Distorting using Sennheiser G3 wireless lav

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Danny1280

Well-known member
I've had this problem off an on using the Sennheiser G3 with my HMC150. Same problem using a rented HPX250.

The sound clips/distorts really badly, and I'm not coming close to clipping on the levels of my LCD.
When I bring the footage into FCP, the waveforms are all severely clipping, even though they are lower than clipping level (if that makes sense).
In other words, the levels on the waveform are not at clipping height, and yet they're all clipping at about half full volume.

I tried switching mic and line input on my camera, still got a distorted/clipping sound in my headphones.
Weird thing is it only happens sometimes randomly.
Batteries are all new in the G3.

Is there a setting in the receiver/transmitter that is sending too hot a signal, or that is creating the clipping even before it reaches the camera?

Thanks in advance...
 
Danny1280 said:
Is there a setting in the receiver/transmitter that is sending too hot a signal, or that is creating the clipping even before it reaches the camera?

Thanks in advance...
Click to expand...
Yes. Go through the settings and turn down the gain on the wireless. Are you monitoring it during recording? Does it sound distorted during recording?
 
You need to set the entire system up for proper gain staging. As you've figured out, there's something upstream that's causing the distortion.

In the transmitter, there's a sensitivity setting. It should be adjusted for each person, so that at normal speaking levels it's hitting about 2/3 of the metered segments. (My guess is that you have this set too high, and the clipping is in the transmitter.)

In the receiver, there's an output level setting (AF). It can essentially output mic or line level, adjusting in increments from (trying to recall without it in front of me at the moment) -18dB to +12dB. Set it to match the input setting on the camera. I tend to keep mine set in the + range for line-level input on the camera, mixer, or recorder.
 
Danny1280 said:
I've had this problem off an on using the Sennheiser G3 with my HMC150. Same problem using a rented HPX250.

The sound clips/distorts really badly, and I'm not coming close to clipping on the levels of my LCD.
When I bring the footage into FCP, the waveforms are all severely clipping, even though they are lower than clipping level (if that makes sense).
In other words, the levels on the waveform are not at clipping height, and yet they're all clipping at about half full volume.

I tried switching mic and line input on my camera, still got a distorted/clipping sound in my headphones.
Weird thing is it only happens sometimes randomly.
Batteries are all new in the G3.

Is there a setting in the receiver/transmitter that is sending too hot a signal, or that is creating the clipping even before it reaches the camera?

Thanks in advance...
Click to expand...

Likely, you will need to turn down the AF Out on the receiver and the Sensitivity on the transmitter.
 
4 possible distortion points:

1) mic mechanically overloading (not possible in this case)
2) transmitter clipping: gain is set too high (most likely here)
3) camera mic-preamp clipping because it is set to mic level input, but receiver output level is set to line (also possible here)
4) camera audio gain set too high (not possible in this case, as you said the levels are not high)

If you can use a wired lavalier reasons # 2 and 3 can not happen. For this reason I use wired mic unless it is impossible for freedom of movement. Also: $10 cable has better sound quality than even a $10000 digital transmitter/receiver system, let's not forget that either.
 
Meters meter, controls control. What I mean is that meters are used to indicate a condition, not define a setting. The fact that the waveform is squashed but doesn't show up full scale in FCP indicates that the clipping is occurring prior to the last gain stage, most likely at the transmitter. As previously mentioned, transmiter sensitivity (which is the first gain stage) should be adjusted so that when the actor is speaking at the loudest part of the scene, the meter should deflect approx. 2/3. For narrative film work, even when used on the same actor, this setting often needs to be changed between scenes depending on the content. It is also dependant on mic placement. My workflow for lav use is as follows:
Find the appropriate place on the wardrobe to attach and hide the mic. This sometimes dictates mic selection if I'm having to shoot thru several layers of clothing, or having to place the mic closer to the chest, rather than the neck. Once the mic is positioned and secured, I connect the transmitter and ask the actor to deliver what they consider to be the loudest dialog in the scene, while I adjust sensitivitiy to 2/3 deflection on the transmitter meter. I clip the transmitter temporarily to the actor, grab my bag, and listen for clothing rustle while I have the actor move around. I'm using a PSC Alphamix into a DR-680. My G3s recievers are fed into the Alphamix with the output gain set to 0db. My input channel on the Alphamix is set to mic rather than line since the G3 recievers output mic level. Once I'm satisfied that the mic is quiet in regards to clothing rustle (this sometimes takes several mic location adjustments and subsequent sensitivity adjustments), I hide the pack on the actor and move on to the next actor.

The point to all this is that typically my reciever output gain setting is never adjusted after being dialed in to accomodate whatever device it's being fed into. Since the OP seems to imply that there is no mixer or external recorder, than the two adjustments which have to be tended to are a) transmitter sensitivity, and b) camera level. Since the G# receiver outputs mic level, the camera shoudl be set for mic rather than line input. Specifically with regards to transmitter sensitivity, this is never a set and forget adjustment but changes based on mic selection, placement, and actor volume level.

DevonH said:
So Alex, if the gain meter on my Marantz PMD 661 is set to 6, then +6 on the AF?
Click to expand...
 
As others have said, sounds like overloading in the transmitter gain setting. But just to be sure, after setting the transmitter properly, check your receiver to camera link settings as well. I assume you're using the XLR cable from receiver to the camera's audio inputs. Set the camera input for the channel on which you're sending the signal to line. Likewise set the receiver output level in its menu to 0dBu. With normal audio coming over the link, set the camera's input controls for proper levels on its audio meters. Sending a line level signal into a mic level input can produce the kind of clipping you're seeing where the input is overloaded before the recording amplifier stages containing the level controls have a chance to tame it. If that's the case the signal arrives at the level control already clipped and turning down the recording level only gives you a less-loud clipped signal. The G3 output level can be adjusted from -30dB up to +12db, from an "instrument" or hot'ish mic level up to a line level - Senn's specs call it a line out and so I'd set the input it's feeding to line as well. The HMC150 specs say its audio input sensitivity is 0dBu when set to 'line' so that should be a good match when the receiver's output level is also set to 0dB.
 
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Don't forget that cameras often have the level control after the first amplification stage.

It's very easy to overload this first stage and have distortion, even though the meters read correctly, as the meters are after the level control and the distortion is happening before the level control.
 
Thanks to everyone for the detailed, expert advice.
I will try all of these out and see what happens.
Thanks again!
 
I've experienced some of the same issues with Sennheiser G3 and HPX250. There seemes to be a big difference between HVX201 and HPX250 regarding mic sensitivity.

When using HVX201 I connect the G3 normally, setting the HVX201 input to mic. This didn't seem to work with HPX250, the signal is much hotter and often resulted in clipping (dialing down the audio wheel on the HPX250 is not solving the case here. Turning this down just differs between clipping and no audio at all, no "middle room"). I'm pretty sure the signal from the G3 is not too hot itself (hence it works fine with same settings on HVX201).

...So it seemes the HPX250 amplifies audio more than earlier cameras like HVX201. And it seeme to amplify so much that it turnes out to be a problem with "normal" settings.

I guess there are two ways of solving this (assuming that the transmitter audio level is correct)
- turn down the audio gain settings in the HPX250 menu
- turn down the audio gain from G3 reciever

Unfortenatly, I haven't the HPX250 available for a while, so I just heard what another guy did to solve it:

Turning the G3 reciever output to +6 db, and setting the HPX250 xlr input to line in. According to him, others settings resulted in lower audio quality. But I don't know how many options he tried, so I'm not sure what's the best sollution here.

Comments on this apreciated!
 
Using line in on the camera instead of mic level is a good idea in general, because it minimizes the effect of the camera's microphone preamps (which are OK, not great, in most of the Panasonic cameras) on the noise level of the recorded signal. Then adjust the output level of the wireless receiver so you get a good signal level with the camera's level controls at around the 50% - 75% range. If the +6 setting on the Sennheiser receiver is what does this, then that's the way to go. That's fairly similar to the settings I use with my G2 wireless and AF100 and HMC80 cameras.

- Greg
 
Greg Smith said:
Using line in on the camera instead of mic level is a good idea in general, because it minimizes the effect of the camera's microphone preamps (which are OK, not great, in most of the Panasonic cameras) on the noise level of the recorded signal. Then adjust the output level of the wireless receiver so you get a good signal level with the camera's level controls at around the 50% - 75% range. If the +6 setting on the Sennheiser receiver is what does this, then that's the way to go. That's fairly similar to the settings I use with my G2 wireless and AF100 and HMC80 cameras.

- Greg
Click to expand...


Yes - this is the correct way to do it. :thumbsup:
 
Greg Smith said:
Using line in on the camera instead of mic level is a good idea in general, because it minimizes the effect of the camera's microphone preamps (which are OK, not great, in most of the Panasonic cameras) on the noise level of the recorded signal. Then adjust the output level of the wireless receiver so you get a good signal level with the camera's level controls at around the 50% - 75% range. If the +6 setting on the Sennheiser receiver is what does this, then that's the way to go. That's fairly similar to the settings I use with my G2 wireless and AF100 and HMC80 cameras.

- Greg
Click to expand...

Thanks for explaining. That makes sense, and helps a lot :)
 
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