Go Back   Cockos Incorporated Forums > REAPER Forums > Dstruct's Casa De Nitpicks

Reply
 
Thread Tools Display Modes
Old 06-29-2017, 01:46 AM   #1
bezusheist
Human being with feelings
 
bezusheist's Avatar
 
Join Date: Nov 2010
Location: Mullet
Posts: 829
Default ReaEQ shows incorrect phase plot? (FIXED)

what exactly is the phase plot showing you on ReaEQ ?
is it supposed to show the actual phase response of the filter ?
and where are the "degree" markings ?
i have checked impulse responses from ReaEQ in other analysis apps and have found the phase plots on ReaEQ to be incorrect, or at least they do not correspond.
has anyone else noticed this ?
is this a bug or intended behavior ?
__________________
I like turtles

Last edited by bezusheist; 06-29-2017 at 01:56 AM.
bezusheist is offline   Reply With Quote
Old 07-01-2017, 06:33 AM   #2
Bri1
Banned
 
Join Date: Dec 2016
Location: England
Posts: 2,432
Default

@bezusheist >


Cockos-please reaspond-thinking it's quite important to investigate all these things further?
Even a little description would be usefull
Bri1 is offline   Reply With Quote
Old 07-01-2017, 08:18 AM   #3
bezusheist
Human being with feelings
 
bezusheist's Avatar
 
Join Date: Nov 2010
Location: Mullet
Posts: 829
Default

well, i never look at a phase plot while actually using an EQ...nor have i ever felt the need to. so it's not "important" to me if it works correctly or not.
my only concern is that if something is technically "wrong", then it should be fixed, regardless of it's relevance to me or anyone else.
(...i feel the same way about Reaper's "normalization" feature being wrong.)
__________________
I like turtles
bezusheist is offline   Reply With Quote
Old 07-26-2017, 01:41 AM   #4
bezusheist
Human being with feelings
 
bezusheist's Avatar
 
Join Date: Nov 2010
Location: Mullet
Posts: 829
Default

Nobody else cares that this is incorrect ?
__________________
I like turtles
bezusheist is offline   Reply With Quote
Old 07-26-2017, 01:51 AM   #5
EvilDragon
Human being with feelings
 
EvilDragon's Avatar
 
Join Date: Jun 2009
Location: Croatia
Posts: 24,790
Default

Apparently?
EvilDragon is offline   Reply With Quote
Old 07-26-2017, 05:10 AM   #6
Fergler
Human being with feelings
 
Fergler's Avatar
 
Join Date: Jan 2014
Posts: 5,205
Default

It probably looks different from other EQs because not all EQs follow the same representation of frequencies. The X axis of the graph is not linear.

Also be sure you are comparing filters perfectly. Can you be sure that the 0-4 'Q' (bandwidth) setting on one EQ is equal to the 0-1 Q setting on another? What if the other one uses 0.025-40, like Pro Q 2?
Fergler is offline   Reply With Quote
Old 07-26-2017, 05:15 AM   #7
bezusheist
Human being with feelings
 
bezusheist's Avatar
 
Join Date: Nov 2010
Location: Mullet
Posts: 829
Default

the way i check the phase response is with an impulse response and measurement software.
so i am not comparing to any other EQ, i am comparing ReaEQ's phase plot to the phase plot generated by a 3rd party software (which is correct).
__________________
I like turtles
bezusheist is offline   Reply With Quote
Old 07-26-2017, 05:17 AM   #8
Fergler
Human being with feelings
 
Fergler's Avatar
 
Join Date: Jan 2014
Posts: 5,205
Default

You will have to go into more details (pics?) of this measureing process.
Fergler is offline   Reply With Quote
Old 07-26-2017, 05:53 AM   #9
bezusheist
Human being with feelings
 
bezusheist's Avatar
 
Join Date: Nov 2010
Location: Mullet
Posts: 829
Default

ReaEQ's phase plot...


Fuzzmeasure phase plot...


i realize that one is up-side down, but the important thing to note is where 90 and 180 degrees are on both plots...
ReaEQ does not show degrees, but the vertical line is 180 degrees...and in the wrong place...the corner should be 90 degrees for this filter.
__________________
I like turtles
bezusheist is offline   Reply With Quote
Old 07-26-2017, 06:31 AM   #10
Robert Randolph
Human being with feelings
 
Robert Randolph's Avatar
 
Join Date: Apr 2017
Location: St. Petersburg, FL
Posts: 880
Default

So, how do we know that Fuzzmeasure's plot isn't incorrect?

What's the predicted phase response for this filter?
Robert Randolph is offline   Reply With Quote
Old 07-26-2017, 07:03 AM   #11
bezusheist
Human being with feelings
 
bezusheist's Avatar
 
Join Date: Nov 2010
Location: Mullet
Posts: 829
Default

Quote:
Originally Posted by Robert Randolph View Post
So, how do we know that Fuzzmeasure's plot isn't incorrect?

What's the predicted phase response for this filter?
Fuzzmeasure gives me consistent measurements with various (brand) filters and seems to be in sync with "ideal" plots. (seems to work fine for IIR filters.) theres a bunch of stuff you can check/make plots for PC, but i am mac so i use what i can get. R.E.W. gives me the same plots.

the filter is a 12 dB Butterworth filter, so you can probably find a bode plot somewhere for the ideal phase response. or even the math.
but like i said, the important thing to note here is for this type of filter's phase response, the corner is at 90 degrees...ReaEQ (with butters Q) shows it at 180.
__________________
I like turtles
bezusheist is offline   Reply With Quote
Old 07-26-2017, 07:31 AM   #12
bezusheist
Human being with feelings
 
bezusheist's Avatar
 
Join Date: Nov 2010
Location: Mullet
Posts: 829
Default

another way to confirm is with a sine wave...(sine Hz = HPF Fc)
100Hz sine wave > 100Hz HPF = 90 degrees phase shift...


edit: i will note i have not checked all of the filter types on ReaEQ, only the HPF so far...
Attached Images
File Type: png Screen Shot 2017-07-26 at 10.28.16 AM.png (25.1 KB, 1107 views)
__________________
I like turtles

Last edited by bezusheist; 07-26-2017 at 07:59 AM.
bezusheist is offline   Reply With Quote
Old 09-21-2017, 12:30 PM   #13
Robert Randolph
Human being with feelings
 
Robert Randolph's Avatar
 
Join Date: Apr 2017
Location: St. Petersburg, FL
Posts: 880
Default

So I think there is definitely a bug with the phase shift display in ReaEQ.



Take this example with a notch filter at 1khz. A notch filter should present a 90° phase shift at 1khz since the correlation being measured is no signal to full amplitude signal, which is 90° rotation.

Taking a measurement confirms this



This is taken with REW and shows the expected 90° shift at 1khz.

Testing against DMG Equilibrium, which has a free phase design mode, confirms the REW measurements are correct.

Last edited by Robert Randolph; 09-21-2017 at 01:31 PM.
Robert Randolph is offline   Reply With Quote
Old 10-13-2018, 09:23 PM   #14
Justin
Administrator
 
Justin's Avatar
 
Join Date: Jan 2005
Location: NYC
Posts: 15,721
Default

Thanks, fixing this -- two issues: the range was not useful, and we had a sin(w) rather than sin(-w), oops.
Justin is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -7. The time now is 01:35 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.