Audio Distortion: What is It and Why Should You Care?

Audio Distortion: What is It and Why Should You Care?

full?d=1513286448.jpg

Image: Copyright Charles Rodrigues estate
Readers of any number of home theater and audio review magazines have surely seen reference to the term distortion, for example: “This component has lower distortion than that component.” The topic has been a major focus of audio performance measurement and, unfortunately, has become the basis for a lot of desktop drag racing competitions. That is, my component has 10-fold less distortion than your component, as yours is .001% THD and mine is .0001% THD. Or, my speakers are flat to 15 Hz, yours are only flat to 20 Hz. My sympathies to anyone that’s engaged in this kind of unhelpful desktop drag racing. Many of you may be wondering: What’s THD? What’s distortion? What is linear vs non-linear distortion? And does any of it matter? Here’s a hint: it’s a numbers game that’s generally meaningless to anything other than a measurement device.

Let me start by making this article very short for most of you with one simple statement: Today’s audio and theater systems have distortion levels that are so low, they’re a complete non-issue. Believe it or not, that statement is generally true as far as distortion is concerned (the exception being linear distortion in the low frequencies). You may now disregard the rest of this article, take heart in the good sound of your system, and sit back and enjoy the music. For the rest of you, let’s dig a bit deeper into distortion and explain why my statement is true. This article is intended as a high-level overview of distortion described in lay terms. Many definitions were changed to be more easily understood by the average enthusiast, not by scientists and engineers.

Distortion Types
When we talk about distortion in sound reproduction, we typically break it down into two buckets: Linear and Non-linear. But, before investigating each of these terms, let’s define distortion, which is any alteration of sound from its intended presentation. Distortion is a change, and we must agree upfront that any change is undesirable, as this was not what the sound engineer, artist, or producer intended for us to hear.

Linear Distortion
Linear distortion is an easier concept than non-linear distortion, and the one that gets the most attention. Linear distortion is simply an alteration to the amplitude of the frequency or phase of the signal (it doesn’t add any new frequencies). Imagine we are playing the telephone game. I whisper a message to you and you repeat it, but you do so with a different pitch (in a deeper voice). The message didn’t change. Nothing new was added. It was just stated in a lower voice. This, at its heart, is linear distortion. And when we talk about distortion, we typically are not talking about linear distortion despite it being one of the most egregious and audible distortions in our system. As you can probably guess, speakers and our room are the biggest contributors to this. Our amplifiers, preamplifiers, receivers, CD players, DACs, computer sound cards, and phones all generally have a ruler flat frequency response with only small variations starting above and below what we can hear; speakers and rooms contribute the most to linear distortion in our sound systems. A future article on room acoustics will help explain the impact of a room. For now, we will treat speaker and room as one. We will also ignore phase issues, as this is a more complex topic to display and explain, but is built on the same principles frequency variation (phase distortions are also far less audible).

Below is a picture of the frequency response of my left speaker and subwoofers. Anything that isn’t completely flat is linear distortion or a change from the original input signal.

full?d=1513286448.jpg



This reflects all the linear distortion that my room and speakers have imposed on the signal, and you can see that it is quite high. Most of these variations from the flat line are significant enough to be very audible to even the casual listener. Yet this is actually a very good response for a speaker in most rooms; we often see much worse.

full?d=1513286448.png


Here we see an example from the recent AV NIRVANA speaker evaluation event. We see the effects of severe linear distortion caused by the room on the tower speakers under test. Note that this distortion has little to do with the speaker itself and instead reflects what the room is doing (Note that these speakers were not used with subwoofers which is the reason for the less smooth bass response).

Now let’s look at this linear distortion differently. The problem with the above graphs is that while measured distortion is quite high (and certainly audible), visible variations overstate audibility by quite a bit. Our ears are very good at filling in the dips you see in that response and we don’t tend to hear them. Our brain can turn that rocky mountainous response into a smooth highway of blissful sound. At high frequencies, our ears don’t even hear most of the distortion we see in a measurement because our ears are also quite good at filtering out reflections. As such, its illustrative to look at a response that focuses on higher frequencies only, but with smoothing. This lets us better see what our ears hear at those frequencies. The next image compares EQ correction to no EQ correction from 500hz to 20khz, EQ is a method to reduce linear distortion.

full?d=1513286448.jpg


As you can see, both look good. As I mentioned, the response was quite good to begin with. The Blue line is the equalized response, and we can see that it’s a bit flatter overall, with less big dips. The Blue line has lower linear distortion. The worst linear distortion in a room is typically at low frequencies, and the biggest cause is the room. Because this topic would take us into room acoustics, I’ll save further explanation of low frequency linear distortion for a future room acoustics article.

Non-Linear Distortion
Non-linear distortion is a minor problem in the vast majority of scenarios; linear distortion tends to dominate most systems. That isn’t to say that most systems don’t have inaudible non-linear distortion, but most modern audio systems have such low levels of non-linear distortion that it’s no longer a major concern (you simply can’t hear its effects). Non-linear distortion is the addition of new frequency content that was not present in the source. Non-linear distortion is also the kind of distortion we think of typically when we hear the term distortion.

Harmonic Distortion
Harmonic distortion is the existence of new frequencies in sound that do not exist in the source. Harmonics refers to the harmonic multiple of the fundamental frequency (fundamental is the sound of the original source frequency before any new frequencies were added). Harmonics are like the symptoms of an underlying condition. This condition is a non-linearity in the reproduction system (i.e, source, amplifier, or speakers). This is a very complicated concept to illustrate when considering musical content, so let’s focus on pure tones. If you had a pure tone of 1 kHz, a 2nd harmonic would be 2 kHz. A 3rd harmonic would be 3 kHz. These harmonics are sometimes called overtones. In musical instruments, these overtones make an instrument sound unique, but in audio systems overtones are typically rather undesirable changes in sound. Imagine listening to a trumpet and then playing it through a fuzz pedal. The trumpet will sound different (perhaps interesting), but it won’t sound like a trumpet anymore. A stereo or home theater system, however, isn’t intended to alter sound. We want it to reproduce content as the artist intended it to be heard. As I said at the start, no distortion is good, it is just that some is less bad than others.

Let’s look at distortion measurement captured using Room EQ Wizard (REW) and my home theater system, taken in room at the primary listening position. The distortion is that of the entire system, including its interaction with the room.

full?d=1513286448.jpg


REW displays any distortion that lies below the noise floor as light grey, because the room is the limiting factor. In this measurement, the cursor lies at 30.5 dB’s and the fundamental is 78 dB, this reflects 0.4% distortion. Each colored line within the graphic is a harmonic, shown because THD stands for total harmonic distortion (an equally weighted composition of the harmonics). However, the audibility of harmonic distortion increases with higher order distortion. That means as the harmonic level increases, we become more sensitive and can hear it at lower volume levels.

Ok, I just tossed several numbers around and you’re probably asking: what’s the bottom line? Is 0.4% THD audible? Unfortunately, the answer is rather complicated. Total Harmonic Distortion is not a measure of the audibility of distortion. In other words, there’s no definitive level of THD that is or isn’t audible until we get to fairly high levels. This concept is thrown around a lot, but unfortunately THD is very poorly associated with distortion audibility. We don’t hear all distortions the same (nor is harmonic distortion the only kind of non-linear distortion of concern). Low levels of higher order distortions (e.g., 5th order or 6th order) are very audible. In fact, very high levels of low order distortion (e.g. 2nd order) may be audible, but we might find it pleasant, and it will likely be masked. If the presence of high distortion (such as a quick dynamic) is very brief, our ears might not hear it. If it is persistent for a long time, we are more likely to notice it. I warned you, it’s complicated! Unlike linear distortion, which we can improve with EQ or room correction, non-linear distortion is far more complex in origin and so harder to reduce.

Masking
Masking refers to the notion that a musical signal with complex distortion, the fundamental will make some of that distortion unnoticeable during normal listening. Masking is caused because the fundamental is louder than and near the harmonic frequency, and so it takes precedence in our hearing. We hear it, but we don’t really hear its harmonics. Auditory masking is a hugely complex topic itself deserving of its own article. Here’s a link to an article on Mpeg-1 compression that discusses the role of auditory masking. Audio compression systems remove important information from musical signals in a manner that we don’t notice readily as a degradation by taking advantage of some of our sound sensitivity issues, such as auditory masking. Auditory Masking

Other Non-Linear Distortions
There are quite a few different kinds of non-linear distortions. This topic is too complex for this article nor does REW measure these distortions. It is very likely that forms of non-linear distortion have a negative audible effect on our sound system, but unfortunately the research into this topic is too sparse to give simple explanations. The effect of these distortions on sound is not well understood and most of the better research contradicts current standards. Here is what we can say: these distortions are not a significant cause of our perceptions of a system’s sound quality. It just isn’t something to lose sleep over.

Causes Of Non-Linear Distortion
Technically speaking, any portion of the signal chain can cause non-linear distortion. However, in a modern audio system the primary cause of significant audible non-linear distortion is either amplifier clipping or the speaker itself. Harmonic distortion increases with level, and as a system’s volume begins to exceed the range at which it can perform as intended, distortion rises until eventually it rises drastically. With amplifiers, this is the point at which the amplifier is exceeding its maximum output. With a speaker, the causes are complex, but typically marks when a speaker exceeds its mechanical limits. For most systems, our goal should be to create a linear range which exceeds the maximum volume at which we ever intend to listen. There is no metric for this, nor is there a simple way to say if a system will exceed your dynamic needs. There are a lot of causes of non-linear distortion that I’ll address in a future article.

Concluding Thoughts: What’s Next?
So, we’ve discussed the basics of distortion. Now what?

It’s important to understand the concept of distortion, both linear and non-linear, because it helps to guide room design, the value of EQ and room correction, and what parameters matter with certain components upstream from the speakers. Over the last 30 years, advancements in electronic and transducer design have allowed components (even inexpensive ones) to have very excellent measured performance. In addition, modern speaker drivers, amplifiers, preamplifiers, and DACs have negligible levels of non-linear distortion. In fact, non-linear distortion levels have become so low that other issues matter far more. Rather than chasing that last few dBs less distortion in a component, we really need to pay a lot more attention to a room’s characteristics and speakers, treating them together as a system. A speaker that measures anechoically flat (i.e., flat response when there are no reflections) will measure anything but flat in an actual room. Our main concern should always be to address the biggest detriments to good sound first. By far the biggest factor effecting the sound quality of any system is the smoothness of frequency response, or its linear distortion. Future articles will address how to measure a room, assess a room and speakers as a system, understand what measurement data means, and how to use that data to make informed decisions on improving the sound of a system. As you’ll see, gathering data and assessing it is easy, and room improvements are often simple, affordable, and highly effective.


Additional Reading:
 

Comments

Todd Anderson

Editor / Reviewer/ Senior Admin
Staff member
Joined
Jan 20, 2017
Messages
5,508
Location
Balt/Wash Metro
My AV System  
Preamp, Processor or Receiver
Denon X8500H
Main Amp
Emotiva XPA-5
Additional Amp
Emotiva XPA Gen3 2.8 multichannel amp
Other Amp
VSX21-THX
Universal / Blu-ray / CD Player
OPPO UDP-205, UDP-203, Panasonic UB820
Front Speakers
SVS Ultra Towers
Center Channel Speaker
SVS Ultra Center
Surround Speakers
SVS Ultra Surround
Surround Back Speakers
SVS Ultra Bookshelf
Front Height Speakers
SVS Prime Elevation x4 (Top Front, Top Mid-Front)
Rear Height Speakers
SVS Prime Elevation x4 (Top Middle, Top Rear)
Subwoofers
dual SVS SB16s + dual PSA XS30s
Other Speakers or Equipment
Behringer 1124p; Aura Bass Shaker Pros; SuperSub X
Video Display Device
JVC RS520
Screen
Carada Cine-White 0 gain
Other Equipment
LG Electronics 65-inch B6 OLED, Sony 65-inch X900F
This is a GREAT read, Matt. Just the kind of information that enthusiasts need access to. I look forward to reading the next one!
 

bkeeler10

Senior Member
Joined
Apr 18, 2017
Messages
324
My AV System  
Preamp, Processor or Receiver
NAD T758 v3
Main Amp
Outlaw Model 7125
Universal / Blu-ray / CD Player
Oppo BDP-103/Panasonic UB820
Front Speakers
Revel Concerta2 F36
Center Channel Speaker
Revel Concerta2 F36
Surround Speakers
Revel Concerta2 M16
Surround Back Speakers
Revel Concerta2 M16
Front Height Speakers
Tannoy AMS 6DC
Rear Height Speakers
Tannoy AMS 6DC
Subwoofers
Rythmik F18 (2)
Other Speakers or Equipment
miniDSP 2x4
Video Display Device
JVC DLA-RS440
Screen
Seymour AV retractable 110" 2.35 AR (UF material)
Thanks for writing that up, Matt. For further discussion, I have a few questions about amplifiers and their distortions.

1. At what percentage of THD is an amp normally considered to be clipping? At what point can it start to threaten the speaker being driven?
2. As I understand it, a solid-state amp can go from "just fine" (less than 0.1% THD) to clipping (1% THD?) very quickly. Like, a 100 watt amp could be fine at 90 watts, and be clipping at 100 watts. Is that generally the case?
3. How do tube amps fit into the distortion discussion?
4. How is it possible to compare amplifier capabilities when the various manufacturers publish data that are not really comparable? (Example: at one extreme, some amp manufacturers publish output levels corresponding to a 1 kHz input signal, one channel driven, and at 1% THD. On the other extreme, a conscientious manufacturer might use a full bandwidth signal, with all channels driven, and at 0.1% or less THD, and publish those output levels). This "specsmanship" as I like to call it, can be found in many audio products and many specification metrics.

Great discussion point, by the way. Looking forward to your future articles and subjects.
 

Todd Anderson

Editor / Reviewer/ Senior Admin
Staff member
Joined
Jan 20, 2017
Messages
5,508
Location
Balt/Wash Metro
My AV System  
Preamp, Processor or Receiver
Denon X8500H
Main Amp
Emotiva XPA-5
Additional Amp
Emotiva XPA Gen3 2.8 multichannel amp
Other Amp
VSX21-THX
Universal / Blu-ray / CD Player
OPPO UDP-205, UDP-203, Panasonic UB820
Front Speakers
SVS Ultra Towers
Center Channel Speaker
SVS Ultra Center
Surround Speakers
SVS Ultra Surround
Surround Back Speakers
SVS Ultra Bookshelf
Front Height Speakers
SVS Prime Elevation x4 (Top Front, Top Mid-Front)
Rear Height Speakers
SVS Prime Elevation x4 (Top Middle, Top Rear)
Subwoofers
dual SVS SB16s + dual PSA XS30s
Other Speakers or Equipment
Behringer 1124p; Aura Bass Shaker Pros; SuperSub X
Video Display Device
JVC RS520
Screen
Carada Cine-White 0 gain
Other Equipment
LG Electronics 65-inch B6 OLED, Sony 65-inch X900F

Todd Anderson

Editor / Reviewer/ Senior Admin
Staff member
Joined
Jan 20, 2017
Messages
5,508
Location
Balt/Wash Metro
My AV System  
Preamp, Processor or Receiver
Denon X8500H
Main Amp
Emotiva XPA-5
Additional Amp
Emotiva XPA Gen3 2.8 multichannel amp
Other Amp
VSX21-THX
Universal / Blu-ray / CD Player
OPPO UDP-205, UDP-203, Panasonic UB820
Front Speakers
SVS Ultra Towers
Center Channel Speaker
SVS Ultra Center
Surround Speakers
SVS Ultra Surround
Surround Back Speakers
SVS Ultra Bookshelf
Front Height Speakers
SVS Prime Elevation x4 (Top Front, Top Mid-Front)
Rear Height Speakers
SVS Prime Elevation x4 (Top Middle, Top Rear)
Subwoofers
dual SVS SB16s + dual PSA XS30s
Other Speakers or Equipment
Behringer 1124p; Aura Bass Shaker Pros; SuperSub X
Video Display Device
JVC RS520
Screen
Carada Cine-White 0 gain
Other Equipment
LG Electronics 65-inch B6 OLED, Sony 65-inch X900F
Awesome Matt!
 

Matthew J Poes

Guest Writer
Thread Starter
Joined
Oct 18, 2017
Messages
1,834
I'll embed my answers into the questions below. First, what is clipping? It refers to the point at which a signal is driven past the voltage and current limits of the amplifier causing the waveform to lose its rounded sinusoidal shape. It clips the rounded edges. Here is a picture to show what I mean:
2D530C08-37FA-4D82-AA52-397DDC89124F.jpeg

It is bad because it creates harmonics which add new frequencies to the sound, it's a kind of non-linear distortion. It sounds bad when it happens.

1. At what percentage of THD is an amp normally considered to be clipping? At what point can it start to threaten the speaker being driven?

A) let me start with a diagram:
26BA2130-D1CE-4C69-A4B0-1E53BAB88018.jpeg
Clipping is technically the point at which the waveform shape begins to clip, and that requires looking at sinewaves on an oscilloscope. The simpler way is to look at a graph like this. We have power along the X axis and distortion along the Y axis. The distortion rises suddenly when the amplifier no longer has sufficient power to reproduce the incoming signal any louder. An amplifier is like a booster taking a signal at a given level and pumping it up. At some point it can't do that anymore because the power supply can't produce any more power and the transistors can't dissipate any more energy. Distortion sky rockets in most modern amps as scene here.

That means we can define clipping as the knee in the above graph. 7 watts at 8 ohms. But that distortion isn't likely audible. At 8 watts distortion is still just .1% and that may not be audible either.

Of course there is a big problem with this. THD doesn't measure the audibility of distortion and so there is not a reliable fixed value. It depends on the makeup of the distortion. There are scenarios where 1% distortion is not audible and where .01% is audible. One fix I like is to just get all distortion to the lowest level, let's say .00001% and then the makeup doesn't matter. That is increasingly becoming reality.

In other words there is no true answer to this. We infer clipping in the way we talk about it, the most conservative approach is to use the knee if present. Not all amps have a knee, then you have to use more sophisticated methods.

As for speaker damage, there isn't a percentage that threatens your speakers. Your speakers can handle a fixed amount of power over time before they overheat and die. A clipped signal has more area under the curve because of its shape so the power is greater. If your speakers can handle 500 watts and you clip a 25 watt RMS amplifier then you might be producing a 100 watt signal but it still won't fry the speaker. If you clip a 200 watt Amplifier, then you might.

2. As I understand it, a solid-state amp can go from "just fine" (less than 0.1% THD) to clipping (1% THD?) very quickly. Like, a 100 watt amp could be fine at 90 watts, and be clipping at 100 watts. Is that generally the case?

A) yes see my answer above. Just remember clipping is a mathematical function of the waveform and that isn't the same as audible. We've been taught to mix this up. Distortion equals bad sound, which is true, but the measures we use don't measure bad sound.

3. How do tube amps fit into the distortion discussion?

A) Tube amps produce different distortion than solid-state amps basically. First, in general they have more even order and more low order distortion. Solid-state amps, especially those with a lot of feedback produce a lot more high order distortion which is audible at lower levels. That means a solid state amp could have audibly worse distortion even though it has lower overall distortion. Tube amps also soft clip. their rise in distortion is gradual and we don't see the same knee often.

4. How is it possible to compare amplifier capabilities when the various manufacturers publish data that are not really comparable? (Example: at one extreme, some amp manufacturers publish output levels corresponding to a 1 kHz input signal, one channel driven, and at 1% THD. On the other extreme, a conscientious manufacturer might use a full bandwidth signal, with all channels driven, and at 0.1% or less THD, and publish those output levels). This "specsmanship" as I like to call it, can be found in many audio products and many specification metrics.

A) you can't. You can never compare specs that don't meet an established standard and the standard can't be manipulated. In reality a scientist would never compare unknown specs because there are too many uncontrolled variables. If everyone used standard test equipment and accepted methods we could compare, but they don't.

The other side of this is that most modern electronics use amplifiers that are largely integrated chips. They are really good to begin with. The distortion is really low, some soft clip automatically, noise is low, etc. It isn't like it was in the 50's and 60's. Most gear in the market today works basically as advertised. With amplifiers the biggest concern is having enough power to avoid clipping.

There are some legitimate audiophile concepts in amplifier sound but they are probably best for another article. There are some esoteric aspects of amplifier performance that could matter in helping an amplifier to sound different but the conditions by which that is true are rare. Most people's rooms are too noisy to hear differences in noise floor or distortion for example.
 

Prof.

Moderator
Staff member
Joined
Apr 15, 2017
Messages
76
Location
South Australia
My AV System  
Preamp, Processor or Receiver
Pioneer VSX-919
Universal / Blu-ray / CD Player
Panasonic Blu-ray
Front Speakers
Voight VH-1 Folded Horns
Center Channel Speaker
Voight VH-1 Folded Horn
Surround Speakers
Behringer Monitors
Subwoofers
BFM THTLP Subwoofer
Other Speakers or Equipment
Anti-mode 8033 Sub Equalizer
Video Display Device
Mitsubishi HC4000 projector
Screen
SeymourAV XD AT Screen..
Remote Control
Logitech One
Other Equipment
Darby Darblett video processor
Very informative articles Matt..Well done.:T
 

Todd Anderson

Editor / Reviewer/ Senior Admin
Staff member
Joined
Jan 20, 2017
Messages
5,508
Location
Balt/Wash Metro
My AV System  
Preamp, Processor or Receiver
Denon X8500H
Main Amp
Emotiva XPA-5
Additional Amp
Emotiva XPA Gen3 2.8 multichannel amp
Other Amp
VSX21-THX
Universal / Blu-ray / CD Player
OPPO UDP-205, UDP-203, Panasonic UB820
Front Speakers
SVS Ultra Towers
Center Channel Speaker
SVS Ultra Center
Surround Speakers
SVS Ultra Surround
Surround Back Speakers
SVS Ultra Bookshelf
Front Height Speakers
SVS Prime Elevation x4 (Top Front, Top Mid-Front)
Rear Height Speakers
SVS Prime Elevation x4 (Top Middle, Top Rear)
Subwoofers
dual SVS SB16s + dual PSA XS30s
Other Speakers or Equipment
Behringer 1124p; Aura Bass Shaker Pros; SuperSub X
Video Display Device
JVC RS520
Screen
Carada Cine-White 0 gain
Other Equipment
LG Electronics 65-inch B6 OLED, Sony 65-inch X900F
Nice, Matt! Great info!
 

mike w

Member
Joined
Jun 28, 2017
Messages
24
My AV System  
Preamp, Processor or Receiver
classe' audio model four
Main Amp
classe' audio model seventy
Universal / Blu-ray / CD Player
marantz sa8005 sacd
Front Speakers
sonus faber Cremona auditor m
Front Height Speakers
36"
Matt: I will echo the sentiments of others - this is good stuff; a refreshing change from the faith based engineering so prevalent on other audio forums. To continue with the metaphor, you need to evangelize more.
 

Matthew J Poes

Guest Writer
Thread Starter
Joined
Oct 18, 2017
Messages
1,834
Matt: I will echo the sentiments of others - this is good stuff; a refreshing change from the faith based engineering so prevalent on other audio forums. To continue with the metaphor, you need to evangelize more.
Thank you so much Mike. If you have any topics of interest let me know.
 

Tony V.

Moderator
Staff member
Joined
Apr 14, 2017
Messages
1,027
Location
Edmonton, AB, Canada
My AV System  
Preamp, Processor or Receiver
Onkyo TX RZ920
Main Amp
Samson Servo 600
Additional Amp
QSC MX1500
Universal / Blu-ray / CD Player
Panasonic 220
Front Speakers
EV Sentry 500
Center Channel Speaker
EV Sentry 500
Surround Speakers
Mission 762
Surround Back Speakers
Mission 762
Subwoofers
SVS PB13u
Video Display Device
Panasonic AE 8000
Remote Control
Logitech 1100
Other Equipment
Denon DT 625 CD/Tape unit, Nintendo WiiU, and more
Thanks Matt, this is the kind of great information that is lacking on other sites.

Would it be safe to say that distortion or clipping is in a way like taking the smooth movement of the driver and making it abruptly stop and reverse in the other direction thus causing damage?
 

Matthew J Poes

Guest Writer
Thread Starter
Joined
Oct 18, 2017
Messages
1,834
Thanks Matt, this is the kind of great information that is lacking on other sites.

Would it be safe to say that distortion or clipping is in a way like taking the smooth movement of the driver and making it abruptly stop and reverse in the other direction thus causing damage?
Thanks Tony.

Are you asking if the reason clipping causes speaker damage is that it causes abrupt changes in cone motion? I guess before I answer I should make sure I understand the question.
 

Tony V.

Moderator
Staff member
Joined
Apr 14, 2017
Messages
1,027
Location
Edmonton, AB, Canada
My AV System  
Preamp, Processor or Receiver
Onkyo TX RZ920
Main Amp
Samson Servo 600
Additional Amp
QSC MX1500
Universal / Blu-ray / CD Player
Panasonic 220
Front Speakers
EV Sentry 500
Center Channel Speaker
EV Sentry 500
Surround Speakers
Mission 762
Surround Back Speakers
Mission 762
Subwoofers
SVS PB13u
Video Display Device
Panasonic AE 8000
Remote Control
Logitech 1100
Other Equipment
Denon DT 625 CD/Tape unit, Nintendo WiiU, and more
Thanks Tony.

Are you asking if the reason clipping causes speaker damage is that it causes abrupt changes in cone motion? I guess before I answer I should make sure I understand the question.
Yes, that is what I am asking
 

Matthew J Poes

Guest Writer
Thread Starter
Joined
Oct 18, 2017
Messages
1,834
Yes, that is what I am asking
I see. I guess I would not characterize it that way, but in some ways we might be splitting hairs. The primary reason that clipping causes distortion is that the amount of power, in watts, that is produced is much higher because the wave is square shaped. The square wave produced by clipping increases the area under the curve, which increases the total amount of power. A number of people have written articles talking about how small amps don't blow speakers, and what they are saying is that as long as a speaker can handle many times more power than the amplifier can produce RMS, then even when clipping that total power would be less and the speaker won't blow. The reason the speakers blow is that the total power it produces when clipping is much higher than the speaker can handle, the voice coil overheats and blows. A square wave has twice the power of a sinewave for a given amplitude!

If you think about it, a sinewave, while rounded, at very high frequencies would have a very sharp and quick transition from one phase to the other. A square wave would have pauses as it goes from one direction to the other. While the transition to the pause is sharp and sudden, I don't see any reason this would damage a speaker. To be honest, I've never really thought about that.

One thing to keep in mind is that all of the above is what happens when feeding sine-wave test signals into an amplifier. In the days of acoustic instruments, that was a fair comparison. In todays electronic world, intentionally creating and adding square waves to a song is not so unusual (and certainly ok), so the same conditions seen under clipping could be experienced with a musical signal. The primary difference is that clipping causes square waves at the limits of the amplifier. A song with square waves probably would not be at the limit, but what if you have a speaker that handles 50 watts rms connected to a 100 watt RMS receiver and now its producing a square wave. If the speakers are inefficient or you just like it loud (I admit that I listen pretty loud), you could exceed the speakers output capability.

Some people argue that square-waves cause worse cooling, but I'm honestly not sure that is true. I think that is based on the shape of the curve and an assumption that the cone is moving less with square waves. I'm not sure that in practice this is a meaningful difference in movement to cause a difference in motion that causes excess heat buildup. I really think its just because there is now more power going to the voice coil.

http://sound.whsites.net/articles/speaker-failure.html
Here is a good reference
 

Tony V.

Moderator
Staff member
Joined
Apr 14, 2017
Messages
1,027
Location
Edmonton, AB, Canada
My AV System  
Preamp, Processor or Receiver
Onkyo TX RZ920
Main Amp
Samson Servo 600
Additional Amp
QSC MX1500
Universal / Blu-ray / CD Player
Panasonic 220
Front Speakers
EV Sentry 500
Center Channel Speaker
EV Sentry 500
Surround Speakers
Mission 762
Surround Back Speakers
Mission 762
Subwoofers
SVS PB13u
Video Display Device
Panasonic AE 8000
Remote Control
Logitech 1100
Other Equipment
Denon DT 625 CD/Tape unit, Nintendo WiiU, and more
Great info, Thanks
 

dabwolf

New Member
Joined
Feb 21, 2018
Messages
5
awesome job putting this together. To be honest, I'm not sure I understand a lot of it, but that's because of my lack of knowledge in audio.
 

Matthew J Poes

Guest Writer
Thread Starter
Joined
Oct 18, 2017
Messages
1,834
That's the point of writing these articles. To provide new knowledge.

Let me know what you don't understand and I can try to explain it differently. It's certainly good knowledge to have. It also helps me learn how best to explain these topics to the average enthusiast who doesn't necessarily care as much about the underlying scientific concepts.
 

ddude003

Senior Member
Joined
Aug 13, 2017
Messages
278
Location
Somewhere Northeast of Kansas City Missouri
My AV System  
Preamp, Processor or Receiver
PrimaLuna Dialogue Premium TubePre (2 channel+sub)
Main Amp
McIntosh MC152 SS Amp (2 channel)
Additional Amp
Yamaha RX-A850 Pro (the other 5 channels lol)
Universal / Blu-ray / CD Player
LG BlueRay
Front Speakers
Martin Logan ElectroMotion ESL
Center Channel Speaker
Martin Logan Motion C2
Surround Speakers
Martin Logan Motion 4
Surround Back Speakers
Martin Logan Motion 4 (yes, another set of these)
Subwoofers
Martin Logan Dynamo 700
Other Speakers or Equipment
Cifte 12AU7 NOS & Genalex Gold Lion Tubes in Pre
Video Display Device
Sony TV KDL50W700B
Remote Control
Audirvana Plus, Tidal HiFi MQA and DSD128...
Other Equipment
Throw rug, saddle blankets and base traps...
Nice treatment of the subject matter Matthew!!! I am looking forward to your next steps here...
 

Matthew J Poes

Guest Writer
Thread Starter
Joined
Oct 18, 2017
Messages
1,834
Nice treatment of the subject matter Matthew!!! I am looking forward to your next steps here...
Thank you! The SBIR article relates to this as SBIR is a linear distortion artifact caused by placement issues. Future articles will likely continue to focus on the things within our control which lead to the most audibly significant problems in sound.
 

Matthew J Poes

Guest Writer
Thread Starter
Joined
Oct 18, 2017
Messages
1,834
There's a lot to read regarding types of distortion wrapped in explanations of human perception and audibility in Dr Floyd Toole's book 'Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms '.
Thanks Barry, that book is an excellent read. This article was meant to be just a very high level and brief introduction to the topic rather than attempt to provide the same depth that Floyd does in his book. None the less we conclude the same way, that linear distortions are far and away the greatest problem plaguing most systems.
 
Top Bottom