Old 05-09-2012, 05:23 PM   #1
signoc
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Default EQ.. is something off?

Please educate me on how to interprete this..
I was trying out some EQs using similar settings.. when I decided to use a spectrum analyzer to match all three EQs as much as possible.

By ear something differed even though the spectrum analysis showed them really close, so I decided to render stems to check them out.

Now.. ReaEQ and Fabfilter, whats going on? It's like they are off center, but DDMF LP10 is not.

Please educate me.. why would an EQ "shift" the waveform "down" like this? And why wouldn't an EQ do it? For me the "shift" seems wrong

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Old 05-09-2012, 05:36 PM   #2
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ReaEq and Pro-Q use minimum-phase filters. What this means (basically) is that they achieve filtering by combining a signal with a time-delayed version of itself. This causes phase-shifting of some frequencies by different amounts to other frequencies, resulting in cancellation ... hence the filters' frequency response. This shifting of component frequencies by different amounts can result in an asymmetric waveform ...

LP10 uses linear phase filters, which means that it doesn't change the relative phase of component frequencies ... it shifts them all by the same amount of time, hence is less likely to cause such noticeable changes in waveform shape as you're seeing above.

Have a play around with the sin and cos parts of this applet - might help to visualise how changes in component frequencies alter waveform shape - http://www.falstad.com/fourier/

... too late night/early morning post, and the above could all be explained much better, but there you go

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Old 05-09-2012, 06:01 PM   #3
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Thank you, after reading this is noticed LP10 had the option to use minimum-phase also(and everything between). Setting to the same ofcourse gives the same asymetric waveform.
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Old 05-09-2012, 06:09 PM   #4
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Re. that applet, I meant to suggest tinkering in mag/phase view, as that's more intuitively informative when thinking about a minimum-phase filter.
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Old 05-16-2012, 08:55 AM   #5
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In ReaEQ you can turn on "Show Phase" and it will give a graphical representation of how drastically the phase is affected.
This phase distortion is why a lot high level recoding engineers recommend using as little EQ as possible, proffering instead to spend as much time as needed to find exactly the right "instrument->room->mic placement->mic model->preamp" chain to get the sound they are looking for straight to tape and use the EQs as a last resort.
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Old 05-16-2012, 09:07 AM   #6
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Quote:
Originally Posted by Schmidty View Post
In ReaEQ you can turn on "Show Phase" and it will give a graphical representation of how drastically the phase is affected.
This phase distortion is why a lot high level recoding engineers recommend using as little EQ as possible, proffering instead to spend as much time as needed to find exactly the right "instrument->room->mic placement->mic model->preamp" chain to get the sound they are looking for straight to tape and use the EQs as a last resort.

Thats very interesting!

I've noticed sometimes the more I eq the worse it sounds,I'd say phase problems are going on left and right.

Thats why I rarely boost anything anymore for one thing
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Old 05-16-2012, 09:23 AM   #7
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What does the original waveform look like?
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Old 05-16-2012, 09:33 AM   #8
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^^^^
I was wondering about that too.

Perhaps you can post 2 or 4 bars worth so we can try it in different EQs? And the ReaEQ settings that you used?
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Old 05-16-2012, 09:37 AM   #9
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Just for the record, Pro-Q has the option of doing linear phase as well; it has 5 different modes.
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Old 05-16-2012, 11:23 AM   #10
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Quote:
Originally Posted by timlloyd View Post
ReaEq and Pro-Q use minimum-phase filters. What this means (basically) is that they achieve filtering by combining a signal with a time-delayed version of itself. This causes phase-shifting of some frequencies by different amounts to other frequencies, resulting in cancellation ... hence the filters' frequency response. This shifting of component frequencies by different amounts can result in an asymmetric waveform ...
Wow, thanks Tim, I didn't realize that was the way ReaEq worked, at least I've never heard it explain this way.

Nor did I realize it would show up in the wav forms like that.
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Old 05-16-2012, 11:50 AM   #11
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Quote:
Originally Posted by Ollie View Post
What does the original waveform look like?
or the eq curves themselves too
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