Cherry Audio Class D Amplifier Review with Measurements!

P

PENG

Audioholic Slumlord
Just keep in mind, this amp puts out twice the power of the Hypex amps in question (and more than twice that of the Purifi). Which is more important, .002% vs .001% THD or 250 watts vs 400 watts? I know there has been some comparisons of .006% vs .001% but that isn't the right comparison since Amir measures at 5 watts. This is actually why. Gene prefers to do a 1 watt test since we listen at or below 1 watt quite a bit. However, most amps are pretty noise limited at 1 watt, so he does 5 watts. That does a better job highlighting the area where the amp is no longer noise limited and is operating in it's most linear range. In this case, the 5 watt test puts it at something like .002% or less. I think I got .0025% into 4 ohms for 10 watts. I can't recall what I posted, it was something like that. Point is, this amp has ever so slightly higher noise and distortion, but produces quite a bit more maximum power.
The Purifi IET400A 425W @ 1% THD, 4Ω. Single channel

If you look at ASR's graph, it is pretty close, 257 W both channels driven, at 0.0002% THD. If you look to 1%, it did get close to 400 W.

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Matthew J Poes

Matthew J Poes

Senior Audioholic
Staff member
I believe in the maxim "too much is just enough" when it comes to power, to avoid any clipping, balanced against the reality that unused power is simply unused, thus wasteful.

I have a hard time figuring the practical need for the power this amp is capable of, at least in a domestic setting. For subs, maybe, but then the exacting specs and performance is overkill. I personally don't own any speakers capable of taking the full brunt of that amp without going up in smoke.
People need more power than they think. I hope to provide some objective data to prove this point more. But I am yet to have a expert in the industry disagree with me on this, and I've seen a few simple studies support this view.

Bob Cordell has done a nice little experiment and I bet if repeated with modern ATMOS movies, his numbers would at least double what he found back then.
This interview has Bob making the same point I've made, you need more than you think.

Here is a description of a little mini-Study Bob did using a clipping and peak power indicator. This concept can be bettered with greater accuracy in modern amps and I've talked to Tommy and Bruno about this. I am hopeful that we can put together a rig that can record all of this data into a log report that we can use to reconstruct both how much power was needed and if/when the amp clipped. I understand that lots of low dynamic range "loud" music wouldn't push the need much. Many people listen at quieter levels. But with average listening levels of 85dB and speakers having average sensitivity, you often need 200-300 watts or more. For movies, 400+ isn't unheard of. Now consider less sensitive speakers, those under 85dB 2.83v/1m, and you easily need 400+ watts for normal average listening levels to handle the normal dynamics of good recordings.

Bob found a need for over 250 watts per channel for a speaker with a sensitivity of 89dB. That was for music. Movies can have 3-6dB more dynamic range than the recordings he mentioned using. Thats 500 watts plus!

Hopefully we can pick this up and turn it into a video/article and maybe show experience. I think people would find it helpful.
 
ski2xblack

ski2xblack

Audioholic Field Marshall
I witnessed the Cordell demo in the flesh. While it demonstrated the dynamic power demands for uncompressed rim shots and such, it also demonstrated that clipping of such transients wasn't really audible.
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Staff member
I witnessed the Cordell demo in the flesh. While it demonstrated the dynamic power demands for uncompressed rim shots and such, it also demonstrated that clipping of such transients wasn't really audible.
I thought he only did the test with one amp? So when you said it wasn't audible, how did you hear it without the clipping? Did he turn it down? Based on my discussion with him, I thought he had said that was a limitation, he couldn't give people an A/B demo of the transients with and without amp clipping.

My own experience is that it is audible, but its totally possible his amp was clipping less or had better clipping behavior than mine. My experience was with a receiver that clipped and a DIY amp I made. Both behaved badly at their limit. He used one of his own amps if I recall, right? My clipping experience also had half the power of his test. I never noticed audible clipping when I used my Acurus amp which has about the same output. I also haven't noticed it with my recent Class D amps.
 
ski2xblack

ski2xblack

Audioholic Field Marshall
It feels like a lifetime ago. No, even with some sort of a/b/x approach, given the transient nature of the signal and brevity of auditory memory, comparing clipped to unclipped transient signals is nigh impossible. Perhaps, as you mentioned upthread, if one is thoroughly acclimated to a squeaky clean, uninhibited rig, that you would pick up on transient clipping in another, maybe. Audible tells are obvious if your baseline is no audible tells. I also recall it being mentioned that it's not just if clipping occurs, but over how long of a duration, and how the amps recover from those clipping conditions. Bob seemed agnostic about transient clipping being audible, more about demonstrating how easily it occurs.
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Staff member
It feels like a lifetime ago. No, even with some sort of a/b/x approach, given the transient nature of the signal and brevity of auditory memory, comparing clipped to unclipped transient signals is nigh impossible. Perhaps, as you mentioned upthread, if one is thoroughly acclimated to a squeaky clean, uninhibited rig, that you would pick up on transient clipping in another, maybe. Audible tells are obvious if your baseline is no audible tells. I also recall it being mentioned that it's not just if clipping occurs, but over how long of a duration, and how the amps recover from those clipping conditions. Bob seemed agnostic about transient clipping being audible, more about demonstrating how easily it occurs.
Yeah that is basically his position. That it’s more important how the amp clips and how it recovers.

unfortunately I have no idea how to measure clipping recovery behavior. I could maybe talk with Bruno to see if has some thoughts.

I know the DIY amp I built was very bad. It was largely in the power supply. I used a Class AB amp designed byAnthony Holton from Holton Amplifiers. It was based on a design he was playing with but designed to have lower noise and distortion. It had special output devices and more global feedback over a wider bandwidth. The amplifier modules were probably good. However he convinced me to use an early switching supply designed for audio. It was a 1000 watt rms supply but was fully regulated. I didn’t get the problems with that at the time and learned a hard lesson. Essentially, I found the amp could be driven into hard sudden clipping and if for short times, the supply self protected causing the amp to clip for a long time. If I pushes it too long, it actually cut out. I thought I was still getting over 600 watts out of it, but eventually I was able to measure it and found it was clipping at least than 200 watts total. Anthony later confirmed he had the same problem. I ended up eventually damaging the amp trying to fix the problem.

the receiver clipping story I’ve told before but a number of people had experienced it. @shadyJ may have. I can’t recall (James do you recall me ever demonstrating for you the onkyo receiver clipping with the Gedlees?). The guy that designed a lot of the speakers for DIY Audio Group is the one who came over and quickly identities what it was. It was quite audible, I just didn’t know what it was. I had heard it before, I just wasn’t sure what I was hearing. An unpleasant hardness is the best description. A sound that makes you want to turn it down. As I noted before, I had thought the tweeter was damaged. I had never listened to the Gedlee speakers via a receiver. Only dedicated amps, so in the 10 years I had owned them, I had never heard it in the Gedlee speakers. This distortion was so audible I would be shocked if everyone couldn’t hear it. No auditory memory problem. It was too extreme.
 
ski2xblack

ski2xblack

Audioholic Field Marshall
I have no idea how to measure clipping recovery behavior
One of Rod Elliot's amp articles, buried somewhere on his site, addresses the recovery aspect, if briefly. It did include some actual measurements of some avr, where the protection circuitry in the amp was responsible for some nasty spikes and squared off ugly waveforms under fairly mild clipping.

How tough a load do those Gedlee present? Seems they gave the onkyo receiver fits. By chance are there 4 ohm pro woofers in those bad boys? Compounding phase angles? They might appear to the onkyo as a really low impedance load, which is just the sort of thing that would either suck the amp dry or trigger some protective nanny circuitry. They're sensitive and resolving, won't veil even slight amp misbehavior. Stridency and anemic bass are telltale signs of clipping. By that point, it's lopping off a lot more than just the occasional transient peak. While load mismatches are rare, this Onkyo/Gedlee pairing may very well be just such a case.
 
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P

PENG

Audioholic Slumlord
People need more power than they think. I hope to provide some objective data to prove this point more. But I am yet to have a expert in the industry disagree with me on this, and I've seen a few simple studies support this view.

Bob Cordell has done a nice little experiment and I bet if repeated with modern ATMOS movies, his numbers would at least double what he found back then.
This interview has Bob making the same point I've made, you need more than you think.

Here is a description of a little mini-Study Bob did using a clipping and peak power indicator. This concept can be bettered with greater accuracy in modern amps and I've talked to Tommy and Bruno about this. I am hopeful that we can put together a rig that can record all of this data into a log report that we can use to reconstruct both how much power was needed and if/when the amp clipped. I understand that lots of low dynamic range "loud" music wouldn't push the need much. Many people listen at quieter levels. But with average listening levels of 85dB and speakers having average sensitivity, you often need 200-300 watts or more. For movies, 400+ isn't unheard of. Now consider less sensitive speakers, those under 85dB 2.83v/1m, and you easily need 400+ watts for normal average listening levels to handle the normal dynamics of good recordings.

Bob found a need for over 250 watts per channel for a speaker with a sensitivity of 89dB. That was for music. Movies can have 3-6dB more dynamic range than the recordings he mentioned using. Thats 500 watts plus!

Hopefully we can pick this up and turn it into a video/article and maybe show experience. I think people would find it helpful.
Thank you again Matthew for this post in which you have covered a lot of ground on this topic. I thought I had read just about every credible (in my opinion only obviously) article Dr. Google could find but I might have missed Cordell's 2007 show one.

There is nothing (could have missed something though as I was speed read..:)) I would disagree based on my own understanding, and experience on the topping of "clipping".

That's why when people come to AH and ask at least once a week the questions related to "Do I need an external amp?, Does my amp have enough juice for my 4 Ohm speaker etc., kind of question.., I would typically ask them to first try and figure out how much power they actually may need for their applications/systems and report back, and go from there. If I think a simple question might suffice, I would high ball it based on their speaker's specs that include manufacturer's recommended amp power, maximum power handling number etc. and state my assumptions.

Some would come back with a number, even with a screenshot of the calculator they used, making it easy for my follow up response, after checking to see if they had input the data correctly, such as speaker sensitivity (important as most calculator are based on a fixed impedance of 8 Ohm), number of speakers and room gain allowance. I don't mean those things are exact, but if one or more are way out of whack then the final results could be almost meaningless. Once a number is reached, then I would typically bump the calculated number up by at least 3 dB, example: if I think they need 100 W, I would suggest a 200 W amp and that is exactly because I am concerned about clipping during peaks, not knowing what their favorite source contents are.

In my case, amps typically output between 0.1 and 0.5 W on average so I know any of my half a dozen power amps will never, or almost never clip.

All in all, clipping or not is not that hard to know as they (or was it I..:D) said, its the distance, speaker sensitivity, impedance, phase angles, and SPL stupid!!

I posted multiple times my experience in comparing my AVR-X3400H (that I tried for about a week) with my separates including the 4B SST and Halo A21, that I couldn't hear any difference whatsoever no matter how hard to try. During that time, I also use REW to check and see if the tiny AVR altered the FR and it didn't. So I am certain it's not THD, FR, DF, TIM of modern well made amps including AVRs, but much more about voltage and current capability such that as long as the DUTs are not pushed close to their limits all would be good. Any time I see someone reporting night and day difference, especially when heard even at "low volume", I would say there's something wrong in their comparison listening setup, or they just say things that's likely wouldn't apply to everyone else.

In your linked Cordell article:

"At the end of the session the attendees were polled in a very informal and unscientific way as to which amplifier they thought was the tube design. They could answer one amplifier or the other, or they could answer that they honestly could not tell which was which.

There were no "night and day" results. Indeed, for many attendees the differences were difficult to hear. Moreover, those who perceived a difference were just as often wrong in selecting which amplifier they thought was the tube amplifier. This shocked all of us."


So yes amps likely would clip more often than people think, but is the "all about SPL stupid" (my simplified version of the truth:D) that would determine whether one's amp would clip and how often.

In this case it was a comparison between a 35 W DIY tube amp and a 250 W Denon power amp. It just showed how silly people get thinking just by replacing their amp with a different brand, or simply adding an external 125 W SS amp to their 120 W rated AVR for two channel listening, they would get better sound quality like opening up their speakers, hearing details they would never hear before.
 
3db

3db

Audioholic Overlord
None of my 3 systems, all AVR driven sound strident or harsh even when pushing the volume into the low 90s sitting 10ft away. It cant be clipping all that much if it sounds clean. I wont be buying a power amp anytime soon sothat rim shots dont clip. If its not audible, where's the value added?
 
B

buckchester

Enthusiast
None of my 3 systems, all AVR driven sound strident or harsh even when pushing the volume into the low 90s sitting 10ft away. It cant be clipping all that much if it sounds clean. I wont be buying a power amp anytime soon sothat rim shots dont clip. If its not audible, where's the value added?
Agreed. This simplest of all things is all too often lost in all of these online "reviews". Just use real world material (music and movies), switch back and forth between level-matched devices blindly and see if you can reliably distinguish between them. If not, then nothing else matters.
 
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panteragstk

panteragstk

Audioholic Spartan
Agreed. This simplest of all things is all too often lost in all of these online "reviews". Just use real world material (music and movies), switch back and forth between level-matched devices blindly and see if you can reliably distinguish between them. If not, then nothing else matters.
Well, the real purpose of a review is to see how a product performs, not whether or not people "need" the product. I don't "need" anything that is reviewed on here or any other site, but I want it and I like seeing new products that do things their own way to accomplish excellent results. I don't care if it's an amp, blender, or turbo kit for my diesel. I probably won't ever buy any of it, but it's neat to see.

Then there's the crowd that 100% would buy this amp because of how well it reviewed. They may actually need all the power on tap.
 
ryanosaur

ryanosaur

Audioholic Spartan
Well, the real purpose of a review is to see how a product performs, not whether or not people "need" the product. I don't "need" anything that is reviewed on here or any other site, but I want it and I like seeing new products that do things their own way to accomplish excellent results. I don't care if it's an amp, blender, or turbo kit for my diesel. I probably won't ever buy any of it, but it's neat to see.
Well said! :)
 
B

buckchester

Enthusiast
Well, the real purpose of a review is to see how a product performs, not whether or not people "need" the product. I don't "need" anything that is reviewed on here or any other site, but I want it and I like seeing new products that do things their own way to accomplish excellent results. I don't care if it's an amp, blender, or turbo kit for my diesel. I probably won't ever buy any of it, but it's neat to see.

Then there's the crowd that 100% would buy this amp because of how well it reviewed. They may actually need all the power on tap.
Well, I do agree that the purpose of a review is to determine how a product performs. I think my suggestion was to precisely determine just that. After all, if a superior measurement is inaudible, then it should be considered irrelevant.

But if what you're saying is if the reviewer can or cannot hear an audible difference, that same conclusion may not hold true for someone else, with different speakers, a different size room, different listening habits? If so, then I would say yes, that is a good point. But I think blind testing could still provide an enormous benefit.
 
ryanosaur

ryanosaur

Audioholic Spartan
Well, I do agree that the purpose of a review is to determine how a product performs. I think my suggestion was to precisely determine just that. After all, if a superior measurement is inaudible, then it should be considered irrelevant.

But if what you're saying is if the reviewer can or cannot hear an audible difference, that same conclusion may not hold true for someone else, with different speakers, a different size room, different listening habits? If so, then I would say yes, that is a good point. But I think blind testing could still provide an enormous benefit.
Your logic is skewed. Whether or not a measurement falls into the category of audibility here is irrelevant. The value proposition of such measurements is up to the buyer, educated or not, to determine applicability to their usage scenario whether it be a passable design at a budget price or a SOTA design at a luxury price (or any of the multitude of options in between). To not report them in a review would be both inaccurate and potentially misleading.

At the end of the day, many of us here do tend to agree that those extra decimal places may be irrelevant, but it speaks volumes to the care and attention to detail of the designer and their capabilities regardless of use case scenario.
It then falls on the buyer to determine their level of commitment whether to pursue such or not.
Some of us may well consider it pointless, considering that in many instances a double blind test may well prove there is little difference between what may be considered a luxury device or that which costs 1/10th the price.
Personally, I think it would be a great disservice for a reviewer to arbitrarily decide that they should just give a pass/fail grade for THD+N, rather than type out 5 or 6 decimal places because they (or most/all) would never be able to hear it.
 
B

buckchester

Enthusiast
Your logic is skewed. Whether or not a measurement falls into the category of audibility here is irrelevant. The value proposition of such measurements is up to the buyer, educated or not, to determine applicability to their usage scenario whether it be a passable design at a budget price or a SOTA design at a luxury price (or any of the multitude of options in between). To not report them in a review would be both inaccurate and potentially misleading.

At the end of the day, many of us here do tend to agree that those extra decimal places may be irrelevant, but it speaks volumes to the care and attention to detail of the designer and their capabilities regardless of use case scenario.
It then falls on the buyer to determine their level of commitment whether to pursue such or not.
Some of us may well consider it pointless, considering that in many instances a double blind test may well prove there is little difference between what may be considered a luxury device or that which costs 1/10th the price.
Personally, I think it would be a great disservice for a reviewer to arbitrarily decide that they should just give a pass/fail grade for THD+N, rather than type out 5 or 6 decimal places because they (or most/all) would never be able to hear it.
I don't think my logic is skewed.

I assume that if you asked most people in this hobby what their primary purpose would be in purchasing new gear it would be to try and improve the sound quality of their system. Now, I did not suggest getting rid of the measurements. I believe they do provide value. They can help people make reasoned assumptions as to whether or not a piece of gear will yield an audible improvement. However, they still do often leave a degree of uncertainty for many people. Blind testing is a way to get us closer to that level of certainty.
 
AcuDefTechGuy

AcuDefTechGuy

Audioholic Jedi
...many of us here do tend to agree that those extra decimal places may be irrelevant, but it speaks volumes to the care and attention to detail of the designer and their capabilities...
Or their abilities to tweak or work the system just to get those extra decimal points? :D

Does the best THD+N and SINAD guarantee that every single thing inside the component is absolutely the best quality?

Or do designers/engineers just have to tweak their components so that they will get the best THD+N and SINAD if they know exactly what the reviewers are looking for?

For example, maybe components like the Marantz AVP and Anthem AVP had great SNR, Crosstalk, and THD numbers on S&V magazine for years because their engineers knew exactly what S&V and Stereophile were looking for in their measurements. But these same AVP didn’t seem to have great THD+N and SINAD from ASR because Amir doesn’t measure the same as S&V and Stereophile. :D

Now that S&V and Stereophile no longer do measurements, and Amir now does more measurements than anybody, Marantz AVP and Anthem AVP engineers may change their approach and tweak their components to get the best SINAD since now they know exactly what Amir is looking for. :D

Just a thought. :D
 
lovinthehd

lovinthehd

Audioholic Jedi
I don't think my logic is skewed.

I assume that if you asked most people in this hobby what their primary purpose would be in purchasing new gear it would be to try and improve the sound quality of their system. Now, I did not suggest getting rid of the measurements. I believe they do provide value. They can help people make reasoned assumptions as to whether or not a piece of gear will yield an audible improvement. However, they still do often leave a degree of uncertainty for many people. Blind testing is a way to get us closer to that level of certainty.
Yeah that improving sound quality gets deep into the significant return category and that can be tough these days with so much gear with very good performance at very good price points....
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Staff member
Or their abilities to tweak or work the system just to get those extra decimal points? :D

Does the best THD+N and SINAD guarantee that every single thing inside the component is absolutely the best quality?

Or do designers/engineers just have to tweak their components so that they will get the best THD+N and SINAD if they know exactly what the reviewers are looking for?

For example, maybe components like the Marantz AVP and Anthem AVP had great SNR, Crosstalk, and THD numbers on S&V magazine for years because their engineers knew exactly what S&V and Stereophile were looking for in their measurements. But these same AVP didn’t seem to have great THD+N and SINAD from ASR because Amir doesn’t measure the same as S&V and Stereophile. :D

Now that S&V and Stereophile no longer do measurements, and Amir now does more measurements than anybody, Marantz AVP and Anthem AVP engineers may change their approach and tweak their components to get the best SINAD since now they know exactly what Amir is looking for. :D

Just a thought. :D
I actually think that the SNR numbers obtained by the two/three sources were about the same, it was more about how the reviewer perceived those. Most receivers have never had outstanding SNR or Crosstalk, but they were deemed good enough. Amir holds things to a much higher standard and it skewed peoples perception.

Amir also requires things to perform at a higher output level than others measured to. While 2 volt was the standard output, it wasn't uncommon for others to measure at 1 or 1.2 volt or to measure at whatever was the max clean output and not really making a big deal about it.

Amir's standards far exceed audibility, its just about good engineering practices. He just wants to see things perform to what is the current state of the art, regardless of how audible that is. The vast majority of products on the market today (of any decent quality) are audibly transparent. The main difference is noise floor, and cost isn't an indicator of that necessarily. Lots of very good receivers have very low noise floor.
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Staff member
Thank you again Matthew for this post in which you have covered a lot of ground on this topic. I thought I had read just about every credible (in my opinion only obviously) article Dr. Google could find but I might have missed Cordell's 2007 show one.

There is nothing (could have missed something though as I was speed read..:)) I would disagree based on my own understanding, and experience on the topping of "clipping".

That's why when people come to AH and ask at least once a week the questions related to "Do I need an external amp?, Does my amp have enough juice for my 4 Ohm speaker etc., kind of question.., I would typically ask them to first try and figure out how much power they actually may need for their applications/systems and report back, and go from there. If I think a simple question might suffice, I would high ball it based on their speaker's specs that include manufacturer's recommended amp power, maximum power handling number etc. and state my assumptions.

Some would come back with a number, even with a screenshot of the calculator they used, making it easy for my follow up response, after checking to see if they had input the data correctly, such as speaker sensitivity (important as most calculator are based on a fixed impedance of 8 Ohm), number of speakers and room gain allowance. I don't mean those things are exact, but if one or more are way out of whack then the final results could be almost meaningless. Once a number is reached, then I would typically bump the calculated number up by at least 3 dB, example: if I think they need 100 W, I would suggest a 200 W amp and that is exactly because I am concerned about clipping during peaks, not knowing what their favorite source contents are.

In my case, amps typically output between 0.1 and 0.5 W on average so I know any of my half a dozen power amps will never, or almost never clip.

All in all, clipping or not is not that hard to know as they (or was it I..:D) said, its the distance, speaker sensitivity, impedance, phase angles, and SPL stupid!!

I posted multiple times my experience in comparing my AVR-X3400H (that I tried for about a week) with my separates including the 4B SST and Halo A21, that I couldn't hear any difference whatsoever no matter how hard to try. During that time, I also use REW to check and see if the tiny AVR altered the FR and it didn't. So I am certain it's not THD, FR, DF, TIM of modern well made amps including AVRs, but much more about voltage and current capability such that as long as the DUTs are not pushed close to their limits all would be good. Any time I see someone reporting night and day difference, especially when heard even at "low volume", I would say there's something wrong in their comparison listening setup, or they just say things that's likely wouldn't apply to everyone else.

In your linked Cordell article:

"At the end of the session the attendees were polled in a very informal and unscientific way as to which amplifier they thought was the tube design. They could answer one amplifier or the other, or they could answer that they honestly could not tell which was which.

There were no "night and day" results. Indeed, for many attendees the differences were difficult to hear. Moreover, those who perceived a difference were just as often wrong in selecting which amplifier they thought was the tube amplifier. This shocked all of us."


So yes amps likely would clip more often than people think, but is the "all about SPL stupid" (my simplified version of the truth:D) that would determine whether one's amp would clip and how often.

In this case it was a comparison between a 35 W DIY tube amp and a 250 W Denon power amp. It just showed how silly people get thinking just by replacing their amp with a different brand, or simply adding an external 125 W SS amp to their 120 W rated AVR for two channel listening, they would get better sound quality like opening up their speakers, hearing details they would never hear before.
But what SPL are we talking about? You've said that before. If someone listens on average to a level at around 85dB that isn't the SPL level you use to calculate the amp needed. For movies, you then need to account for 20dB of headroom for dynamic peaks. Straight calculations of that necessitates often unrealistically high power levels at reasonable listening distances of 3-4 meters.

Most speakers are way over-rated for their sensitivity figure so using that as a baseline can be misleading. The saving grace being that the in-room sensitivity increases. As an extreme example, a lot of typical consumer speakers have a sensitivity between 85dB 1w/1m and 87dB 1w/1m. A straight SPL calculation of that show that for a listening distance of 3 meters, 10 watts would cover the average SPL fine. However, 1000 watts is needed to handle the 20dB peaks that the movies may contain. I know, its unlikely anyone is really trying to use such low sensitivity speakers for such high output, but the point remains, if anyone is really trying to do that, they are absolutely clipping their receiver, no way they aren't. And I don't believe its inaudible. Numerous studies have looked at that, its quite audible. People claiming they don't hear it either are listening at much more benign levels (most music has very little dynamic range) or simply don't know what they are looking for. I stand by that is a likely reality.

as one example where this was explored. Worth getting for members.

Your REW test wouldn't be able to test for clipping properly. Clipping is something that happens during dynamics. The most you could do, and it would still be a problematic method of testing, would be to test at the very high level at which clipping should be taking place. However, the energy contained in a sweep wouldn't induce that because its such a tiny narrow band of energy, that the amplifier would be putting out way more power than it could with a musical or full range signal. You would need white noise to do that but then you cant extract distortion. So a sweep test wouldn't be proving anything useful. Thats the wrong test.

What Bob did and what I am planning to do is a much better way to address this. The multimeter and sweep tests don't accurately reflect what is really going on.
 
P

PENG

Audioholic Slumlord
But what SPL are we talking about?
I was talking about 105 dB peak SPL.

Your REW test wouldn't be able to test for clipping properly. Clipping is something that happens during dynamics. The most you could do, and it would still be a problematic method of testing, would be to test at the very high level at which clipping should be taking place. However, the energy contained in a sweep wouldn't induce that because its such a tiny narrow band of energy, that the amplifier would be putting out way more power than it could with a musical or full range signal. You would need white noise to do that but then you cant extract distortion. So a sweep test wouldn't be proving anything useful. Thats the wrong test.
I never use REW to tell me what my peak spls are anyway. I just make sure I have enough "power" on hand to achieve 105 dB, by calculations, and then to size my amp I would allow for about 6 dB of extra headroom, on top. That isn't hard for me to achieve as I rarely listen to more than 80 dB average, 70 dB from 10 to 11ft most of the time is about it as loud as I can tolerate and enjoy. So I know my 4 ohm rated 400 W A21 and 500 W 4B SST will never clip for my needs.

What Bob did and what I am planning to do is a much better way to address this. The multimeter and sweep tests don't accurately reflect what is really going on.
Understood. Multimeters are not the right tool for sure, though my Fluke 87V's 250 micro second peak capture is pretty good.

I think we do have to keep things in perspective though, that for a lot of people who listen to no more than 95 dB peak SPL from just one speaker that has sensitivity 87 to 90 dB/2.83V/m, nominal impedance 4 to 8 Ohm, sitting less than 4 meters away, their 200 W/300 W into 8/4 ohms amp is not going to clip. So much is hinged how how loud one listen to, distance and speaker sensitivity.

Here's a demo/video, you can see the big blue meters show around 1 W average, rarely peaked pass the 12 W mark. Those are real watt meters, though I doubt they probably won't always capture the highest peaks. But then the truly power hungry 800 D3 are not the kind of speakers that a lot of people have.

At request: B&W 800 D3 playing Norah Jones - YouTube
 

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