Does a clipping amp damage speakers? |
Post Reply | Page <1 2345> |
Author | ||
Liteworks
Registered User Joined: 29 April 2008 Location: Cambs / Luton Status: Offline Points: 383 |
Post Options
Thanks(0)
|
|
The clipping it's self isn't the cause of loudspeaker failure, it's the symptom of the problem, i.e. 'not enough rig for the gig' (as the yanks say on PSW), your hitting the end stop on the amp (and speakers if powered properly) and most likely going well pasted them. Lost of people, especially nearer the bottom end of the game, tend to have mediocre amps (and speakers) and push them to hard to get anywhere near enough spl (also an amp driven hard into clipping sounds louder which add's to the issue), while a system powered with an amp that is rate at the same RMS figure as the drivers sounds like a good idea, once it's driven hard it's then producing far more output (with far more distortion) and the drivers get burnt. The question asked is probably slightly wrong (or being answered slightly wrong), as clipping it's self does not damage speakers, but it usually indicates there is a problem that will result in a loudspeaker failure. Certainly from the pov of operating a PA system, different ball game if your talking about guitar amplifiers for instance (as Bob mentions in the QSC forum I posted a link to). matt |
||
GEB
Old Croc Joined: 13 November 2009 Location: East Midlands Status: Offline Points: 1993 |
Post Options
Thanks(0)
|
|
The experts would say your talking crap dude and don't know your arse from your elbow! No DC in a clipped amplifier signal I'm afraid!
|
||
Peter Papp [PKN]
Registered User Joined: 17 June 2010 Location: Budapest Status: Offline Points: 203 |
Post Options
Thanks(0)
|
|
There are different type of clipping events from various reasons.
When the peak range of signal reaches or exceed the rail Voltages of the amplifier it is Voltage clipping. When the output current exceeds the current limit of an amplifier it is Current clipping. Any type of clipping means awful level of signal shape distortion so it means that the output is NOT the level amplified input (it would be the basic function of a power amplifier)... Very few amps have the ability of proper Voltage and Current limiting which would prevent clipping and maintain the integrity of signal in most of the cases happening on the user side. The event of clipping is bad in every technical aspects and need to avoid it however there are some guys who like this effect due to added extra sounds in the output :-) The clipping seriously increase the THD, typically by several tens of %... sounds pretty bad. The clipping strongly increases the AVERAGE Power level and heat dissipation across the voice coil The clipping could create extra harmonics which located may outside (lower / higher or booth) of the actual speaker and this way may hurt the mechanical structures. At the moment of clipping the amplifier completely looses control of speaker movements! Most of the professional amplifiers are not DC coupled and even few Hertz Hi-pass filtering located somewhere in the signal chain so there is no DC in the clipped signal. However in case of heavy clipping the output signal could be just like a square wave with typically 2X higher average power levels than normal sine has. Most of the speakers would not survive even driven by continuous full amplitude sine wave (at their rated power..) so you can imagine what the square does! Edited by Peter Papp [PKN] - 14 May 2012 at 8:59pm |
||
_djk_
Old Croc Joined: 23 November 2004 Location: United States Status: Offline Points: 6002 |
Post Options
Thanks(0)
|
|
"an amplifier output stage in clip which would be dumping DC from the
rails into the speaker, "
This description is incorrect, and is NOT what is causing the problem. "Clipping = greater average power" During the un-clipped portion of the program material. The extra power from the added harmonics it trivial. The difference between a sine wave and a full square wave (which a clipped audio signal is not) is only 3dB. Clipping occurs largely on transients in the program material. On most well designed amplifiers most people cannot detect clipping by ear unless it is driven more than 10dB into clipping, or for more than 40mS of duration. At 120 BPM the clipping might be for 40mS + 40mS, of for 80mS of every second. 92% of the time the amplifier will not be into clipping. BUT With 10dB of input overdrive, even if you have a peak limiter that keeps it from clipping, the increase in average power of 10dB during the un-clipped 92% portion of the program material will increase the long-term average power to the driver to the point where it may fail. The at most 3dB increase of power for the short duration of the clipping is trivial compared to the 10dB increase in long-term average power during the un-clipped portion of the program material. I will try to explain why certain amplifiers can cause mechanical damage to woofers when clipped when I have some time later on, it will take quite a bit and require the reader to understand a bit of amplifier circuits and design. Off to work I must go. |
||
djk
|
||
slaz
Old Croc Joined: 27 November 2009 Location: London E2 Status: Offline Points: 2713 |
Post Options
Thanks(0)
|
|
I'm no expert, but I would have thought the "corner" of a risng waveform sharply clipped would "resolve" to significant harmonics - which - in the case of a passive Xover system could chuck a fair bit of extra power into (e.g.) a compression driver. |
||
REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON
|
||
Andy Kos
Old Croc Joined: 15 May 2007 Location: Southampton Status: Offline Points: 3035 |
Post Options
Thanks(0)
|
|
Has anyone mentioned damping factor? Particularly in clip conditions?
|
||
just a guy with a warehouse and a few speakers... www.bluearan.co.uk
|
||
Steve_B
Old Croc Joined: 29 September 2007 Status: Offline Points: 1587 |
Post Options
Thanks(0)
|
|
I can't really add anything of a technical nature that has
not already been covered. However, for a rig user point of view, I think it is
bad to get into the mindset that everything will be fine as long as the amps
don't clip. As Matt (Liteworks) said, the problem is usually 'not enough rig for the gig' . If you
are blowing drive units, you have reached the limit of the transducer making
the noise. Using a bigger amp to go louder won't work. Many years ago (1970s) we ran into a problem of blowing
compression drivers. This was an active system. Initially we had considered the
rig to be harsh sounding when pushed. An oscilloscope. showed that the bass
amps were clipping. The distortion was masked to a large extent by the acoustic
low-pass filter that was a folded horn. The compression driver amps still had
plenty of headroom and continued to get louder, hence the harshness. The
solution was to compress/limit the high frequency amps. This got rid of the
harshness, but now the compression drivers were failing more often. It has to be remembered that back then 20W power handling in
a compression driver was a lot. The compressors were doing what they should and
knocked back the peaks. The average power level went up far enough to fry the
voice coil. It might surprise some that signal clipping has been used as
a form of protection. From a paper published by Electro Voice entitled “An electronic
loudspeaker enhancement and protection device”, they state that for preventing
damage caused by over excursion, clipping the signal can be a good thing. “In order to limit the diaphragm excursion to a safe level,
it is necessary to prevent voltages that exceed the excursion-voltage
limits from reaching the speaker
terminals. If this voltage limiting is accomplished using gain reduction, then
the extremely fast attack time which is needed, and the requirement of absolute
peak protection, can result in excessive overlimiting. This is a serious form
of dynamic distortion of the program material. Another method of limiting the
voltage at the speaker terminals is to clip the signal. This method is
preferable because the signal is only affected during the offending transient,
and the signal path gain is instantly restored. While clipping is not a subtle
form of distortion, speaker diaphragm crashing is much worse.” |
||
_djk_
Old Croc Joined: 23 November 2004 Location: United States Status: Offline Points: 6002 |
Post Options
Thanks(0)
|
|
"I'm no expert, "
Far, far from it.
"but I would have thought the "corner" of a risng waveform sharply clipped would "resolve" to significant harmonics - which - in the case of a passive Xover system could chuck a fair bit of extra power into (e.g.) a compression driver."
A sine wave with all its odd harmonics out to infinity is a square wave. A square wave only contains 3dB more energy than a sine wave. Heavy clipped program material does not look as bad as a square wave. A trivial amount of power increase.
At the risk of repeating myself:
"The at most 3dB increase of power for the short duration of the clipping is trivial compared to the 10dB increase in long-term average power during the un-clipped portion of the program material."
"Has anyone mentioned damping factor? Particularly in clip conditions? " That is why you want to clip the input to the power amplifier.
"This method is preferable because the signal is only affected during the offending transient, and the signal path gain is instantly restored. While clipping is not a subtle form of distortion, speaker diaphragm crashing is much worse.”
|
||
djk
|
||
audiomik
Old Croc Joined: 06 April 2010 Location: Bath, UK Status: Offline Points: 2962 |
Post Options
Thanks(0)
|
|
think that you may be not be looking at the full picture here
When an asymmetric waveform, as very often occurs with a music program source, containing a combination of two different frequency components (or more) is run into clip; Inter-Modulation Distortion (IMD) occurs. This amongst other artifacts will produce a product equal to (F1 - F2) plus a whole series of others which are the sums and differences of the two (or more) 'fundamental' frequencies present in the original signal plus other distortion products. Say for example that your two frequencies are at 80Hz (F1) and 50Hz (F2), for simplicity, then (F1 - F2) = 30Hz which you have carefully filtered out prior to the signal being sent to the Amplifier so as to not exceed Xmax for your 'Speaker..... but is now reintroduced, additional to the original signal, as you have over-driven your Amplifier into a non-linear mode (clipping). The same occurs with the method of using back to back diodes or equivalent circuitry to peak limit signals by clipping before your Amplifier input but after your High Pass filtering. Shifting the values of the example frequencies also shows how HF Compression Drivers can be damaged by out of band frequencies after the LMS/Analog active crossover filtering. FFT Analysis of the composite clipped signal will easily show this - see previous post. Now with an Amplifier rated to give a maximum* output within the sine-wave power capability of the 'Speaker being driven then this might not be a problem, but if the Amplifier is of larger capability then expect problems. There is plenty of information readily available on IMD and it's causes on the Net Mik Edit: add comment on frequency variation * Maximum output is the power when the Amplifier is driven well into clip and is twice the sinewave rated output. Edited by audiomik - 15 May 2012 at 11:19pm |
||
Warning! May contain Nuts
plus springs, washers, screws, etc, etc. |
||
soulray2
Registered User Joined: 02 January 2011 Location: Glasgow Status: Offline Points: 332 |
Post Options
Thanks(0)
|
|
I'm no expert, GEB, but this is my general/pragmatic understanding of this too! As a rule of thumb, if you're using an amp which is more powerful than the rating of your speakers, (because you like the headroom or sound quality etc), then you best not drive it into clip, because it can then deliver more long term power than your speakers can handle! If you're using a 50w amp on a 500w speaker, knock yourself out! |
||
"Moderation in all things, particularly moderation!"
|
||
steve153
Registered User Joined: 03 March 2012 Status: Offline Points: 14 |
Post Options
Thanks(0)
|
|
This thread has been so informative, cleared up so many areas of confusion for me in regards to the topic. However, how true is the above statement? Is to protect the speaker cone (and the life of your amplifier) the only reason you don't send a clipped signal into a speaker. Does it a clipped signal affect the sound drastically in a negative way?
|
||
JR.junior
Old Croc Joined: 14 December 2009 Location: Slovenija Status: Offline Points: 1789 |
Post Options
Thanks(0)
|
|
Yes, you'll get distortion.
Edited by JR.junior - 15 May 2012 at 12:50pm |
||
Support the scoop technology, larger mouth plays louder!
|
||
Post Reply | Page <1 2345> |
Tweet |
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |