Linear Phase EQ

jseveriniii · 14th February 2007, 01:05 PM

Anyone have the will to explain this concept a little?

netrom · 14th February 2007, 01:51 PM

"Regular" filters will affect the phase on a signal (Which isn't necesserally a bad thing in the world of audio, but can be a problem in seismic data for instance).

Good explanation from wiki:

"Since the group delay of a filter that has linear phase (or generalized linear phase) property is constant, all frequency components have equal delay times. So the distortion due to the frequency selective delays are not present which is mostly a desired feature. However, a filter with non-linear phase has a group delay that varies with frequency, resulting in phase distortion".

http://en.wikipedia.org/wiki/Linear_phase

gainstages · 14th February 2007, 04:42 PM

good response.

just so you know, some times the phase coloration contributes to the "character" of the EQ. The linear phase EQ becomes most important when you want dead on accuracy in your adjustments, not coloration, smearing, etc. just use the right tool at the right time.

someone help me out here, but if my mind is working today, i believe that phase coloration, shift, smearing etc is most prominent when boosting the eq, rather than when cutting. correct?

Jim Williams · 14th February 2007, 05:57 PM

Read the reprint of Dean Jensen's AES paper on linear, non-linear phase.

Jim Williams
Audio Upgrades

bassman · 14th February 2007, 06:06 PM

The thing about linear phase is that in order to eliminate phase shifts, the filter must necessarily introduce a pre-ring, that is a very very slight singal modulation PRIOR to a transient waveform. Good Lin EQ's keep this to a minimum, bad ones can have audible pre-ring when using extreme settings.

Lin phase sounds good for some material, min phase eq's sound good on other material (read "drums"). It totally depends on the program, just like everything else audio under the sun.....

OK, shameless plug here.....

I have a book out that covers this topic and many others relating to DSP and plug-ins as they are used today in mixing, mastering and post work. It is called "Plug-In Power" and can be found here:

http://www.amazon.com/Plug-Power-Com.../dp/1592009530

Hopefully, it can be of use to you.

Thanks,
ashley

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14th February 2007, 01:05 PM	#1
jseveriniii Gear nut Join Date: Oct 2006 Location: Los Angeles, CA Posts: 133	Linear Phase EQ Anyone have the will to explain this concept a little?

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14th February 2007, 01:51 PM	#2
netrom Gear maniac Join Date: Jun 2006 Posts: 177	"Regular" filters will affect the phase on a signal (Which isn't necesserally a bad thing in the world of audio, but can be a problem in seismic data for instance). Good explanation from wiki: "Since the group delay of a filter that has linear phase (or generalized linear phase) property is constant, all frequency components have equal delay times. So the distortion due to the frequency selective delays are not present which is mostly a desired feature. However, a filter with non-linear phase has a group delay that varies with frequency, resulting in phase distortion". http://en.wikipedia.org/wiki/Linear_phase

14th February 2007, 04:42 PM	#3
gainstages Lives for gear Join Date: Feb 2007 Location: Georgia Posts: 586	good response. just so you know, some times the phase coloration contributes to the "character" of the EQ. The linear phase EQ becomes most important when you want dead on accuracy in your adjustments, not coloration, smearing, etc. just use the right tool at the right time. someone help me out here, but if my mind is working today, i believe that phase coloration, shift, smearing etc is most prominent when boosting the eq, rather than when cutting. correct?

14th February 2007, 05:57 PM	#4
Jim Williams Lives for gear Join Date: Feb 2004 Location: beautiful Carlsbad, CA Posts: 4,326	Read the reprint of Dean Jensen's AES paper on linear, non-linear phase. Jim Williams Audio Upgrades

14th February 2007, 06:06 PM	#5
bassman Gear nut Join Date: Mar 2005 Location: Newport, KY Posts: 97	The thing about linear phase is that in order to eliminate phase shifts, the filter must necessarily introduce a pre-ring, that is a very very slight singal modulation PRIOR to a transient waveform. Good Lin EQ's keep this to a minimum, bad ones can have audible pre-ring when using extreme settings. Lin phase sounds good for some material, min phase eq's sound good on other material (read "drums"). It totally depends on the program, just like everything else audio under the sun..... OK, shameless plug here..... I have a book out that covers this topic and many others relating to DSP and plug-ins as they are used today in mixing, mastering and post work. It is called "Plug-In Power" and can be found here: http://www.amazon.com/Plug-Power-Com.../dp/1592009530 Hopefully, it can be of use to you. Thanks, ashley