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NEW!! QOTD continued...

Discussion in 'Question of the Day' started by wolf825, Dec 6, 2003.

  1. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    Since no one has officially passed on the torch to post the next question of the day or taken up another question, I'll post a simple batch to pick things up again.. Whomever gets a topic right can post a NEW question in that same topic (lights, sound general stagecraft). So you don't have to know ALL of the topics to post an answer or new question! Anyone who Wins and answers ALL the questions below gets to post questions in ALL topics for the next round to challenge the masses. So whether you can answer the sound or all of them--have fun and post away!

    -------------------
    Lights:
    What is the benefit to using cast aluminum/magnesium C clamps over the older STEEL ones?

    What is Black-Wrap and Black-Tack used for on a lighting instrument?? (bonus Q!)

    What are the SAE (or metric for our friends not in the states) socket sizes for a C-Clamp Square bolt and a Yoke Bolt?


    Sound:

    What is a compressor and give an example of how it would be used, and why?

    What do the settings Ratio, Threashold, Release and Attack do? (bonus Q!)

    Name as many different types & styles of Mic's that are made (not brands--looking for types and styles here ;) ).


    General Stagecraft:

    What is Marley and why must it be "kicked"?

    What is the difference between a Bridal and a Basket? (bonus Q!)

    What does Countersink mean in carpentry and for what?


    KNOT-TIEING SUPER BONUS QUESTION:

    What is Whipping and Frapping?

    ----------------------

    Enjoy....

    -wolf
     
  2. The_Terg

    The_Terg Active Member

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    I will vouch for sound ;)

    A compressor is a signal processor that is deisgned to limit a given audio signal to a certian level. A compressor, unlike a limiter, is designed to carefully begin lowering the gain of the audio signal once it has breached the Threshold level. The main difference between a compressor and a limiter, is that the limiter simply cuts all audio above the threshold, making sure that NO peaks are above the threshold. Most compressors, however, are made to systematically reduce the gain above the threshold, to preserve the asthetics of the sound (you wouldn't want someones vocals to simply start clipping at the threshold level, now would you.....

    Definitions:
    Ratio - The amount of reduction of audio, above the threshold level. The ration is represented like this:
    db above threshold : db gain allowed to increase.
    *note* if this is set to infinity:1, the compressor will work exactly like a limiter, cutting everything above the threshold.

    THreshold - The level at which audio begins to be reduced. Ideally, this should be a gain slightly lower from the maximum peak, because the threshold defines when the compressor BEGINS to reduce the signal.

    Attack - The speed (in MS) in which the compressor is 'allowed' to alter the gain of the audio signal. If you set this really low, then the compressor will always be compressing the signal. If it is high, then the compressor will 'wait a second' before the audio reaches it's ideal level.

    Release - Similar to attack, but the speed (in MS) in which the compressor returns the gain to normal. So, if the compressor hits an audio peak, a fast gain will amplify the signal right back to where it was before. If its slow, the audio signal will seem softer than normal right after a peak.

    Mics:
    Well, lets see:

    we have Dynamic mics - standard diaphrams and coils, no amplification otherwise.

    2 types of condenser mics- (both use Phantom Power)
    A standard condenser mic, uses a capacitor to create electrical charge between the coil and backplate, resulting in an increase in gain
    An electret-condenser mic will simply have a small amplifier inside it to increase gain.

    Then there are something like Carbon mics and Ribbon mics, both of which I know nothing about.

    ;)
     
  3. DMXtools

    DMXtools Active Member

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    Slight correction on microphones. Older condenser microphones (and even some newer "tube" condenser microphones, use a high-voltage power supply to generate an electric field between two electrodes, usually a fine wire mesh. One electrode carries a positive charge, the other a negative charge. A conductive diaphram placed exactly between the electrodes will have no charge. If it is moved, by air pressure, toward the positive electrode, the diaphragm will become positively charged. If it is moved toward the negative electrode, it will become negatively charged. These charges are very small and require amplification, right in the body of the mic to be able to put a useable signal onto the cable.

    Newer "electret" condenser microphones work in exactly the same way. The difference is the source of the electric field. In the 1960's, scientists at Sony came up with a way to manufacture thin sheets of plastic with a permanent electrical charge. They called this material "electret." An electret condenser microphone makes the electrodes out of this material, eliminating the need for a high-voltage power supply (but not the need for an amplifier). Almost all condenser microphones made today use this electret material.

    The Phantom Power on your mixing console is used to supply power to the amplifier in an electret condenser microphone. It's not enough (48 volts is typical) to generate the electric field for an old-style condenser (often 300 volts or more) - those will always have an outboard power supply.

    Ribbon microphones are similar to dynamic microphones, in that they generate electrical energy through the interaction of a coil of wire with a magnetic field. I don't know how to explain better without drawing a picture - and I don't think I can do that here. I'll try to get something up on my website in the next couple days.

    Carbon microphones used to be pretty common in telephones and CB radio mics, where low-cost and high output were much more important than sound quality. I don't think they've ever been used in entertainment sound-reinforcement.

    Crystal microphones use the piezoelectric effect. Certain crystaline materials will generate an electrical current when subject to mechanical stress. Attach a diaphragm to a piezoelectric crystal and the sound vibrations will cause the crystal to generate an electrical signal. Strictly high-impedance, they're very rare in sound reinforcement applications with one exception - the old Astatic "green bullet" crystal microphone (long out-of-production) is still considered the best mic in the world for blues harmonica.

    John
     
  4. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    DMXTools,
    EXCELLENT mic descriptions and excellent information that you for sharing such descriptive details--and here I was thinking I would stump most folks on Carbon mics and other rareties.. I'll have to have a few "extra hard" sound Q's just for you in the future.. ;)
    And FWIW, the plastic was coated to create an "electret" was interestingly enough coated with a thin electroplating technique using Gold, and retained its static charge not only to create microphones but also to create a lot of the miniature ear-piece speakers in use today in some of the small telephone headsets for example.

    You win the sound QOTD--so post your sound Q's to challenge the readers. Thanks for playing!

    wolf
     
  5. chizle97

    chizle97 Member

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    that last one was mine I forgot to log in. sorry bought that
     
  6. Nephilim

    Nephilim Active Member

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    I'm going to say:
    It's either weight considerations or electrical conductivity.

    I'm guessing to fix physical problems with the casing?

    Being a metric transplant in an Imperial country, I'm going to go off my head with 7mm for the set bolt, ~12mm for the clamp bolt, and what, 22mm for the yoke bolt.


    Compressor and limiter was covered admirably up there, I'll add that some manufacturers like to specify attack and release times in dB/sec (that's dBu I spose). Some fancy compers have a Hold control which it the amount ot time between the input signal falling below the threshold and the compression being released.

    Something also worth noting is "knee-hardness". The concept of a knee comes from an input-output dB graph; any compressed signal will have a bend in the line. Hard-knee systems don't touch the signal below the threshold, and apply the full ratio above the threshold. Soft-knee systems gradually apply the compression with the knee centred on the threshold. Some really fancy ones have variable knees.

    I'll add that you see different pickup patterns in microphones;

    Omnidirectional - the mic picks up relatively equally in all directions.

    Cardioid - the pickup pattern, if graphed, looks like a heart. It picks up more from the front, less from the sides, and very little from the rear.

    Super/Hypercardioid - more exaggerated than the cardioid.

    'Shotgun' - a very highly directional mic, will only pick up in a small width in direct line of the mic body; generally uses extra elements to actively cancel out sideways input.

    Mid-Side and Figure-8 - special multi-capsule designs that offer special pickup patterns; Mid-Side has a forward facing and one or more sideways-facing elements; these are generally used for point stereo mics like the Shure VP88 (sorry, brand name). Figure 8 mics offer lots of pickup in two directions, but very little in a line 90deg from those directions. The perfect duet mic.


    I don't know what Marley is, nor the difference there, but countersinking is where you drop the head of your nail or screw to be level with the surface it's in to prevent actors from hurting themselves.


    An awful lot of that goes on at the local Starbucks.

    Cail
     
  7. Joren_Wendschuh

    Joren_Wendschuh Member

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    Lights:
    What is the benefit to using cast aluminum/magnesium C clamps over the older STEEL ones?
    less weight for smashing peoples heads in, especialy when on the end of a long shaft. wouldent call it a benifit though... I like the older steel ones. much more solid, and also, grip the pipe better, while feeling like they wont bend or fall apart.

    What is Black-Wrap and Black-Tack used for on a lighting instrument?? (bonus Q!)
    terminology might be wrong, but im pretty sure its use for wrapping the individual wires coming out of the instrument, and going to the plug. a sort of fiberglass webbing

    What are the SAE (or metric for our friends not in the states) socket sizes for a C-Clamp Square bolt and a Yoke Bolt?
    metric is evil, and should only be used in science and math courses.

    Sound:

    What is a compressor and give an example of how it would be used, and why?
    a device that is often tossed upon a vocal chanel, to 'compress' the amplitude of the waveform, after a certain level, to both help save your speakers, and also your ears, not to mention, controling those nasty peaks sometimes present when feedback occurs
    What do the settings Ratio, Threashold, Release and Attack do? (bonus Q!)
    ratio: the RATIO that the amplitude of the wave is reduced after the certain point that is called the threashold. for instance, a 4:1 ratio, a peak of 4db over, is chopped down to a peek of only 1db above the threshold.
    Threshold: the maximum level that can be pushed through the compressor, without any gain reduction, anytihing above it, is reduced by the set ratio.
    Release: the amount of time before the 'clamped down' compressor brings the signal back up to the 'uncompressed' level.
    attack: the time that the peaks are let through... longer, and the peeks are more noticable, shorter, and they become almost Not noticable, as the compressor kicks in almost instantaniously.


    Name as many different types & styles of Mic's that are made (not brands--looking for types and styles here ;) ).
    dynamic, cardiode, super card, ultra card, phantom powerd...

    General Stagecraft:

    What is Marley and why must it be "kicked"?
    marley is one of my stage hands, and he must be kicked cause he's quite slow... physical violence is the only way to get him to move.
    What is the difference between a Bridal and a Basket? (bonus Q!)
    a bridal is from a wedding, while a basket is what is stood in, with railings, while in most 'genie' type equiptment. I like baskets. they taste good, and come filled with stuff usualy.
    What does Countersink mean in carpentry and for what?
    the top of the screw or other fastening device is below or at the level of the surounding material it is holding, be it wood, metal, duct tape, what have you. it is used when feeling nice towards the actors, and your stage crew members, so that things dont get caught upon the fastening devices.

    KNOT-TIEING SUPER BONUS QUESTION:

    What is Whipping and Frapping?
    select parts of BDSM treatment for your actresses. we wont go into more details here though.
     
  8. Source4

    Source4 Member

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    As mentioned above Aluminum C clamps wont rust or get stuck.

    Black-Wrap is a heat resistant adhesive tape used on gobos and gels on a fixture to block off light


    Square bolt Socket size is 1/2" and the yoke bolt is 3/4". I think?
     
  9. OnWithTheShow

    OnWithTheShow Member

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    Dont know whether I should answer. Are these questions more for those who are learning? Or are they for everyone?
     
  10. ship

    ship Senior Team Emeritus Premium Member

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    The questions after the initial phase of them are for everyone. Expets on the questions at least for the first week or so might be best off doing the PM type thing so as not to spoil the answers. That's my opinion. At this point shoot, whatcha thinking Mr. Lincoln?

    For what it's worth, unless the bolt of a aluminum clamp is also aluminum, it just might be rusting and making life just as difficult. Also aluminum when in contact with something that is rusting, it will become pock marked and show rust as if it were rusting. Found that out the hard way. Possibly very dependant upon the grade. I would assume that by "older" steel clamps Wolf means cast iron ones which are fairly rust restant ones, as opposed to bent steel ones such as a J-Clamp. What's the ruling on this Wolf??? Aluminum verses steel verses iron getting stuck...

    Getting hit over the head by a aluminum/magnesium one verses a cast iron or steel one... what's going to hurt most??? Where is the nearest froshmen, we need to play test this concept. Yohoo... Oh whell, I'll just have to test the theory on the fresh college graduates he he he.
     
  11. sallyj

    sallyj Member

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    Marley is a brand name for dance floor, and is generically used for almost any portable dance floor, much to the irritation of some dancer people I know. The Marley company is no longer in business, actually. It (dance flooring) being a plastic/vinyl flooring material, will expand and contract with use and temperature fluctuations. It should lay out for a day or so to acclimate before it is kicked, or stretched and taped down. If it isn't properly kicked and a genie/ladder/scenery is rolled over it, then humps will form, which not only look sloppy, but could pose a trip hazard for the dancers.

    The benefits of an aluminum/mag clamp over Steel - the rust thing sounds good. Also, I don't think Aluminum will just snap and break if one tightens it down too much. I have done it to steel ones.

    Black wrap is a brand name. It is essentially black foil, and used to block light leaks in lighting instruments, or if your performing institution is too cheap to buy them, they can be used as ghetto barn doors. And because it holds it's shape, no tape is required. Black tak sounds like sticky black wrap, but I am not familiar with it.

    SAE size for square bolt- I will guess 1/2". SAE size for the yolk bolt- maybe 5/8". My c wrench never told me what size. :wink:


    My two cents.
    SJM
     
  12. Inaki2

    Inaki2 Active Member

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    Ok, I'm not a stagecraft guy here. What do you mean with kicking? I'm assuming by the explanation that it means making sure its flat..somehow.

    As for the black...whatever in lighting, never heard of it before, and I've seen too many different answers posted.
     
  13. sallyj

    sallyj Member

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    QOTD

    By kicking, I mean shuffling your feet across the medium being stretched flat. You just shuffle with a vengance.
    As for Black wrap, I think Rosco makes it. Great American Markets does too. Check it out online at a theatrical supply house.

    SJM
     

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