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Lav mics - omni vs cardioid / phase cancellation

Discussion in 'Sound, Music, and Intercom' started by jamsession, Feb 10, 2008.

  1. jamsession

    jamsession Member

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    Hi, I've checked the other wireless threads, didn't see this covered, and since I'm looking for a experience with a specific aspect, decided to make a thread for just that aspect for quick reference.


    ordering some wireless mics (Shure SLX with a couple extra Countryman B3s - to mic actors in advance and switch bodypacks as needed...)

    Will be micing various methods - over hairline (halo), ear, and taped on.

    and am wondering if cardioid lav mics are better way to go, to avoid phase cancellation when multiple actors are close together
    PRO: less phase cancellation?
    CON:
    1) - mics look a little bigger, a factor for hiding mics
    2) - if mic gets rotated, you're hosed.

    or use omnis:
    PRO: 1) Don't have to worry about orientation
    CON: 1) phase cancellation when actors are close.

    so I'm guessing omni, but would appreciate any experience with unidirectional (cariod, supercardiod) lavs.


    WL93 (SLX14/93)
    Miniature condenser lavalier mic for speech applications.
    Omnidirectional

    WL184 (SLX14/84)
    Premium condenser lavalier mic for speech applications.
    Supercardioid

    WL185 (SLX14/85)
    Premium condenser lavalier mic for speech applications.
    Cardioid


    How are the WL93s? I wonder if I can/should order the SLX1 bodypacks without a mic, and just order B3s? Or if they are decent mics, it's probably economically feasible to get the package and order a few extra B3s.
    From what I see so far, the WL93s come stock in black? (invisibility issues)

    thx
     
  2. Andy_Leviss

    Andy_Leviss Active Member Premium Member

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    Absolutely not, cardioid lavs are pretty useless in theatrical use. The only time cardioids are ever considered for actor-worn mics in theatre are on headsets, and even then, for various reasons (tone, sensitivity to placement, etc) omnis are still preferable. I recently left an off-Broadway musical making significant ue of cardioid headsets, and as much as they were necessary to solve a very specific problem (need for punchy backing vocals in concert-style numbers with blazing loud stage volume from an onstage salsa band), they brought their own long list of issues with them in trade.

    Cardioid lavs are only of limited usefulness in talking head type events, IMHO, and have no place in theatrical reinforcement.

    Just my two cents,
    Andy
     
  3. jamsession

    jamsession Member

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    cool - kinda figured that, thx for the confirmation, Andy.

    Cheers,
    Jam
     
  4. soundlight

    soundlight Well-Known Member

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    Yah, always use omni lavs for theatre.

    For reference, I've seen dozens of high-end productions that use the Shure WL93 elements. They're cheap, effective, and you can stock extras easily. Plus, they are quite small for the price and easy to mount. You can also get them in a tan color as well. Also, I really like the tie/costume mount clips for the WL93's, they work really well (in high school, we couldn't do hair or cheek mounting because there was no one dedicated enough to sound to go through that, so we always clipped to costumes). But always keep some spare clips around, they're cheap and it's always good to have spares when one gets broken/lost/thrown out accidentally by the wardrobe folks.
     
  5. jamsession

    jamsession Member

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    thx - I'll see when ordering the units if I can get them in tan, or if that's just a replacement option. 'preciate it.

    How does a polarity switch work in the real world? (some mixers have them... once mine gets in I'll play with it. ) or as a treavelling engineer would you add on a box for your most common say 3 actors who are together often? and if I understand it, they would be in and out of phase if they moved 1/2 wavelength apart (a finger width apart or so for a soprano voice?) - so I dont understand how that would be consistent. although, it seems an easy matter for an electrical person to create a box that does that - plug 2-4 mics into it, and it auto-inverts the phase for 1 mic where 2 mics are phase-cancelling each other) or am I way off on that?

    thx
     
  6. museav

    museav CBMod CB Mods Departed Member

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    A polarity switch would simply change how the phasing varied by frequency, frequencies that were in phase they would then be out of phase and vice versa, it would change the effects but not make them go away. The phasing issue isn't just about being in or out of phase, you can also be anywhere between those absolutes, and as the physical relationships change the effects also change.

    Where you more commonly might use the polarity switch is for something like mics on both sides of a snare drum (switching one) or a mic inside a kick drum. Basically when a mic's physical orientation is inverted to how the natural sound travels.
     
  7. jamsession

    jamsession Member

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    Thx, yeah, that was my understanding, it would seem to be useful in studio situation where the mics arent moving and you might even have a more limited freq range as in micing one fixed instrument (guitar amp) where you are double micing.

    there's lots of reasons I'd want to single mic.

    I did see a neat technique by an experienced engineer who turned up the instrument mixer to get some hiss "white noise" and moved the 2nd mic around and you could hear when it was in phase with the other. The other guys in the room all experienced engineers, were like, ok - he knows how to record guitars. pretty cool.
     
  8. Andy_Leviss

    Andy_Leviss Active Member Premium Member

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    All it's really useful for is things like matching the polarity of the kick drum mic (which is usually on the resonant head of the drum) with the rest of the kit, or matching the polarity of a bottom mic on a snare drum with the top. It's rarely useful as more than a placebo for other phasing issues. It has nothing to do with phase, no matter how it may be often mislabeled; phase and polarity are entirely unrelated, although a simple sine or square wave 180-degrees out-of-phase will resemble that same wave with reversed polarity.

    See this thread:
    http://controlbooth.com/forums/showthread.php?p=47295

    --A
     
    jamsession likes this.
  9. BNBSound

    BNBSound Active Member

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    I'm a big fan of the 93's myself, use them exclusively when I'm able. Perfect for pinning to costumes, hiding in hair, etc. I used to have problems with phase cancellation when two actors get too close together, but if you're really careful about setting up your gain structure you can avoid that most of the time, and the few times you just can't get around it, you just have to mix around it and take one mic down when it happens. Leave the "polarity" buttons alone. (Not phase, although it's abbreviated the same)

    I usually don't even bother trying to make entrances and exits at the first rehearsal we have the wireless on. Directors usually want to scream about sound quality and timing, but you have to get them to back down. After you make it sound brilliant once they'll start to trust you. But seriously, take that whole first night and just get the gain structure and the EQ as perfect as you can. Then once everyone starts to sound natural the director will settle down and you can get busy worrying about your cues.
     
    jamsession likes this.
  10. sloop

    sloop Member

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    We have been having excellent luck using the AT892-TH MicroSet from Audio Technica.

    [​IMG]

    Pretty much invisible on the actor and great sound.. A little skin tape to keep the mic in place on the cheek..
     

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