David Waelder Posted December 7, 2007 Report Share Posted December 7, 2007 I am a fan of the short Neumann microphones - the KMR 140, 150, 185 etc. They have served me well on many projects. Lately I have been noticing some noise when I use them in a quiet environment with a cordless boom configuration. They are very quiet - at least, quiet enough for movie work - when hard wired but there is an undertone of noise when hooked up to a radio transmitter. I can only describe this noise as a crackling hash. It is sufficiently background that I have successfully used the mikes outdoors, or in noisy interiors, without harm but it is disturbing when used indoors in a quiet environment. At first I thought it was a problem with my radio transmitter or, possibly, interference from an on-cart IFB transmitter. Maybe one of the battery chargers I keep on the cart throws off some RF that I would notice only in a critical listening situation. Well, I ran some careful tests and I'm pretty sure it isn't any of those things. I have swapped out transmitters, receivers, locations of gear on the cart, mixing panels, antennae, etc. etc. I have used components in different combinations and different locations. I have simplified hook-ups, eliminating patch panels, using whip antennae directly on the receivers, etc. I have pulled all AC power delivered to the cart with no effect. I have exchanged phantom power supplies and also measured voltage at the terminals (52 volts with no load) and eliminated those as culprits. So, with all these tests, I am confident that it's not: the transmitter (Lectro 200 series & 400 series) the phantom power supply the receiver the antenna the position of the receiver on the cart whether other elements are operating on the cart whether or not AC power is delivered to the cart which mixing panel is in use No matter how I configure things, the short Neumanns (I tested 2) make noise and a longer Neumann (KMR 81) is quiet. It's a consistent pattern. One of those Neumanns was recently in Connecticut to correct a problem with susceptibility to RF interference. The service shop put in a new circuit board so it is fitted with the very latest electrical design. (And, by the way, has been very RF resistant ever since.) So, my question to the group is: How do I proceed now? One obvious solution is to purchase a pair of the new Sennheiser 8050s (or a pair of MKH 50s or one 8050 and one 8040). I am seriously considering this or some variation. But that's an expensive solution and I want to make some investigation before going that route. Has anyone else experienced this problem? Is there a reasonable solution? Possibly some sort of filter trap in the cable from the transmitter? Thanks for your help. (& sorry for the long post) David Waelder Quote Link to comment Share on other sites More sharing options...
Yanna Posted October 9, 2019 Report Share Posted October 9, 2019 Hey David, its been a long time since your post, but I have a similar problem with my kmr 185’s. I can’t use them wireless in quiet indoor places. I use the lectrosonics plugon or a ssm with 48V supply. did you find a solution for that? thanks Quote Link to comment Share on other sites More sharing options...
soundchris Posted October 9, 2019 Report Share Posted October 9, 2019 Maybe this little device from AudioLtd can help you: http://www.audioltd.com/tech-articles/a-filter-rf-filter-for-balanced-microphones/ Quote Link to comment Share on other sites More sharing options...
David Waelder Posted October 9, 2019 Author Report Share Posted October 9, 2019 Regrettably, I never did identify the cause of the noise I heard with some Neumann mikes in a radio boom situation. I did learn that the shotguns (KMR 81 & KMR 82) are electronically different than the shorter mikes but I don't recall how they differ. The Audio Ltd device is probably worth a try but I'm not sure that the noise came from RF interference. Rather, I think it was some sort of incompatibility between the components. But, worth a try. I acquired a set of Sennheiser 8050's and the mysterious noise problem was never heard from again. David Quote Link to comment Share on other sites More sharing options...
Johnny Karlsson Posted October 9, 2019 Report Share Posted October 9, 2019 I haven’t looked at the actual specs, but just an idea to check: maybe this mic needs a full 48v phantom supplied. This would explain why it sounds fine when hard wired. Quote Link to comment Share on other sites More sharing options...
engaudio Posted October 9, 2019 Report Share Posted October 9, 2019 I gave up using my km185 because it was too noisy for quiet talkers (hard wired). My kmr81 would buzz around fluro lighting, otherwise I loved the sound of the neumanns. They both were stolen a few years ago and replaced with a mkh50/dpa 4017, I use the mkh50 probably 90% of the time now. Grant. Quote Link to comment Share on other sites More sharing options...
David Waelder Posted October 10, 2019 Author Report Share Posted October 10, 2019 3 hours ago, Johnny Karlsson said: maybe this mic needs a full 48v phantom supplied. That is, indeed, a good line of inquiry. And, it was one of the first things I investigated. That’s not it. Quote Link to comment Share on other sites More sharing options...
joinwooHK Posted October 10, 2019 Report Share Posted October 10, 2019 just plug the mic hard wire to the recorder ,and then turn on other suspect one by one ,You then find which one causing interference or it is self noise of the boom transmitter Quote Link to comment Share on other sites More sharing options...
chrisnewton Posted October 14, 2019 Report Share Posted October 14, 2019 I have also had problems with a KM150 for wireless boom. With a Lectro butt-plug the KM150 didn't work at all. I needed a phase reversal adaptor to make it work. I believe it's because my older KM150 is pin 1 hot. With a Sony UWP-D plug on TX the KM150 worked fine, but I did get occasional RF "hash" in some circumstances. works just fine hard wired. My MKH8060 has zero problems with plug ons of any stripe. Quote Link to comment Share on other sites More sharing options...
David Waelder Posted October 14, 2019 Author Report Share Posted October 14, 2019 1 hour ago, chrisnewton said: I needed a phase reversal adaptor to make it work Yes, that’s a known issue with the Neumann mikes. However, it doesn’t seem to be related to the noise issue. That seems to be some sort of incompatibility between circuits but the particulars remain a mystery. (At least to me) This problem was one of the reasons I stopped using phantom power supplies, like the Denecke 48v unit, in favor of the Sound Devices MM series preamps. At a distance of a dozen years I no longer accurately remember the sequence of attempted remedies. I’m not sure if use of MM preamps was a remedy or if the issue wasn’t resolved until I acquired the Sennheiser 8050’s. David Quote Link to comment Share on other sites More sharing options...
traut Posted October 14, 2019 Report Share Posted October 14, 2019 I used Neumanns with a VdB 48 v cable to Audio Ltd xmttrs. Worked great. Quote Link to comment Share on other sites More sharing options...
Manel Posted January 11, 2021 Report Share Posted January 11, 2021 On 10/15/2019 at 5:56 AM, David Waelder said: Yes, that’s a known issue with the Neumann mikes. However, it doesn’t seem to be related to the noise issue. That seems to be some sort of incompatibility between circuits but the particulars remain a mystery. (At least to me) This problem was one of the reasons I stopped using phantom power supplies, like the Denecke 48v unit, in favor of the Sound Devices MM series preamps. At a distance of a dozen years I no longer accurately remember the sequence of attempted remedies. I’m not sure if use of MM preamps was a remedy or if the issue wasn’t resolved until I acquired the Sennheiser 8050’s. David Hi David, can I ask you what mounts are you using with your 8050? Cheers Quote Link to comment Share on other sites More sharing options...
David Waelder Posted January 11, 2021 Author Report Share Posted January 11, 2021 5 hours ago, Manel said: Hi David, can I ask you what mounts are you using with your 8050? Cheers I've been using the Rycote Invision mounts. They've worked well for me. David Quote Link to comment Share on other sites More sharing options...
Manel Posted January 14, 2021 Report Share Posted January 14, 2021 Thanks a lot. I tried Inv-Lite but is no good. I'll try the lighter one. Quote Link to comment Share on other sites More sharing options...
Trey LaCroix Posted January 18, 2021 Report Share Posted January 18, 2021 On 1/14/2021 at 2:14 PM, Manel said: Thanks a lot. I tried Inv-Lite but is no good. I'll try the lighter one. The Cinela OSIX is great with the 8040/50. Don’t own an 8050 but have boomed with that combo and it was great! Quote Link to comment Share on other sites More sharing options...
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