Looking for a good lavalier mic that is impervious to GSM / cell phone interference

[Luke Arndt]

Originally Posted by Greg Miller

Still, the OP said he had problems only when the phone was near the unbalanced cable, between the capsule and the connector, and not with the cable from the connector to the preamp. If that is truly the case, then I feel pretty confident that a balanced mic (like the SM11) would solve his particular problem.

That sounds encouraging.

I might have the terminology wrong, but here's the explanation in layman's terms:

The microphone itself (with the tie clip) has a thin wire that connects to the power pack. The power pack then outputs via XLR to the mixer.

The noise does not seem to come in on the XLR cable -- only on the thin wire between the microphone and the power pack. The intensity does not seem to vary if you slide the phone up or down this thin wire, leading me to believe that it's not necessarily the microphone itself, but just this thin wire that's picking up the noise.

[Richard Crowley]

Originally Posted by Luke Arndt

The noise does not seem to come in on the XLR cable -- only on the thin wire between the microphone and the power pack. The intensity does not seem to vary if you slide the phone up or down this thin wire, leading me to believe that it's not necessarily the microphone itself, but just this thin wire that's picking up the noise.

There is a (small) possibility that you can filter out the RFI using a ferrite bead aound that thin mic cable. The most effective would be to put 3-4 turns through a ferrite torroid, but that would be pretty clunky with a torroid big enough to pass the microphone head through. Or you could try some of the "snap-on" beads like those on this page...

Ferrites | AllElectronics.com

[Greg Miller]

Interesting suggestion, Richard. Your suggestion about several turns of mic wire through the ferrite is absolutely correct, and the snap-on type would make that easy to implement. FWIW, I've ordered from All Electronics before, they're reputable.

RF is very strange, in that it travels on the outside surface of a conductor, and does not penetrate to the inside. When cellphone RF intercepts the shield on the mic wire, it travels mostly on the outside of the shield. Ferrite acts like a low-pass filter, stopping the RF from traveling any farther along the wire. Using ferrite, as close as possible to the point where the wire enters the preamp or bodypack, would prevent [a lot of] the RF from continuing along the shield and into the preamp.

As you point out, there are still other ways that RF can get into the audio. But if the OP is really in love with his present mics, investing a few dollars to try some ferrite is certainly a worthwhile experiment.

[Pete Cofrancesco]

I do depositions for a living and only a couple of times encountered cell phone interference out of hundreds of depos. If there's a cell phone issue you politely ask for the phone to be shut off or moved away from the mic. I think you're making to much of this and like others have said wireless is a bad idea. One last thought this issue could be due to something else. Have you ruled out your mixer? What are you using for a mixer btw?

[Luke Arndt]

Originally Posted by Pete Cofrancesco

I do depositions for a living and only a couple of times encountered cell phone interference out of hundreds of depos. If there's a cell phone issue you politely ask for the phone to be shut off or moved away from the mic. I think you're making to much of this and like others have said wireless is a bad idea. One last thought this issue could be due to something else. Have you ruled out your mixer? What are you using for a mixer btw?

My mixer is a SignVideo ENG-44.

I'm fairly positive the mixer is not the issue. It appears that the only point of entry is between the microphone itself and the thin wire that connects the microphone to the power pack

If you don't mind, Pete, perhaps you can share what kind of microphones you use. I'm definitely open to buying new mics that handle the interference better.

It's not always a big deal, but sometimes somebody may have an iPhone in a shirt pocket just inches away from the mic. In a case like this, if there's a lot of phone activity, it can seriously mess with the audio.

[Richard Crowley]

There are a great many situations where people (participants, audience, etc) are asked to turn off their cell phones. I would think that a formal legal deposition would certainly be a place where the attorneys would be concerned about having the uninterrupted attention of the deponent or witness (as well as everyone else in the room). I am rather surprised that this is even a problem at all. If the attorneys didn't ask for cell phones to be turned off, as the videographer, I would take the initiative and state the conditions for proper behavior.

No electret microphone is immune from interference from a cell phone mere inches away.

[Shaun Roemich]

Originally Posted by Richard Crowley

There are a great many situations where people (participants, audience, etc) are asked to turn off their cell phones. I would think that a formal legal deposition would certainly be a place where the attorneys would be concerned about having the uninterrupted attention of the deponent or witness (as well as everyone else in the room). I am rather surprised that this is even a problem at all. If the attorneys didn't ask for cell phones to be turned off, as the videographer, I would take the initiative and state the conditions for proper behavior.
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Originally Posted by Pete Cofrancesco

If there's a cell phone issue you politely ask for the phone to be shut off or moved away from the mic

I don't do depo's but I do live television, web streaming and convention/conference work and MOST people seem to think "turn OFF your cell phone" means "turn it to vibrate or silent". I have ACTUALLY been told by speakers that "this is good enough and that's all I'm going to do".

Again, in a legal deposition, you may well have more influence but I can attest to TRYING to do the right thing and having been thwarted. Not once or twice but DOZENS of times.

[Richard Crowley]

Originally Posted by Shaun Roemich

I don't do depo's but I do live television, web streaming and convention/conference work and MOST people seem to think "turn OFF your cell phone" means "turn it to vibrate or silent". I have ACTUALLY been told by speakers that "this is good enough and that's all I'm going to do".

Again, in a legal deposition, you may well have more influence but I can attest to TRYING to do the right thing and having been thwarted. Not once or twice but DOZENS of times.

In that case, the production decision has been made by others, and any cell phone interference was pre-authorized by the "producer" so it is no longer my concern. End of discussion.

[Luke Arndt]

I understand it might not technically be my fault if somebody refuses to shut their phone off or thinks I want them to only turn the sound off, but I guess I'm more concerned with the end result.

It seems like some pieces of equipment deal with the GSM interference better than others, so my goal is to just give myself the best chance possible to have a clean audio feed, knowing that it's not always doable to have all the cell phones off all the time. Knowing how attached people can get to their phones, I sure would love a way to not even have to make that an issue for people.

Again, thanks for all the input, guys!

[Greg Miller]

This whole issue -- turning off every phone, whose job it is to enforce the rule, and who is responsible if someone doesn't comply -- may be an interesting philosophical discussion, but it's not a technical solution. Why belabor the point?

Everyone knows you're recording a deposition. You don't need a "micro-mic" that's nearly invisible. Get the mic that is technically right for the job, and you can forget all the other issues.

Originally Posted by Luke Arndt

It appears that the only point of entry is between the microphone itself and the thin wire that connects the microphone to the power pack

I'm definitely open to buying new mics that handle the interference better.

Then get the SM11 dynamic, which is fully balanced, and you should never have to think about cellphone interference again.

Any electret will be susceptible to some degree... you'll never know how much until it's too late. Do you want to make this an endless research project, or do you want to have clean audio every time? If the latter, just get the SM11 dynamic and get on with recording. My gosh, they're only $100 at B&H, it doesn't get any better than that.

[Pete Cofrancesco]

Originally Posted by Luke Arndt

My mixer is a SignVideo ENG-44.

I'm fairly positive the mixer is not the issue. It appears that the only point of entry is between the microphone itself and the thin wire that connects the microphone to the power pack

If you don't mind, Pete, perhaps you can share what kind of microphones you use. I'm definitely open to buying new mics that handle the interference better.

It's not always a big deal, but sometimes somebody may have an iPhone in a shirt pocket just inches away from the mic. In a case like this, if there's a lot of phone activity, it can seriously mess with the audio.

I use Audio-Technica AT899. These are very similar to what you're using, they just have a smaller more professional looking mic, but they still have the thin wire from the mic to the power adapter module. In fact all wired lavs are going to be setup this way. It wouldn't be feasible to run a shielded xlr to a lapel mic.

I use the same mixer but had to send it in for repair due to noise issues. Btw, I don't have a high regard for the SignVideo mixer, I've used better cleaner sounding ones. Note that ungrounded power can cause issues too.

As to phone use, the atty taking the depo and the witness shouldn't be using a phone, which only leaves the other atty which you can turn down his mic since he only makes periodic objections.

[Greg Miller]

Originally Posted by Pete Cofrancesco

but they still have the thin wire from the mic to the power adapter module. In fact all wired lavs are going to be setup this way. It wouldn't be feasible to run a shielded xlr to a lapel mic

Pete, I hate to be picky... maybe we have an issue with the term "lapel mic." What you say is true of electret lapel mics, but it is not true of "all wired lavs."

The Shure SM11 is sold as a "miniature dynamic lavalier microphone." It is 1.5" long, and 9/16" diameter. It is supplied with a tie clasp and a tie tack. It could easily clip on a lapel, for deposition recording.

The SM11 is dynamic, not electret. It is truly balanced. The data sheet says, "Cable: non-detachable two-conductor, shielded." This mic is balanced all the way from the mic body to the XLR connector. Unlike electrets there is no "power adapter module" and there is no unbalanced wiring. If you don't take my word for it, read the data sheet, or look at the info on the B&H product page.

Indeed, the SM11 is unusual; there are few other current-day dynamic lavs. Since it is dynamic, it is balanced end-to-end. That's what makes it a unique solution for Luke's problem.

Sorry to be repetitious here (I realize I've already said the above in post #17 and #20) but people seem to be missing the point that this is a fully balanced dynamic, and not an electret.

[Greg Bellotte]

Originally Posted by Greg Miller

"miniature dynamic lavalier microphone." It is 1.5" long, and 9/16" diameter.

MINIATURE? Do they make a tie clip for the SM58 too? :-)

[Greg Miller]

I can remember when SOTA lavalier mics were really lavaliers, worn on a cord around the neck. And they were only slightly smaller than an SM57 is today. Sorry if some of you youngsters don't have the same frame of reference. ;-)

The SM11 is indeed quite small for a dynamic lav, and it would be quite comfortable clipped to a lapel for depositions.

Besides, if this solves the GSM problem for all time, do you really care if this microphone looks like... a tiny microphone? Would you rather have a mic the size of a kernel of corn, and interference from cellphones? I thought we were looking for a technical solution to GSM interference, when recording depositions.

[Luke Arndt]

Originally Posted by Greg Miller

I can remember when SOTA lavalier mics were really lavaliers, worn on a cord around the neck. And they were only slightly smaller than an SM57 is today. Sorry if some of you youngsters don't have the same frame of reference. ;-)

The SM11 is indeed quite small for a dynamic lav, and it would be quite comfortable clipped to a lapel for depositions.

Besides, if this solves the GSM problem for all time, do you really care if this microphone looks like... a tiny microphone? Would you rather have a mic the size of a kernel of corn, and interference from cellphones? I thought we were looking for a technical solution to GSM interference, when recording depositions.

That SM11 sounds wonderful. I think I'll try to get my hands on one. If that works, it will make life a lot easier. :)

And you're right. In a case like this, I don't really mind if the microphone isn't the absolute thinnest.

If I get my hands on the SM11, I'll be sure to report back with how it performs!