Clipping & Underpowered Speakers

[Deleted member 46664]

This is also very helpful. So, there is such a thing as listening at safe levels and then a single instrument pushes it over the limit and causes short term clipping?

Happens all the time ...

 

[killdozzer]

It might help to inject some understanding of the dynamics of music at this point...

First of all, if your SPL tests are reading about 80db on a steady tone, on properly produced music (not this highly compressed 0 dynamic range garbage they crank out today) you are probably getting peaks that are 10 to 15 db higher than your steady tone average as well as quiet segments that could be 20 to 30 db lower. (Streaming services now normalize at -16dbfs for just this reason)

Music is not steady state... that's why you need "headroom" in an amplifier. So, for example... you have a pair of speakers rated at 85db @ 1 watt .... When you get that + 15 db peak of a snare drum or gunshot you are asking your amplifier for about 30 watts of power, with a 1 watt average! So, yes, an under powered amplifier is going to clip ... rather noticeably.
(Handy calculator ... HERE)

But it's a bit more complex than that... music has a natural decay in that as frequency increases, power tends to ramp down somewhat as higher pitched sounds are easier to hear. Something like 60% of musical power is under 250hz with the rest being in a tapered decline. Also, musical notes end at about 5khz with practically everything above that being harmonics for timbre (voicing). Most of musical sound is actually below 10khz so by the time you get above that, there really isn't a lot of content to be had... and the demands on your amplifiers will be much less. (This is also how they get away with putting a 20 watt tweeter in a 100 watt speaker)

The problem with clipping an amplifier is not just audible distortion... The clipping will almost always happen in the bass region of the music, producing an almost square wave output. Square waves are loaded with harmonics and some of them will reach well into the 30khz region, which is abnormal for a speaker to handle. Then just to make it worse, when you do clip an amplifier you are also feeding through the treble content of the music at much higher than normal levels. Put these two effects together and you end up with an overheated tweeter that just might give up on you. (Yes, I just told you that most "blown tweeters" are usually caused by not having enough amplifier power.)

So what's the takeaway from all this?

Well, most people listen at about 1 to 2 watts of average power --and yeah, that's pretty LOUD-- but with well produced music that can create demands for 30 to 50 watts of power on peaks. So trying to figure this out with test tones is something of a snipe hunt. You really do need calibrated power meters connected to your amplifier outputs and an SPL meter to get a good handle on it.

This is also why most speakers have 2 power ratings. We've all seen the "20 to 100 watts" thing before. The lower value is recommended amplifier power to get comfortable listening levels without clipping. The higher rating is the maximum safe amplifier power before you start melting down your woofers. Of course anyone listening at 100 watts of average power is going to be deaf in very short order... so my general advice is to buy an amp in the upper end of your speakers power ratings and call it a day.

Gosh that got long ... hope it helps.

Oh, no. Not long at all. Very informative and I thank you most sincerely. It was well put.

So, when I listen to a song that starts with a very deep tone... Like this one for example:

The fact that the deep tone sounds quieter after she starts to sing, you would ascribe to the production side of the things? It has nothing to do with amp being short of breath? I ask because it is less obvious with better speakers. Maybe it's not the amp being short of breath, but speaker not being capable of this task...

 

[Deleted member 46664]

The fact that the deep tone sounds quieter after she starts to sing, you would ascribe to the production side of the things? It has nothing to do with amp being short of breath? I ask because it is less obvious with better speakers. Maybe it's not the amp being short of breath, but speaker not being capable of this task...

If it is properly produced, most likely they turned it down so that it would not overwhelm the vocals.

I might also suggest Dire Straights "Calling Elvis" as a test track... those guys are VERY well produced.

Also don't forget that our perception of sound is relative. Try a simple experiment with yourself sometime ... in a noisy room, focus in on one conversation... note how you can dig it out from under louder sounds and everything else seems to get quieter. Your notice of this bass note reducing when she starts singing could well be psychoacoustic, not mechanical.

 

[antcollinet]

This is also very helpful. So, there is such a thing as listening at safe levels and then a single instrument pushes it over the limit and causes short term clipping? And of course, this wouldn't happen if the amp had more power...

Then there's the case of the anniversary Denon amp that is rated 2x80 into 8, but has enough reserve which is, I guess, achieved by having large capacitors.

Right - but ver short term clipping of that transient type is not typically audible.

 

[killdozzer]

psychoacoustic, not mechanical.

I wasn't going to go down this road since I've noticed it's much more pronounced on a sound bar then on my main system. Maybe I was wrong.

 

[Deleted member 46664]

I wasn't going to go down this road since I've noticed it's much more pronounced on a sound bar then on my main system. Maybe I was wrong.

Well, whenever human ears are involved we do need to consider the psychoacoustics of a situation.

Anyone wanna take a guess how often I've pulled out test gear to confirm I'm really hearing what I think I'm hearing?

 

[Spkrdctr]

Nit picking .... but ...
The amp doesn't have to clip ... you could simply turn down the volume.

That bit of common sense is sadly lacking around here most days. Great post!

 

[Cote Dazur]

All that clipping conversation made me wonder, since it is seen by many as the evil of all evil, but what does an amplifier clipping sound like?

 

[gnarly]

My 2c...

For me, amp clipping simply means the amp has run out of voltage and/or current to drive the speaker.
And that is across all frequencies, and for all complex waveforms.

So by definition, if the amp is not clipping, it is operating linearly, and speakers will perform properly.

That said, I'm personally convinced many (maybe even most) home audio setups occasionally clip due to a lack of sufficient amplification.
Low to average every day listening, probably not. But who doesn't play a rocking or rousing tune, and crank it up from time to time?

Most everyone has seen some simple numbers based off speaker sensitivity, where we first see how how listening SPL compares to 1 watt sensitivity, and then adjust that for how much amp headroom is needed.
You know, say the speaker is 85 dB sensitive, and I'm happy with that at LP.
And then for power needed , add 6dB for each doubling of distance from 1m.
And add a doubling of amp power needed for each 3dB of peak to average headroom desired.
So for me, 85 dB at about 4m listening distance (+12 dB), and desiring 18 dB headroom, I need 30dB of amp output above 1 watt.
Let's say we get 3 dB just from the peak vs RMS math, so we only need 27 dB....which is 2^9th or 512 watts.


(BTW, we REALLY should be working with voltage not power for headroom calcs...
Personally i like at least 21 dB headroom. I don't begin to understand LUFS and R128 specs, but it appears the broadcast standard would advise for 23 dB headroom)



Mind you, I'm not saying we listen, or want to listen, at 85 dB that often.....but sometimes we do, and without the requisite power/voltage we aren't hearing unclipped music.


OK you say, but I never listen above 75 dB......and have plenty of headroom...

Well, what about bass boost, or a downward tilting house curve......that drops the starting1 watt sensitivity assumption. Significant headroom is used up with bass boost.
And what about the spectral content of the music...can have the same peak to average SPL biasing factor, as bass boost or house curve..

What meter setting is being used to assess the average SPL preferred at listening position? Slow or Fast?
If C weighted, using flat full range pink noise, peak to average reads +15 dB on REW's LCeq SPL meter.
If A weighted, peak to average reads +18 dB on the LAeq meter.
These are both with pink noise having only a 12 dB crest factor. ...not the minimum 18 dB desired (by most) for music.

If we haven't used Z-weighting in assessing our average listening position SPL, i think we are misjudging headroom needed by 3 to 6 dB if using C or A weighting.
Slow vs Fast can bias away another another 2 dB of apparent headroom.

Transients are so much faster, and higher in SPL, than shown by regular SPL meters with only Fast or Slow integrations.
(give REW's SPL meter a good try...it's a nice mete,.... Average, Max, Min, and Peak...it even data logs)


Anyway, point is, unless we are doing some careful and calibrated SPL measurements, i don't think we see how stacked the numbers are typically against us, for true unclipped music........when we want to turn it up ...and that it takes less turning up than we often think, ime/imho.

PS whew....apologize for the length...

 

[AdamG]

I'm interested in something quiet specific; is there such a thing as speakers NOT getting enough power to perform as they should*, but amp NOT going into clipping?

(*As they should according to their own specs, not some unrealistic expectation.)


Is this possible? Or is it that if speakers lack power the one and only scenario is that the amp will start to clip?

Even more specifically; is it possible that the result of lack of power sounds like attenuation in certain freq without amp going into clipping?

Here is a good read about how Dynamic Range of Music can effect how much Amplification power you may need. Once you Establish a baseline for your Speakers, room, distance from speakers, and normal listening levels. Then apply Dynamic Range of various music to determine how much headroom your Amp may need to deliver full un-clipped sound reproduction. The answer is dependent upon your specific gear and room arrangement. The best you can hope to do is going to be based on worst case scenario for you. Several goals could help. Like never clipping or occasional minimal clipping. Only you can decide this.

The below linked article is just to get you started doing your homework:

How Much Power?

Power requirements for hi-fi listening.

sound-au.com

 

[killdozzer]

My 2c...

For me, amp clipping simply means the amp has run out of voltage and/or current to drive the speaker.
And that is across all frequencies, and for all complex waveforms.

So by definition, if the amp is not clipping, it is operating linearly, and speakers will perform properly.

That said, I'm personally convinced many (maybe even most) home audio setups occasionally clip due to a lack of sufficient amplification.
Low to average every day listening, probably not. But who doesn't play a rocking or rousing tune, and crank it up from time to time?

Most everyone has seen some simple numbers based off speaker sensitivity, where we first see how how listening SPL compares to 1 watt sensitivity, and then adjust that for how much amp headroom is needed.
You know, say the speaker is 85 dB sensitive, and I'm happy with that at LP.
And then for power needed , add 6dB for each doubling of distance from 1m.
And add a doubling of amp power needed for each 3dB of peak to average headroom desired.
So for me, 85 dB at about 4m listening distance (+12 dB), and desiring 18 dB headroom, I need 30dB of amp output above 1 watt.
Let's say we get 3 dB just from the peak vs RMS math, so we only need 27 dB....which is 2^9th or 512 watts.


(BTW, we REALLY should be working with voltage not power for headroom calcs...
Personally i like at least 21 dB headroom. I don't begin to understand LUFS and R128 specs, but it appears the broadcast standard would advise for 23 dB headroom)



Mind you, I'm not saying we listen, or want to listen, at 85 dB that often.....but sometimes we do, and without the requisite power/voltage we aren't hearing unclipped music.


OK you say, but I never listen above 75 dB......and have plenty of headroom...

Well, what about bass boost, or a downward tilting house curve......that drops the starting1 watt sensitivity assumption. Significant headroom is used up with bass boost.
And what about the spectral content of the music...can have the same peak to average SPL biasing factor, as bass boost or house curve..

What meter setting is being used to assess the average SPL preferred at listening position? Slow or Fast?
If C weighted, using flat full range pink noise, peak to average reads +15 dB on REW's LCeq SPL meter.
If A weighted, peak to average reads +18 dB on the LAeq meter.
These are both with pink noise having only a 12 dB crest factor. ...not the minimum 18 dB desired (by most) for music.

If we haven't used Z-weighting in assessing our average listening position SPL, i think we are misjudging headroom needed by 3 to 6 dB if using C or A weighting.
Slow vs Fast can bias away another another 2 dB of apparent headroom.

Transients are so much faster, and higher in SPL, than shown by regular SPL meters with only Fast or Slow integrations.
(give REW's SPL meter a good try...it's a nice mete,.... Average, Max, Min, and Peak...it even data logs)


Anyway, point is, unless we are doing some careful and calibrated SPL measurements, i don't think we see how stacked the numbers are typically against us, for true unclipped music........when we want to turn it up ...and that it takes less turning up than we often think, ime/imho.

PS whew....apologize for the length...

HEY, hey, now!!! That's way more than 2c! If not whole two bucks.

Thank you for your thought and contribution. The only thing that is kinda left hangin' is this question whether is there any other type of sound degradation or deterioration due to lack of power other than clipping. Some posts hint at that, but no one took that brave step and said a final yes or no. What is your opinion on that? Is it either/or - either it's clipping or it's working properly?

I don't think my speakers are underpowered at the moment. I have LS50, the first series and the recomm. was 20-100. I got an 110wpch into 8 amp that behaves quite good into 4 ohm loads. It's all fine now. But I had some plans of changing the amp and am trying to figure out the absolute top power rating needed because i don't want to pay for something I'm not going to use. The fact that active LS50 have 230w amps built inside is not really helping me.

 

[killdozzer]

Thank you very much @AdamG247 ! I'll enjoy reading it. However, the question I keep repeating simply because I want to know is 'un-clipped' the only thing I'm chasing is this one:

I think I’m getting a feel for the original post. Sometimes it helps me to understand if I rephrase the question, so that’s what I’ll do here.
What happens electrically, and what does it sound like, when an amp is faced with an impedance dip lower than what it is able to compensate for (the case of the so called hard to drive speaker). Does the amp then clip, and is that the only possible response? Or does the amp simply “run out of steam” and not reproduce that section of music with the same volume as the rest? And if that’s the case, does what you hear coming out of the speaker differ from what you hear when you listen to a speaker with frequency response errors in the same region, or does it sound the same?
Have I got it, @killdozzer ?

Is the clipped / un-clipped the only issue I should worry about? I'd be more than happy if it is, don't get me wrong. I'm not looking for something to fret about. I just want to know.

 

[AdamG]

Thank you very much @AdamG247 ! I'll enjoy reading it. However, the question I keep repeating simply because I want to know is 'un-clipped' the only thing I'm chasing is this one:

Is the clipped / un-clipped the only issue I should worry about? I'd be more than happy if it is, don't get me wrong. I'm not looking for something to fret about. I just want to know.

Well that is what you named the Thread. So in terms of replying to your initial questions. Yes. However, everything changes if you get different speakers, change your room, move closer or further away from the speakers. Assuming none of this changes and you know the answers to the above baseline data. You are starting to talk in circles perhaps? Just go figure out what you have right now. To determine if you are even possibly clipping your kit now.

 

[dc655321]

The fact that active LS50 have 230w amps built inside is not really helping me.

Hang on to your neuroses: it's actually 280W woofer + 100 W tweeter, per speaker.
You're welcome!

 

[Spkrdctr]

Thank you very much @AdamG247 ! I'll enjoy reading it. However, the question I keep repeating simply because I want to know is 'un-clipped' the only thing I'm chasing is this one:

Is the clipped / un-clipped the only issue I should worry about? I'd be more than happy if it is, don't get me wrong. I'm not looking for something to fret about. I just want to know.

The entire discussion all rests on how loud you want to drive low sensitivity speakers. If you want to crank them to near live performance levels then yes, you need a buttload of power plus extremally good speakers that can handle the load. For any regular person, if you listen at levels in the 70db range then you do not need a buttload of power. So everyone has to decide what their personal level of listening is. If you plan on having it LOUD once or twice in its life to show off to your friend, then you don't have to worry about clipping. If you plan on damaging your hearing with regular use of 90db or higher music, then you will need a lot of power. It all depends on what you need. So, how loud do you want to go? That is the very first question to be answered. There are a few online calculators that will give you the power needed for certain loudness/speaker sensitivity. There was a fairly simple one around but I don't have the link. Maybe Adam or someone has it handy. You just plug in your numbers and it spits out a fairly accurate number for the power you need. Plus with it you can see how changing one item affects the power needed. It is fun to play with. Also, there is nothing wrong with occasional minimal clipping. You will not hear it. But again, it all depends on what you want.

 

[AdamG]

The entire discussion all rests on how loud you want to drive low sensitivity speakers. If you want to crank them to near live performance levels then yes, you need a buttload of power plus extremally good speakers that can handle the load. For any regular person, if you listen at levels in the 70db range then you do not need a buttload of power. So everyone has to decide what their personal level of listening is. If you plan on having it LOUD once or twice in its life to show off to your friend, then you don't have to worry about clipping. If you plan on damaging your hearing with regular use of 90db or higher music, then you will need a lot of power. It all depends on what you need. So, how loud do you want to go? That is the very first question to be answered. There are a few online calculators that will give you the power needed for certain loudness/speaker sensitivity. There was a fairly simple one around but I don't have the link. Maybe Adam or someone has it handy. You just plug in your numbers and it spits out a fairly accurate number for the power you need. Plus with it you can see how changing one item affects the power needed. It is fun to play with. Also, there is nothing wrong with occasional minimal clipping. You will not hear it. But again, it all depends on what you want.

Power calculator

 

[killdozzer]

Hang on to your neuroses: it's actually 280W woofer + 100 W tweeter, per speaker.
You're welcome!

Oh thank you! @dc655321 I'll put in a good word with St. Peter when I meet him.

But I was citing the first series:

 

[killdozzer]

The entire discussion all rests on how loud you want to drive low sensitivity speakers.

No, not at all. It's all about whether there is such a thing at all. I think all the questions about room, SPL, distance to the LP are all completely irrelevant. Even if you're not at home that day your speaker will either have some sort of set back in performance due to lack of power or it won't. The question is does it exist? Does any other type of SQ problem occurs when the amp lacks power? It's completely independent of room dimensions.

The same goes for the deterioration in SQ of any system. Something other than clipping will either happen or not. You're free to take any speaker for example and any room setting. It may not happen at YOUR listening level, but will it happen at all?

 

[killdozzer]

Well that is what you named the Thread. So in terms of replying to your initial questions. Yes. However, everything changes if you get different speakers, change your room, move closer or further away from the speakers. Assuming none of this changes and you know the answers to the above baseline data. You are starting to talk in circles perhaps? Just go figure out what you have right now. To determine if you are even possibly clipping your kit now.

No, you see, you keep giving a different answer all the time. Any speaker, any room, move wherever, it doesn't mater. You have a speaker and an amp and you start raising the volume. You keep raising and raising. Forget about the preferred listening level. You keep pushing the speaker (you can put cotton in your ears, it doesn't mater), you keep pushing it AND before it starts to clip will there be any other type of distortion?

 

[gnarly]

HEY, hey, now!!! That's way more than 2c! If not whole two bucks.

Thank you for your thought and contribution. The only thing that is kinda left hangin' is this question whether is there any other type of sound degradation or deterioration due to lack of power other than clipping. Some posts hint at that, but no one took that brave step and said a final yes or no. What is your opinion on that? Is it either/or - either it's clipping or it's working properly?

Yep, my 2c suffered some serious inflation Lol

I thought I did step up though by saying....

"So by definition, if the amp is not clipping, it is operating linearly, and speakers will perform properly."

No clipping, no worries. Do note that by clipping, i include the inability to drive low impedance loads (or capacitive in the case of ESLs).
Either the amp has the balls or not. (I guess one nut should be named volts and the other nut amps....haha)