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Topic: minimum phase vs linear phase eq (Read 4201 times) previous topic - next topic
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minimum phase vs linear phase eq

Hello eveyone,

I've been searching for a mastering type high quality eq, after being highly disappointed with Sound Forge included eq's.

My criteria: High sound quality (really hard to define)
CPU usage: mostly a non issue
Delays: non-issue
I do like Waves Q10'S sound, but in my quest I've been reading about linear phase eq's vs other types, it got me intrigued and so I got to test one (PLParEQ) that had both modes, linear phase or minimum phase.
I've read that both have different type of artifacts, but basically the problem with MP is phase shift (frequency-dependant delay) and with LP, pre-echo.

My question revolves around the audibility of these artifacts.

I've ABX myself trying to discern between the two. During the test, I had the impression that bass was not as tight with MP than with LP. LP also sounded more natural, with better soundstage and imaging. MP sounded more like one big ball of sound, "slower" bass, and almost as if lower freqencies of the bass guitar would come earlier than the attack... But I still liked that sound, it reminds me of some songs I would listen on 33 rpm records...

Here are the results:

Code: [Select]
foo_abx 1.3.3 report
foobar2000 v0.9.6.2
2009/04/16 16:54:37

File A: D:\DATA\Musique\Best\Others - LP MP3\06 I Wish - RST2.wav
File B: D:\DATA\Musique\Best\Others - LP MP3\Stevie Wonder - I Wish - RST.wav

16:54:37 : Test started.
16:56:13 : 00/01  100.0%
16:56:52 : 01/02  75.0%
16:57:16 : 02/03  50.0%
16:57:40 : 03/04  31.3%
16:58:03 : 04/05  18.8%
16:58:41 : 05/06  10.9%
16:59:04 : 06/07  6.3%
16:59:26 : 07/08  3.5%
16:59:44 : 08/09  2.0%
17:00:12 : 09/10  1.1%
17:00:32 : 10/11  0.6%
17:00:50 : 11/12  0.3%
17:01:08 : 12/13  0.2%
17:01:40 : 13/14  0.1%
17:02:03 : 14/15  0.0%
17:02:28 : 15/16  0.0%
17:02:37 : Test finished.

 ---------- 
Total: 15/16 (0.0%)


I wonder if it would make sense to use LP eq's for low frequencies, because maybe the ear is more sensitive to phase shift at such frequencies (is it ?) and use MP eq's for higher freuquencies.
What is the treshold of audibility of pre-echo, and of phase shift ?
Would it be possible to derive the phase shift from the amplitude response of an MP eq,
and calculate the pre-echo amount of a LP eq for the same amplitude response,
together with a table of thresholds of audibility for these 2 artifacts at different frequencies ?
And perhaps automate this process into a general purpose multi-band hybrid LP/MP eq with automatic mode selection ? (with manual override in case one likes the artifacts)

Thanks