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Old April 26th, 2008, 08:25 PM   #1
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Clipping in Sennheiser Evolution G2 500 Series?

Hey all,

We are using the Sennheiser Evolution G2 500 Series wireless lav mics. A lot of the time we like them, but we've been getting a lot of clipping that seems to be coming from within the mic or transmitter. We see the waveform and it is definitely not clipping in the camera (Canon XH-A1), but it is clipping somewhere.

We set them to -30dB when someone is loud, and -20db when someone is not. My partner in production is a former pro audio engineer, and has played every way that he can with the gain structure to get it to stay clean, but nothing quite works.

Is anyone else having this problem? Is there clipping within the transmitter (or mic) that is just unavoidable?

Any input is helpful, thanks in advance.
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Old April 27th, 2008, 02:03 PM   #2
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Bump.

I am the aforementioned audio guy. Just one more thing about this curious distortion from the Sennheisers-- that is that the meters on the transmitter/receiver don't show clipping either (nor low bat). Obviously when we are clipping in the transmitter, we just need to turn the sensitivity on the pack down more. But if the meters in the transmitter aren't clipping, we really shouldn't be hearing any distortion.

Any other Sennheiser G2 500 users out there?

Thanks.
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Old April 27th, 2008, 02:31 PM   #3
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Hi. I use the Sennheiser G2 500 Rx+Tx set.

Not sure I follow you. You say "it is definitely not clipping in the camera", which is, surely, recording AFTER the Sennheiser RX+Tx have both done their job and fed the (unclipped - as you say) signal to tape.

So what has this got to do with the Sennheiser kit? The problem must lie later in the workflow? Or am I missing something?
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Old April 27th, 2008, 03:35 PM   #4
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Have you played around with mic placement? They tend to distort if you place the mic to close to the source.

It *could* just be a limitation of the system itself. Have you ever noticed that the top notch mics used for The Tonight Show can pick up the faintest whispers and yet never distort with loud sounds. You get what you pay for.
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Old April 27th, 2008, 04:30 PM   #5
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John - yeah, getting what you pay for is part of it for sure.

Martin - No, I didn't say it makes it to the camera unclipped... on the contrary I'm almost certain that it is clipping before it gets to the camera. I have seen camera clipping in the wave form and it is very different... this signal is well within the camera's dynamic range but clipped on it's own.
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Old April 27th, 2008, 10:39 PM   #6
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what mic is on the TX??
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Old April 27th, 2008, 10:49 PM   #7
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If the recorded material is not exceeding the max SPL of the mic, then something's not set correctly, or something's defective. Most often it's the camera's input being overloaded, and you don't seem 100% sure that this is not the case. When you are 100% sure it will be time for service on the Senn equipment.
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Old April 28th, 2008, 12:08 AM   #8
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Greg - not sure of the model number on the mic... the one that comes stock with the $500 package. Trying to find it on B&H now and for some reason having problems finding it.

David - the only reason I've said I'm not certain the camera is not overloading is because even though I am an electrical engineer by training, there is still a lot I don't know so I'll never claim 100% certainty. The reason I'm pretty darned sure that it is not overloading the camera's input is that in looking at the waveforms of the captured video, I have clips that reach twice the level and do not clip at all. I can see the waveforms with this problem... they never reach 50% of the max capacity of the camera to record clean audio and yet they are hard clipped at that level. It looks for all the world like the camera is faithfully reproducing a clipped signal that it is receiving.
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Old April 28th, 2008, 01:44 AM   #9
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Hmmm, would like to know where you got a G2 500 package for $500. I'll take several!! The TX alone is worth that.

In any event, if you are using the ME-2 mic (usually gray collar plug at TX) then I'd suggest another mic. It's a cheap element and I would only use it as a last resort. I can see it getting overloaded easily with loud levels. If you only paid $500 for the package that's probably the mic in question. As suggested, you can try putting some space between the mic and sound source to help reduce the level. Remember if the mic overloads, everything downstream will be bad as well.

The MKE-2 EW is a much better mic, and can handle significantly higher sound levels. You can identify this mic by both a black collar TX plug, and a serial number band molded around the cable near the plug. The "EW" suffix version has a slightly reduced output level that will not overload the TX input. The MKE-2 is my personal fav for lav mics, I own many and use them for a variety of sources and it's rare that I clip one of these mics.

I would strongly suggest you utilize the headphone jack on the 500 RX and a decent pair of cans to verify the output quality of the mic and wireless path. This headphone out will isolate the mic/rf from anything else you have it connected to and make isolating your trouble easier (its one of the reasons to spend $$ for the 500's). If the sound here is bad, you will have to determine if settings on the TX/RX can improve your problem, or if the mic is at fault (overloaded, or even just a bad mic...). If the RX out is good, then you will have to look downstream for other issues. Don't forget that the RX has an adjustable output, you may have it too high for the A1's mic inputs...I usually use -24 out to feed a mic input.

One more thing...before you do any of this...turn your RX on and your TX off. Make sure that your RX shows NO rf signal (green RF light should NOT be on). If there is any signal, retune to a new channel that has NO other signal present. Interference with other signals can sometimes cause distortion...
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Old April 28th, 2008, 08:44 AM   #10
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Greg,

Wow - I have mislead you, sorry. It is the G2 100 series, and yes it is the ME-2 microphone (package is $550). Sorry if I wasted any brain time there.

So now... with the cheapest components all around, we're left figuring out which cheap component we must replace to get the best sound :).

We'll take a look at the MKE-2 EW. My guess is that the mic is out biggest issue. Or does this being the 100 series tip you off to something else?

Sorry again... was working too quickly on this end and got that wrong.
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Old April 28th, 2008, 01:21 PM   #11
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100 series...too bad, i had my hopes up for a deal! :-)

Did you confirm a interference free channel? after that, you need to monitor the RX for quality. not as easy with the 100's lack of phones jack.

re-reading your earlier post concerning less than full level, yet clipped audio. you could very well be overdriving the camera input. need to know two things. is your camera input set to mic or line in-and what is the AF OUT setting in the RX menu?

ok, three things. are you connecting the RX to the A1's XLR input, or the 1/8" jack?
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Old April 28th, 2008, 04:11 PM   #12
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Hey Barry, I'm an EE by training too. Tacking on "by training" implies that we wound up doing something else. I teach high school physics. What do you do?

Anyway, having read your post #8 now I get why you think it's not the cam input. The thing is that the same logic applies to whatever actually is producing the clipping. It seems that it must be intermittent. I'm thinking defect, with the mic or the mic circuit being the likeliest candidates.

The transmitter supplies 9V to the mic, even though the unit is only powered with two AA cells, so there's a DC/DC boost converter in there.

What's the typical duration and spacing of the clipping?
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Old April 28th, 2008, 04:37 PM   #13
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Don't know if this will help or not but being a bit uncertain about such things myself I took a G2 100 pair, set the transmitter (with the supplied Sennheiser Lav) to maxium sensitivity, set the receiver output to +12, connected a high impedance scope and whistled. Clipping set in above 3 Volts peak. Waveforms at up to 3 volts were nicely rounded. Louder ones were clipped at 3.5 volts. 3.1 volts turns out to be +12dBm into a 600 ohm load or +12dBu - just what the display says (but there is no dBu indication on it nor does the manual, on cursory examination at least, say what the output level is). Thus if everthing is working normally (including making sure it is the transmitter that has captured the receiver and not something else) you shouldn't be clipping as long as the audio peak light doesn't come on (or the bar hit it's right hand end) and the camera can handle 3 volts (+12 dBu) peak.
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