What exactally is Sound "Clipping"

[tblake]

Hey guys, I've been kind of reading through these forums, and some mention sound clipping. What exactally is this? And how is it prevented, or stopped? I'd just like to know, as I really know nothing about speakers, and best head unit settings. All I know how to do is install. Also, if anyone would know how to set a pioneer deh-p6500 set for best sound quality, please share. I get the sound set good for one song, but it sounds bad for others. I have factory speakers, and no subs. Just the head unit. Thanks for everything guys.

[sr20de4evr]

The headunit feeds the amp a signal, it's actually the exact same signal that's on the + and - terminals at the amp's output (or at least it should be, if it's not then you have a crappy amp ), but it's much smaller. Take an amp that does 200x1 @ 4ohm for example, at full output it will have 28Vrms between the + and - terminals on its output (square root of 200*4), but your headunit only has 2, 4, or 6V preouts (normally). This means that before that signal can go from the amp's input to the amp's output, it needs to be amplified. If you have 2V preouts then it needs to be increased by a factor of 28/2 = 14. If you have 4V preouts then it needs to be increased by a factor of 28/4 = 7. The amount that the amp has to increase the incoming signal to reach full output is the gain. If your gain is set too low, then even at full volume on your headunit, you'll never get full output from the amp. If your gain is set too high, like say you have 4V preouts, but a gain of say 10 (if you turned the knob up too high) the amp would be trying to put 4*10 = 40V on it's terminals, but it's not powerful enough to put out 40V, it can only do 28V, so the nice pretty sine wave is oscillating back and forth, it crosses the 0V line and rises up towards its 40V peak, but when it hits 28V the amp says "not a chance bitch" and just levels off instead of rising up to where its supposed to be. It looks kinda like if you have a nice pretty sine wave and you take a hacksaw and cut off the top and bottom of the wave. That's clipping

Another analogy is a kid jumping on a bed in a room. The height of the ceiling is the power capability of the amp (more powerful amps would have a higher roof). At normal listening volumes the kid is jumping up and down on the bed and everything's fine, but if you try to turn up the volume/gain too high the little kid will jump higher and higher until he hits the roof. At that point he can try and jump as hard as he wants, but he can never pass through that roof, he just hits it and can't go any higher.

here's a good pic of a clipped wave vs a normal wave:



the easiest way to prevent it is with properly set gains

[PaulD]

hey, that's good pics of clipping .... what might have been even more helpful is to show one with a max signal (for the given rail) next to a heavily clipped one - it will show the real problem. The area under the curve (average power) will be so much higher on the clipped signal, it's how an underpowered amp blows speakers.

[sr20de4evr]

like this?


that's actually a square wave, but if you clip an amp enough it will start to look like that


like Paul said, even though they have the same peak voltage, the white will have DOUBLE the power of the yellow due to the extra area under the curve. So that 200rms amp is now putting out up to 400rms if it's clipping

[PaulD]

there you go, an excellent visual demonstration of why clipping kills a speaker ...... the poor thing just never gets a rest

[CBFryman]

ya know what really soundsl ike ass? a triangular signal...lol. oh and for the first time in a long time i am listneing to a clipped signal on purpose. I had an old 8" off the wall woofer in my room. i told my dad what speakers and all i wanted to get and he was like "well you have a whole bunch of stuff in your closet, use that" well i am going to fix that. i have the gain turned all the way up on anotehr off the wall 200w amp and i have 9v preamp outputs going into it (thanks to a friends pioneer EQ) it sounds like pure ass when i turn it up....i figure this speaker will last about a week....

[bumpinstang77]

If your trying to set gains by ear......I've found late night tip to be very helpful........ In to highest of the three bass notes and the lowest of the three (not the middle on though) The bass will actually kind of fade in and out a little bit (look att he subs and you will really see it) Plus on the highest of the three notes its REALLY easy to hear the clipping because the note will sound little harsh and higher pitched then it should be and not very smooth at all...... that's last resort if you on't have a DMM or oscope.