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Possilbe to over-drive LMa transmitter lectro?

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Hal Beery
Possilbe to over-drive LMa transmitter lectro?
on Feb 12, 2012 at 5:22:33 am

I've been using Lectrosonic wireless gear for years and never had a hitch. Recently I purchased some new series 100 kits. UCR100 with LMa transmitter. The first project entailed a "compromised" situation where I ony had a tram lav on a singer/guitar player and a sennheiser shotgun with an LMa on a second musician. Everytime the musicians began singing and playing loudly (accoustic only), it seemed the signal got overmodulated/over driven. it broke up. I adjusted the output levels, etc... but didn't get satisfaction.

Back in the hotel room, I simulated the situation and was able to duplicate the problem by singing loudly into a lav and the shotgun. The wave forms were not overdriven.

I'm using a Sony EX-1r to shoot/monitor the sound.

Also... (this may have to go to the EX1 forum) I was not able to get satisfactory input levels into the camera at LINE level. Yes, all the switches were properly set. What goes????

Thanks,
Hal


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Jordan Wolf
Re: Possilbe to over-drive LMa transmitter lectro?
on Feb 12, 2012 at 5:54:34 am

It is very possible, even likely, that the microphones themselves were being overdriven. At what stage - that's the answer I think you're seeking. Most manufacturers are aware that their microphones can only handle a certain amount of SPL before audible distortion occurs. Using the built-in pad or a less-sensitive element is the only way around this issue other than moving the mic further away from the source.

Wolf
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Ty Ford
Re: Possilbe to over-drive LMa transmitter lectro?
on Feb 12, 2012 at 4:18:32 pm

Hello Hal and welcome to the Cow Audio Forum.

You have several places where the audio can be overdriven.

The mic itself, either at the capsule or, with condenser mics, at the capsule or in the mic's following electronics. The best mics have pads is in between the capsule and the electronics. If the capsule is overloaded, you have no choice but to move the mic. If that mic has a pad after the electronics and either the capsule or electronics are being overdriven, you're cooked.

If it's just the mic electronics that are overdriven and the pad is between the capsule and the mic's electronics, you can probably pad the electronics and save the audio.

The inputs to transmitters are also capable of being overdriven, even if the mics are not. If the transmitters are set up for lavs, simply adding a condenser mic with a larger diaphragm, like a shotgun mic, will likely require downward adjustment of the transmitter mic sensitivity to prevent the transmitter input from being overdriven.

Finally there's the output of the receiver. If everything upstream is OK and you misadjust the gain staging between the receiver output and the camera or recorder input, you can distort there as well.

My guess is that the problem was overdriving the transmitter. BTW, to compensate for different performance levels, Countryman makes three sensitivities of their B6 mics; Standard, for most uses, Mid, for theater and Low, for powerful vocals (e.g., opera)

Regards,

Ty Ford


Want better production audio?: Ty Ford's Audio Bootcamp Field Guide


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Steve Kownacki
Re: Possilbe to over-drive LMa transmitter lectro?
on Feb 12, 2012 at 8:23:49 pm

Ty nailed it with the need to monitor the whole signal chain. I'm using Senneheiser G3s to an EX1, here's my setup.

G3 transmitter with Countryman B6 standard capsule, input gain on xmit set to -18 or -21 depending on source SPL. With orig Senn mic, input set to -24. This is for general speaking, not music, but each mic requires input adjustment on the transmitter.

If going straight into camera, output of rcvr set to 0, input of camera set to -35 mic level input, input level control knob set to 5- that gives me some easy adjustment. The receiver cannot generate anywhere near enough output to use line input.

I use an older Sennheiser ME80 supercardioid with K3U pow supply, cam input set at -59 (if I remember) with the level control on 5.

Most of the time I use a mixer in between, but the settings above took me a while to figure out to get stellar sound with no distortion. I find the EX1 to be extremely finicky and even on all manual control there seems to be some auto attenuation at higher levels that can throw off the metering vs what you hear.

Another thing to do is plug headphones directly into the output jack of the receiver and listen to the quality of sound before it enters the camera.

I also noticed on the Lectro manual "Important Note: Before using transmitters with the UCR100 Receiver, make sure they are set to
100 Series Compatibility Mode. Refer to your transmitter’s Quick Start Guide for instructions on how to change compatibility modes." Not sure what that refers to but another source of unsatisfactory sound.

Steve






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Ty Ford
Re: Possilbe to over-drive LMa transmitter lectro?
on Feb 12, 2012 at 8:29:54 pm

Thanks Steve, but you add a couple of VERY valid points.

Also, there are professional cameras out there that say they take line level, but you can't really hit them with much more than -10 or -12 or they'll crackle.

I have a client who hires me for studio stuff and their two cameras are like this. I have learned, for them, it's better to go in mic level because they are OK there.

Regards,

Ty Ford


Want better production audio?: Ty Ford's Audio Bootcamp Field Guide


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Hal Beery
Re: Possilbe to over-drive LMa transmitter lectro?
on Feb 13, 2012 at 4:14:04 am

Thanks ya'all. I'm afraid I've been victim of my own good luck. I've never had problems like this in similar circumstances. Several times I shot a very "robust" lecturer who frequently sang a tune or two as part of his presentation with only a lav (and a sure 57 on the guitar but the lav always sounded very nice on its own channel) and the guy wailed into those mics. So ...... I never had the learning curve I'm now faced with. I did manipulate the TX sensitivity dial during the performance in desperation to get it fixed. Also the reciever when it seemed the max input sounds were adjusted within range on the TX. Obviously if i'd had enough mic cable i would have gone that route. I presume that the test recordings we did prior to the shoot were incomplete because the other musicians were not present (to add more db's )... THANKS FOR YOUR DETAILED COMMENTS! and to cut to the chase, WHAT GEAR DO YOU RECOMMEND FOR COMPACT (I'm in south india, trying to get what i can when i can and hoped to double up on my available gear.. i.e. two tram lavs, a Senn shotgun, a sony stereo mic, two sets of the afformentioned Lectro kits... I also have a Zoom 4n recorder that seems to do a great job when manually set)?
THANKS!!!
Hal
(PS.. primary objectives are a documentary based on interviews and occasional local musician performances. nothing fancy)



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