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  • Questions about phase issues in Vienna Suite

    Hi,

    So personally I haven't encountered any serious phase problems.  But I was still curious...

    (1) I was wondering if the Vienna Suite equalizer is linear phase?  What about the "master EQ"?

    (2) Would it be possible to know more about exactly what types of filters are implemented in "A", "B", and "C" for the Master EQ?   Admittedly, knowing the filter types probably won't affect my mixing, just interested.

    (3) Is comb filtering a problem with power panning?  Or is there some magical way that I'm not aware of that phase is not an issue?   So far, I haven't felt this to be a problem, because personally I squash individual instruments to mono, and the ensemble instruments, like strings or horn ensemble seem to have natural comb filtering for their timbre anyway...   but I wonder if I may have encountered this with timpani where it seems to become more muffled if I try to reduce its stereo image.

    (4) I also am not sure if I've encountered phase distortion or not.  What would it sound like?  For example, if I hear the "crunch" of stacatto strings seem to be out of sync from the attack of the pitch of the note, would that be phase distortion?

    Best,

    Shawn


  • On second thought, squashing things to mono still probably deals with comb filtering problems, right?

    Regardless, I look forward to hearing if anyone has experienced phase issues.


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    @suon said:

    Hi,

    So personally I haven't encountered any serious phase problems.  But I was still curious...

    (1) I was wondering if the Vienna Suite equalizer is linear phase?  What about the "master EQ"?

    (2) Would it be possible to know more about exactly what types of filters are implemented in "A", "B", and "C" for the Master EQ?   Admittedly, knowing the filter types probably won't affect my mixing, just interested.

    (3) Is comb filtering a problem with power panning?  Or is there some magical way that I'm not aware of that phase is not an issue?   So far, I haven't felt this to be a problem, because personally I squash individual instruments to mono, and the ensemble instruments, like strings or horn ensemble seem to have natural comb filtering for their timbre anyway...   but I wonder if I may have encountered this with timpani where it seems to become more muffled if I try to reduce its stereo image.

    (4) I also am not sure if I've encountered phase distortion or not.  What would it sound like?  For example, if I hear the "crunch" of stacatto strings seem to be out of sync from the attack of the pitch of the note, would that be phase distortion?

    Best,

    Shawn

    Hi Shawn, sorry for the slightly delayed reply.

    ad 1) Neither Vienna Suite EQ nor Master EQ are phase-linear. For a track EQ linear-phase algorithms are rarely used due to the pre-echoes and ringing they introduce, and also for mastering it is advisable to use them with caution.

    ad 2) While it would need Martin Saleteg ("ms" on these pages - Vienna Suite's main developer) to answer this question in detail, I can tell you the memory hook _I_ use: Type A is best to be used "A"bove 1kHz, type B is optimized for the use "B"elow 1kHz ("B"ass is also a nice one 😉 ...), while type C is the least specialized one and relies on a more "C"onventional algorithm.

    ad 3) Comb-filtering shouldn't occour at all when using PowerPan, but there's nothing "magic" about it. Everything it does is done with volume (i.e. amplitude), not in the frequency domain. If you experience any frequency-related artifacts, it was most likely already inherent to the signal before panning.

    ad 4) What do you mean by "phase distortion"?

    Kind regards,


    /Dietz - Vienna Symphonic Library
  • OK, thanks for the reply =)

    I think "phase distortion" is when frequency content stays the same, but the phase of the various frequencies change relative to each other -- as I understand it, this is the side-effect of standard EQ filters.  I'm not sure how it sounds, and I'm not sure whether its really significant for audio, so that's why I asked about it.


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    @suon said:

    OK, thanks for the reply =)

    I think "phase distortion" is when frequency content stays the same, but the phase of the various frequencies change relative to each other -- as I understand it, this is the side-effect of standard EQ filters.  I'm not sure how it sounds, and I'm not sure whether its really significant for audio, so that's why I asked about it.

    Actually, a natural filter will always produce phase shifting. Holding up your palm in front of your mouth while singing, will introduce a frequency rolloff and phase shift. I wouldn't call it a side effect. I was never really fond of linear phase filters for musical equalization myself, except for purely technical matters such as antialiasing filters.


  • Q: I was wondering if the Vienna Suite equalizer is linear phase?  What about the "master EQ"?

    A: No. I am considering adding linear phase options (even though I'm not too fond of LP filters myself).

    Q: Would it be possible to know more about exactly what types of filters are implemented in "A", "B", and "C" for the Master EQ?

    A: They are simply three different ways of calculating filter coefficients, which give different sonic character. It is up to you to pick the one you prefer.

    Q: Is comb filtering a problem with power panning?  Or is there some magical way that I'm not aware of that phase is not an issue?

    A: If the stereo source is recorded with a coincidental pair (X/Y or M/S), phasing should be minimal. Any recording that has spaced microphones, will naturally result in certain comb filtering when narrowed. But spaced-mic recordings tend to sound "larger"...

    Q: I also am not sure if I've encountered phase distortion or not. What would it sound like? For example, if I hear the "crunch" of stacatto strings seem to be out of sync from the attack of the pitch of the note, would that be phase distortion?

    A: I really don't follow... I thought "crunch" was more of a distorted guitar feature :)


  • OK, that makes a lot of sense about the coincidental pair.  Thank you very much for the reply!

    The "crunch" I was referring to is most easy to hear on staccato or spiccato notes, or any notes where the players try to have an immediate and slightly harsh attack.  In the past, I have had problems (I can't remember if it was with VSL or another library) where this "harsh attack" was oddly out of sync from the onset of the main timbre of the strings.  Has anyone else encountered that before?  I havent reproduced that problem in a while, but if I come across it again, maybe I'll post an example.

    ~Shawn