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Author Topic: Need help with Sennheiser EW 112-P G3 system  (Read 2217 times)

Jeff Roden

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Need help with Sennheiser EW 112-P G3 system
« on: May 09, 2018, 09:26:15 AM »

I have 2 Sennheiser EW112-P G3 systems that I use for live audio during weddings in a DJ setup.  The receivers get plugged into a Mackie 1202VLZ4 mixer.  I set the input level on the transmitter to where it doesn't clip during normal speech (usually -30dB to -20dB depending on the speaker). Then I set the preamp gain (preamp has +60dB of gain) to where it peaks right around 0dB on the mixer.  I then adjust the channel level to the highest I can get it without distortion.  However, the volume from the speakers seems too low and when I adjust the channel level, I start to get squealing feedback from the speakers (QSC K12's and K8.2's) but the volume of the person speaking is too low.  Am I missing something?  I figured it was likely an issue with my gain staging.  I'd like to find the optimum settings to get the best sound out of this Sennheiser system as possible and just be able to leave it.  Thanks in advance for any help.
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Don Boomer

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Re: Need help with Sennheiser EW 112-P G3 system
« Reply #1 on: May 09, 2018, 11:56:00 AM »

Then I set the preamp gain (preamp has +60dB of gain) to where it peaks right around 0dB on the mixer. 

This one sticks out to me. You are probably running 10-20 dB too low right here.

Feedback is not related to “gain structure” but rather to system gain.

Gain structure is all about getting the best signal to noise without getting distortion. But in the real world, if you don’t hear too much  noise in your system and you don’t hear distortion then you are at a place where it doesnt really matter anyway.
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Don Boomer
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Jeff Roden

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Re: Need help with Sennheiser EW 112-P G3 system
« Reply #2 on: May 09, 2018, 04:38:28 PM »

This one sticks out to me. You are probably running 10-20 dB too low right here.

Feedback is not related to “gain structure” but rather to system gain.

Gain structure is all about getting the best signal to noise without getting distortion. But in the real world, if you don’t hear too much  noise in your system and you don’t hear distortion then you are at a place where it doesnt really matter anyway.

Thanks for your reply.  I didn't have the preamp pegged out on the mixer, but it was probably 80-85 percent of the maximum.  You're saying I should crank the preamp all the way up then?  I don't think I could set the gain on the transmitter itself any higher, I'm keeping it right around 50-60 percent on the input level from the lavalier mic.
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Russell Ault

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Re: Need help with Sennheiser EW 112-P G3 system
« Reply #3 on: May 09, 2018, 06:22:55 PM »

Thanks for your reply.  I didn't have the preamp pegged out on the mixer, but it was probably 80-85 percent of the maximum.  You're saying I should crank the preamp all the way up then?  I don't think I could set the gain on the transmitter itself any higher, I'm keeping it right around 50-60 percent on the input level from the lavalier mic.

I think you might have missed Don's most important point: if your problem is feedback (which it sounds like it is), feedback has basically nothing to do with gain staging. Changing where in the signal path the gain comes from (the transmitter, the console, the speaker, etc.) won't solve your problem. (Incidentally, your settings don't sound particularly wrong to me, but that's neither here nor their.)

Lavs as typically used are inherently more feedback-prone than hand-held mics because the microphone is always placed at some considerable distance from what you're trying to pick up (i.e. the person's mouth). If you want to increase how loud someone can be out of your speakers without feeding back, you'll need to get the person to speak louder, move the mic closer to the person's mouth, move the speakers further away from the mic, or some combination of the above. For higher (but not typicallt lower) frequencies pointing the speakers away from the mic can also help. You might also be able to apply EQ to reduce the level of the frequencies that are feeding back, but this is can be of limited benefit when the mics are moving around in relation to the speakers (or if the air temperature changes, for that matter). Also, your gain before feedback drops for every mic that's unmuted simultaneously, and two unmuted lavs in close proximity to each other will tend to interact, which can also produce feedback, so it's beneficial to only have mics unmuted when someone is actually speaking into them (although this can be challenging to achieve).

-Russ
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Rob Spence

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Re: Need help with Sennheiser EW 112-P G3 system
« Reply #4 on: May 09, 2018, 07:34:41 PM »

The 1202 has a pfl button on the channels. Press it, talk as loudly as you are ever likely to and adjust the preamp gain until you are seeing about 0 on the meter.

Set the mains out at a little less than 0.

Then use the channel fader or rotary to set the volume you need.

The feedback is telling you that the placement of the mic is in the pattern of a speaker. The output of the speaker is getting back into the mic and being amplified again. ...

Are you using a booth monitor?
Is the mic being sent there?

Have you read the fine manual for the 1202? Mackie actually (used to) produce Informative and entertaining manuals.



Sent from my iPad using Tapatalk Pro
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Don Boomer

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Re: Need help with Sennheiser EW 112-P G3 system
« Reply #5 on: May 09, 2018, 08:19:51 PM »

Hey Jeff

These percentages you are talking about don’t really have much importance. The general idea with gear is you should run it as hot as you can at each stage but without going into distortion or clipping. So if you can run as close to the threshold of distortion that will give you the greatest signal to noise ratio. Thatks probably not as important as it sounds however.

If you only run your preamp up to 0 with the loudest possible signal coming into the channel then you are losing about 20 dB of signal to noise ratio. But since you can really only calibrate a system with a fixed known signal (certainly not a microphone with who know what that might get stuck in front of it) you really need to allow for the unforscene. Part of this will depend on how well you can control what sources get stuck in front of your mics, your skill level and your tolarance for distortion. Personally I’d rather have a little hiss in he system than some crunching distortion.

So back to my first point. Are you hearing distortion?  Are you hearing too much hiss?  If the answer to both is no then further optimazation of your system won’t really matter much.

Feedback is another story altogether. Feedback IS a deal breaker and every kid and old lady in your audience can hear it. Basically you have to break the cycle of the sound from your speakers getting into your mics at the same or a higher level than sound is going into your mics. Getting mouths closer to mics is the cheapest thung you can do that will get you the most desired results. Careful speaker placement and aiming in relation to your mics is also important but probably harder to do. The next step is getting your speakers tuned to your venue (and mics) but that is more difficult and requires some skills. You should consider adding a feedback manager such as those from Sabine or DBX. Even in a poorly tuned system they are likely to get you a 6dB or better increase in gain before feedback with minimal impact to your sound quality.
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Don Boomer
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Jason Glass

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Re: Need help with Sennheiser EW 112-P G3 system
« Reply #6 on: May 09, 2018, 09:39:30 PM »

Hey Jeff

These percentages you are talking about don’t really have much importance. The general idea with gear is you should run it as hot as you can at each stage but without going into distortion or clipping. So if you can run as close to the threshold of distortion that will give you the greatest signal to noise ratio. Thatks probably not as important as it sounds however.

If you only run your preamp up to 0 with the loudest possible signal coming into the channel then you are losing about 20 dB of signal to noise ratio. But since you can really only calibrate a system with a fixed known signal (certainly not a microphone with who know what that might get stuck in front of it) you really need to allow for the unforscene. Part of this will depend on how well you can control what sources get stuck in front of your mics, your skill level and your tolarance for distortion. Personally I’d rather have a little hiss in he system than some crunching distortion.

So back to my first point. Are you hearing distortion?  Are you hearing too much hiss?  If the answer to both is no then further optimazation of your system won’t really matter much.

Feedback is another story altogether. Feedback IS a deal breaker and every kid and old lady in your audience can hear it. Basically you have to break the cycle of the sound from your speakers getting into your mics at the same or a higher level than sound is going into your mics. Getting mouths closer to mics is the cheapest thung you can do that will get you the most desired results. Careful speaker placement and aiming in relation to your mics is also important but probably harder to do. The next step is getting your speakers tuned to your venue (and mics) but that is more difficult and requires some skills. You should consider adding a feedback manager such as those from Sabine or DBX. Even in a poorly tuned system they are likely to get you a 6dB or better increase in gain before feedback with minimal impact to your sound quality.

^What Don said.^

This is what parametric and graphic equalizers were originally designed for.  You must determine the frequency (frequencies) feeding back through the system and attenuate it (them) an appropriate amount AND ONLY AN APPROPRIATE AMOUNT and at the appropriate bandwidth per frequency.  Not to be crude or dismissive, but this stuff is Live Audio 101. Okay, maybe 201, but not postgraduate.  Too much individual frequency attenuation destroys audio fidelity, reduces overall volume, and actually causes feedback at other frequencies when gain is increased to overcome the perceived volume reduction introduced by your EQ.

FWIW, you could spend 4 years at university studying this, but the only real way to master it is to do it, over and over, fail several times, and figure out how it works and what procedures work for you.

And it doesn't matter whether the source is cabled or wireless, although wireless admittedly introduces complications to the process.  Gain structuring, companding, and bandwidth limiting are all compromises commonly introduced by RF vs. copper.  However, first and foremost are mic selection, mic placement, and performer skill.  As many in our biz are fond of saying, "The source is where the output is determined."

Jeff Roden

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Re: Need help with Sennheiser EW 112-P G3 system
« Reply #7 on: May 20, 2018, 12:10:20 PM »

Thanks very much to everyone for replying.  This gives me great insight and new things to try. 
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Mike Caldwell

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Re: Need help with Sennheiser EW 112-P G3 system
« Reply #8 on: May 20, 2018, 07:07:15 PM »

If your putting the lapel mics on people with no vocal projection and speak at whisper levels knob turning is only going to do some much then it just is what it is.

If your using these for the wedding ceremony and it's outside that will be a little easier until it starts raining, the wind kicks up and it's 95 in the shade.

ProSoundWeb Community

Re: Need help with Sennheiser EW 112-P G3 system
« Reply #8 on: May 20, 2018, 07:07:15 PM »


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