How can an underpowered amp damage speakers???


Standard Member
Um, you do mean RMS and not PMPO right? I just bought a couple of 100w RMS speakers (200w PMPO each).


Distinguished Member
Ignore the PMPO rating. Such ratings are unattainable in normal circumstances and only achievable in a lab. It is very unlikely that you'd blow 100 watt speaker in an average sized room, not unless you intend playing audio at level louder than normal for prolonged periods? You'ere more likely to damage your hearing than blow the speakers. PMPO would cover brief periods of use as opposed to constant wattage. All amps output higher wattage than there ratings indicate for brief periods during playback. Issues arise when the wattage that is constant is greater than the RMS rating awarded to a speaker. RMS is in reference to the potential continuos power which is more important for you to know than the PMPO rating. The only way you'd blow the 100 watt speakers is if turning the amp's volume up so that the amp is near its maximum ability. If having to do this to attain acceptable volume levels then I'd suggest you look at both a bigger amp and more capable speakers.
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Novice Member
Hi all

My current set up is a Cambridge am5 25 watt per channel and two tannoy v4s (nominal power output 100 watt max rms 200). I did not know about this problem when buying the combo as it was my first hifi system and I was relying on advice from the sales staff (richer sounds). I opted for the am5 as it was within my budget and I overspend a bit of the speakers (for my budget) and it is only for use in a small room so I figured I didn't really need that much power. Are my speakers at risk? For the record I don't generally set the volume on my amp beyond half way for long periods of time, if this makes any difference.

I realise this is a old thread but hell, let's see how long this thing can last.
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Well-known Member
If your not running the amp at full volume (the absolute max) I think your safe as my understanding would be that your not at any real risk of clipping so the current being supplied to your speakers should be a nice healthy AC variant. Maybe others can offer greater technical reassurance but I can't see any real problems with what you have.


Well-known Member
A quick Google suggested the v4 have a recommended amp power of 10 watts so you should be quite happy to continue enjoying your set up


Active Member
i think what is being missed here is a speakers sensitivity
a speaker rated at say 87db at 1 watt 1 metre from axis would need more power to drive than a speaker rated at 90 or 92db to produce the same noise levels in the same room

the speaker sensitivity might not be an issue but can be a factor when using relatively low powered amps


Standard Member
Your V4's have a sensitivity of 91dB, which is reasonably sensitive.
Your amp is also not too low powered. Driving it to clipping levels will be damaging.
If you avoid trying to imitate a disco, you can happily enjoy your setup without worries.


Novice Member
I like old threads that won't die, because the information retains relevancy. Too many people gripe at exhumed threads, apparently even forum admins elsewhere. But if a poster has something to contribute, why not? Keep in mind a Google search led be to this thread, and is interesting to read.

I found another link containing good information on clipping, but nowhere can I find information related to under-driving powerful speakers that rely on air cooling for the voice coil to survive high power input for extended periods, and likewise, a high powered speaker being under-driven with a powerful amplifier running frequencies too high for the driver's air cooling design, that is dependant upon lower frequencies moving the voice coil in and out can cause localized voice coil heat buildup! Smell that?

If you go to 18 Sound website, and look at the extended bass speakers, they have a 1400w program, and 2400w program respectively. The later employs more technical air cooling, though they both operate on the same 'air pump,' and/or passive heat dissapation into the basket principal.

I have seen high powered speakers burn the lower part of the voice coil as a direct result of over-under powering, ie: To much power in higher frequencies, that does not have the speaker operate within it's optimal cooling range, where the speaker does not 'pump' enough air to cool. In one instance, the part of the voice coil closest to the spider is severely burnt, whilst the rest of the coil is darkened, but will survive. As such, the cooling ports of this other one particular speaker may also not be directed downward toward that burnt area enough by design, somewhat regardless of it's 'accidental' operation at that time, or improper use of it's working range.

So in the case of the two 18 Sound speakers I mentioned, buying the one that is twice the program (recommended measured amplifier pink noise output) will definately suffer by design from being under-driven by an amplifier capable of half that power. Speaker suspension may be more rigid, and not facilitate low power voice coil movement to get the air moving sufficiently, thus heat can build in the voice coil, and surrounding chassis metal mass.

The bottom line here is, speakers are designed to operate in recommeded tolerances, and people should be mindful of this, and not use 15" mid-range speakers as high frequency drivers without putting some lower frequencies in the cross-over settings to get that air moving, and move the voice coils past the side cooling vents, as well as dispelling heat from the assembly.

Some things to be mindful of not discussed much elsewhere. Not all speakers are like this in the low powered realm, it almost always applies to high powered speakers though. A different twist on under-powering speakers aside from clipping.

i think what is being missed here is a speaker's sensitivity
I thought that about Donald Trump regarding Mexicans. (I'm Aussie.)
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Novice Member
Hi Everyone-

I'm relatively new here. I have read this thread just now and would like to ask your help. I have an ELAC Debut B6 speakers with Marantz SR 6000 DC Stereophonic Receiver. I have read the following for the speakers:

Recommended amplifier power: 30 to 120 wpc
Nominal/peak power handling: 50 / 120 wpc
Nominal impedance: 6 Ω; minimum 6 Ω

It says rec amp power is between 30 and 120 watts per channel and my Marantrz has the following specifications:

Power output: 70 watts per channel into 8Ω (stereo)

Frequency response: 18Hz to 40kHz

Total harmonic distortion: 0.03%

Damping factor: 60

Input sensitivity: 2.7mV (MM), 160mV (line)

Signal to noise ratio: 72dB (MM), 80dB (line)

Output: 450mV (line)

Semiconductors: 12 x IC, 29 x transi

So the amp can drive the speakers, right? Now the worst part, I played a vinyl using this setup and kind of turned the volume up to 12 o'clock. It played 3 songs straight but on the 4th, 5th and 6th, it stopped in the middle or the first minute of the song. No sound is produced but everything is running. What I have observed is that the meter from the amp just went to zero.

I have tested the speakers on the other amp with almost the same spec (70wpc), and the speakers are working fine at low volume.

My question now is, did I damage my speakers? I'm just afraid that I did and i will be forced to go back to the store and repair/change the speakers but I'm not sure about the warranty stipulations if I was the one who did the damage. Anyway, my concern is if I damaged the speakers or am I worrying too much since it is working at low level volume? Any help is appreciated.

For the amp, it has a damaged balance and kind of not in shape so I sent it to a technician to fix the balance of left and right plus reconditioning by changing some capacitors.


Perry the sound guy

Novice Member
Q. Is it possible to underpower a speaker?
A. No! That is just as dumb as it sounds.
I have been in this business over 40 years, and believe me, speakers are damaged by too MUCH power, not too LITTLE!
If you are blowing speakers, switching to a larger amp will not stop it. You wil just blow them faster.
To prevent blowing speakers - Turn It Down!
If you are the kind of person that pushes things until something gives, it will probably result in blown speakers. (And speeding tickets.)
As far as distortion; the speaker does not know if the signal is distorted or is supposed to sound that way. It just moves to reproduce whatever signal it is given. And the point is moot because most modern day power amps have clip limiting so they don't distort anyway.
Shockingly, I have seen suggestions that you should use a power amp with 2 or 3 times the power of the speaker. That will be great if you like blown speakers, but seriously, is a bad idea. A 200 watt speaker needs a 200 watt or less power amp. That is what the ratings are for!!!!!
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Distinguished Member
A 200 watt speaker needs a 200 watt power amp. That is what the ratings are for!!!!!
Sorry, but what is a 200 watt speaker? Are you stating its rated handling ability or the rated minimum wattage the manufacturer recommends? Neither would require a 200 watt power amp. Note that a 200 watt power amp has dynamic power that peaks with a wattage higher than 200 watts. And no, a speaker that has a rated handling ability of 200 watts doesn't need a 200 watt amp.

There's far more to pairing an amp with speakers than you appear to be inferring:
How To Match Speakers And Amps | The Master Switch

A Beginners Guide To Matching Speakers and Amplifiers

The Truth About Matching Amplifier Power to Loudspeakers

The only time the wattage output by the amp is something you need to match is when ensuring the amp can attain the minium recommended wattage required to drive those speakers. There's never any requirement to use an amp rated with the speaker's maximum handling ability and even if you did then you'd need to be pushing that amp as hard as you can in order to attain that level of output.

Can you blow a speaker? YES.

Can you under power a speaker? YES.

Matching amplifiers to speakers is less about wattage and more about the resulting SPL within the space they are used.
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Perry the sound guy

Novice Member
Have fun with your blown speakers.
Stop perpetuating the idiotic idea that less power blows speakers.
That is like breaking the speed limit by driving too slow.
Peak ratings are BS. The only rating that matters is RMS.
I have been doing this since 1967 and I have probably seen more blown speakers than you have, and they were NOT blown by amps that were too SMALL!
Stop trying to make something complicated out of something so simple.
(I looked at your articles. None of them say that speakers are blown by amps too small. They mention distortion, but modern power amps have clip limiters and don't distort.)
Guitarists play all out distorted all the time and don't blow speakers. That is, unless they OVER-POWER them.
It has nothing at all to do with Sound Pressure Level . . . Blowing speakers has only to do with POWER!
(Correction: "a 200 watt or less power amp."). {Happy now?}
Minimum power is just a suggestion, like 'serving size' on your bag of chips. That is not what we are talking about.


Distinguished Member
I've not perpetuated anything and simply pointed out that you are as bad by suggesting you should pair speakers that have a maximum handling ability of 200 watts with a 200 watt amp. A 200 watt amplifier is just as able to blow those speakers as one rated twice as powerful.

You introduced yourself by stating manufacturers rate speakers for a reason to only then contradict yourself by now saying that the rating is only a suggestion?


Distinguished Member
I think someone needs a lesson in what happens when you apply a square wave to a speaker...

Clipping increases the distortion to the point that the signal gets squared off. As a driver attempts to stop and start instantaneously as it gets as close as possible to reproducing the signal, the current increases exponentially - as the coil is moving in one direction and the amplifier attempting to drive it in the other. This causes the speaker to fail much more quickly than providing it with too much power - which steadily overheats the driver.

If the driver moves far enough for the voice coil to leave the safety of the magnetic flux, then it becomes just a coil and this will fail much more quickly than as if it was part of the magnetic motor function. This I concede, will cause failure of (normally) the HF unit if too much power is applied and in domestic HiFi is the normal failure point when amps are grossly mismatched to speakers.

Some speakers are designed for relatively high levels and high distortion. Guitar amplifiers are 1 example. the voice coils are over-sized and there's no HF unit to fail. Modern high power PA speakers will be protected by electronic clip protection in the amplifier - which will either drop the whole signal down to a non-clipping level or uses look ahead compression to reduce the peak. HiFi amps do not have this sort of protection, as it can affect sound quality. Compression drivers normally used in PA speakers are also less susceptible to overload than conventional tweeters, as the diaphragm is better controlled, keeping the coil within the magnetic field.

You should try to match an amplifier to a speaker wherever possible, but a 1000W amplifier is much less likely to damage a 300W speaker than a 100W amplifier is. In domestic hifi where the relative levels are much less, it's an overstated problem IMHO

I must confess to only having 25 years experience in pro-audio, having worked with and for some of the biggest names in the business plus a degree in electrical and electronic engineering and 5 years audio design experience...


Active Member
Back in the day watching the tank scene as it shudders over the rubble in saving private Ryan I could smell burning,I thought how realistic is that,only to look up at my two height speakers enveloped in smoke oops .It seems that five past midnight on my A1 did indeed introduce fatigue.And they still work go figure,unlike the tweeters on various kef centre speakers over the years.
The answer for me monkey coffins with high sensitivity ,anything over - 20-25 sends my tinnitus into overdrive


Distinguished Member
Yes! A record in reviving an old thread without a doubt. I started reading the posts and saw Uncle Eric :eek: and then looked at the date.

It is a real pity is was revived because the first long explanation is wrong!

Nothing to do with DC burning out tweeters. This is blocked by the hi pass capacitor in the crossover network.

The real reason is that when you clip a sine wave or program material and turn it to something like a square wave you generate a lots of powerful high frequency harmonics which reach the tweeter and burn it out!
THAT makes sense. :thumbsup:


Distinguished Member
THAT makes sense. :thumbsup:
It calls into question the wisdom and danger of forums for knowledge. Everyone chips in with something they thought they have learnt and thought they understood from a post they read somewhere. In the end you get a mish mash of misinformation. So much better to do this stuff at school or university and understand the science of what is happening without interpretation. In the end the right explanation is simple and makes sense.


Distinguished Member
Stop perpetuating the idiotic idea that less power blows speakers.
Of course you are 100% correct if you don't drive the amplifier into clipping. You may be tempted to do this and that is why people say using an under powered amplifier could be a liability!

Just to repeat the explanation. The tweeter, midrange and woofer powers have been calculated for normal program material i.e. music. The woofer will be able to handle the most power and the tweeter the smallest.

If you drive an amplifier into clipping the output power and frequency distribution is no longer as per normal natural program material and how the designers of the speaker had intended. Suddenly with clipping, normal wave forms become squared off producing a string of harmonics. So even a medium frequency note, if clipped, will produce high frequency harmonics which go to the tweeter causing overload. For example a frequency note of 1000Hz, squared off will produce odd harmonics of 1000Hz x3, x5, x7, x9 etc. So you can see that now, the 1000Hz note will be producing frequency harmonics of 5000Hz, 7000Hz 9000Hz …. that will be directed to the unfortunate tweeter. The distribution of power has changed and that is not what the speaker designer had catered for. Very quickly your tweeter will burn out.

The advise is always, keep the amplifier volume below the clipping point.

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