Sennheiser AVX + Zoom H6 interference?

[Bruce Watson]

[Troy Grady] “And the AVX units plug right into it with no additional cables, and no analog interference in the signal – they’re digital over the air.”

RFI is RFI, it doesn’t care if your signal is analog or digital. There’s nothing magical about digital encoding that will save it from RFI. You can increase the ability to recognize and correct missing or deformed bits in the packet, but if your ECC code has to get bigger than the the data it’s trying to protect, where do you stop? For example, computer data on DAT tapes used to be able to find and correct errors 17 consecutive bits wide — the ECC bits well outnumbered the data bits to do it though (1024 ECC bits for every 768 data bits IIRC). Not exactly efficient, that. I’m just sayin’ that “digital reliability” has its cost.

As to your noise problem, try increasing the separation between the transmitter and the receiver. See what that does to the noise. No, I’m not kidding.

The problems you are having with radio mics are why I always say that wireless is a last resort. Not a first, but a last resort. If I can use a cable, I always use a cable. For sit down interviews I *always* use a balanced XLR cable. It sounds better, it’s way more reliable, it’s way cheaper, no latency issues, etc.

[Alan Lloyd]

Touching the unit and having the noise decrease could be significant.

Just out of curiosity, is there anything HD-SDI in proximity that’s not using properly rated cabling?

[Ty Ford]

Hello Troy,

Is it possible that the preamps in your recording studio have transformer inputs and the rest of your gear does not?

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford\’s Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford\’s Blog

[Troy Grady]

Hi Bruce! Thanks for the notes. We’d love to do a wired setup but we do a mix of walking and talking and sitting and talking, and the wireless affords us that flexibility. It’s also less to pack in the bag. When it works, it sounds great.

I probably misspoke re: the digital-over-the-air signa, but in general, every digital wireless system I’ve used has delivered a lower noise floor, more neutral frequency response, less intermittent compander noise when the talent speaks or stops speaking, and no occasional analog “hits”. In this case the buzzing seems way out of spec.

We did another shoot over the weekend where the receivers were plugged into six-foot XLR cables and located away from the recorder, and away from each other, and that seemed to work. Not sure how reliable that’s going to be though. And it really defeats the purpose of plug-receivers with integral XLR jacks.

[Troy Grady]

Hi Alan! Thanks for the response. Nothing with an SDI output on it in our bag. Even when I just use the Zoom on its own, with no other gear fired up, I’m getting this interference when the receivers are plugged directly into the XLRs on the recorder.

[Troy Grady]

Hi Ty-

Indeed, the studio runs on 16 channels of transformer preamps. Over the weekend we did another shoot with the Zoom where the receivers were plugged into six-foot XLR cables into the Zoom, and located as far away from each other and the recorder as possible. Those recordings were (as best I can tell) noise free. But I don’t know how reliable this is going to be moving forward.

[Bruce Watson]

[Troy Grady] “We did another shoot over the weekend where the receivers were plugged into six-foot XLR cables and located away from the recorder, and away from each other, and that seemed to work. Not sure how reliable that’s going to be though.”

Interesting how that works. It’s almost like magnetic interference. Whatever it is, you’re not the first to experience it, nor to find out that spacing the transmitter and receiver away from each other is “the cure” for it. I’m thinking Sennheiser has some work to do on the AVX line. But it’s new, and all new stuff gets refined after the engineers see what really happens in the field.

[Troy Grady]

In this case proximity to the recorder seems to be what’s doing it, not so much proximity to the transmitters. It’s when you bring the compact little receiver units near the Zoom unit, and also near to each other while being near the Zoom, that the buzz is more prominent. Which is a shame because the receivers are designed to directly plug into portable recorders without the need for cables.

The effect is random and I’m not sure I’m properly isolating this, but that appears to be in broad strokes what’s happening. Whether it’s a shielding issue with the Zoom, or something with the AVX, I don’t know. My fear is that it’s more like a dreaded “inter vendor” interaction between both units, which neither company is aware of / can fix.

[Ty Ford]

Hi,

I spoke with Lachlan Brennan at Sennheiser and he was kind enough to do some work and find an answer. Please note below.

Now that I have had the chance to confer with some colleagues I wanted to touch base with you regarding this AVX issue. Based on what I have heard from various colleagues it appears that this is a sporadic issue and it depends on the specific Zoom H6 recorder being used as to whether the issue presents itself. With some recorders there is no issue and with some recorders there is the issue.

Often with digital systems there is more proximity sensitivity than there is with a traditional analog system and depending on how the various components are grounded/shielded there could be “noise” issues. With the digital systems like AVX and EW D1 we needed to redesign the lavaliere microphones that connect to them to have more shielding so that proximity noise was not an issue.

I suspect that with older Zoom H6’s there may be a slight grounding or shielding issue that can cause noise when the receiver is in close proximity. This would not be an issue with an analog system but could present issues like those described with a digital system.

A work around would be to use a short extension cable to get a little distance between the receiver and the Zoom H6.

Also you might want to note that if any members of the site do need Technical Support they can reach the Tech Support Team on 1-(877)-736-6434 option 3 in the phone menu and we are more than happy to assist them.

Have a great day.

Lachlan

Want better production audio?: Ty Ford\’s Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford\’s Blog

[Troy Grady]

Ty-

Thanks so much for following up here, and sorry for the slow response time. I did actually place a call to Sennheiser a few weeks ago and the tech I spoke to wasn’t aware of any H6 compatibility issues. Since then, I’ve noticed the interference with other devices. Namely, a Centrance MicPort Pro portable audio interface, which has been dead reliable for a decade. In use with a MacBook Pro and a six-foot mic cable, I was still getting interference no matter how much distance I put between the receiver, transmitter, and MacBook.

I’ll probably put in another call so they’re aware of this. If it’s simply, as Lachlan says, the digital wireless is a little problematic with interference, that’s a shame. These were pricey units and the sound quality is good when they work.

In the mean time we’ll be looking into those new Tascam body pack recorders, the DR-10L, for anything where wireless isn’t strictly necessary. Those look pretty cool and the price is right.

Troy