Do low powered amps damage speakers?

[Puffin]

From what you have said above it could be that some might not be aware of clipping at 10% or may even prefer it

[Macca]

THD has to be up in the 20% area before you can reliably hear it.

This is why pro amplifiers usually have clipping indicators/level meters

[dave2010]

The problem is that different distortions have different levels of audibility and clipping is a fairly mild one by comparison.

Early in my acoustics career, I was given a demo of the effect of distortion using purposely generated distortion levels of 1% and 10%, and the demo went like this:

- Listen to a 1kHz sine wave - nice and smooth
- Listen to the 1kHz sine wave with 1% distortion added - not so smooth
- Listen to the 1kHz sine wave with 10% distortion added - Awful - ragged and harsh!

The source was then changed to a pierce of music and repeated. This time i heard
- Music with no distortion added - sounded fine
- Music with the 1% distortion added - sounded bad and obviously distorted.
- Music with the 10% distortion added - sounded barely any different to the undistorted signal! Maybe just a touch harder across the top end and with a somewhat curtailed bass, but the results were far less obvious than the 1%

Well obviously this was confusing, but the key was in the type of distortion. To make the 1%, the signal had a deliberate shift in the zero-crossing point of the AC signal introduced. To generate the 10%, clipping was added. The 1% therefore affected every frequency at any signal level, whereas the 10% only affected the peaks and mostly at the bass end.

Basically, unless you're clipping really hard, or really know what you're listening for, clipping isn't always easy to detect.

So what happens if instead of listening to Beethoven or whatever, you listen to some electronic music - which has been made with who knows what kind of waveforms, white noise, wide spectrum noises of all sorts, and deliberately introduced distortion? The sounds might be reproduced "cleanly" by the amp, but the source material has inherent problems. Would electronic music be more likely to blow speakers - tweeters, etc.?

[walpurgis]

Is this actually a problem?

It's not one I've ever had and I don't necessarily listen at low levels, even with lower powered amps. I've never blown a tweeter. (but I have blown a bass driver ).

Anybody paranoid about it can always get a NAD amplifier with the 'soft-clipping' facility though.

[dave2010]

Have a read of this article from Mackie (studio equipment manufacturers). It briefly explains how:

https://mackie.com/blog/what-clipping

That's an interesting article. The point that the clipping presents an essentially DC signal for a short period of time to the speaker is a good one, though the argument that there is a 100% efficiency at heat generation is perhaps quesionable. I'm guessing that the reality is that coils can overheat if such clipping is maintained, and that is something to be avoided. No speakers are 100% efficient at converting electrical energy into sound, so there must always be some heat generated in the transducer. The issue then is how effectively the heat is dissipated, and whether the heating has an adverse and permanent effect. It possible that the movement of the speaker cones could help to dissipate heat.

An interesting subject to think about.

Grant's point about clipping producing high frequency components is AFAIK correct, and maybe the strength of those components is strongly related to the magnitude of the (intended) lower frequency sounds.

It's also interesting to know/note that maybe clipping isn't always obvious, but might still damage the drivers.

[Haselsh1]

A good few decades ago I had a Naim 42/110 combo that managed to blow the right tweeter in my then QLN mark ones. Still no idea what the hell happened but it has never happened since.

[Macca]

Is this actually a problem?

It's not one I've ever had and I don't necessarily listen at low levels, even with lower powered amps. I've never blown a tweeter. (but I have blown a bass driver ).

Anybody paranoid about it can always get a NAD amplifier with the 'soft-clipping' facility though.

never happened to me either but it does happen. Years ago i built some speakers for a DJ mate who was fed up of blowing tweeters on his domestic speakers. I used Motorola piezo-electric units since you can't blow them. Not the world's best tweeters but for electronic dance music (which was all he listened to) they were fine.

[Macca]

So what happens if instead of listening to Beethoven or whatever, you listen to some electronic music - which has been made with who knows what kind of waveforms, white noise, wide spectrum noises of all sorts, and deliberately introduced distortion? The sounds might be reproduced "cleanly" by the amp, but the source material has inherent problems. Would electronic music be more likely to blow speakers - tweeters, etc.?

I don't think so, on the other hand if I was going to set out to deliberately blow drive units electronica is what I'd use.

Any distortion, even if it is on the recording, can damage a drive unit. Barring a fault you'd still really have to go for it though.

[Haselsh1]

I guess in short, no, low powered amps do not damage speakers unless you run them so that they can do no other. Music I suspect has little or no bearing on the outcome. There is no reason why it should after all some screaming guitar is not really very different from some screaming TB303.

[sailor]

Yes, low powered amps can damage speakers.

A blown tweeter is a sign of insufficient power. If the volume is turned up and the amp can't supply the power it will clip and the harder it clips the more square wave it becomes. A square wave is simply a sine wave with added harmonics which are higher multiple frequencies of the fundamental.

Even allowing for 10 to 20dB peaks the tweeter usually gets only a small portion of the power until the amp starts clipping. The resultant square wave with its associated high frequencies at high power is sent to the crossover which does its job and sends the highs to the tweeter.

If we take a 100W speaker the tweeter would be fine if it could only handle 20W. Now if this speaker is driven by a 40W amp which will easily produce over 80W when clipping and the XO sends that to the tweeter then do not be surprised when it cooks.

Drive the same speaker with a 500W amp and a higher SPL could be realised without tweeter damage. Too much power now will damage the woofer instead, that is if you ignore lots of complaints from the poor thing which will be frapping against the end-stops with gusto and emitting some interesting smells.

When I had my little business I would, after Christmas, New Year and other such celebrations, prepare for the arrival of speakers with (you guessed it) blown tweeters.

I disagree with the 'mackie' take on this. There is no DC component at all in a square wave, it being the high frequency harmonics that produce a wave this shape. If there was DC it would not get past the tweeter's series cap.