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Re: [micbuilders] clarity in the 125-500Hz range

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  • Jason May
    Rob, it seems to me that perhaps some of what your hearing is a result of the phase inaccuracy inherent in cardioid mics (I believe bob cain suggested this
    Message 1 of 24 , May 1, 2005
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      Rob, it seems to me that perhaps some of what your hearing is a result of
      the phase inaccuracy inherent in cardioid mics (I believe bob cain suggested
      this earlier). For your application, I would strongly suggest some B&K
      Omni¹s (or even earthworks perhaps though they might be a bit noisy) and an
      extremely phase accurate preamp. Also, the very wide spacing you used will
      present it¹s own phasing problems. I know my suggestions probably aren¹t of
      much help, but I thought I¹d share my thoughts. It does sound like a
      beautiful area to record. Thanks for the experiment, always interesting.



      Jason


      [Non-text portions of this message have been removed]
    • Rob Danielson
      ... Thanks for the suggestions, Jason. A few folks do use B&K s in the field, I ve wanted to hear how they sound with the gain cranked up for years. Maybe
      Message 2 of 24 , May 1, 2005
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        At 3:40 PM -0400 5/1/05, Jason May wrote:
        >Rob, it seems to me that perhaps some of what your hearing is a result of
        >the phase inaccuracy inherent in cardioid mics (I believe bob cain suggested
        >this earlier). For your application, I would strongly suggest some B&K
        >Omni¹s (or even earthworks perhaps though they might be a bit noisy) and an
        >extremely phase accurate preamp.

        Thanks for the suggestions, Jason. A few folks
        do use B&K's in the field, I've wanted to hear
        how they sound with the gain cranked up for
        years. Maybe someday. I do use mbho 603/D100's
        and mkh20s omnis and they perform identically in
        this regard.

        I do agree the muddiness does sound like its from
        sort of interferece of which phase cancellation
        is a type. But any phasing you're hearing would
        be identical to that if the mics were 5" apart
        because the left and right signals are discrete,
        at least in excess of 110dB. My guess is that
        phase inaccuracies from the MP2 mic preamp would
        be well documented as its a very popular pre for
        making M-S recordings and M-S relys on phase
        relations for imaging. Perhaps northerners have
        to develop a liking for sparseness and air. Rob D.

        > Also, the very wide spacing you used will
        >present it¹s own phasing problems. I know my suggestions probably aren¹t of
        >much help, but I thought I¹d share my thoughts. It does sound like a
        >beautiful area to record. Thanks for the experiment, always interesting.
        >
        >
        >Jason
        >

        --
        Rob Danielson
        Film Department
        University of Wisconsin-Milwaukee
      • ebenj@pacbell.net
        From: Rob Danielson ... Now this shoots down the theory that I was working up which was that it has something to do with the pressure
        Message 3 of 24 , May 1, 2005
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          From: "Rob Danielson" <type@...>

          >I do use <snip> mkh20s omnis and they perform identically in this regard.
          Now this shoots down the theory that I was working up which was that it has
          something to do with the pressure gradient pattern of the NT-1As and the
          concomitant proximity effect. If you hear more or less the same thing with
          omnis then I have to discard that theory.

          >I do agree the muddiness does sound like its from sort of interferece of
          which phase cancellation
          >is a type.
          I wonder if it could simply be a case of the incorrect playback level? By
          incorrect, I simply mean that the playback level may be higher than the
          actual acoustic level at the recording site.

          Let me get back on my stump and think out loud. It is known that the growth
          of loudness is not the same at low frequencies as it is at mid frequencies.
          We tend to think of dB SPL (Sound Pressure Level) as representing loudness
          (a perceptual phenomenon) but it doesn't. Phons are a measure of loudness
          level and they have approximately the same size as dB but they are
          nonlinearly related to the acoustic level in dB, particularly at low
          frequencies. I think that most people in this forum know that the threshold
          of hearing is higher at low frequencies than at mid frequencies (about 0 dB
          SPL at 1 kHz, 76 dB SPL at 20 Hz!), but what they may not know is that once
          the threshold is passed at low frequencies, the sound grows louder (in
          phons) at a more rapid rate at low frequencies than at mid frequencies.

          So a 76 dB SPL 20 Hz tone is equally at loud as a 0 dB SPL 1 kHz tone. But
          the loudness of the 20 Hz tone grows more rapidly such that at 100 dB SPL
          they are about equally loud. In other words, the 20 Hz tone increases as
          much in loudness with a 24 dB change in level as the 1 kHz tone did with a
          100 dB increase in level.

          Back to the question of what is causing the loss of clarity? That is the
          question, isn't it? If the low-frequency sounds are perceived as being
          louder than they actually were on-site at the time of the recording, then
          they exert a greater masking influence on the sounds above and below them in
          frequency. That masking of higher-frequency spectral components could be
          perceived as a loss of clarity.

          Well, it's a theory.

          Eric
        • Rob Danielson
          ... And thus an explanation of why a biamp d speaker system allows the (non sub) woofer to portray significantly greater clarity in the mystery range? That is
          Message 4 of 24 , May 1, 2005
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            At 4:48 PM -0700 5/1/05, <ebenj@...> wrote:
            >From: "Rob Danielson" <type@...>
            >
            >>I do use <snip> mkh20s omnis and they perform identically in this regard.
            >Now this shoots down the theory that I was working up which was that it has
            >something to do with the pressure gradient pattern of the NT-1As and the
            >concomitant proximity effect. If you hear more or less the same thing with
            >omnis then I have to discard that theory.
            >
            >>I do agree the muddiness does sound like its from sort of interferece of
            >which phase cancellation
            >>is a type.
            >I wonder if it could simply be a case of the incorrect playback level? By
            >incorrect, I simply mean that the playback level may be higher than the
            >actual acoustic level at the recording site.
            >
            >Let me get back on my stump and think out loud. It is known that the growth
            >of loudness is not the same at low frequencies as it is at mid frequencies.
            >We tend to think of dB SPL (Sound Pressure Level) as representing loudness
            >(a perceptual phenomenon) but it doesn't. Phons are a measure of loudness
            >level and they have approximately the same size as dB but they are
            >nonlinearly related to the acoustic level in dB, particularly at low
            >frequencies. I think that most people in this forum know that the threshold
            >of hearing is higher at low frequencies than at mid frequencies (about 0 dB
            >SPL at 1 kHz, 76 dB SPL at 20 Hz!), but what they may not know is that once
            >the threshold is passed at low frequencies, the sound grows louder (in
            >phons) at a more rapid rate at low frequencies than at mid frequencies.
            >
            >So a 76 dB SPL 20 Hz tone is equally at loud as a 0 dB SPL 1 kHz tone. But
            >the loudness of the 20 Hz tone grows more rapidly such that at 100 dB SPL
            >they are about equally loud. In other words, the 20 Hz tone increases as
            >much in loudness with a 24 dB change in level as the 1 kHz tone did with a
            >100 dB increase in level.
            >
            >Back to the question of what is causing the loss of clarity? That is the
            >question, isn't it? If the low-frequency sounds are perceived as being
            >louder than they actually were on-site at the time of the recording, then
            >they exert a greater masking influence on the sounds above and below them in
            >frequency. That masking of higher-frequency spectral components could be
            >perceived as a loss of clarity.
            >
            >Well, it's a theory.
            >
            >Eric
            >

            And thus an explanation of why a biamp'd speaker system allows the
            (non sub) woofer to portray significantly greater clarity in the
            mystery range? That is certainly true. I like your hunch that the
            disproportionate amount of work that the speaker (capsule too?) is
            being asked to do at the lowest Hz's is behind it somehow. Try this
            blind test: Take a recording with lots of inherent low end pink noise
            (or the demo) use parametric EQ to momentarily create a big (~+18dB)
            boost at 20Hz. Now do the same at ~60Hz. Go back and forth making
            temporary boosts and pay attention to what you can hear during the
            boosts in the mystery range. Maybe use headphones?

            We use the term "coloration" to refer to a faint "tuning" of the
            signal created by a mic, pre, and a-d. At the mic capsule level, do
            some the phenomena thought to be responsible for this do their thing
            in these 3 lowest octaves? It strikes me that what we have in common
            here-- inside and outside, city and remote-- is that with high gain,
            the mics are getting, proportionally, a lot of very low frequency
            content. Look at the first curve in the demo- that's the spectrum
            coming through the mixing chain. I added a sharp -12dB cut at 20hz
            too that's not showing on the eq curves too. Anechoic chamber anyone?
            Rob D.



            --
          • Rob Danielson
            I came across Eric s graph comparing messured noise from NT1-A and other mics. I ve been wondering if the increasing lower end distortion could also be
            Message 5 of 24 , May 11, 2005
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              I came across Eric's graph comparing messured noise from NT1-A and
              other mics. I've been wondering if the increasing lower end
              distortion could also be contributing to the muddiness or is the
              percentage of the signal that is distorted too low?

              http://f3.grp.yahoofs.com/v1/YJ-BQoSF64dBBaVp9-4YBFeFtno1hLyh0q9eEUPqYPL5dQ9pPEFhYstdfZCPKJloVX6vft4GeL9QiISUESxVDWuhWMaKqKCprtMUECkEKeB_6DEQE3XA-l8W/Mic%20Measurements/comparison%20of%20microphone%20noise.pdf

              Can distortion produce simplified bands like the eaggerated tones? Rob D.
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