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Are your lavs working properly?


Michael Miramontes

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 You should know though...

Yes, I assumed the same thing. However, after speaking to a post sound mixer I was able to learn how some lav issues may not be quite apparent to the mixer. Yet, when being heard in a post-sound session you can clearly hear how a lav may not be quite optimal anymore.  

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Since I've been using Sankens, I've only had the connectors go with a snap crackle or pop.  Since I use the waterproof lectro transmitters, I always cringe when I hear that sound, as it means a night's work with magnifying lens, soldering iron and an ample supply of curse words.

 

Every once in a while, I'll listen to all of them using a tone generator and see if they have differing levels at different frequencies.  But usually you can tell when a mic goes off by the way it sounds in comparison to the other ones you have out on the talent. 

It used to happen from time to time back when I was using Trams.  Usually a mic would lose it's high end and become rather ugly and midrangey sounding.

 

Cheers,

Brent Calkin

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Once a year I'd take mine to Mark at LSC. He'd put them in the "chamber" and plot them for me. 1/2 hour labor (although it probably took a bit longer). It usually just confirmed that I wasn't crazy when one sounded a little off, but confirmed I was crazy because it was only off a tiny bit.

Considering placement and costume differences, the mic would have to off considerably for post to complain. That ought to be obvious to your ears, especially if you A/B your mics from time to time.

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A few years ago, my Sankens sounded a little dull to me, also felt a few dB down. I asked Sanken about it. These were not heavily used, and were just about three years old. The answer i got was - any lav that uses a pre-polarized transducer is bound to lose the pre-polarization in time. Additionally, sweat, grime, humidity contribute. 

 

Before the start of any project, actually well before, i check all my lavs for consistency in terms of sound and sensitivity. 

 

Senator has always said that lavs should be considered disposable items. a little tough i know - when one is paying 400-500$ each. however, it may be sensible to think in terms of the number of days of shoot one has used them for and thereby justify replacement from time to time... 

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From a post POV: please check, every now and again, for distortion as well as noise/bandwidth. Record some dialog and listen to them on good speakers, comparing pairs of lavs at a time.

 

Worst thing for me is 2-shots where the mics don't match... and there's so much distortion on one, that it limits how much we can tweak eq to match them.

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From a post POV: please check, every now and again, for distortion as well as noise/bandwidth. Record some dialog and listen to them on good speakers, comparing pairs of lavs at a time.

 

Worst thing for me is 2-shots where the mics don't match... and there's so much distortion on one, that it limits how much we can tweak eq to match them.

I think that's the ticket. I'm going to make it a point to listen to my lavs on good speakers and really crank them up

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in my experience the placement of a Lav is so much more important to how it sounds than it's actual frequency response under testing conditions So it might be difficult for post to claim the Lav has been defective.

On the other hand I think Lavs ARE to be considered somehow as the disposables. AB testing often shows differences, but I keep them as long as they sound acceptable for me. I would never purchase a used Lav on ebay though.

Can anyone suggest a test bench arrangement for Lavs we could set up with a PC and some dedicated software?

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that's kind of what I was interested in seeing too. 

I was thinking about a piece of software to track the ageing of a mic: 

So, when you buy a mic, you create a new 'item' in the 'inventory' and it records its initial performance in a test and then say every 6 months (or after gruelling smoke, water, sweat etc driven gig :-) you test it again and map the deterioration - giving us some idea when to schedule replacement. Maybe the sort of thing a mic manufacturer could see some benefit in.

Although i also agree with just using our ears.

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...

So, when you buy a mic, you create a new 'item' in the 'inventory' and it records its initial performance in a test and then say every 6 months (or after gruelling smoke, water, sweat etc driven gig :-) you test it again and map the deterioration - giving us some idea when to schedule replacement. Maybe the sort of thing a mic manufacturer could see some benefit in.

...

Too many variables, both in manufacture and in use.

Listening is #1. Comparing several of the same model to each other will usually tell you what you really need to know.

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Can anyone suggest a test bench arrangement for Lavs we could set up with a PC and some dedicated software?

Yes, you need to buy a test box (basically a small anaechoic chamber), a calibrated speaker and a white/pink noise/sweep generator. And an analyzer, plus software. NTi (a Neutrik spin-off) makes such things. Higher end solutions are available, too, but even the NTi stuff will set you back several thousand $, which are probably better spent on lavs...
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@Jeff and Constantin: You are certainly right, never give up trusting your ears. But that is the problem:

 

Just only the B6's in my LAV Box sum up to 12 units, that is where AB testing is getting a complex task. And (for worse) the outcome is always disturbing: because they never sound identical, and this is not limited to the B6 only! I guess it is a matter of wear and tear over time.

For my peace of mind I have stopped ABing all my Lavs. If I experience  acoustic issues with one, in a quiet moment I quickly test it whith the bah-bah-essesss-yellingyelling-listen-to-the-ambience test and if it sounds like OK it goes back to the others. I know some units from experience that have a certain sound colour and I try to use them on specific actors throughout the production if the combo has proven to work out well, but this is kind of voodoo as there are so many variables in the game.

 

So it would be a tempting idea to see an up-to-date frequency response chart for each Lav, because it would provide a good base to  compare the listening experience of almost 30 units and to really be able to classify what I can hear in a more standardized way.

 

But if situated within the 1000€+ category, this investment it is way down on the list ;-)

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Perhaps see if there's someone in your area with the gear. As I wrote earlier, I'd take mine to Location Sound in Los Angeles about once a year.

I had one slightly underperforming one, which I marked. It's a tiny bit flatter in the typically boosted COS-11 area. I only place that one if I'm out of all other options and it can be placed "open".

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As long as they're all being measured in the same spot, you'll at least get a "relative" frequency plot even without that anechoic chamber and calibrated speaker. You'll quickly see if one candidate has strange peaks or treble loss. You might even, depending on software, be able to "normalize" the plot to a known (measurement mic) plot.

Not perfect, not academic, but better than guessing.

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I totally get the whole "use your ears" way of doing it. However, I'm hoping that all of us try to do our job to the best of our ability and if we notice something then we would correct it, right? Well, when I visited Henchman when he was mixing a show I was able to clearly hear how one mic may have been bad. I mean, it really did sound terrible. So, that got me to thinking that maybe, just maybe, the mixer wasn't able to hear it on his headphones whereas in a studio it was plain as day. Heck it could have even been a bad transmitter or other piece of gear. My point is that using one's ears may not be full proof. Or, maybe that mixer really did know the mic was bad but didn't really care enough to fix it? Who knows? Either way, I just want to be sure I don't poop on the next guy when I turn my files in. 

 

I think RPSharman has a good point. If LSC or any of the other dealers provided this as a service then I would surely be delighted to take my mics in and most likely end up buying a whole bunch of other stuff while I'm waiting. 

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  • 3 weeks later...

As long as they sound good, they are operational... the cable and  the connectors are fine ... they are good to go....  

   Maybe A/B them with a known newer one, with the same console settings to check if in doubt...  You should know though...

 

+1

Use the best test instruments you already have (they're free): your ears! Listen to the mic, do a simple A-B comparison to a newer mic, save your money that you might spend on all that expensive test gear and buy a new mic!

+1

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