KM184 - glitchy noise on string 4tet recording

[mathieujm]

No particular noise but the natural effects of special strings playing techniques.

Edit : yes i didn't push the volume enough... Cell phone. My little DR05 don't like cell phones as well. But my real mics never had this problem.

[NorseHorse]

You are hearing a cell phone.

[mahler007]

Originally Posted by NorseHorse

You are hearing a cell phone.

Is this true!?!?
If so, wow... is it only certain kinds of mics that are susceptible to this kind of interference?

Thanks,
Andrew

[Schallfeldwebel]

A cellphone indeed. You never know where it comes from. Probably a bad cable, I don't think the microphone, must have been pretty close, and I do not suspect the Neumann, unless something is wrong with that microphone.

[Rolo 46]

Neutrik make an XLR to defeat RFI, the emc .

EMC Series - Neutrik

[mahler007]

Originally Posted by Schallfeldwebel

A cellphone indeed. You never know where it comes from. Probably a bad cable, I don't think the microphone, must have been pretty close, and I do not suspect the Neumann, unless something is wrong with that microphone.

Great, thanks so much. This is a load off my mind.

Assuming the mic is OK, is there any way to avoid this in the future? It seems like if the cable were bad, I would have experienced another problem, like a loss of gain or connectivity in that particular channel.

Am I overlooking something?

Thanks,
Andrew

[mahler007]

Originally Posted by Rolo 46

Neutrik make an XLR to defeat RFI, the emc .

EMC Series - Neutrik

Great — thanks. Good to know!

A

[Lotus 7]

Also to consider: Were you using the same type of mic cables on each channel?

I occasionally record in a downtown venue (a hotel ballroom) located in a high rise building very near another building with an array of TV transmitters on the roof. Had some nasty (59.94 Hz) vertical scan rate buzz in several mics. I was using some quality "regular 2-wire" balanced mic cables and some 4-wire Star Quads. The double-balanced Star Quads were quiet and apparently rejecting the RFI. Made me a believer and I now only use double-balanced cables on location.

Some cables have better braid coverage (often varies from about 92% [poor] to 100% [great], thinner insulation on the conductors which causes the cable capacitance to be higher (better RFI filtering), and/or different twisted-pair winding pitch (which can also affect RF rejection).

Now that all USA TV transmission is fully digital, the potential for interference into audio is even higher near transmitters.

[Lou]

hahahaaha. We've recorded that noise before and used it in radio imaging to **** with people.

[Foldedpath]

The KM184 apparently went through a small redesign a while back (maybe 10 years?), and the newer production versions are rumored to be a little more resistant to RF. I don't know if there was an actual problem with the original design, or if they were just beefing up resistance to the effect that will hit any mic if the RF field is strong enough. Here's a comment from David Satz about it on the Neumann forum (2nd post in):

Microphone Applications - Km 184 and km 185

I own two KM184's bought about 15 years ago, so they must be in the original series, and I've never had an RF problem with them. I've read elsewhere (can't remember the source) that the problem is reduced or eliminated when using preamps with transformer inputs, which is what I tend to use with my 184's anyway. So maybe that's one thing to investigate if an RF-resistant cable doesn't do the trick.

Also... no kidding... I've heard that wrapping the mic in tinfoil works (presumably including connection to the cable connector shell). Do they make tinfoil in a black color?

[David Spearritt]

Not sure a plug replacement will fix the problem. Under their instruction, we sent a number of early KM184's back to Neumann for a board replacement, as some tracks on the board "resonated" with the cell phone 900MHz and caused the interference noise in your sample recording.

[Lotus 7]

Originally Posted by Foldedpath

...Also... no kidding... I've heard that wrapping the mic in tinfoil works (presumably including connection to the cable connector shell). Do they make tinfoil in a black color?

It could very well help if it is local RF pickup. They do make aluminum foil in black (but the Neumann and Schoeps certified versions (with logos) cost a lot more).

However, probably not a good idea to wrap the front grill of the mic.

[tourtelot]

Originally Posted by mahler007

Great, thanks so much. This is a load off my mind.

Assuming the mic is OK, is there any way to avoid this in the future? It seems like if the cable were bad, I would have experienced another problem, like a loss of gain or connectivity in that particular channel.

Am I overlooking something?

Thanks,
Andrew

Yes. Tell the people in the studio, on the stage, around your location array etc. etc. to turn off (OFF! Not silent) their f'ing cell phones. It is a constant battle that I fight on television series sets; actors are unaware that their phones cause a problem and sometimes don't believe me when I tell them. Always great to walk out after a take and say "someone still has a phone on." Everyone denies it, of course and then I'll see some one of them sneak into their pocket and fish around for their phone. Dummies!!

D.

[Foldedpath]

Originally Posted by tourtelot

Yes. Tell the people in the studio, on the stage, around your location array etc. etc. to turn off (OFF! Not silent) their f'ing cell phones. It is a constant battle that I fight on television series sets; actors are unaware that their phones cause a problem and sometimes don't believe me when I tell them. Always great to walk out after a take and say "someone still has a phone on." Everyone denies it, of course and then I'll see some one of them sneak into their pocket and fish around for their phone. Dummies!!
D.

Good in theory, but hard in practice, except on a film/video set where there should be more control. Yes, there's no excuse on a set, but concerts are different.

I went to a concert last night (Natalie MacMaster, fabulous Cape Breton fiddler and band) where I reminded my wife to turn off her cell phone. She said she had already done it, putting it on vibrate.

That's not off, but the world at large thinks it's "off" and I don't think it's worth arguing the point. I could have had my wife turn it completely off, in respect for any legit recording being made at the concert, but that wouldn't affect 500 other people with their cell phones in the hall, set to vibrate. You can't fight against all those pending baby-sitter calls. And isn't there a regular ping for cell phones even when they're turned off?

[tourtelot]

Agreed of course; you can't make a whole auditorium of paying patrons turn their phones off. That wasn't my point. But you have to be rather closer than 5th row center for cell phones to get into any professionally wired recording rig. My mics sit a foot over the perpetrators' heads. My phone, at the sound cart doesn't get in unless I set it on the deck alongside the recorder But talent should be forewarned that a silenced cellphone on stage could well ruin their great work. That should be a fairly easy group to police, in theory. I always give my players "the talk" and mostly, it is well received. Self-centered actors are a harder sell.

D.

[Lotus 7]

And unfortunately, it's not going to get any better with virtually everyone carrying one or more wireless devices and the wireless services offering higher and higher bandwidth uploads and downloads.

A system that was interference-free last year may not be so next week.

Currently in the US we have cellular voice on 850, 1700, 1900, & 2100 MHz, G3 digital on all of those frequencies and G4 digital on all of those plus 700, 800, 2500 & 2600 MHz. Additionally, in weak reception areas like most performance spaces, the phones will switch up to maximum transmitter power levels as soon as they detect a reduced received signal.

The public simply doesn't understand that even when their phone is set for "silent" and they don't answer a call, their phone sends a ring acknowledgement response whenever it receives an attempted call.

It's very important to have well shielded equipment with good RFI rejection, and will become even more important in the future.

[Pearlslut]

I have been using a pair KM184s (about 15 year old) for location stereo recording and have been plagued by digital cell phone pulse. It is worse the closer the mics are to the audience. There is one particular church where the players are right in front of the 1st pew so the mics are right in the audience. I've been saving up and finally sprung for a matched pair of Schoeps CMC6 w MK4 heads.

I just did a recording in the same church and the only change with my equipment was swapping out the 184s for the MK4s. The result was that I didn't hear anything other then clean clear instruments playing music! NO digital anything! The schoeps are vastly superior to my ears for this application and they don't have the problem with RF noise. Howard

[amfortas2006]

The new Neumann KM-A series have took care of that problem.. Or so they say. I'm using mine and have not noticed that cell phones are a problem. I also use Neutrik EMC series XLR connectors with them... (Enchanced RF screening)

[matthewd]

We have encountered this type of interference more often as a result of a mobile, especially Blackberry in the control room close to the preamps or desk. I am not saying we haven't had it at the other end of the chain but it is quite embarrassing when you tell the musicians off for having their phones on only to find it is yours in the control room which is causing the issue. A few years ago we used to dismiss the loud GSM type noise you often got on the basis it was always heard on the monitors but never made it onto the recording. This 3G type interference however does make it onto the recording and so we insist on flight mode in the control room.