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soultinter 
Copper - Posts: 170
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Joined: January 16, 2004
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Posted: September 26, 2006 at 8:29 AM / IP Logged  

This is probably a little dumb, but I need a thorough explanation of Clipping and exactly how to recognize it. It seems that this is the #2 cause of subwoofer failure and I feel like i don't properly understand the situation and how to explain it. Thanks for being tolerant.

aznboi3644 
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Posted: September 26, 2006 at 8:35 AM / IP Logged  
Go to www.bcae1.com
right hand side..find it...and has a lot more you can learn
bellsracer 
Silver - Posts: 703
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Joined: January 14, 2006
Location: United States
Posted: September 26, 2006 at 12:10 PM / IP Logged  

Clipping is taking the electrical signal and pusing it beyond the abilities of the component. A speaker works by alternating the positive and negative back and forth to move the speaker and make sound. (Alternating current or AC) Using an oscilloscope you will see that the signal is a smooth curve (wave) that moves up and down. Clipping is taking the signal and putting a flat spot in the curve. ie DC current. When DC occurs during the AC power wave it is "clipping" the peaks and valleys off the wave.

How this affects speakers is that the speaker will get to the power waves clipping point. (Say on the peak) Then the DC kicks in and "kicks" the speaker sideways. Then when AC continues on the wave, the speaker's voice coil is still kicked sideways and grinds down the pole and magnet structure's wall. Then at the other end of the wave (the valley), the clip kicks in again and kicks the speaker the other way. AC continues and grinds the voice coil up the other side. Now do this at 50Hz and now your speaker is grinding the voice coil 100 times per second. Bye Bye speaker.

Now many shops will do their gain setting by ear by listening to when the speaker starts grinding at the wall. The truth of the matter is that, if you are already hearing the grinding, then there is at least 15-20% distortion and possibly damaging the speaker. A little saying that many of the uber-veterans (those who have been doing this since the 60s - 70s) will tell you that if you can "hear" the beginning of the clip, you can hear grass grow. They once proved it too by asking a bunch of shops to gain set the amps. When the oscilloscope was taken to the amps afterwards, 98% of them at at least 15% distortion and clip on the signal.

Best way to maximize your power and keep the clip from entering is to use the oscilloscope. It'll show you exactly how much clipping you have. Just add or lose gain until you are right at the edge of making a clip. Maximum power without the clip.

Hope this helps. Good Luck!

aznboi3644 wrote:
Go to www.bcae1.com
right hand side..find it...and has a lot more you can learn

We found various mentionings of clipping and a rough description of overpowering an amp creates the clip, but nothing specifically describing the clip. Where did you find it here?

Never send your ducks to eagle school.
The difference between ordinary and extraordinary is that little extra.
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sprawl85 
Copper - Posts: 204
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Joined: March 15, 2006
Location: United States
Posted: September 26, 2006 at 12:33 PM / IP Logged  
Just buy quality amplifiers that dont' clip. I have seen a lot of amps that I couldn't get to clip if I tried. Or keep some ED subs around because if you send a clipped signal to them it sounds like someone is beating a piece of sheet metal because of high tight the gap is on them.
edit: I forgot the original question by the time I posted this, but I figured I'd add my 2 cents anyway since you already got a technical definition.
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DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: September 26, 2006 at 1:08 PM / IP Logged  

Uh, bellsracer, a DC signal will not "kick the speaker sideways."  Where did you get that?

The real danger of a clipping amplifier is the power delivered by a clipped signal can be several times the expected power level of a non-clipped signal and speakers can be blown due to overpower.

Here's some resources: http://www.bcae1.com/2ltlpwr.htm, http://sound.westhost.com/clipping.htm

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bryantobando 
Copper - Posts: 64
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Joined: November 29, 2005
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Posted: September 26, 2006 at 1:44 PM / IP Logged  
Clipping is like jumping on a bed with a low ceiling. If your bed is really spring (in this case, the amplifier is really powerfull and the speakers can't take it), when you jump, you'll hit your head on the ceiling. Though, if the ceiling was higher, you would have more head room and you wouldn;t hit your head. (in this case, your speakers can handle the power the amp is outputting). That is why you get those flat peaks on the waves on an oscilliscope. Its a wierd explanation, but that is how they tought me and it made more sense. But it has nothing to do with DC signal.
haemphyst 
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Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: September 26, 2006 at 3:04 PM / IP Logged  
bellsracer wrote:
Clipping is taking the electrical signal and pusing it beyond the abilities of the component. A speaker works by alternating the positive and negative back and forth to move the speaker and make sound. (Alternating current or AC) Using an oscilloscope you will see that the signal is a smooth curve (wave) that moves up and down. Clipping is taking the signal and putting a flat spot in the curve. ie DC current. When DC occurs during the AC power wave it is "clipping" the peaks and valleys off the wave.
There is no "putting" a flat spot on the waveform. An amplifier is built with a given, set voltage, both positive and negative, called "rails". When the input signal tells the amplifier to "turn on" more than the rails are capable of producing, the waveform is "clipped off". That is what clipping is.
bellsracer wrote:
How this affects speakers is that the speaker will get to the power waves clipping point. (Say on the peak) Then the DC kicks in and "kicks" the speaker sideways. Then when AC continues on the wave, the speaker's voice coil is still kicked sideways and grinds down the pole and magnet structure's wall. Then at the other end of the wave (the valley), the clip kicks in again and kicks the speaker the other way. AC continues and grinds the voice coil up the other side. Now do this at 50Hz and now your speaker is grinding the voice coil 100 times per second. Bye Bye speaker.
There is one I have NEVER heard before. Where did you get that description from? I did tell you I'd call you on anything...
bellsracer wrote:
Now many shops will do their gain setting by ear by listening to when the speaker starts grinding at the wall. The truth of the matter is that, if you are already hearing the grinding, then there is at least 15-20% distortion and possibly damaging the speaker. A little saying that many of the uber-veterans (those who have been doing this since the 60s - 70s) will tell you that if you can "hear" the beginning of the clip, you can hear grass grow. They once proved it too by asking a bunch of shops to gain set the amps. When the oscilloscope was taken to the amps afterwards, 98% of them at at least 15% distortion and clip on the signal.

Best way to maximize your power and keep the clip from entering is to use the oscilloscope. It'll show you exactly how much clipping you have. Just add or lose gain until you are right at the edge of making a clip. Maximum power without the clip.

You are correct... The BEST way to set gains is with an oscilloscope, but not everybody has a 'scope sitting around in their garage! I do, and I use it, but clipping is quite the audible distortion... An o-scope is not always necessary. I can PROMISE you, that if I were set in a car I would be able to hear the onset of clipping, pretty much immediately. I can hear clipping in a recording, even if the amplifier is NOT clipped.
sprawl85 wrote:
Just buy quality amplifiers that dont' clip. I have seen a lot of amps that I couldn't get to clip if I tried. Or keep some ED subs around because if you send a clipped signal to them it sounds like someone is beating a piece of sheet metal because of high tight the gap is on them.
edit: I forgot the original question by the time I posted this, but I figured I'd add my 2 cents anyway since you already got a technical definition.
There is NO SUCH THING as an amplifier that can't be clipped. ANY amplifier, if pushed beyond it's capabilities can be driven past the rails, resulting in clipping!
bryantobando wrote:
You are prolly clipping because you have the volume or the gains of the amp all the way up. You should turn up the volume and gains maximum 3/4's up.
MORE wrong information. The "gain control on an amp is NEVER "just set". It should always be adjusted carefully, first by ear, then with instumentation, if available.
bryantobando wrote:
Clipping is like jumping on a bed with a low ceiling. If your bed is really spring (in this case, the amplifier is really powerfull and the speakers can't take it), when you jump, you'll hit your head on the ceiling. Though, if the ceiling was higher, you would have more head room and you wouldn;t hit your head. (in this case, your speakers can handle the power the amp is outputting). That is why you get those flat peaks on the waves on an oscilliscope. Its a wierd explanation, but that is how they tought me and it made more sense. But it has nothing to do with DC signal.
Another pile of "clipping crap". Clipping is an INTERNAL ELECTRICAL condition, it has NOTHING whatsoever to do with anything mechanical or external. The jumping on the bed analogy is completely wrong.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
kfr01 
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Posted: September 26, 2006 at 9:06 PM / IP Logged  
Thank god for haemphyst.
New Project: 2003 Pathfinder
stevdart 
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Joined: January 24, 2004
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Posted: September 26, 2006 at 10:48 PM / IP Logged  

kfr01 wrote:
Thank god for haemphyst.

Clipping -- posted image.

Read and learn, people.  Help keep this forum at the top of the information food chain where it's been since '02.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
bellsracer 
Silver - Posts: 703
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Joined: January 14, 2006
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Posted: September 27, 2006 at 3:30 AM / IP Logged  
DYohn wrote:

Uh, bellsracer, a DC signal will not "kick the speaker sideways."  Where did you get that?

~snip~

  Like I said in earlier posts, the owner of the shop likes to play with every dynamic possible. He has a friend in the structure dynamics business and he wanted to see exactly what a sub is doing during a clipped signal. While studying the high speed, the sub wants to go further (newton's law) but lacking the energy to do so the mass wants to keep moving forward but due to the flat response in the power the mass shifts slightly. This usually occurs at 25% THD on the signal.

As for DC on the wave form. Like I said, a DC form will show up on the scope during a clip. DC on an oscilloscope will just show up as a flat line. During a clipped signal, the flat line shows up in the wave.

haemphyst, thanks for the heads up and no grudge. Reading your post is right. I was trying to describe it without getting technical. Well w/e. Like a couple of others, I was trying my best to describe what is going on. I guess I'm just not as good.

Never send your ducks to eagle school.
The difference between ordinary and extraordinary is that little extra.
The 3Ls of life: Learn from the Past, Live for the Present, Look to the Future.
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