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What actually is 'clipping"?

Discussion in 'Archived Threads 2001-2004' started by Cagri, Jan 31, 2003.

  1. Cagri

    Cagri Second Unit

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    I don't know if this is the right place for this question, actually I had a more specific thread in the receivers area
    which in the end did not answer my question totally but helped about my specific problem. I did lots of searching but I could't find the answer still: What really is happening when an amplifier said to be "clipping" ? OK, the main thing causing clipping is to crank up the volume and the amp cannot put enough power and thus clipping, or for example my -still to be replaced- kr5050d blinks "clip" if the input source is too high ( I even don't know if this is the same clipping as the other, i.e. when you crank the volume w/out enough power). But what actually is going on inside the amp when it is clipping? Is it sending bad signals to the speakers or is something getting fried in it or what? And apparently clipping ddoes not always happen with high volume as my kr5050 'clips' with a high input even at very low volume... Can anyone explain or privide a link for me please ? Thanks!
     
  2. Vince Maskeeper

    Vince Maskeeper Producer

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    Audio is basically electrical signal routed from place to place. When dealing with seperate components, or seperate stages inside your receiver- between certain stages the signal can be boosted or cut (like with the master volume or with individual channel gain)...

    But the problem is, each stage has a maximum amount of level it can allow to pass into it. When the energy coming in exceeds the amount that is desired, the stage is overloaded and part of the signal is distorted (the wave form is chopped off without completing its cycle, thus "clipping" the signal).

    If you think of it like a two-man eating contest- where a partner is shoving food in your mouth. If the partner attepts to pass food to you at a rate exceeding what your can deal with at one time, you will likely lose part of the original dish all over the place.

    The signal chain for audio is very similar- there are set tolerances at which each stage can deal with signal- and if you exceed this level- the signal quality will be distorted.

    What happens during clipping depends on the construction of the components, and the level of overload. Mild clipping simply results in distorted audio, waves that have been butchered (or "square waves" because the top and bottoms have been clipped)--- this will almost certainly damage speakers if left for a period of time.

    With heavy overload you can damage the input stage of the particular device.

    Hope that helps

    Vince
     
  3. Cagri

    Cagri Second Unit

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    Great explanation thanks Vince.
    One more thing though that is still not totally clear for me, - having been a complete stranger in electronics-
     
  4. Vince Maskeeper

    Vince Maskeeper Producer

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    If your amp is "blinking" clip-- chances are you will only damage the speakers. This "blinking" into clip means you are only exceeding the max desired input occasionally, and probably by small amounts for fractions of a second.

    In a case like that, strong waves are being clipped, creating a "squaring" of the wave (again- just think of a wave with the top and bottom squashed to flat)--- because a speaker really travels physically how the electrical wave is structured- it can't properly produce a squared wave- and you will eventually burn the coil out trying.

    But as far as the amp itself goes, you PROBABLY won't do any damage to it with that mild clipping. Again- depending on how the amplifier is built and how it is designed-- but most often it takes a serious input signal to completely burn out the input stage of an amplifier (but that's not to say it can't happen, I see it happen pretty often actually).


    Another thing to remember is that there are literally dozens of potential points for clipping to occur in a signal chain. Even if you have an integrated receiver product, you can still potentially create an overload between the internal preamp and amplifier devices...

    If you think about it, during any stage of the process, if the level of signal exceeds the maximum headroom level of the next stage in the chain-- you will get some form of clipping:
    -- Microphone elements can be overloaded and clip when recording on set.
    -- Microphone preamps can be overloaded from excessive signal from a microphone.
    -- Tape machines can be overloaded while recording the sounds from the preamps.
    -- Mixing Consoles, Effects Preocessors, Tape machines can be overloaded while mixing the film
    -- Encoders can be overloaded while creating DD or DTS digital tracks from the stems.
    -- D/A converters can be overloaded while reading the DVD in your home.
    -- Input stage on the preamp device can be overloaded while taking the signal from the D/A converters.
    -- Input stage on the amp can be overloaded by overdriving the master volume (or individual channel levels)
    -- Speaker can be overdriven by supplying too much power.

    etc, etc, etc

    So the audio chain is a very important thing to keep an eye on. Understanding the basic ideas of headroom and ideal operating levels is important to getting good sound and maximizing the health of your gear!

    You will often see lunkheads who will turn their stereo up all the way (probably in their car, but sometimes at home)- and will blow up speakers. they assume their big powerful amplifiers just sent too much wattage to the speakers- but the truth was that the volume boost in the preamp portion of the stereo was likely exceeding the inputs of the amplifier (or even exceeding it's own output maximum)-- resulting is a horribly distorted signal that fried the speakers.

    I've said it a hundred times on this forum-- wattage rarely damages speakers- distorted signal is usually the problem. I have routinely put 1000+ watts to drivers rated for 250 or 400 watts-- without issue. Because the extra amplifier power meant I was running at 25% potential the whole time- resulting in a preamp and amp stage running very conservatively-- and giving me nice clean signal!

    If you have to run so hot as to clip the electronics to achieve output levels you desire, you should consider more amplifier power!

    -Vince
     
  5. Cagri

    Cagri Second Unit

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    Thanks Vince, totally clear now. Great explanation.
     
  6. Shanil

    Shanil Extra

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    What does it sound like when your speakers are clipping?:b
     
  7. Cagri

    Cagri Second Unit

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    Shanil, it is the signal that is clipped, not the speakers. And if that signal is clipped when the volume is high, then you hear a noisy sound which doesn't actually belong to the software. It is like there is something on top of the speaker, like two glasses, hitting each other and putting out a sound, maybe someone else will put it in words better. But when the reason of clipping is the source signal being too high,and the volume is low, you don't (or I don't) hear that type of distortion. The signal is still clipped though.

    One thing I wonder, is clipping a one shot killer or does it make gradual damage to speakers? I mean if a speaker gets distorted signal for some period but still sounds fine, can you say that it hasn't been affected at all or can you not?
     
  8. Brad Wood

    Brad Wood Stunt Coordinator

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    One thing to mention when people talk about clipping, is that when an amplifier signal is clipped, the amplifier outputs a square wave that is essentially twice it's maxiumum power output capability. On top of that, a square wave is not a natural state of things, and speakers don't like to try to reproduce them, so even at low levels, clipping is dangerous. That's why so many people say that it's more dangerous to under power a speaker than to over power them.

    That being said, Vince had alot of great things to say about keeping the signal chain steady. In pro sound, we call it gain structure. In the large scale PA systems that I run, we use amps that put out 5000 watts bridged to banks of subwoofers, and thousands of watts to full range cabinets. That kind of wattage can do serious damage, so it's very important that input signals, processors, faders, output signals and crossovers are all set optimally for minimum noise and distortion. Of course, we also limit the begeeezus out of the signal just in case. The same thing applies at home. You wouldn't want to put a limiter on your home theater, but gain structure is just as important at home, as on the road.
     
  9. Cagri

    Cagri Second Unit

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    Is clipping a one shot killer or does it make gradual damage to speakers? I mean if a speaker gets distorted signal for some period - such as mine-, but still sounds fine, can you say that it hasn't been affected at all or can you not?
     
  10. Cees Alons

    Cees Alons Moderator
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    Cagri,

    If it kills the speaker, the speaker is dead.
    Clipped signals tend to generate more heat in the speaker coil than non-clipped musical signals. Thus, at a level that even may not sound too hard to the ears, the coil may melt. Clipped signals won't (gradually) "degrade" your speakers.

    Cees
     
  11. Brian Johnson

    Brian Johnson Supporting Actor

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    I was reading this and another thread and was wondering. They were saying a underpowered amp could also damage a speaker? The reason I am worried is I have a [email protected] ohm monoblock amplifier powering my SVS 25-31CS (rated at [email protected] The amp does have a "peak" light but I havent ever seen it come on, and I do run the amp full power.
    Am I at danger to damage the sub?
    I am looking to buy the Samson 700 (350w X 2) but this may be a few weeks.
    While I am asking, I was planning on using channel 2 of the samson to power my bass shakers. Each shaker is 50w rms wired in a series to make 'em 100watt [email protected] The samson at 8 ohm puts out 230 watts. I assume I can adjust the output of the amp to not 'overdrive/blow' the bass shakers?
    P.S. Can anyone explain how the samson gets its input? I dont see any RCA Line-In/Out? I guess I should ask SVS this, but thought I would ask while I am here.

    Thanks
     
  12. Cees Alons

    Cees Alons Moderator
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    Brian,

    Why they say that is to warn people.

    If you have an overpowered amplifier (compared to your speakers and, especially the room your using it in), you won't easily set it too loud: you tend to protect your ears and those of others.

    But when the amplifier is underpowered, compared to the room (or the use of that room, i.e. a lot of people, talking and shouting, while you try to get your speakers be heard above that, or outside in the open), you may send your amplifiers into clipping (even without noticing it). Clipping amps even sound louder (but distorted, which may be less obvious in a crowd). The power of the clipped amp may then exceed the power your speakers can handle.

    So in the first case, an overpowered amp will send undistorted signals, carrying less power to your speakers, while in the latter case an underpowered amp will send distorted overpowered signals.

    Of course, it's always best to match the amps and the speakers. Also note, that it's the environment and not as much the speakers that dictate whether or not the amp is to be considered "under"- or "over"powered in this case!

    Cees
     

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