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-   -   What the ?? mic problem (https://www.dvinfo.net/forum/wedding-event-videography-techniques/121718-what-mic-problem.html)

Matt Bishop March 3rd, 2008 03:51 PM

What the ?? mic problem
 
So first off I'll say that I do use a backup recorder on my audio so my wedding video will not be ruined....but this was too close for comfort.

I began picking up major interference at a wedding last week. I tested everything and it was just fine, but about halfway through the ceremony I started to hear some static. It starts really soft and builds until I can't hear anything but that. Then sometimes it will cut out and and i'll have perfect audio again. I have had this happen before with this mic but it was very brief and I figured it was just random interference. Now I'm not so sure. I didn't have this problem the last time I worked at this church so it shouldn't be a location issue either. I was only 25 ft from the couple so it wasn't a matter of distance or being blocked by something.

I have a sennheiser g2 wireless system and am running the XLR adaptor into a beachtek DXA-4. I've never had any problems with this before and I have 2 sony vx2100 setup the same way so I'm pretty sure it's not my setup.

I have talked to different people at sennheiser and I'm starting to get conflicting answers so I figured I would ask all of you wonderfully smart people :-) before I hassle with sending it in. I just wanted to make sure it wasn't something stupid on my part with my audio setup.

Here is a 1 minute grab from the wedding so you can hear what I'm talking about. once it built back up , it stayed for the rest of the ceremony .

http://www.mediainnovations-online.com/mic.wav

I appreciate any help or ideas!!!!!

Matt

Michael Liebergot March 3rd, 2008 05:00 PM

I don't think that it was the mic, sounds like it was a frequency problem with the wireless. Did you check the Sennhesier frequency chart for your areas transmission area, to make sure that you have the best frequency band for your surrounding areas?

Did you do a frequency sweep of the venue before the ceremony, with all wireless transmitters turned on (except yours).

Just because you didn't have a problem with a previous job before at this church doesn't meant that something in the area (not just church) couldn't interfere with your wireless.

But it does sound like a frequency problem.

Waldemar Winkler March 4th, 2008 10:23 PM

Oh yeah, I get that a lot when battery power begins to fade. However, with a battery voltage drop there is usually no return of transmission clarity. Things generally go from bad to worse.

Clearly, something is causing interference, but I wouldn't think local TV station broadcast a possible culprit because TV broadcast is constant ... you would always have the problem all of the time. Although I haven't really researched the actual frequencies, I'd take a close look for wi-fi, leaky microwave ovens, etc, within the building. Something that is sometimes on and sometimes off emits a strong enough signal (20 to 50 milliwatts) on the frequencies your wireless system uses to render them inert.

I wonder if there is a downloadable application freely available that can utilize the built-in antennas of laptop computers to identify broadcast frequencies? Once the problem frequency was identified it could be associated with typical consumer or industrial products, thus narrowing your search.

Matt Bishop March 4th, 2008 10:31 PM

I was using a range of frequencies that, according to sennheiser, is a vacant range in this area so I don't think that would be an issue. Of course it is wireless and some interference is always an issue. I always have new or fairly new batteries in both units so I ruled that out at the very beginning. Again, it wasn't just this location. This wasn't the first time this happened ...it's just never been that bad. thanks for all your input.

There is another business in the area that has the identical setup as I do and they've never had a problem...The only difference is that they have the units with frequency in 700s while mine are in the 500's. Could that be the issue? Could there be more airwaves being used at a lower frequency and therefore more chances for me to get interference??

George Bean March 4th, 2008 10:49 PM

Is this the only wireless you are using? Want to verify two transmitters are not to close either distance or frequency.

Sometimes my nextel cell phone will cause interference on our wireless so I try to keep it a safe distance away.

I had a similar situation with two of our sennheisers turned out it was a bad mic cable. Very difficult to determine because it was not consistent. Once I changed to a different mic into the transmitter the static was gone.

Matt Bishop March 4th, 2008 10:59 PM

Yes this is the only system we are using. At this particular ceremony there were no other mics being used (wired or wireless) There was nothing else within 25 ft of myself with the receiver or the groom and the transmitter.
I actually got a new xlr cable sent to me the first time this happened but I ruled that out after it did the same thing with that one.

George Bean March 4th, 2008 11:22 PM

the xlr cable; is it going to the transmitter in or is it from the receiver out to the beachtek?

is your transmitter the lapel with mic/line input, handheld one piece, or xlr plug?

Matt Bishop March 4th, 2008 11:28 PM

The transmitter is the ew100 g2 wireless with lapel mic.

the receiver has an xlr cord that runs into the beachtek and the beachtek runs into the 1/8 mic input on the vx2100.

I've used it this way because I have more control over the levels as opposed to using the supplied mini plug that would run the receiver right into the camera via mini.

George Bean March 4th, 2008 11:35 PM

thats the same setup

the cable that was bad on mine is the actual lapel mic cable, seems it often gets tangled when packed away between use.

if you get the static again try plugging in a different mic with mini plug into the transmitter and see if there is any difference. also check and see what the squelch settings are. hope this helps.

Steven Davis March 5th, 2008 07:46 AM

Well I was looking for my long post on my Sennheiser G2100 issue, it's somewhere on this board.

But my experience is, that I ended up going with a frequency range that was not what the Sennheiser chart recommended. It says I need a A range, but with A range I had interference constantly, and was only able to find like one frequency that had 4 free.

Once I switched out, things are much better. When I was having problems with my A range, I called TV stations, radio stations etc and could never really hammer out what the issue was.

The people at Sennheiser were great. I just think there are stations, radio, HD whatever that may not always be listed on a chart.


So I would check with someone who has a different range and see if that makes a difference. It did for me.

Steven Davis March 5th, 2008 07:50 AM

I found it http://dvinfo.net/conf/showthread.php?t=99304

John Moon March 5th, 2008 10:14 AM

I met with a Sennheiser rep in January and he did say that cell phones can interfere with wireless mics. We had a similar instance but the feedback would spike and fall off and then later would get the same thing. No particular pattern. We now make sure that the Groom, Groomsman and Officiant turn their cell phones completely off to avoid this problem.

Waldemar Winkler March 5th, 2008 10:58 AM

In thinking this over I am leaning more and more towards he idea of a WI-FI network causing the problem. I ran into this same situation last spring when one of my wireless mics produced a similar hiss. Since the problem occurred in a venue quite familiar to me I was certain something had changed recently. I asked the building's telephone technician if he had made any major changes in the last few months. New WI-FI networks was the answer, although he couldn't tell me the exact frequencies being used.

Will your mics work in another location?

Matt Bishop March 5th, 2008 12:34 PM

about 80% of the time they work perfectly, but this is the 4th wedding that I've had this problem at so it does work at other locations but at the same time I have had this exact same problem in more than one place. And those locations weren't even in the same general area.

Steven Davis March 5th, 2008 12:43 PM

Quote:

Originally Posted by Matt Bishop (Post 837806)
about 80% of the time they work perfectly, but this is the 4th wedding that I've had this problem at so it does work at other locations but at the same time I have had this exact same problem in more than one place. And those locations weren't even in the same general area.

And that is the reason I tried a different frequency range. That reason exactly.

Matt Bishop March 5th, 2008 12:45 PM

That's what I'm about ready to try now since I mentioned that other videographer has the C model and they've never run into this.

Peter Ralph March 5th, 2008 02:14 PM

were you using brand new batteries & were they registering fully charged on the meter in the senn?

all sorts of environmental factors can degrade batteries - and that sounds like a battery problem to me.

Matt Bishop March 5th, 2008 02:22 PM

they registered at the 3/4 full mark. I usually use them until they at half and then I'll change them out. I haven't noticed a trend with that but I haven't really kept track of the relationship between the battery and the times I had problems.

Steven Davis March 5th, 2008 02:28 PM

Quote:

Originally Posted by Matt Bishop (Post 837812)
That's what I'm about ready to try now since I mentioned that other videographer has the C model and they've never run into this.


One thing I started doing was looking at what the facilities used. For instance, I would go to a church and make a mental note of what frequency they were using, and the one frequency I wasn't finding was mine. hehe.

Peter Ralph March 5th, 2008 03:06 PM

my g2 battery meters only have 3 bars - if it shows 2 bars the battery may only have 35% of its charge left.

does your meter have 4 bars? - if so your approach is reasonable - if not I would bet your problem was caused by low battery. The problems you are experiencing don't sound like wireless interference.

even with 4 bars personally I wouldn't start a shoot unless all 4 were showing - AAs are cheap

Matt Bishop March 5th, 2008 04:43 PM

Yeah mine is the same with 3 bars so I meant to say 2/3. I didn't ever figure with 2/3 I would be low enough to cause these types of problems. I just tested the batteries that were in there for that wedding and all 4 tested in the lower area of the good range. I always use energizer alkaline batteries. Could that really effect it that much even though they're still testing at a decent amount?

Peter Ralph March 5th, 2008 05:05 PM

AA batteries are 1.5V - so 2 will give you 3V. Just about all the pro wireless units run on 9V batteries - which are several times the price. My AT101 uses 2 9V batteries in the receiver.

senn are pushing it using AAs - they need all the help they can get.

Bill Busby March 5th, 2008 05:10 PM

I have the G2 & use rechargeable batteries & when I 1st got it, out of curiosity I left the transmitter on with fully charged 2800mAH AA's & it powered for nearly 12 hrs. The 2 bar indication is where the majority of the useable power is. It's when it gets down to 1 bar when you need to start thinking about swapping out :)

Bill Busby March 5th, 2008 05:25 PM

Quote:

Originally Posted by Peter Ralph (Post 837917)
AA batteries are 1.5V - so 2 will give you 3V. Just about all the pro wireless units run on 9V batteries - which are several times the price. My AT101 uses 2 9V batteries in the receiver.

senn are pushing it using AAs - they need all the help they can get.

Peter, that makes no difference. It's based on design... not voltage.

Peter Ralph March 5th, 2008 05:29 PM

absolutely right Bill - the unit will keep on transmitting for 12 hours or more.

If you can tolerate the interference you can certainly save yourself a buck or two.

Good tip - I think clean audio is way over rated anyway

Bill Busby March 5th, 2008 05:41 PM

Quote:

Originally Posted by Peter Ralph (Post 837928)
If you can tolerate the interference you can certainly save yourself a buck or two.

I suppose I should have been more clear. I don't have interference issues unless it gets down to the point there's not enough usable voltage & is on the verge of shutdown. Isn't that how most if not all wireless systems are designed?

Waldemar Winkler March 5th, 2008 06:29 PM

Quote:

Originally Posted by Matt Bishop (Post 837812)
That's what I'm about ready to try now since I mentioned that other videographer has the C model and they've never run into this.

Well, whatever the source of the interference, it is clear it is affecting the frequencies your mic systems are using. Changing frequencies will likely solve the problem.

Peter Ralph March 5th, 2008 07:46 PM

Bill- with rechargeable batteries there is typically no warning - you go from clean signal to noise in a few seconds

But with regular batteries wireless signals degrade in the way Matt describes, the noise comes in softly and intermittently for a while well before the signal fails completely. Monitoring with headphones you can often recognize the problem in time to deal with it.

This is the main reason most audio pros stay away from rechargeable AAs.

Recently Lectro have started recommending the iPower/Lithium 9V chargers but IME the Lectros can run on semi-depleted 9Vs much more reliably then the senns on semi-depleted AAs.

Matt Bishop March 5th, 2008 08:03 PM

Peter,
When you are referring to interference coming in slowly what kind of time are talkin about. Most of the time when this happen it's about 15 seconds from clean to horrible. I'm just curious if you are referring to a longer time for it to actually go bad if it was being caused by the battery....a few minutes to degrade rather than a few seconds?? For the batteries I'm using it seems rather fast to go from good to bad. AT the same time, I have had it go out and then come back and be fine for the rest of the ceremony so I think that type of situation would rule out a battery issue. Just thinking outloud.

Peter Ralph March 5th, 2008 08:49 PM

a weak battery will reduce the signal/noise ratio, making the unit more susceptible to interference. The actual progress will depend on which unit is weakened - typically the receiver will deplete the battery much faster than the transmitter. The only way to know for sure is to replace the battery and see if the problem disappears.

Ask around and I think you will find that just about everyone will recommend replacing the battery well before it reaches the "marginal" state that you are reporting.

Why not scoot over to the audio forum?

One troubleshooting tip - describe one problem in detail and see if you can get to the bottom of that - don't assume that all the problems you have ever had with audio are caused by the same thing.

HTH

Jared Meyer March 5th, 2008 09:51 PM

I'm sorry you're having trouble with your sound, Matt, but it's really good to see I'm not the only one with this problem. :)

I have the G2 and have seen the exact same symptoms since I purchased it last year. Happened on about 3 or 4 different wedding shoots last season.

I use brand new batteries for each ceremony. Positive it's not battery-related.

http://www.dvxuser6.com/uploaded/9324/1187726869.mov

It starts slow and builds, but it also occasionally pops really loudly and then clicks off. There's two different segments from the ceremony joined together in this audio clip, listen all the way to the end for the pop where the static completely shuts off.

I'm not much of an audio guy, sad to say, but I'm hoping the more info we're able to compile on this problem the better chance someone wiser will be able to diagnose it...

Matt Bishop March 5th, 2008 09:54 PM

which g2 frequency model are you using A, B or C ?

Thanks for the clip...sounds EXACTLY like what I'm getting. Annoying isn't it!! :-)

Jared Meyer March 5th, 2008 10:00 PM

Yeah, it's absolutely infuriating. And I hate knowing that it could be any one of a number of different things.

This is the "A" model, 518-554 MHz.

Mike Bisom March 5th, 2008 10:33 PM

Well that stinks... I have a Sennheiser G2. But I also have a Lectrosonic's and I can tell you that is the ONLY wireless system I will purchase going forward. I had trouble with my original wireless and I finally sprang for the Lectrosonic. Definitely the best out there.

Mike

Peter Ralph March 6th, 2008 11:24 AM

lectro are top banana no question. The G2 is a budget product but it's none too shabby. For weddings? Who can afford all those lectros?

This problem can be solved in a few minutes:

change the battery
change the frequency
if the problem is still there go to a clean location or run it alongside another g2

- if that doesn't pinpoint the problem - send the unit in for service or replacement.

Millions of these units have been sold - and 99.9999% of users are happy.

Matt Bishop March 6th, 2008 12:10 PM

I do appreciate all the help and your suggestions but they wouldn't be able to fix the problem in the situations that I've had them...

I ALWAYS test the mics before hand and as I have said, usually have new to fairly new batteries in them. When I test them and everything is great, I have no reason to adjust anything. Then halfway through the vows it starts cutting out, I cant do anything about it. I can't change out the batteries or change frequencies in the middle of that so I'm stuck.

That's the worst part about this whole situation...it's so random that it's hard to determine or even narrow down a cause.

Michael Liebergot March 6th, 2008 12:53 PM

Quote:

Originally Posted by Matt Bishop (Post 838331)
I do appreciate all the help and your suggestions but they wouldn't be able to fix the problem in the situations that I've had them...

I ALWAYS test the mics before hand and as I have said, usually have new to fairly new batteries in them. When I test them and everything is great, I have no reason to adjust anything. Then halfway through the vows it starts cutting out, I cant do anything about it. I can't change out the batteries or change frequencies in the middle of that so I'm stuck.

That's the worst part about this whole situation...it's so random that it's hard to determine or even narrow down a cause.

Matt forgive me if you mentioned that you did this, but did you do a frequency sweep before using the wireless. I don't mean a test of the mics, but rather a frequency sweep of the venue to see if there are no shared frequencies being used.
If you have never done this, you should, as this is a must for wireless work in the field.

Again forgive me if you know how to do this, but in case you don't...

1. Turn off ALL of your transmitters
2. Make sure that ALL transmitters that will be used are turned on (except yours)
3. Turn on your receiver and see if there is any activity going on
4. If your receiver shows there is activity, then try another band
5. Once you find a good band (with no activity), then set your transmitters accordingly

Again, this is not a mic test, but a wireless test.
Your mics and wireless will work just fine, until another transmitting device is turned on (could be another wireless system the church has, Wifi etc.). This is why it's important to make sure that all transmitting devices are turned on (except yours) when testing.

Again sorry if you already mentioned that you did frequency sweeps. But this might still be useful for those who don't.

Peter Ralph March 6th, 2008 12:53 PM

ok - if you only shoot weddings you can't troubleshoot on the job.

Here is what I would do -

hook the senn up to a laptop and record ambient sound direct to disk using an audio app. Leave it run for a few hours. When recording is finished check the audio waveform - any noise will be immediately visible. Checking 2 hours of video this way will only take a few seconds.

repeat with different variables until the problem is pin-pointed.

One thing - as mentioned receivers eat up batteries much faster than transmitters. So if this problem does come up during a wedding and you are not sure you have fresh batteries you can always try switching out the batteries in the receiver.

Mike Bisom March 6th, 2008 02:04 PM

Lectrosonics are top banana!

And they aren't really that expensive, all things considered. Meaning you will never need to replace your Lectrosonic. You will have them longer that ANY camcorder. You save yourself a lot of these headaches (how much is that worth). We had a priest mic'ed with the G2 and the groom with the Lectrosonic. When the priest was at the other end of the sanctuary, but still in the sanctuary, the Sennheiser started to break up. The groom was outside the church and I still got a clear, clean signal from inside the sanctuary. For me, that's priceless. Especially when you don't have the opportunity to "tweak" many things during an event. I am be no means an audio engineer, but I have spoke with audio professionals enough to know that there is just too much for me to know/understand about build quality. Sure, I can find an open frequency, but if the unit doesn't provide a strong enough signal, with decent pre-amp connections, noise rejection, off-axis whatever... then what is it worth? And I don't know squat about all that. Find an open frequency & work. That is why I love the Lectrosonics!


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