easy guidance.

 

This type of deficient behavior may be exhibited on some music passages by certain class A, A/B, and especially class D amplifiers, with their open loop bandwidth insufficient to deal with such combination of the speaker and music passage.

I feel this statement is made up. I don't think it based in theory or reality.

 

Audibly, such deficiency may manifest itself as a lack of transparency, and timing errors, especially in music produced by dozens of instruments playing at once.

But we go back to testing at 2,4,8 ohms, which is sufficient for 99.9% or more of speakers will provide all information needed on where the amplifier will clip, and testing with a reactive load will provide no additional information. How would you even related it to your speaker that you intend to use?

[END BOOK]

 

This is just me, learning as I am going, finding it easy to counter your arguments, some of which I have a high confidence are flawed.

 

 

 

Taro Mochi 7.4 oz each Frozen Desserts - Walmart.com

https://www.walmart.com/browse/food/frozen...

@crymeanaudioriver , there you go!

 

https://www.biline.ca/audio_critic/mags/The_Audio_Critic_20_r.pdf (page 16 on)

Italics mark content contributed by crymeanaudioriver

A lot of trash in this collection of articles unfortunately.

I see it differently. Sure, we learned quite a bit since these articles were written. Yet, the time during which they were published marked presence of many amplifiers designers and manufacturers in North America. They knew what they were talking about.

Interesting that you linked to the specific article on the power cube. They say in that article,

We do not perform such separ-
ate IM distortion tests here because they characterize the
same nonlinearities identified by the THD tests. A non-
linearity that gives rise to a high 20 kHz THD will also
cause inband distortion products in a multitone test. A
full-scale 20 kHz test has the advantage that it has the
maximum rate of change of any inband test signal and it
characterizes both even- and odd-order nonlinearities
[Borbely 1989], [Jung 1979]. Transient intermodulation
effects [Otala 1970] are also covered in this test.

I assume you agree with all that written above as well, or only what suits you?

A typical “moving the goalposts” / “straw-man” rhetorical manipulation. That discussion of IM correlation with THD is still conducted in the context of the amp’s linearity under best conditions, not in the context of the linearity of system comprised of amp+speaker.

The article you link talks, often, about the performance of the current limiter inside the amplifier. If the amplifier is running into a current limit, it is clipping. If you are running your amplifier into clipping, then you are beyond the limits of the amplifier.

Current limiting occurs in amps without specific current limiting circuits too. As an example, a heating up power transformer coil may in effect serve as a current limiter. Another example is insufficiently sized capacitive power bank.

Look at the curves of THD vs output power characteristics of amplifiers, and you’ll see that typically, there is a rise in THD (and by extension in IM) long before the amp clips. The degree of such deterioration is typically frequency-dependent too.

This is indeed one of the mechanisms explaining the phenomenon of some of the amps distorting significantly more while they are connected to a speaker compared to when they are connected to a dummy resistive load.

Note the only example they show of oscillation, the issue yielded by non-resistive tests, shows oscillation occurring at 2 ohms, 60 degrees, and 1 ohm 30 and 60 degrees. This is important as it relates back to this article on ASR you linked:

Yes, occurrences when a commercially sold amplifier becomes unstable and turns into a generator while connected to a specific speaker are rare. Even though, the thread referred below has a description of a surprisingly common-case instance of that.

However, just like with the discussion of THD and IM, we need to take into account that the amp-speaker system can “ring” for some time, instead of turning into a self-supporting generator. Some of the replies in the thread below describe precisely such occurrences.

Complex Load for Power Amplifier torture testing

This specific issue is discussed, as they talk about how many speakers have both very low impedance and very large phase shift. The conclusion is very few.

Yes, this is one of the aspects discussed there.

The “conclusion”, if we were to derive any, is that in certain segments of the world market, predominantly preferring smaller speakers with simpler crossover topologies, there are indeed fewer opportunities for a given amp to exhibit ringing, and even fewer opportunities to exhibit runaway self-generation.

However, some of the replies highlight the fact that in some other  market segments, including that of affluent audiophiles, larger speakers employing exotic transducers and much more sophisticated crossovers are more prevalent, and thus the events of ringing and self-generation are much more probable.

Hence why the consensus that resistive testing into low enough impedance is sufficient.

There is no such consensus in that discussion. Interested readers can go there and see for themselves. I would roughly split the multitude of members posted there onto three categories:

1. Designers and restorers of amps from Western countries. They are for comprehensive testing with non-purely-resistive loads.
2. Designers of amps from China. They are for limited testing with non-purely-resistive loads.
3. Vendors selling amps made from pre-built blocks, Amir, and some of Amir’s followers. They maintain that testing on purely-resistive load is not ideal, yet good enough for predicting amp’s performance in 99.99% of cases.

Elsewhere there is a call to include 2 ohm testing which I think I have seen on some more recent tests.  It is probably important to identify from the articles linked that the worst issues are with tube amplifiers, lauded by audiophiles and rarely tested by ASR. When they are, the result is not positive.

Behavior of most amplifiers, including tube ones, does depend on the value of purely-resistive load, yet the change in behavior is much more predictable with the change in just the resistance value.

Thus, while testing on 2 ohm has its merit, it appears from the discussion that testing on non-purely-resistive loads is of more interest to people with practical experience in designing and repairing amps.

The other threads you posted from ASR are primarily not technical discussions about testing, but more banter from what appears to be the less technical members. Not everyone on ASR is technical.

Unless a member is an unscrupulous dealer pushing some version of snake oil, most of the “banter” deserves consideration, in my opinion. I give full credit to Amir for filtering out vast majority of such snake oil salesmen. However, the story doesn’t end there.

Similarly to doctors giving zero credence to patients describing their symptoms, and only relying on the results of locally available objective tests, amp designers and restorers only relying on simple measurements aren’t likely to keep their clientele for long.

Also, quite a few replies there were redacted: one can see quotations from them and references to them, but not the original replies in their entirety.

If you are going to participate in a thread putting down a web site you should probably learn how that site works, or at least the "Click to expand" button.

Ignoring your not so subtle attempt of slighting me, a person whom you obviously don’t know much about.

There is nothing redacted.

Once again, interested readers can go there and see for themselves. They’ll find the traces of reductions exactly as I described them.

The forum has a very good quote and reply system unlike another one I am thinking of.

Indeed, ASR runs on a more modern discussion platform than Audiogon. The “reply system” in practice also includes so-called moderation subsystem, or, in simpler terms, censorship features.

A discussion site without actively working moderation quickly devolves into pointless incomprehensible mess, mostly frequented by spammers.

Yet a discussion site with overreaching moderation generates its share of issues, both for regular members and site owners. I maintain that the ASR moderation has been such since about 2021.

Here we differ too. As technical as the dedicated ASR discussion thread was, it didn't touch on stochastic behavior of non-linear time-dependent systems, of which a practical multi-transducer loudspeaker is a prime example.

Attaching such a system to an approximately linear, approximately time-independent power amplifier leaves the combined system still non-linear and time-dependent.

The math describing non-linear time-dependent systems is far more sophisticated than the one underlying the simple measurements that Amir uses.

At first, that appears to be a lot to unpack. However, it can quickly be taken as a deflection. The topic at hand is the test of amplifiers. Specifically in this case resistive testing.

Nope, topic at hand is relevance of the testing Amir does on specifically power amplifiers to the subjective perception of audible distortions contributed by amp A vs amp B when connected to a specific speaker.

Note that I don’t discuss Amir’s testing of DACs, which I personally find entirely satisfactory and providing huge value to the community.

Neither I discuss Amir’s testing of loudspeakers, which Amir positions as in effect partial, only providing about 70% of information needed for a purchasing decision.

My position, as is the position of majority of ASR members with practical experience in designing and repairing power amplifiers who cared to express their opinions, is that the testing Amir has been conducting is marketed as more definitive than it shall be based on scientific understanding of the limited nature of the tests.

Attaching such a system to an approximately linear, approximately time-independent power amplifier

This negates all the other words used in the last paragraph. By your admission, the amplifier is time independent, approximately at least. That a speaker is not, is not relevant to the discussion.

OK, let me give you another analogy. Imagine if we assigned championship titles in boxing based on tests involving a boxer and a punching bag.

Boxer would be performing prescribed sequence of moves of varied amplitude and frequency, and we would be measuring, let’s say, acceleration of the bag’s center of mass in relation to the ideal acceleration expected at the execution of a specific move.

Case (A). A very heavy bag - let’s say weighting 8 times the average human weight - would approximate a linear time-invariant system pretty well. That’s an analog of 8 Ohm purely resistive load. Whatever the boxer does would translate pretty unambiguously into the bag’s acceleration.

Case (B). A lighter bag, let’s say ½ of the average human weight, would sway under the punches, thus failing to remain a linear time-invariant system from the boxer’s point of view, yet it would be still somewhat predictable. That’s an analog of ½ Ohm purely resistive load.

The geometry of the bag and the rope it is suspended on would now influence the system dynamics stronger. An audiophile analogy would be thermally induced deviations of the load resistance value, and parasitic capacitance of the cable leading to the resistive load.

Case (C). Now imagine that instead of the single heavy bag, the boxer would be punching a system of four bags: one of them, still somewhat heavy, used for punching, and the other three with differing weights interconnected with the first bags and between each other with a system of springs, ropes, and pulleys. In addition, the ropes would be threaded through a system of friction pads, with friction coefficients strongly dependent on the pads temperatures.

The goal of the boxer remains the same: the center of the mass of the bag he is punching must exhibit a specific pattern of acceleration. Only now the bag is also pushed and pulled by other swinging bags via the springs and the ropes threaded through friction pads and pulleys. This is analogous to how an amp must work when attached to a practical speaker.

Obviously, the task of boxer in case (C) is more complicated that in case (A). And the champion of case (A) won’t necessarily be the champion of case (C). The testing of power amps Amir is doing is analogous to case (A). What audiophiles are interested to know is analogous to case (C).

The only relevance would be if speakers drifted from a maximum of 30 degrees phase shift to 60 degree when they got hot and this is not identified in the ASR discussion linked. Is that what you are claiming? 

Indeed, thermal drift of a transducer coil resistance value due, to ,say, a loud music passage, is a factor that a good amplifier must somehow compensate for. Yet even if we remove the friction pads in the system of bags described above, its behavior will remain pretty sophisticated, and very different from a behavior of a single heavy punching bag.

While being a crude analogy, the visuals of the system of bags give insights of where an amp testing close to perfect on a 8 Ohm purely resistive load could fail miserably on auditioning involving a specific sufficiently large and sophisticated loudspeaker.

One of the cases is simply running our of amp’s power supply current capacity. A music passage may be such that at some point all the bags will be moving towards the boxer, overwhelming him with the combined impulse.

Such deficient behavior is usually exhibited by amplifiers of all classes with power supply sized insufficiently relative to the speaker and music characteristics.

Audibly, such deficiency usually manifests itself as “lack of dynamics”. Once again, it may be not outright clipping, but rather increased distortions as the amplifier approaches its power limit.

Another case is quick stochastic oscillations of the bags,  excited by a complex music passage. It can overwhelm ability of the boxer to punch quickly enough to counteract the resulting irregular oscillations of the bag he is punching.

This type of deficient behavior may be exhibited on some music passages by certain class A, A/B, and especially class D amplifiers, with their open loop bandwidth insufficient to deal with such combination of the speaker and music passage.

Audibly, such deficiency may manifest itself as a lack of transparency, and timing errors, especially in music produced by dozens of instruments playing at once.

@thecarpathian 

I had to look that up. I have never had Mochi stuffed with ice cream.  This is standard, in a tub fare in the freezer section. I was trying to find it on their website, but it is not there.

We should all expand our horizons and got out for Taro ice cream. My local Walmart of all places has it.

I shall look for it tomorrow! Talking about the mochi or the standard fare?

ASR hasn't measured an AGD amp (probably too expensive). 

@fleschler , if AGD provided the amplifier on loan, I expect they would measure it.

That settles it. We’re going out for Australian Ice Cream!

 

We should all expand our horizons and got out for Taro ice cream. My local Walmart of all places has it.

So @henry53 , MIEE, industrial engineering. Quick perusal indicates very little in the way of electrical engineering in that study. Light on related physics as well. I should have been more clear, but it should have been obvious.  Obviously none of us are electrical engineers or close enough to speak with authority. I would have settle for a strongly related physics degree.  I expect my PhD/MD is as relevant, and significantly more relevant on the research side. Are we all happy now?

 

In this instance regarding some "unknown" test. What I have said to concise and clear AMR frequently users totally useless data to draw even more useless conclusions.

 

You have neither proven the uselessness of ASR testing, nor have you provided alternatives. A simple question for you @henry53 , if testing of a cable by ASR, say a simple interconnect, in a typical system (nothing their systems are not made of expensive components), reveals that by all the measurements they do, there is no change, and in both cases, everything tested is well below acceptable audible limits, do you believe that cable will have no audible impact? Yes or No?

 

You claim totally useless data. However I note in their testing:

Noise levels: Noise is relevant, audible, and can be distracting for some. At high volumes, even low noise levels, can audible.

THD:  @djones51 noted above they are now testing down to 2 ohms impedance, and a quickly check shows many different frequencies. Apparently it is full sweep from very low power to full power or low signal level to high signal level. Many audiophiles who like tubes claim they are more linear at low signal levels. This test should cover that concern adequately.

IMD: Reading their test protocol, this is done at 32 different frequencies. Do you not agree this would be a reasonable simulation of music?  Audiophiles often write that IMD is more important, or that higher harmonics of distortion are important. Would this test not reveal all of that quickly?

Jitter:  For DACs, jitter is injected on serial cables and how well the DAC rejects jitter is measured. Jitter is also measured for all the inputs. I could probably find a thousand comments on this forum alone about the importance of low jitter. Are you claiming it is not important?

AC Harmonics:  Using very very distorted AC on inputs to DACs and amps to measure the effects. I would find a similar 1000 comments on importance of AC power on this forum. Do you not agree?

Speakers?:  Far more tests than I have seen from any publication or website on speakers. When I read the discussions that follow, all of it seems not only relevant, but all of it can be translated into physical aspects of how the speaker will sound and how it may work out in your room.  Is this not all useful?

 

I keep pushing the limits of my knowledge responding, but I don't see others pushing themselves to learn more.  Your comment about useless data does not appear warranted.  I have also asked you, what critical data that defines how something sounds is missing since you feel all the data they collect now is useless. Can you not answer this question?

That settles it. We’re going out for Australian Ice Cream!

Pine-Lime Splice for me...

@henry53 admits that the ASR measurements provide enough resolution that they are beyond audible limits, but appears to be claiming they must make some other unknown test. For a cable, especially a digital cable, or power conditioner tested by measuring the whole system I can't imagine what that is.  The tests are extensive. I am not an engineer but it is obvious that all those complaining are not either.

Yes I am a forensic Engineer BSc(Hons) C.Eng. M.I.E.E M.I.Prod.E to be exact. A great portion of my career investigating accidents including being on a Royal Commission as a crown investigator in Australia on one of the most significant accidents ever to occur. As such I deal with evidence every day. As per above and continuously in this discussion I am quoted as saying things never said or even implied. In this instance regarding some "unknown" test. What I have said to concise and clear AMR frequently users totally useless data to draw even more useless conclusions.

I do not trust @crymeanaudioriver opinion(s).   ASR site is replete with anecdotes and foolish statements concerning cables, especially digital cables.    I've tried half a dozen digital cables and none of them sound the same, not even close.  I bet they measure the same though, 75 ohms, similar capacitance, resistance, inductance although I have no tests proving that other than a voltmeter.   I decided based on listening.   None of the cables had specs although five had extensive explanations concerning their construction.  

I am very interested in hearing Atma-Sphere GaNFET and AGD Productions GaNTube  amplifiers.  I've heard a few Class D amps that sounded very good at audio shows, better than many solid state A/B amps, especially high powered older SS.  I suspect they measure well even if they don't measure "perfect".  ASR hasn't measured an AGD amp (probably too expensive).   Both of my custom built tube amps sound better than the Atma-Sphere tube amps but the latter are very good (and very hot running).  Who knows, Atma-Sphere states that the new Class D amp sounds better than his tube amps.  I'd like to hear both his and AGD's.  

 

So one example is a scientific result?

Thought the net result had to be repeatable, verifiable. 

I can tell the difference in the 6 amplifiers I own and the speakers, blind tested and verified by my cat. 

There was a head phone amplifier reviewer on Youtube, somewhat respected, that claimed with 100% certainty he could tell two amplifiers apart. Someone challenged and he took up the challenge. I applaud his willingness to be public about the result. The result? In a blind test, he could not tell the amplifiers apart. Not at all.

again, the idea that a handful of measurements conducted by the members of one site somehow

 

Several pages of measurements.

Decades of scientific experiments.

Lack of scientific studies to prove otherwise, or demonstrations that have anything approaching scientific validity.

 

fundamental issues like "what to measure" are far from settled

Concerning DACs, interconnect cables, power cables, and to simplify, anything before the output of an amplifier, I have seen no evidence that it has not been settled.

Amplifiers and how they may interact with a speaker? There is room to explore extreme ends of products. I am not aware that the challenge that two amplifiers with low distortion, high damping, and matched frequency response withing 0.1db has been broken yet.

Speakers? There is no one that claims measurements of speakers are settled or will ever be settled.

It is fine to make claims, but it is good to have data other than your personal feeling, the feelings of others, and the marketing sheet to back it up.

 

One thing just struck me. As passionate as the people in this thread are that ASR is wrong, I see no effort to prove ASR wrong. You have all the tools you need. Your ears, and your systems. All you need is an impartial person to run an experiment and record the results.  You probably need someone with a more scientific bent to set up the experiment, but it is not very hard. I raise the point before. I am sure the users at ASR would be thrilled to help you set up an experiment.

I don't expect any of you to do it though. I cannot do it. It is too easy to say I am biased if I hear no difference. You are biased to find a difference.

 

There was a head phone amplifier reviewer on Youtube, somewhat respected, that claimed with 100% certainty he could tell two amplifiers apart. Someone challenged and he took up the challenge. I applaud his willingness to be public about the result. The result? In a blind test, he could not tell the amplifiers apart. Not at all.

 

 

I do.

I also consider you a troll @cindyment  err  ​​​​@crymeanaudioriver 

 

Do you consider Apple a Chinese company?

Maybe understanding what the word troll means in the context?

That treads a fine line between humor and trolling. 

NAD is effectively a Chinese company with Banking in Canada.

 

They have a contract manufacturer in China, like Apple, and everyone else. Do you consider Apple a Chinese company?

again, the idea that a handful of measurements conducted by the members of one site somehow invalidates the actual musical listening experiences of generations of listeners just seems kind of absurd. you can learn a lot from measuring gear, but how that translates into "what sounds good" is where things get murky. i can go to ASR right now and say "rogue sphinx is a killer little amp for the money. ive owned it and it rules. trust your ears" and people who have never even heard one will immediately score points off me because it measured "bad". like buddy, try it and then there might be a conversation. otherwise you’re just repeating someone else’s argument

also, axo1989 posted links to some contentious threads there and i recommend checking them out - despite how some of those fellas speak to others, fundamental issues like "what to measure" are far from settled

NAD is effectively a Chinese company with Banking in Canada.

Great many EU companies still making Tube, A/B amplification that is highly regraded.

The dinosaur wont die and they still sound GREAT! No matter what the crybabies and Amir say. Oops, Amir only measures never listens. 

I think they are effectively Canadian now

 

 

@nonoise ,

Trolls are so adept at dancing on the head of a pin. 

Maybe less snark, more valuable contribution?  Maybe understanding what the word troll means in the context?

 

Trolls are so adept at dancing on the head of a pin. 

@prof  I wonder if many of the people participating in this topic will realize that what they are writing, the way they write it, and how they misrepresent ASR, Amir and measurements in audio, will not be perceived by many who read this as a definitive debunking of ASR, but as a definitive debunking of their own beliefs?

 

European companies large and small are pushing the envelope especially in speaker design, class D amps, active DSP controlled full systems.

 

Is NAD a European company any more? I think they are effectively Canadian now.

Trolls keep on trolling, get your rocks off!

 

 

 

@henry53 

AMR continues to make measurements that appear extremely accurate but have no reference whatsoever to audible sound.

I don't see how that is an accurate account of what ASR is doing.

The whole point of the measurements are always with respect to the audible consequences, or not, of those measurements.  The speaker measurements for instance arose BECAUSE of how they have been correlated to audible differences in speaker design.  Amir often explains the audible consequences of the measurements, and also listens and reports any relevant audible consequences.

If you mean to reference their measurements of things like SINAD, then once again, it's all in the context of audibility - that is, "will this be audible?" and the answer can be yes or no depending on the measurement.  A lot of the SINAD differences are in to the inaudible range, but that's the point - ensuring they are in the inaudible range.

I agree that it can look a bit silly to keep chasing ever greater SINAD numbers once we are well in to the inaudible range.  However, in the bigger picture, the fact the measurements allow us to know the gear in question has distortion elements that are inaudible is the main point.

 

Not what this thread is about Mr Jones. Never was. I own several Class D amplifiers. This was about Amir and ASR.

Some of you need to climb out of your bubble. It's a whole new world out there. European companies large and small are pushing the envelope especially in speaker design, class D amps, active DSP controlled full systems

Some of you need to climb out of your bubble. It's a whole new world out there. European companies large and small are pushing the envelope especially in speaker design, class D amps, active DSP controlled full systems. 

Propaganda?? 

 

Going back to the days when NAD's amplifiers were designed by the late Björn Erik Edvardsen, I have always been impressed by the company's conservative and competent engineering. The NAD C 298 continues that tradition but, with its "Eigentakt" class-D output modules, sets a new standard for combining very high power with supremely low distortion.—John Atkinson

 

 

Do not feed them..cry cry cry.

When ASR fanboys (stooges?) feel the need to keep posting propaganda it is not about ASR, it is about trying to denigrate and flame anything and everything, This is the ASR culture today and former members of ASR have already confirmed that in this thread (thank you by the way). Their borg queen tried coming here and he basically self destructed already through senseless, defenseless and relentless spamming. All they are doing is proving what the OP initially said, over and over.

@djones51 it is easier to throw stones than make a meaningful argument. That is why they throw stones at me. I only entered the topic as the behavior was so poor. @henry53 admits that the ASR measurements provide enough resolution that they are beyond audible limits, but appears to be claiming they must make some other unknown test. For a cable, especially a digital cable, or power conditioner tested by measuring the whole system I can't imagine what that is.  The tests are extensive. I am not an engineer but it is obvious that all those complaining are not either.

 

 

The Boxem Arthur 4222 mono amp was tested to 2 Ohm. I'm not sure what tests aren't relevant to audible sound. Distortion and THD+N certainly are as well as FR to power. Perhaps you don't understand what all can be measured and how it relates.

@juanmanuelfangioii 

Agreed... Audio Science Review Karens are best ignored.

AMR continues to make measurements that appear extremely accurate but have no reference whatsoever to audible sound.

@tsushima1 agreed!  Stop feeding the trolls 😈 they then die a slow death cause they feed off the 💩. Please take it personal @crymeanaudioriver  

Gentlemen and Ladies, Why supply oxygen to this Amir Familiar !  Simply choose to ignore the noise. 

Providing strings of measurements that all demonstrate factors beyond anything that can be heard by anyone or have any effect whatsoever on the sound that can be heard is totally futile, making decisions on such data is totally ridiculous.

 

@henry53 the only way to interpret your statement above is that ASR is measuring to sufficient accuracy to far exceed human hearing. In a PM, you also stated -80db IMD is also inaudible, so that further supports a claim that ASR is measuring well beyond audibility.  Can we assume the same is true of their noise measurements?

 

The concept of preference has been raised many times in this topic and even Amir has said he is not here to tell you your preference. He did state that it was in your best interests to take into consideration the results when he tests, and his tests show no change. I think USB cables, and power conditioners were in that statement and likely others.  @henry53 , are you saying you agree with ASR, at least in this instance?   Or are you staying there are as yet undiscovered tests, which Amir is not doing. If so, can you allude to what those tests may be?

@fair 

https://www.biline.ca/audio_critic/mags/The_Audio_Critic_20_r.pdf (page 16 on)

A lot of trash in this collection of articles unfortunately. Interesting that you linked to the specific article on the power cube. They say in that article,

We do not perform such separ-
ate IM distortion tests here because they characterize the
same nonlinearities identified by the THD tests. A non-
linearity that gives rise to a high 20 kHz THD will also
cause inband distortion products in a multitone test. A
full-scale 20 kHz test has the advantage that it has the
maximum rate of change of any inband test signal and it
characterizes both even- and odd-order nonlinearities
[Borbely 1989], [Jung 1979]. Transient intermodulation
effects [Otala 1970] are also covered in this test.

I assume you agree with all that written above as well, or only what suits you? 

The article you link talks, often, about the performance of the current limiter inside the amplifier. If the amplifier is running into a current limit, it is clipping. If you are running your amplifier into clipping, then you are beyond the limits of the amplifier.

Note the only example they show of oscillation, the issue yielded by non-resistive tests, shows oscillation occurring at 2 ohms, 60 degrees, and 1 ohm 30 and 60 degrees. This is important as it relates back to this article on ASR you linked:

Complex Load for Power Amplifier torture testing

This specific issue is discussed, as they talk about how many speakers have both very low impedance and very large phase shift. The conclusion is very few. Hence why the consensus that resistive testing into low enough impedance is sufficient. Elsewhere there is a call to include 2 ohm testing which I think I have seen on some more recent tests.  It is probably important to identify from the articles linked that the worst issues are with tube amplifiers, lauded by audiophiles and rarely tested by ASR. When they are, the result is not positive.

The other threads you posted from ASR are primarily not technical discussions about testing, but more banter from what appears to be the less technical members. Not everyone on ASR is technical.

Also, quite a few replies there were redacted: one can see quotations from them and references to them, but not the original replies in their entirety.

If you are going to participate in a thread putting down a web site you should probably learn how that site works, or at least the "Click to expand" button. There is nothing redacted. The forum has a very good quote and reply system unlike another one I am thinking of.

 

Here we differ too. As technical as the dedicated ASR discussion thread was, it didn't touch on stochastic behavior of non-linear time-dependent systems, of which a practical multi-transducer loudspeaker is a prime example.

Attaching such a system to an approximately linear, approximately time-independent power amplifier leaves the combined system still non-linear and time-dependent.

The math describing non-linear time-dependent systems is far more sophisticated than the one underlying the simple measurements that Amir uses.

At first, that appears to be a lot to unpack. However, it can quickly be taken as a deflection. The topic at hand is the test of amplifiers. Specifically in this case resistive testing.

Attaching such a system to an approximately linear, approximately time-independent power amplifier

This negates all the other words used in the last paragraph. By your admission, the amplifier is time independent, approximately at least. That a speaker is not, is not relevant to the discussion. The only relevance would be if speakers drifted from a maximum of 30 degrees phase shift to 60 degree when they got hot and this is not identified in the ASR discussion linked. Is that what you are claiming? 

Providing strings of measurements that all demonstrate factors beyond anything that can be heard by anyone or have any effect whatsoever on the sound that can be heard is totally futile, making decisions on such data is totally ridiculous.

By crymeanaudioriver:

@fair  -- All that typing, and all that work, but not even a minute of research to understand why a resistive load is used for amplifier testing.

"Cute", isn't it? A typical example of a "gentlemanly" statement considered normal at ASR these days.

It took me a bit longer to understand this item. I think I spent almost 30 minutes, but now I am comfortable with the answer.

At this point a replying person usually goes into explaining what relevant educational, professional, and life experiences he had over prior 30 years to come to his understanding of the issue at hand. I know better now. I won't.

I also know now that everyone uses resistors for testing including Stereophile. Stereophile has a simulated speaker load, but this measurement provides no additional information that cannot be ascertained in other measurements.

This is emotionally a very strong, and technically a very wrong statement. For details, please see:

https://www.biline.ca/audio_critic/mags/The_Audio_Critic_20_r.pdf (page 16 on)

and

Measuring Power Amplifiers with Reactive Loads

I quickly found at least 6 and probably there are many more discussions on using complex loads for amplifier testing on ASR. I had to Google to understand some of the terms, but I muddled through. Even the stronger proponents of complex load testing, after the discussion progressed, agreed it was of limited and would only be valuable with an extreme speaker and a marginal amplifier.

I did such search too, yet got quite different results. There are a number of threads where the issue comes up, yet remains unresolved. For instance:

hypex power ratings

What is it about McIntosh?

KJF Audio MA-01 Review (Multi-channel Amplifier)

Review and Measurements of Accuphase E-270 Amplifier

 

One thread, dedicated to the subject, appears to be expressing virtually all conceivable points of view, yet it is inconclusive as well. Also, quite a few replies there were redacted: one can see quotations from them and references to them, but not the original replies in their entirety.

Complex Load for Power Amplifier torture testing

 

I thank you for encouraging me to look into this as I sort of understood it, but had not delved deep enough. It was a less complex topic than I was expecting.

Here we differ too. As technical as the dedicated ASR discussion thread was, it didn't touch on stochastic behavior of non-linear time-dependent systems, of which a practical multi-transducer loudspeaker is a prime example.

Attaching such a system to an approximately linear, approximately time-independent power amplifier leaves the combined system still non-linear and time-dependent.

The math describing non-linear time-dependent systems is far more sophisticated than the one underlying the simple measurements that Amir uses.