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When the centrepoint of a waveform is below/abov the neutral

Posted: Thu Mar 17, 2011 4:32 am
by WatchYourStep
If that title made ANY sense to you whatsoever, then it was a complete fluke. What I want to know is, what causes a waveform to oscillate about a point that is not the middle of the amplitude spectrum? K I give up trying to use words to describe this, take a look:

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Re: When the centrepoint of a waveform is below/abov the neu

Posted: Thu Mar 17, 2011 6:04 am
by Sirius

Re: When the centrepoint of a waveform is below/abov the neu

Posted: Thu Mar 17, 2011 7:35 am
by Karoshi
Damn beat me to it, i cant see the pics but yeah DC Offset. In an electronic circuit you would whack a capacitor in series with the signal line, but this isnt electronics so i dont know how you get around it lol.

oh in FL Studio it has a 'remove DC offset' function

Re: When the centrepoint of a waveform is below/abov the neu

Posted: Thu Mar 17, 2011 11:44 am
by macc
The remove DC offset function in a typical DAW will not do the trick in cases like this - it will shift the entire wave up, so for example the very end where it fades out will no be above the line. Doh!

Just use a high pass filter set to 1Hz, that will take care of it. Just be sure to do it before you limit ;)

Re: When the centrepoint of a waveform is below/abov the neu

Posted: Thu Mar 17, 2011 6:20 pm
by WatchYourStep
Very cool, thanks everyone! The filtering trick is genius, I'd have never thought of that.

In theory, would it damage your speakers to play a signal that was composed of simply a sustained DC offset? Ie: would your speaker cone be damaged by being held at its farthest "out" or "in" position w/o springing back?

Re: When the centrepoint of a waveform is below/abov the neu

Posted: Sat Mar 19, 2011 9:11 am
by Basic A
WatchYourStep wrote:Very cool, thanks everyone! The filtering trick is genius, I'd have never thought of that.

In theory, would it damage your speakers to play a signal that was composed of simply a sustained DC offset? Ie: would your speaker cone be damaged by being held at its farthest "out" or "in" position w/o springing back?
Nope, zero crossings yes, but offset, nope.

Re: When the centrepoint of a waveform is below/abov the neu

Posted: Sat Mar 19, 2011 3:27 pm
by WatchYourStep
Basic A wrote:
WatchYourStep wrote:Very cool, thanks everyone! The filtering trick is genius, I'd have never thought of that.

In theory, would it damage your speakers to play a signal that was composed of simply a sustained DC offset? Ie: would your speaker cone be damaged by being held at its farthest "out" or "in" position w/o springing back?
Nope, zero crossings yes, but offset, nope.
It's bad to play a continuous zero crossing ie: no input?

Re: When the centrepoint of a waveform is below/abov the neu

Posted: Sat Mar 19, 2011 4:40 pm
by Basic A
WatchYourStep wrote:
Basic A wrote:
WatchYourStep wrote:Very cool, thanks everyone! The filtering trick is genius, I'd have never thought of that.

In theory, would it damage your speakers to play a signal that was composed of simply a sustained DC offset? Ie: would your speaker cone be damaged by being held at its farthest "out" or "in" position w/o springing back?
Nope, zero crossings yes, but offset, nope.
It's bad to play a continuous zero crossing ie: no input?
Huh?

A zero crossing is when the waveform cuts cut at a point other then zero causing a right angle fall/click noise. Or at least, thats how I was using the word.

Re: When the centrepoint of a waveform is below/abov the neu

Posted: Sat Mar 19, 2011 4:58 pm
by WatchYourStep
Basic A wrote:
WatchYourStep wrote:
Basic A wrote:
WatchYourStep wrote:Very cool, thanks everyone! The filtering trick is genius, I'd have never thought of that.

In theory, would it damage your speakers to play a signal that was composed of simply a sustained DC offset? Ie: would your speaker cone be damaged by being held at its farthest "out" or "in" position w/o springing back?
Nope, zero crossings yes, but offset, nope.
It's bad to play a continuous zero crossing ie: no input?
Huh?

A zero crossing is when the waveform cuts cut at a point other then zero causing a right angle fall/click noise. Or at least, thats how I was using the word.
So if I understand waveforms correctly, wouldn't a square waveform be filled w/ these?

Re: When the centrepoint of a waveform is below/abov the neu

Posted: Sat Mar 19, 2011 4:59 pm
by lyons238
Basic A wrote:
WatchYourStep wrote:
Basic A wrote:
WatchYourStep wrote:Very cool, thanks everyone! The filtering trick is genius, I'd have never thought of that.

In theory, would it damage your speakers to play a signal that was composed of simply a sustained DC offset? Ie: would your speaker cone be damaged by being held at its farthest "out" or "in" position w/o springing back?
Nope, zero crossings yes, but offset, nope.
It's bad to play a continuous zero crossing ie: no input?
Huh?

A zero crossing is when the waveform cuts cut at a point other then zero causing a right angle fall/click noise. Or at least, thats how I was using the word.
is it bad for your speakers yes or no? :) your sentence confused me lol sorry.

Re: When the centrepoint of a waveform is below/abov the neu

Posted: Sat Mar 19, 2011 6:39 pm
by Ldizzy
how does it sound? like a hiss or suhin? :6:

Re: When the centrepoint of a waveform is below/abov the neu

Posted: Sun Mar 20, 2011 4:46 pm
by marktplatz
WatchYourStep wrote:
Basic A wrote:
WatchYourStep wrote:
Basic A wrote:
WatchYourStep wrote:Very cool, thanks everyone! The filtering trick is genius, I'd have never thought of that.

In theory, would it damage your speakers to play a signal that was composed of simply a sustained DC offset? Ie: would your speaker cone be damaged by being held at its farthest "out" or "in" position w/o springing back?
Nope, zero crossings yes, but offset, nope.
It's bad to play a continuous zero crossing ie: no input?
Huh?

A zero crossing is when the waveform cuts cut at a point other then zero causing a right angle fall/click noise. Or at least, thats how I was using the word.
So if I understand waveforms correctly, wouldn't a square waveform be filled w/ these?
I think that, even if the audio data coming to a speaker is an ideal square wave, the speaker's physical inability to move instantaneously between the peak and trough positions causes a low-passing (albeit at very high frequency cutoff) that removes the wave's harmonics above a certain high level. But I would imagine this could still be harmful to the speaker, especially the higher the amplitude of the square wave. The same question applies with sawtooth waves. My guess is that this isn't usually an issue because unfiltered pulse and sawtooth waves sound much too harsh (to my ears, anyway) to be useful? But I don't know, maybe people do use them for certain fx sometimes?

Re: DC offset, I've had issues with this a couple times recently in Reason, and so for any other Reason users experiencing this, it was easy to fix by sticking an EQ either on the sound causing the problem or on the whole mix, and just switching on the LO CUT button on the EQ. This is the same kind of solution as the 1Hz high-pass mentioned above. In one case it was obvious that it was a radically downpitched field-recorded sample that must have contained some low-pitched sound at its original pitch, which then became a troublesome infrasonic wave when downpitched and layered. So for that I just put the EQ directly on the sampler. (I suppose trying to high-pass the low sound out of the original sample might have been the best thing to do.) It doesn't seem to cause trouble putting it over the whole mix though; sub-bass is not audibly affected as far as I can tell, nonetheless I would recommend trying to put it as early in the signal chain as possible and certainly before compression/maximization/limiting as aforementioned.