2. amps-preamps
  3. 160970-147909

Still confused about clipping after reading all the articles.

From what I read, I understand what’s happening when the amp is clipping and the subsequent square wave form that could cause heat issues for voice coils. What I don’t understand is why would an amp allow itself to consume more power than it could handle in the first place.

1. More specifically, in the integrated amp scenario (amp with a volume control), let’s say you’re using a max power 80w integrated amp to drive a 87db@1w@1m speaker, if you turn up the volume on that amp, would it just max out at roughly the speaker playing 105db and it would not go louder - how could clipping happen then? Meaning the integrated amp should not throw a signal at itself stronger than it could handle?

2. For stand alone amp, I get that the input signal is not really under control of the amp and is more or less fed by the preamp so clipping could happen when the pre-amp is throwing big signals, but why wouldn’t the amp try to reject the signal the moment it senses clipping to protect the speaker?

3. Another related confusion is, how is it possible that sometimes I see powered active speakers blown because it’s trying to play too loud? Would it be true that the amp in those active speaker should always be designed to operate within the limit of its power handling? Could active speakers (say your Macbook speaker or iPhone speaker) enter clipping? I’ve never seen blown MacBook speakers even though people play at max volume all the time.

4. Could the source material itself be encoded to cause clipping? Let’s say a malicious sound mixer create a song with super quite music to force listener to turn the volume all the way up, but then there is a sudden loud noise encoded, would this push the amp into clipping?

5. Lastly, let’s say a speaker can handle 150w of power, and the speaker amp can output a maximum of 150w of power, even if the amp clips, does it mean it won’t damage the speaker? Could amp that’s rated at 150w per channel deliver much more than 150w in transient?

I might completely misunderstand some concepts here. But want to get some clarity.

bwang29
cd318
2,636 posts
 
@cakyol,

'It is ALWAYS safer to use a higher power amplifier on a speaker but ALWAYS MUCH MORE dangerous to use an amplifier which is under powered for a speaker, especially if the amplifier has no anti clip circuitry.'



Yes, that's been a key principle of mine during the past 30+ years.

My first serious amp, the now near legendary NAD 3020a had a feature they called 'soft clipping' as described in this link provided earlier by @rodman99999.

http://www.thefactoryaudio.com/blog/2017/1/28/soft-sabotage

I think I did eventually turn it off as suggested by the author William Crampton, but during the times it was left on you could actually hear the sound getting soft and rubbery if you turned the volume up too far past 12 O' Clock.

With an adequately powerful amp and reasonably efficient speakers the only thing to watch out for is sustained high volume levels which can burn out the voice through overheating. 

Thankfully that only happened once when my brother got carried away by blasting out some heavy metal that burned out one of the mid/bass drivers. It was cheap enough to get a replacement and never happened again.


Although the end result (driver damage) might be similar the causes are different.

Clipping, I believe, is caused by continuously overdriving the amp beyond its power reserves.

Overheating damage on the other hand is caused by the prolonged overdriving of the speakers. Too much power for too long.

A situation that's not likely to happen with modern speakers unless you wish to invite ear damage.

Both are dangerous but clipping is the more common risk of the two as even low efficiency speaker designs tend to have high power (heat) handling capabilities. 


@rego,

Good link. It's easy to forget just how magical the whole process of converting electrical signal into room filling sound is.
rodman99999
6,129 posts
 
Again; clipped amplifier signal/voltage is NOT, "DC".      It’s actually a mix of high frequency harmonic distortions and intermodulation components.      Much of which are typically directed, to whatever a crossover’s high-pass filters allow, first.    https://blog.teufelaudio.com/clipping-when-your-amplifier-is-no-match-for-your-speakers/     and: https://www.theaudiogarage.com/everything-youve-wanted-know-audio-distortion-part-2/   
cd318
2,636 posts
 
@rodman99999 ,

Good article. I was still a bit puzzled why clipping particularly tends to blow out tweeters.


'Since a clipped signal contains a high number of high frequency harmonics, tweeters are especially at risk for damage. These high frequency tones not present in the original signal are directly fed to the tweeter by the speaker’s crossover. The result can be a burned voice coil, i.e. permanent damage to your system.'
twoleftears's avatar
twoleftears
5,318 posts
 
The graphs in Atkinson's measurements of amps in Stereophile are quite helpful.  He pushes amps to their limit, and you can see the line heading skyward in the graph where it goes into clipping.  He also specifies % of distortion allowed to measure maximum watt output, a % figure that he tends to relax with tube amps.
macbrett
7 posts
 
@cd318  The reason tweeters are susceptible to damage from an amp clipping is that the distorted (flat-topped) waveform contains huge amounts of high frequency energy that are not there if the undistorted wave had been able to reach a normal peak. In particular, it’s the squared-off leading and trailing corners that are the culprits. After passing through the speaker’s crossover which blocks the low frequency (DC) flat part of the wave, these corners appear as large positive and negative spikes of energy to the tweeter

These spikes only happen during clipping. The sharper the corner, the higher the spike. Normal musical content doesn’t contain nearly as much high frequency energy as these spikes. Tweeters are just not able to dissipate this, and the fine wire of the voice coils will melt like a fuse very quickly.
More to discover