How Does a Speaker/Reciever Get Damaged?

Wharfedale Speakers

sumitkpandit

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What makes sense to me is following...
- If we drive a speaker with a powerful enough amplifier that can push more power to the speaker than its RMS power or even Peak Power handeling, it will blow out the speaker coil.
- If we drive a speaker with very low impedance with a reciever that is not meant to handle that low impedance, the amplifier in the reciever overworks to produce that power and gets upset.

But I have also heard that when you pair a low output reciever to a high RMS speaker, you end up destroying it. This does not make a lot of sense to me. Can someone explain this? My idea is that the stress on the speaker is only dependent on the power we are supplying to it.

For sensitivity I totally understand that higher sensitivity is better, you can hit higher levels with low power. What about the impedance? If your reciever can supply 70 W to a 8 ohm speaker is it not better to get a 6 ohm speaker if it supports to get more power from the reciever? Is sensitivity also releated to impedance somehow?
 

Passive_audio_enthusiast

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When you push an underpowered amp to make your speakers loud, the amp would just go into Clipping. This would sent DC likE signal to a speaker. The voice coil of the speaker normally go forward and backward with ac signal and but with more constant signal the amount of time the coil getting stuck at a point increases. This eventually heats up the coil and sometimes burns it or partly burning or deforming the round shape to a distorted round shape. In all these cases we hear distortion thereafter from the speaker.

Another problem is the crossover circuits are mostly designed to work on AC as capacitors filter AC signals(audio signals are AC) when a FLAT signal comes through, it lets them pass and in case of very thin coils like tweeters the damage is more easily done as now the caps say(3.3,4,7,5,6 and so on-most common values in series with have in series with tweeter)would let the full range signal pass through immediately burning the coil.

With partial burns of coil, the drivers would still work but with now we have less number of turns of the coil, resulting in a different frequency response which isn’t ideal and a crossover see a different impedance which screws up whole design of the speaker. If one driver fails therefore it screws up the response of the other one too in the same box.
 

sumitkpandit

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So all of this happens when one over-drives an amplifier. But how can someone overdrive an amplifier? Are we not limited by the manufacturer or circuitry inside? I mean I can only increase volume of my system to 100%. Which should mean that amplifier should be able to only output so much power even on 100% volume.

Even if I try to hit a certain level with a speaker, the worst that should happen is that I turn my volume knob all the way to the final position but still miss that level. Still having clean sound.

May be peaks are the one that can cause damage because they come distorted. But the simple solution should be to only crack amplifier volume up to 90% or something leaving some headroom for the peaks. Isn't it? May be some setting in the reciever menu to not let volume go beyond a mark.
 

yogitashwer

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What makes sense to me is following...
- If we drive a speaker with a powerful enough amplifier that can push more power to the speaker than its RMS power or even Peak Power handeling, it will blow out the speaker coil.
- If we drive a speaker with very low impedance with a reciever that is not meant to handle that low impedance, the amplifier in the reciever overworks to produce that power and gets upset.

But I have also heard that when you pair a low output reciever to a high RMS speaker, you end up destroying it. This does not make a lot of sense to me. Can someone explain this? My idea is that the stress on the speaker is only dependent on the power we are supplying to it.

For sensitivity I totally understand that higher sensitivity is better, you can hit higher levels with low power. What about the impedance? If your reciever can supply 70 W to a 8 ohm speaker is it not better to get a 6 ohm speaker if it supports to get more power from the reciever? Is sensitivity also releated to impedance somehow?
Hi,
Speaker wires may be the most common culprit to damaged speakers, receivers and amps. Consumers were convinced they need 10AWG -12AWG monster speaker wires to get good sound. If the wire is not trimmed properly and has whiskers it can short output transistors. Failures in tweeters, midrange and mid bass speakers are caused by ELECTRICAL and/or MECHANICAL power handling issues. Most failures occur from ELECTRICAL failure caused by applying too much power to the speaker's voice coil.. Distortion is not damaging to a speaker
 

Passive_audio_enthusiast

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So all of this happens when one over-drives an amplifier. But how can someone overdrive an amplifier? Are we not limited by the manufacturer or circuitry inside? I mean I can only increase volume of my system to 100%. Which should mean that amplifier should be able to only output so much power even on 100% volume.

Even if I try to hit a certain level with a speaker, the worst that should happen is that I turn my volume knob all the way to the final position but still miss that level. Still having clean sound.

May be peaks are the one that can cause damage because they come distorted. But the simple solution should be to only crack amplifier volume up to 90% or something leaving some headroom for the peaks. Isn't it? May be some setting in the reciever menu to not let volume go beyond a mark.
Simple answer is amps don’t have anything in their output to avoid clipping unless it’s NAD, which used to have a feature called soft clipping which I guess is limiting the power to the power amp section when pushed beyond a point. I don’t know how it exactly works. But every amp clips at some level it depends on how much current your particular speaker draws from the amp. A very hard to drive speaker with low sensitivity may not sound very loud even when it’s turned to the max on the volume dial but at the same time would be clipping the amp. A very high sensitivity speaker even when you dial the volume to max even though it may be extremely loud may drive the amp into clipping. So you have two different speakers two different levels of power from the amp. The first low sensitive speaker would be damaged if it’s running for long.

Difficult things for amps are low impedance a and low sensitvity. Again if even don’t trust the impedance rating of the speakers given by the manufacturer as the last word as imepance is a frequency dependent variable. It goes up and down depending on what freq is playing.

It’s much more complicated than what specs say always. So the safest bet it just to have raw power at the disposal from the amp and keep the loudness level to sane levels. Another solution is Bi amp speakers so that even if woofers draw more current the amp connected to midrange and tweeter won’t clip. Woofers can handle clipping more than mids and tweeters
 

sumitkpandit

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So, I guess getting as sensitive speaker as possible is the way to go. And with my budget, it has to be Taga Harmony TAV-606 v.3 5.0 Speaker System. Now I need to do some real life maths.

Lets say, I'll be listening to them from a distance of 4 m with peaks going no more than 90 dB and connected to a reciever which does 70 W per channel with 2 channels driven 20 - 20,000 Hz at 8 ohms with total harmonic distortion less than 0.1 %.

So the speaker having 90 dB sensitivity (front left and front right) will need only 16 W per channel to hit the desired level.

1 m - 90 dB - 1 W
2 m - 84 dB - 1 W (considering 6 dB drop with doubling of distance)
4 m - 78 dB - 1 W
4 m - 81 dB - 2 W (considering 3 dB rise with doubling of power)
4 m - 84 dB - 4 W
4 m - 87 dB - 8 W
4 m - 90 dB - 16 W

If I try not to inflate volume higher than this, my reciever and speaker both should trive for years without any problem. Right?

But one part of calculation which I did not consider is the impedance. Speakers have impedance of 6 ohm and the reciever power output is rated with 8 ohm impedance. How does this change the calculation?

If I calculate for all channels with a room size of 5.196 m x 3.464 m, because sensitivity and distance of speakers are different it goes like this

Speaker - Sensitivity - Distance - Power required to hit 90 dB peaks
L/F - 90 dB - 4 m - 16 W
Center - 88 dB - 3.464 m - < 32 W
Surrounds - 86 dB - 2 m - < 16 W

So, it still goes hardly to (16 * 2 + 32 + 16 * 2) = 96 W which is sufficiently less than recievers rating (70 * 2) = 140 W total. Is this calculation right?
 
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IndianEars

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But I have also heard that when you pair a low output reciever to a high RMS speaker, you end up destroying it. This does not make a lot of sense to me. Can someone explain this? My idea is that the stress on the speaker is only dependent on the power we are supplying to it.
In this post I will answer only the above question.
(There are other questions in your posts 1 & 3 and ofcourse post 8 above, which I could answer in separate posts.

Since queries have been multiple, I will do my best to keep my answer in this post specific to the query and as brief as possible. If my answer is too brief, let me know, and I will be happy to elaborate.

To understand why a Low Powered amplifier ( say 30 Watts per channel) can damage a speaker rated at a higher power (say 100 Watts per channel), we need to appreciate the Following 3 Key concepts:

1. THE LOUDSPEAKER
Loudspeakers typically consists of multiple drivers, each driver is designed to optimally work within a relatively narrow range of frequencies. As an example, a 3 way speaker will have:
  • One or more LF (Low Frequency) Drivers also called Woofers
  • One or more Mid Frequency Range Drivers (Earlier called Squawkers) or just Mid Range Drivers
  • One or more HF (High Frequency) Drivers, also called tweeters.
Most of the Power (50% to 70%) in music is contained in the Low Frequencies. Woofers in a loudspeaker are therefore designed to handle most of the Loudspeaker power. So the Woofer drivers in a 100 Watt rated Loudspeaker will usually be able to handle 80 Watts or More.

About 20% to 30% of music power is contained in the midrange. Hence, the midrange drivers in a 100 Watt rated Loudspeaker will usually be able to handle 30 Watts or More.

Only 10% to 20% of music power is contained in the High Frequencies. Hence, the Tweeters a 100 Watt rated Loudspeaker will usually be able to handle around 10 Watts. Keep in mind that a tweeter diaphram needs to make small and fast movements, so its best to keep its dimensions and mass of the moving parts, small. This also implies lower power handling capacity for Tweeters.

2. THE AMPLIFIER

The "Rated Power" of an amplifier is the power it can deliver with minimal (specified as 0.1% or whatever) distortion.
The amplifier can usually deliver (20% to 30%) higher power but with a lot of (30%) distortion.
So a 80 Watts per channel amplifier, will typically deliver even 100 Watts of power with 30% distortion.

3. DISTORTION

Just as all matter is composed out of atoms, similarly, a mathematician called Fourier proved (Fourier's Theorem) that all sounds can basically be considered to comprise of Sine Wave frequencies. So sine waves are the basic building blocks of all Musical notes / sounds. These sine wave consist of a "Fundamental" or the basic frequency + Harmonics (or musical over tones)

When a note is distorted (say, by the amplifier, because it has run out of power), the distorted note contains Far more Harmonics ( ie higher frequencies) than the original more.

Hence when a 300 Hz Tone (normally handled by the robust Woofer) is Distorted, the distorted note will have new frequencies at all Multiples of 300 Hz ... these will include:
3,000 Hz (Delivered to the Midrange)
6,000 Hz & 12,000 Hz delivered to the delicate Tweeter.

Lets take some illustrative figures:
An 80 Watt Amplifier, driven hard into distortion at a Party ... Putting out 100 Watts of Highly distorted (30% distortion) sound power.
So 30% of 100 Watts ie about 30 Watts will be Harmonics that are delivered (un-necessarily) to the Midrange or Tweeter!

Suddenly, the Distorted music has Far more Mid Freq & High Freq content that the Mid Range Driver and Tweeter can handle.

Tweeters are usually the 1st to blow in a damaged speaker,
and the above (hopefully :)) illustrates why a low powered amp can destroy Higher power rated speakers.
 

COOLDUDE7808

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its actually very simple ....you must buy an amp which is capable of supplying more power than the speakers need . This is the only way you can protect your speakers and amp both . Amps are rated for 8 /4 / 2 Ohms and speakers generally specify amp wattage range .

Now typically audiophile has budgetary constraints and wants more ...so we will hear all sorts of arguments about size or room , How loud you will play , kind of music , how some low rated amps are actually powerful , speaker senstivity , etc etc ....now all these are very valid points and does work in different scenarios BUT there is always an element of risk involved .

My Marantz PM7001 and 8005 have gone into protection mode at times . Luckily no damage to speakers . But PM11S2 not even once in the last 5 yrs .
 

sumitkpandit

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In this post I will answer only the above question.
(There are other questions in your posts 1 & 3 and ofcourse post 8 above, which I could answer in separate posts.

Since queries have been multiple, I will do my best to keep my answer in this post specific to the query and as brief as possible. If my answer is too brief, let me know, and I will be happy to elaborate.

To understand why a Low Powered amplifier ( say 30 Watts per channel) can damage a speaker rated at a higher power (say 100 Watts per channel), we need to appreciate the Following 3 Key concepts:

1. THE LOUDSPEAKER
Loudspeakers typically consists of multiple drivers, each driver is designed to optimally work within a relatively narrow range of frequencies. As an example, a 3 way speaker will have:
  • One or more LF (Low Frequency) Drivers also called Woofers
  • One or more Mid Frequency Range Drivers (Earlier called Squawkers) or just Mid Range Drivers
  • One or more HF (High Frequency) Drivers, also called tweeters.
Most of the Power (50% to 70%) in music is contained in the Low Frequencies. Woofers in a loudspeaker are therefore designed to handle most of the Loudspeaker power. So the Woofer drivers in a 100 Watt rated Loudspeaker will usually be able to handle 80 Watts or More.

About 20% to 30% of music power is contained in the midrange. Hence, the midrange drivers in a 100 Watt rated Loudspeaker will usually be able to handle 30 Watts or More.

Only 10% to 20% of music power is contained in the High Frequencies. Hence, the Tweeters a 100 Watt rated Loudspeaker will usually be able to handle around 10 Watts. Keep in mind that a tweeter diaphram needs to make small and fast movements, so its best to keep its dimensions and mass of the moving parts, small. This also implies lower power handling capacity for Tweeters.

2. THE AMPLIFIER
The "Rated Power" of an amplifier is the power it can deliver with minimal (specified as 0.1% or whatever) distortion.
The amplifier can usually deliver (20% to 30%) higher power but with a lot of (30%) distortion.
So a 80 Watts per channel amplifier, will typically deliver even 100 Watts of power with 30% distortion.

3. DISTORTION

Just as all matter is composed out of atoms, similarly, a mathematician called Fourier proved (Fourier's Theorem) that all sounds can basically be considered to comprise of Sine Wave frequencies. So sine waves are the basic building blocks of all Musical notes / sounds. These sine wave consist of a "Fundamental" or the basic frequency + Harmonics (or musical over tones)

When a note is distorted (say, by the amplifier, because it has run out of power), the distorted note contains Far more Harmonics ( ie higher frequencies) than the original more.

Hence when a 300 Hz Tone (normally handled by the robust Woofer) is Distorted, the distorted note will have new frequencies at all Multiples of 300 Hz ... these will include:
3,000 Hz (Delivered to the Midrange)
6,000 Hz & 12,000 Hz delivered to the delicate Tweeter.

Lets take some illustrative figures:
An 80 Watt Amplifier, driven hard into distortion at a Party ... Putting out 100 Watts of Highly distorted (30% distortion) sound power.
So 30% of 100 Watts ie about 30 Watts will be Harmonics that are delivered (un-necessarily) to the Midrange or Tweeter!

Suddenly, the Distorted music has Far more Mid Freq & High Freq content that the Mid Range Driver and Tweeter can handle.

Tweeters are usually the 1st to blow in a damaged speaker,
and the above (hopefully :)) illustrates why a low powered amp can destroy Higher power rated speakers.
Thank you @IndianEars for taking time to provide the best explanation I have seen so far. I appreciate your patience and effort to put down this elaborate answer. This also gives me hope that my other queries will also be answered satisfactorily.

Regarding distortion you said that it is composed of unnecessary harmonics. Also in some places I have heard it being expressed as cut-off of the sine wave at both extremes crests and troughs. Which some people also refer to as DC part of the signal. Which I understand is equally hard for drivers to deal with, being stuck in extreme position for longer time. Whatever distortion may be, it affects speakers adversely. And you made it very clear why distortion happens.

I think this leads us to discuss about my last post where my calculation shows I shall never feel need to crack my receiver enough to distort output signal. Isn't it?
 

sumitkpandit

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its actually very simple ....you must buy an amp which is capable of supplying more power than the speakers need . This is the only way you can protect your speakers and amp both . Amps are rated for 8 /4 / 2 Ohms and speakers generally specify amp wattage range .

Now typically audiophile has budgetary constraints and wants more ...so we will hear all sorts of arguments about size or room , How loud you will play , kind of music , how some low rated amps are actually powerful , speaker senstivity , etc etc ....now all these are very valid points and does work in different scenarios BUT there is always an element of risk involved .

My Marantz PM7001 and 8005 have gone into protection mode at times . Luckily no damage to speakers . But PM11S2 not even once in the last 5 yrs .
Agree @COOLDUDE7808 . Budget is really a factor that is always at the base of everything. But risk also walks hand in hand I guess.

There is no risk free state other than being mindful of your systems capabilities. Even supplying more power than the speaker needs can also blow the coil. Isn't it? I think is not about what speaker needs, but what volume do we need.

If we are gonna plan for an outdoor party/concert, getting an amplifier is the way to go. But in a 14' x 14' room, we risk our ears if we play volumes that justify the amplifier cost or risk our money going unused if listen at safe volumes. What do you say? Isn't risk always there for one or the other thing?
 

IndianEars

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Regarding distortion you said that it is composed of unnecessary harmonics. Also in some places I have heard it being expressed as cut-off of the sine wave at both extremes crests and troughs. Which some people also refer to as DC part of the signal. Which I understand is equally hard for drivers to deal with, being stuck in extreme position for longer time. Whatever distortion may be, it affects speakers adversely. And you made it very clear why distortion happens.
To elaborate slightly on Clipping.

Below is a picture of a sine wave that has clipped (not allowed to rise and fall to its full value)
download.png
The new waveform (in Blue) is different from a Sine wave. Hence by Fourier's Theorem, it can be considered to comprise of the Original Sine wave + Many Harmonics .... This explains where the Harmonics arise from.

SYMMETRICAL & UNSYMMETRICAL CLIPPING

The area enclosed by the clipped sine wave (negative and Positive halves) is the symmetry.

Fourier's Theorem further states that if ANY waveform (Clipped or otherwise) is symmetrical about the horizontal axis (Usually Zero Volts) its will contain ONLY Odd order Harmonics

Hence ANY SHAPED symmetric Waveform of (for example) 1,000 Hz will contain ONLY 3,000 Hz, 5,000 Hz, 7,000 Hz and so on. A symmetric Waveform will NOT contain even order (2,000 Hz, 4,000 Hz, 6,000 Hz etc)

Only an UNSYMMETRICAL waveform will have even order harmonics.

The DIFFERENCE between the area enclosed between the clipped Negative & Positive portions (ie the full Blue line and the Green Line), is the DC part of the signal.

So the Amount of asymmetry is the DC component.



In the diagram above, though there is Substantial Clipping, it is symmetrical, so there will be:
  • Only Odd harmonics
  • Zero DC
In Fourier's Theorem, the Remainder term is the DC component. ;)
 

OM_2K19

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To elaborate slightly on Clipping.

Below is a picture of a sine wave that has clipped (not allowed to rise and fall to its full value)
View attachment 62061
The new waveform (in Blue) is different from a Sine wave. Hence by Fourier's Theorem, it can be considered to comprise of the Original Sine wave + Many Harmonics .... This explains where the Harmonics arise from.

SYMMETRICAL & UNSYMMETRICAL CLIPPING
The area enclosed by the clipped sine wave (negative and Positive halves) is the symmetry.

Fourier's Theorem further states that if ANY waveform (Clipped or otherwise) is symmetrical about the horizontal axis (Usually Zero Volts) its will contain ONLY Odd order Harmonics

Hence ANY SHAPED symmetric Waveform of (for example) 1,000 Hz will contain ONLY 3,000 Hz, 5,000 Hz, 7,000 Hz and so on. A symmetric Waveform will NOT contain even order (2,000 Hz, 4,000 Hz, 6,000 Hz etc)

Only an UNSYMMETRICAL waveform will have even order harmonics.

The DIFFERENCE between the area enclosed between the clipped Negative & Positive portions (ie the full Blue line and the Green Line), is the DC part of the signal.

So the Amount of asymmetry is the DC component.



In the diagram above, though there is Substantial Clipping, it is symmetrical, so there will be:
  • Only Odd harmonics
  • Zero DC
In Fourier's Theorem, the Remainder term is the DC component. ;)
I still get nightmares of Fourier's Theorem :p
 

IndianEars

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I got nightmares too.... One of my Worst Math Topics in Engineering.

Only understood its significance years later.

If only our Profs had explained it better .... But it was taught by Math Profs, Not Electrical Engg Proffs.

(Same issues with Lag & Lead Compensation for stability)
 

IndianEars

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I think this leads us to discuss about my last post where my calculation shows I shall never feel need to crack my receiver enough to distort output signal. Isn't it?

I presume that you are referring to this post of yours, below ?

So, I guess getting as sensitive speaker as possible is the way to go. And with my budget, it has to be Taga Harmony TAV-606 v.3 5.0 Speaker System. Now I need to do some real life maths.

Lets say, I'll be listening to them from a distance of 4 m with peaks going no more than 90 dB and connected to a reciever which does 70 W per channel with 2 channels driven 20 - 20,000 Hz at 8 ohms with total harmonic distortion less than 0.1 %.

So the speaker having 90 dB sensitivity (front left and front right) will need only 16 W per channel to hit the desired level.

1 m - 90 dB - 1 W
2 m - 84 dB - 1 W (considering 6 dB drop with doubling of distance)
4 m - 78 dB - 1 W
4 m - 81 dB - 2 W (considering 3 dB rise with doubling of power)
4 m - 84 dB - 4 W
4 m - 87 dB - 8 W
4 m - 90 dB - 16 W


But one part of calculation which I did not consider is the impedance. Speakers have impedance of 6 ohm and the reciever power output is rated with 8 ohm impedance. How does this change the calculation?

If I calculate for all channels with a room size of 5.196 m x 3.464 m, because sensitivity and distance of speakers are different it goes like this

Speaker - Sensitivity - Distance - Power required to hit 90 dB peaks
L/F - 90 dB - 4 m - 16 W
Center - 88 dB - 3.464 m - < 32 W
Surrounds - 86 dB - 2 m - < 16 W

So, it still goes hardly to (16 * 2 + 32 + 16 * 2) = 96 W which is sufficiently less than recievers rating (70 * 2) = 140 W total. Is this calculation right?

The Calculations are correct, but I would differ on the SPL required (or is it just me ? ;) )

I would like Atleast a peak SPL of 100 dB... I am strictly a 2 channel guy, and I want atleast 100 dB SPL.

If I was watching Home Theatre, I would probably want higher SPL's (the brain's attention is pulled between audio & the Video experience).
 

COOLDUDE7808

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yes risk is always there ...but a relatively powerful amplifier minimizes the risk . When your speakers are driven more efficiently, automatically the control over volume button will happen . My room is not very big ...but when I move from one room to another or I am taking a shower , I need to play in slightly higher volumes and that's where PM11S2 helps . I have used less powerful amplifiers like PM7001 for more than 5 yrs and based on my own experience ...I would say invest in a good amp (SQ + Power) and then look for Speakers .

Generally Coil burning due to more power is very rare ...since the speakers draw power from the amp based on musical peaks/volume .......Amp does not belt out the entire power which is mentioned in the specs . So in my case I will never use the entire 100/200 Watts ....but this reserve power really helps in many ways . Conversely audiophile logic is why waste money on something which is not required - Which means maybe 50 Watt amp is enough so invest the money on speakers and CD player . Also when somebody says " Generally I listen to music in low volumes " etc . The Key word here is Generally (not Always) . This logic is what results in damaged speakers and amp .
 
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