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Old July 25th, 2014, 04:21 PM   #1
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Basic audio question about attenuation

Hi all,

I am an idiot when it comes to audio but I buy the basic equipment so I can at least have good audio. Just bought some today so the following will soon be my audio gear

-Sennheiser wireless lavalier G2
-ZOOM H5
-Line to Mic Attenuatior cable

Thing is what is the best setup level-wise. I mean I can decrease the audio level on the receptor and the transmitter. I will have the attenuation cable and I can adjust the record level on the ZOOM.

Which one should I prioritize record level-wise?

Thanks
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Old July 25th, 2014, 04:42 PM   #2
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Re: Basic audio question about attenuation

The audio level must be set on the wireless transmitter to avoid over-modulating which will distort the audio.
The audio level on the receiver can be set to whatever level you need to feed into the destination equipment.
And often, you have the option of line-level or mic-level.
The destination (recorder, mixer, camcorder, etc.) may also have options for line-level or mic-level inputs.
Typically, you can set the receiver and the destination equipment to match (both mic-level or both line-level).
So you shouldn't need an attenuator.
Whether to use mic-level or line-level between the receiver and the destination gear is an experiment only you can conduct with your own unique combination of gear.
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Old July 25th, 2014, 05:47 PM   #3
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Re: Basic audio question about attenuation

You don't need that att cable. Set the transmitter to -21 and the receiver to -12- this is a good starting point for mic level - plug it in using the supplied treaded cable out to male XLR. plug headphones in th H5 and set the volume level with the wonderful knob.

Sound is very important and you've made a good choice in getting these two items. Good headphones will also help you discern the quality of the recording. Meters only tell you quantity. Meaning the recorder could be getting great levels from the AC vent instead of the intended target.
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Old July 26th, 2014, 12:21 AM   #4
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Re: Basic audio question about attenuation

I would guess that the preamps in the h5 are better than those in the g2 so I would stay with a g2 output around -12. Definitely don't try and drive that g2 near line level (0) then compensate by attenuating.
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Old July 26th, 2014, 09:47 AM   #5
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Re: Basic audio quesshtion about attenuation

"Set the transmitter to -21 and the receiver to -12, this is a good starting point for mic level"
I would concur with Craig. This would be a good starting point, however it depends on the actual SPL source. BTW, this is not a set-it-and-forget-it parameter.. neither is the frequency selection, both need frequent checking and adj. for optimal performance.
If so desired, the receiver can be set to feed a +4dB line-level input by raising the receiver's 'AF output' to +12dB. However on some devices, this may yield a slightly low meter reading and the input devices input level would need to be raised, so mic level settings would be better in cases where clean gain is not available.. typical for budget gear
FWIW, I would estimate the G2/3s nominal operating level (with the 'AF output' set to +12dB (max)), would fall around 0dB. (with the x-mitter adjusted properly)
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Old July 26th, 2014, 11:49 AM   #6
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Re: Basic audio question about attenuation

Thanks fellas!

Rick : I was just looking for a base reference, get used to it and adjust accordingly depending on the situation.

Looks like I will be stuck with an attenuating cable cause the order has gone through. I shop my gear at B&H and I was looking for a Y cable that would also let me monitor audio. They have about 10 flavor of them and they ALL have the -25dB feature. Except one but it's reviews are not all glowing so I went ahead and it the attenuating one.

It's this one :

Kopul ACH4-25MON Line-to-Mic Attenuator Cable ACH4-25MON B&H

Do you know of one such Y cable that works fine but doesn't attenuate?

Thanks
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Old July 26th, 2014, 12:01 PM   #7
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Re: Basic audio question about attenuation

That cable is designed to go between an audio recorder output and a camera with mic-only audio input and no headphone output, like a dSLR. You haven't mentioned if you are using this audio gear with a camera and if so what model.
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Old July 26th, 2014, 01:43 PM   #8
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Re: Basic audio question about attenuation

Sorry about that.

Yes my camera is a Canon 60D

Is this a good buy then?
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Old July 26th, 2014, 03:40 PM   #9
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Re: Basic audio question about attenuation

A radio mic system is actually 2 electronic devices....The transmitter (Tx) and the receiver (Rx).

Firstly you need to set up part one.... the Tx levels need to be set correctly (not over driven and not to low) and thats why there is a level adjustment that can be changed. For example a loud yelling man will need a different setting than a nervous bride saying 'I do'. Most Tx units have some metering or lights to indicate levels and when they are over the correct input gain.

When you have part one set correctly it sends it via a radio frequency to part two the receiver Rx, this receives the signal and then sends the audio signal out.... the output level can be adjusted to suit the needs of the camera / mixer input. Some cameras need mic level (most DSLRs are like this) and other cameras can handle 'line' level.

So a well adjusted 'system' is a combination of both of these units set correctly, the TX and Rx.

Leaving them on a medium 'preset' level is like setting a cameras focus / iris to a medium setting and hoping for the best.

The key thing is to monitor the audio with headphones.....ALWAYS. You wouldn't use a camera without a viewfinder would you?

Radio mic systems aren't hard to set up....infact a lot simpler than a camera (tripod setup / leveling, balancing, correct color temp, iris settings, framing, resolution etc etc)

The Sennheiser manual has very good instructions on how to set the system up properly.
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Old July 26th, 2014, 04:37 PM   #10
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Re: Basic audio question about attenuation

Thanks Brian, indeed the manual offer loads of information but my gripe was about how to reconcile all attenuation across four different devices and which one should I prioritize and this is not covered in Senn's manual :)

What about the pilot, is that a test that you do before every shoot like a white balance or it is to be used in special circumstances only ?

Thanks
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Old July 27th, 2014, 08:23 AM   #11
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Re: Basic audio question about attenuation

Quote:
Originally Posted by Phil Gosselin View Post
Thanks Brian, indeed the manual offer loads of information but my gripe was about how to reconcile all attenuation across four different devices and which one should I prioritize and this is not covered in Senn's manual :)

What about the pilot, is that a test that you do before every shoot like a white balance or it is to be used in special circumstances only ?

Thanks
Pilot tone is not a test, it is a feature that works as part of the squelch system to help prevent other nearby transmitters from 'breaking squelch' and causing noise. Your transmitter sends an inaudible tone along with the audio and the receiver only switches from mute to receive when it detects the tone. See the manual page 40.

You don't need the splitter cable between the recorder and the camera to be able to monitor your recording. The H5 has both line and headphone outputs. Using a straight through attenuating cable connect the line out of the recorder to the camera's mic input. Meanwhile connect your headphones to the recorder's headphone output.

Set the transmitter level for the maximum deflection of the meter without lighting the 'peak' indicator (a rare flicker is okay).
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Old July 27th, 2014, 08:29 AM   #12
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Re: Basic audio question about attenuation

<duplicate post - deleted>
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Old July 27th, 2014, 11:02 AM   #13
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Re: Basic audio question about attenuation

Quote:
Originally Posted by Phil Gosselin View Post
...my gripe was about how to reconcile all attenuation across four different devices and which one should I prioritize and this is not covered in Senn's manual :)
Well, you don't reconcile all across all.

The process is known as gain staging, that is, you set appropriate settings at each stage. E.g. the transmitter attenuation is setting the preamp gain for a particular mic and sound source. If you do it correctly, its affect on what happens three steps down the chain is preserve quality.

At the risk of repeating what the knowlegable posters wrote above:
In gain staging, you start at the source and optimize each stage, in order.

1. transmitter gain/att. This puts the mics signal in the sweet spot of the transmitter's processing. Set it too low; you'll get more noise. Set it too high; the system will be overloaded and you'll get more distortion.

2. Receiver AF output gain/att. Just a volume control. Here you look towards the device you're feeding. Does it do better with a hotter or colder signal? Typically you don't want a setting on the Receiver where you'll have to boost it a lot on the Zoom H5, as that tends to bring up the noise in the Zoom's preamps. One method during setup would be to set the Zoom to 50, then bring up the receiver gain until source audio peaks at -12db on the meters. Then, during operation, only touch the recording volume on the Zoom as needed to keep the peaks at -12 or so.

3. Your 60d only accomodates a mic-level signal at its input. The attenuating cable will take the low line level out of the Zoom and pad it down to mic level. As Steve wrote, the Y for monitoring with headphones isn't needed for this particular recorder, but it should work just fine.

4. The 60d's recording level is difficult to get to unless you've installed Magic Lantern. It's in the menus, and you can't adjust it or see meters while recording. The glories of using a still cam for video ;-(
This is one of the reasons you're using an external recorder. But, you do want a good signal here, too, that peaks at -12db or so (between too noisy and too overloaded), so you can use the recording for synchronization in post... and if something goes wrong with the Zoom you have a backup.
So, do adjust it appropriately when you set up, then during the shooting you're looking at the Zoom's meters and adjusting gain as needed there. The 60d is downstream of this, so you're also appropriately controlling the recording on the cam.

(I recommend manual recording level on the 60d. If you *do* need to use its recording for something, the quality will be much better on manual than auto)

Please review what I wrote above - start at the source, then set the levels at each stage. Don't jump around. This is gain staging. Its purpose is to set the output of each stage to a level appropriate to the input of the next stage. Get to the sweet spot between low-noisy and high-distorted at each stage.

Leave pilot tone switched on... learn to rig the mic (search this forum)... wear the headphones always... don't forget to hit the red button!
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Old July 29th, 2014, 07:25 AM   #14
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Re: Basic audio question about attenuation

You're in Seattle.

Call Charlie Tomaras and relax.

Charles Tomaras Productions

Regards,

Ty Ford
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Old July 29th, 2014, 02:24 PM   #15
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Re: Basic audio question about attenuation

Gee, thanks guys that is AWESOME info!

Of course when will come the time that a client's need is a tad too complex, I'll simply hire a sound man ;)

What about in post :

-Do you normalize or not?

-Also, say I record and interview with my G2 plugged in the ZOOM, this will give me a mono track. What is the best course of action in post : A) Duplicate the layer and put one on the left and the other on the right OR combine the channels to it get to be "stereofied" instantly? To be honest I don't hear any difference one way or the other but thought I might ask

Thanks again
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