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Old July 2nd, 2008, 06:40 PM   #1
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Lav mic: Need pointers

Hi all, sorry if this is a question that has been asked a ka-zillion times before, but...

I have this system:

Sennheiser Evolution G2 100 Series - Camera Mountable UHF Lavalier Wireless System with EK100G2 Receiver SK100G2 BodyPack Transmitter and ME4 Microphone (A 518-554MHz)

It works pretty good if the person who is mic'd is not moving... But how can I avoid those brief "Hissss" and pops?

Are those brief hiss/pops something I can fix with squelch and/or bank settings on the wireless system? If so, can you give me tips on the best settings for avoiding unwanted feedback?

Many thanks in advance!

Cheers,
Micky
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Old July 2nd, 2008, 07:01 PM   #2
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If by "hiss" you mean a frying sound underneath the voice of the wearer that is caused by poor signal to noise ratio. The only fix is to improve the coupling between transmitter and receiver which most simply done by moving the two closer together. However, in some cases, removing obstacles between the two may serve as well. This assumes that the chosen channel is clear. In some instances co-channel interference can introduce a hiss as well. Monitor the receiver with the transmitter off and choose a channel which indicates no received r.f.

If by "hiss" you mean ear-splitting noise at or near full scale on the receiver's audio output indicator this means that the carrier has been lost altogether. This obviously happens and persists if the receiver is turned off or moves too far away but can also happen briefly when the receiver and transmitter come into a geometry where a reflection of the r.f. arrives at the proper amplitude and phase such that cancellation of the direct path takes place. This is equivalent to turning the transmitter off. Squelch senses a loss in carrier and mutes the receiver. You lose audio but the mic goes silent rather than blasting you with noise. It can still be very frustrating. You have good copy 99% of the time interspersed with 1/2 second dropouts. Diversity systems prevent this.

The pilot serves somewhat the same function as squelch. If the receiver cannot hear the transmitter's pilot tone it mutes the output. This protects against an interferer of sufficient strength to keep the squelch open.

Other than buying a diversity receiver there isn't much you can do about this except try to keep the path between transmitter and receiver short and unobstructed.
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Old July 2nd, 2008, 07:13 PM   #3
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Hisses & pops with this system are probably RF dropouts.

Generally (and this is true for any wireless, not the EW100G2 in particular):

Orient the transmitting and receiving antennae in the same plane. Usually this means work to get the receiving antenna vertically mounted on the camcorder, matching the usual vertical orientation of the transmitting antenna. I use a small ball-head with hot shoe bottom and 1/4"x20 thread in the top. If this is a mystery after reading I could shoot and post a picture.

Work closer. Or, work the receiver closer.

Avoid work in commercial buildings with metal-studded walls when possible. Or, plan to get the receiver a lot closer.

Search for less troublesome frequencies. No specific advice here - if you are close to the bottom of the available freqs, try towards the top, or vice-versa.

Finally, occasionally you'll get RF dropouts because of other users on the same or nearby frequencies. There's nothing for it other than to keep track of what freqs you've had trouble with and don't use them in the future. Some of these will recur every time you're in that area of town - maybe public service bands, tv stations, commercial radio... here in Portland I have occasional problems with a tram pa system...
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Old July 3rd, 2008, 06:22 AM   #4
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Quote:
Originally Posted by Seth Bloombaum View Post
):
Orient the transmitting and receiving antennae in the same plane. Usually this means work to get the receiving antenna vertically
Theoretically the antennas wires should be parallel to one another. In practice the orientation does not matter that much as you can easily verify by placing the transmitter on a non metallic support outdoors, walking the receiver far enough away so that the r.f. meter isn't full scale and rotating the receiver. Theoretically if the transmitter is vertical and the receiver antenna horizontal there should be no coupling between the two (0 r.f. indication). You will probably see little change except perhaps when the tip of the receiver antenna is pointed at or close to the transmitter. These antennas and the way they are mounted (including the way the receiver goes on the camera) produce elliptically polarized, nearly isotropic patterns (if they didn't they wouldn't be very useful). Multipath and obstructions tend to have a greater effect than antenna orientation. Nevertheless, parallel orientation is like the proverbial chicken soup. It can't hurt.
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Old July 3rd, 2008, 08:48 AM   #5
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Mickey:

Not a direct answer to your inquiry but your post is a textbook example of why NOT to use wireless except when absolutely necessary. All wireless, even the really expensive ones occasionally will output lousy sound quality. I don't know how those reality guys can deal with five or even ten channels of wireless at a time with issues like this, it would drive me crazy as a mixer.

Dan
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Old July 3rd, 2008, 09:07 AM   #6
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Quote:
Originally Posted by Dan Brockett View Post
I don't know how those reality guys can deal with five or even ten channels of wireless at a time with issues like this, it would drive me crazy as a mixer.
It drives them crazy. They simply know that 90% of what they shoot will end up on the cutting room floor. We shot 16 hours of material for a 23 minute reality show, and wireless was everywhere from the standard transmitters, to wireless hops to wireless boom.

Wayne
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Old July 3rd, 2008, 02:43 PM   #7
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Hi A. J., Seth, Dan, and Wayne! Thanks for the quick replies and interesting and informative conversation. I really appreciate it. :)

Quote:
Originally Posted by A. J. deLange View Post
If by "hiss" you mean a frying sound underneath the voice of the ...<snip>... transmitter off and choose a channel which indicates no received r.f.
Ah, excellent tips!

I think I need to spend more time finding a clear channel... The last time I filmed, I was at the Olympic Track and Field Trials... There was not a lot of time for me to find a clear channel, so I just went with the one that was already programmed into the wireless devices from our last shoot. :{

Quote:
Originally Posted by A. J. deLange View Post
If by "hiss" you mean ear-splitting noise ...<snip>... second dropouts. Diversity systems prevent this.
I think I have been experiencing both (frying sound underneath voice, and ear-splitting noise)...

Very frustrating indeed though... A Diversity system sounds interesting, Googling now.

Whoa! $$$$$... They must work really well.

Quote:
Originally Posted by A. J. deLange View Post
The pilot serves somewhat ...<snip>... transmitter and receiver short and unobstructed.
Great info!

Quote:
Originally Posted by Seth Bloombaum View Post
Orient the transmitting and receiving antennae ...<snip>... If this is a mystery after reading I could shoot and post a picture.
Oooh, nice tip! Yah, I did not think of that.

I have always setup the transmitter vertically, and the reciever horizontally (on hotshoe of camera).

Also, I think I can visualize your setup... did you jury-rig your ball-head hotshoe setup, or is this something I could purchase?

Quote:
Originally Posted by Seth Bloombaum View Post
Work closer. Or, work the receiver
That definitely makes sense. :)

Quote:
Originally Posted by Seth Bloombaum View Post
Avoid work in commercial buildings with metal-studded walls ...<snip>... tv stations, commercial radio... here in Portland I have occasional problems with a tram pa system...
Top notch advice from a fellow Oregonian! Thank you Seth! I really appreciate it. :)

Quote:
Originally Posted by A. J. deLange View Post
...<snip>... Nevertheless, parallel orientation is like the proverbial chicken soup. It can't hurt.
Hehe, well stated. :)

Quote:
Originally Posted by Dan Brockett View Post
Not a direct answer to your inquiry but ...<snip>... like this, it would drive me crazy as a mixer.
Ah, yes. I think I have learned the hard way that wireless audio can make for a lot of headaches later on.

Although, I have had great results with our Sennheiser wireless hand-held microphone... I think I have been really lucky... No feedback and/or hiss/pops using that device so far (knocking on wood).

Quote:
Originally Posted by Wayne Brissette View Post
It drives them crazy. They simply know that 90% of what they shoot will end up on the cutting room floor. We shot 16 hours of material for a 23 minute reality show, and wireless was everywhere from the standard transmitters, to wireless hops to wireless boom.
Wow! I never really thought about reality shows and audio until recently.

I just assumed that the reality shows had the $$ to buy equipment that would generate perfect audio signals. :)

I would love to get a job as an intern on a reality show... Survivor would be cool! It would be so amazing to learn all of the ins/outs of how they handle audio/video.

Speaking of TV shows... Yesterday I was watching Bizarre Foods with Andrew Zimmerman, and I was amazed at how clear his audio was... I mean, they were climbing up a rock cliff, and his voice was as clear as day -- I did not even see a lav mic hooked to his shirt.

This is the episode I am refering to (I could not find a clip of him climbing the rock cliff.)

So, in that scene (him eating fermented shark meat), how do you think they captured audio? Was it just shotgun mic, or maybe they used a boom?

I really wish I could find a clip of him climbing up the rock cliff though... The audio was emaculate!

Anyway, just to summarize all of your excellent tips:
  1. Improve coupling between transmitter and reciever: Move the two closer together.
  2. Remove obstacles between the reciever and transmitter.
  3. Monitor the reciever with transmitter off, and choose the clearest channel.
  4. Buy a diversity system for high-end and professional solution.
  5. keep the path between transmitter and reciever short and unobstructed.
  6. Orient the transmitting and receiving antennae in the same plane (Theoretically the antennas wires should be parallel to one another.)
  7. Work closer. Or, work the receiver closer.
  8. Avoid work in commercial buildings with metal-studded walls when possible. Or, plan to get the receiver a lot closer.
  9. Search for less troublesome frequencies: if you are close to the bottom of the available freqs, try towards the top, or vice-versa.
  10. Keep track of what freqs you've had trouble with and don't use them in the future (Some of these will recur every time you're in that area of town.)
  11. Only use wireless when absolutely necessary.

Thanks again all! I really appreciate all of your professional feedback and advice.

Have a great day!
Cheers,
Micky
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Old July 3rd, 2008, 03:19 PM   #8
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Quote:
Originally Posted by Micky Hulse View Post
Wow! I never really thought about reality shows and audio until recently.

I just assumed that the reality shows had the $$ to buy equipment that would generate perfect audio signals. :)
Most of these shows don't have a regular crew. What happens is they come to an area, talk with somebody who works that area, and they hire that person/crew. The production company usually works with a couple of different people in most areas, if they don't they get recommendations from people they have worked with.

What's important to remember that usually the camera department doesn't own their own gear (smaller indie pictures are the exception), usually these are either rented or owned by the production company. Sound is a different matter entirely. Usually when you hire a sound mixer, he (or she, but there are very few female sound mixers) has his own equipment. What they have depends on how long they have been in the business, and what types of productions they have been working on. On larger productions, you have two contracts. One for your services, if it's a union picture, then that would be your tier rate, and then one for your equipment which is negotiated when you get hired. The real issue is on union pictures, the production company must escrow crew salaries. However, the equipment rental is entirely between you and the production company. So, if you ever have trouble collecting that part of the bill, the union won't help you out.

This really was a long winded way of saying the quality of equipment varies from shoot to shoot. Sometimes there will be minimums. For example, they might say the wireless has to be Lectro 211s, but if you show up with Lectro 411 systems, Zaxcom 900 systems, or Audio LTD systems, they aren't going to say anything to you. However, if you show up with Sennheiser G2 systems, they might have issues with that.

Reality shows are total run and gun and the truth is I'm surprised most sound as good as they do when you consider that you have no control over A/C, or other noises inside a building (unlike a picture where you turn off the A/C, refrigerators, and other noisy appliances). Few people who work on reality shows love doing them, but the money is usually good so people do them.

Wayne
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Old July 5th, 2008, 03:49 PM   #9
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Hi Wayne! Many many many thanks for your reply! Very informative. :)

Quote:
Originally Posted by Wayne Brissette View Post
Most of these shows don't have a regular crew. What happens is they come to an area, ...<snip>... turn off the A/C, refrigerators, and other noisy appliances). Few people who work on reality shows love doing them, but the money is usually good so people do them.
Wow! That is interesting.

Makes me wish I knew more about audio... There is so much to learn.

Also makes me wish I lived in a bigger city! My small town does not have much going on in terms of movie productions... Hmmm, well, maybe nearby Portland, but not Eugene.

Anyway, thanks a billion for clarifying and for sharing your expertise. :)

Have a great day!
Cheers,
Micky
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Old July 5th, 2008, 11:58 PM   #10
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Just as an observation...

Don't forget when using a wireless rig, that there's no rule that says the receiver HAS to be mounted on the camera.

For some reason, I've witnessed a LOT of shooters rig the receiver to a camera that's 75 feet away physically from it's transmitter and then spend an hour frustrated about their audio - changing batteries and futzing around re-orienting the antennas.

For some odd reason they don't make the mental leap that there's nothing wrong with pulling the damned receiver off the camera and re-positioning it just out of the picture - say 10 feet away from the talent - then running an XLR balanced audio cable from said receiver back to the camera input.

Proximity solves a LOT of wireless issues.

Oh, and by the way, on the subject of the rock climbing video - it's not really hard to get decent wireless results out in nature far away from all sources of RF and where there's a clear line of site between transmitter and receiver.

It's a LOT more challenging to get good audio in, for example, a retail store with 90 overhead fluorescent light units with original ballasts that were wired in 1969 - while forced into a camera location adjacent to an escalator that has a half dozen similar era electric motors constantly pulling the stairs under load up to the second floor.

Far from civilization, away from motors, ballasts, crowd noise, background music, paging, etc. and with JUST maybe some wind to contend with???

Wireless heaven.
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Old July 6th, 2008, 12:36 AM   #11
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Hi Bill, thanks for the help!

Quote:
Originally Posted by Bill Davis View Post
Don't forget when using a wireless rig, that there's no rule that says the receiver HAS to be mounted on the camera. ...<snip>... re-positioning it just out of the picture - say 10 feet away from the talent - then running an XLR balanced audio cable from said receiver back to the camera input. Proximity solves a LOT of wireless issues.
Ah, yah! Nice point. :)

Thanks for pointing that out.

Quote:
Originally Posted by Bill Davis View Post
Wireless heaven.
Hehe! Well said! That does make a lot of sense. :)

Thanks for the great info Bill!

Cheers,
Micky
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Old July 6th, 2008, 03:53 AM   #12
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Dear Mickey,

I have two recommendations:

1. Ensure that the "Pilot" feature is on. I assume that it is, but if it is not, you will get loud hisses when the transmitter is out of range. If it is on, then the hisses, for this one reason, will not occur (for the most part).

2. Use the G2's Scan feature to find a clear channel. The correct procedure is in the manual.

This is important if you are using only one system. It is imperative if you are using multiple systems.

The Scan feature will:

a. Find all of the open channels in one bank of channels.

b. Select channels that will not interfere with each other.

This is very important. Otherwise, you could be creating your own interference by using channels that are incompatible with each other.
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Old July 6th, 2008, 04:55 AM   #13
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Open Channels:

Most scanners built in to wireless receivers are not "smart" enough to know the space between the video and audio carriers of an NTSC TV channel is not really open. Your scanner may like that frequency for the moment it looks at it, but you'll be disappointed because that's where high frequency video information is transmitted and it will interfere with your wireless.

As such, having a chart of local TV station frequencies can be very helpful.

Regards,

Ty Ford
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Old July 6th, 2008, 08:00 AM   #14
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Ty makes a good point, as always.

With the Sennheiser G2 100 units, you manually select the "Bank", which consists of 4 channels within a frequency range.

So you can sometimes avoid your local Television channels by selecting a proper bank.

Here is a link to the Sennheiser USA Frequency Finder:

http://www.sennheiserusa.com/newsite...qfinder-ew.asp
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Old July 6th, 2008, 12:38 PM   #15
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I have a G2 system and I think it's the best thing out there for the money. However, you can't just use it out of the box, and the manual is pretty bad. Here is a link to a short training video that tells you what you need to know: http://www.dvcreators.net/products/s...movieframe.htm
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