Wireless mic questions at DVinfo.net

Rob Harlan · July 30th, 2010, 07:43 AM

Re: wireless lav tie-clip mic on groom during ceremony - a couple of recent issues:-

1] After testing in church before the ceremony, all sounded good through the camera headphones. Camera input levels were set as normal. I was away from headphones for a while, until the bride had arrived down the aisle. Upon plugging back in at the beginning of the service... aural chaos: a squelchy, clipped, nasty sound from the Reverend. He was using a radio lapel mic of his own, which probably wasn't turned on (or nearby) when I made the initial test.

After some flapping with my mic receiver (moving the thing around, adjusting the aerials, taking mic plug out and back in, switching mic off and on, treble checking the audio levels etc) it looked like I was stuck with this problem so I quickly switched to my only alternative at the moment which is my shotgun microphone. Not ideal but after holding its own during the Reverend's bits, I tried the wireless mic in again one more time and mercifully the 'interference' had passed.

My wireless mic system is a mains powered unit, and I connect through the 3.5mm jack to the camera. Also I have a rather skinny 3.5mm jack in/out extension lead connecting it to the camera (so I can have some flexibility of movement with the receiver plugged into the mains).

Question: is it likely my lack of XLR connection could have contributed to the initial audio fuzz? I have recorded services when the Reverend has a radio mic before with no issues - but perhaps my luck had run out using the 3.5mm mic jack method? Or would an XLR have made little or no difference to this situation? I have 4 'channels' on my radio mic transmitter/receiver, but even if I changed channel on my receiver I would not have been able to reach the groom once the ceremony started to change his trasmitter to the corresponding channel.

2] Editing some ceremonies, I notice when scrutinising the radio mic audio that in some locations there seems to be a little 'background fuzz' rears its head when the officiant speaks. By this I mean that although the voice recording seems well balanced, loud and quite clear, I can however sometimes detect a faint 'mushiness' in the background of the louder voices - as if something, perhaps a 'digital' symptom of some sort, is attacking the clarity of the spoken words. This seems to come in especially when the officiant (usually the loudest at the ceremony) speaks, and goes away when his/her sentence is over.

This issue doesn't strike me as 'interference', because I can only sense it when someone is actually speaking - i.e. when the mic has 'work to do' I suppose. My radio mic is UHF by the way. The issue is not noticeable on normal listening, but when I am sound editing with the headphones on and look for it, I can hear it.

Anyone well versed in wireless sound recording then: could the 3.5mm jack connections (rather than XLR) and/or thin extension wire I'm using be a cause of any of these issues? Is upgrading to the popular Sennheiser kits a must, or will I likely encounter the same problems?

Thanks for any advice.

Chris Harding · July 30th, 2010, 07:01 PM

Hi Rob

I think that using a mains based unit is the start of your issues as it will certainly not be designed for wedding video at all. I personally use Azden UHF pairs which have never given me an issue but even with the correct units there is no guarantee that you will always have perfect reception. You cannot control external sources!!!

If you are going the radio mic route then choose a pro unit with the receiver on your camera and all on battery. Don't be tempted into the cheap UHF sets from Asia...they seldom work correctly so choose a brand name that is made for the job.

You might also want to consider dropping a Zoom H2 into the groom's pocket which will be virtually safe from any influences ..however you will have to sync the audio in post!!!

Chris

Philip Howells · July 30th, 2010, 09:56 PM

Rob, I think we need considerably more details than you've provided - not least whether the officiant's radio mic was on the same or near frequency. Personally I'd never consider jacks of any sort - not only is the connection not secure but the actual contact area in the connection is a small point, a minute part of the metal surface. One tiny bit of dirt in the wrong place and you're sunk. In contrast XLRs lock and each pin is grasped by its socket.

Like Chris I'd never use any mains unit at a wedding - you never know what else is on the ring and in the UK at least it avoids you being asked by an officious Heath and Safety person to see your PAT testing certificate. I've even seen a Registrar put on her H&S hat and demand the hotel disconnect and remove an intriguing array of mains adapters and extensions supplying power to a critical display.

If the answers you get here aren't very helpful you might try posting a similar but different question in the sound section of this forum. There are some very clever people there.

Rob Harlan · July 31st, 2010, 09:40 AM

My wireless mics do not seem to display frequency, they simply have 4 options for channels.

Next time I will ask the officiant to switch on his own mic while I run pre-ceremony test, and change the channels on transmitter and receiver if there are issues. I'll also buy a jack to XLR lead which I think will help.

I guess I will upgrade to one of the battery-powered Sennheisers shortly - about six times as expensive as my current wireless setup, but if they are more reliable performers all round then I suppose a wise investment.

Paul R Johnson · July 31st, 2010, 10:06 AM

The clue here is 4 channels. You have a consumer intended, license free system that gives you a one in four chance of being on the same channel as the vicar! (Assuming he has the same kit). These frequencies in channel 70 are not suitable for interference free use in an unknown environment, and from 2012 will be even worse, as all the users of lower channels suddenly get cellphone interference, and shift up into an already busy slot.

There is no problem whatsoever with using mains powered receivers - the only downside is the cable. If you have the gain set so that levels do not exceed the maximum the camera input can handle without distortion, then the problem you found is most likely to be intermodulation from an adjacent frequency - this can be a mild burble, or a nasty distortion but doesn't sound like the distortion you get when accidentally driving an input too hard. Connectors can fall out (with non-locking jacks), or even get bent if the cables are tugged - but if you've got suitable cables and can manage them properly, I'd be happy using them. Mains receivers are also usually diversity - making drop outs less likely - only expensive radio systems that work on batteries have this feature. Cheaper ones don't!

Cheap radio systems are like balancing on a high wire - at some point, you'll fall off! Cheap ones often have good performance, and sound quite good, lulling you into a false sense of security.

It's really common for me to have to provide alternate radio kit when visiting people's kit misbehaves - almost every week a piece of nice, expensive radio kit makes nasty noises - and it's far simpler to be able to just hand them something else that I know will work.

I did a Cannon & Ball show in a big theatre at the seaside. During the show, a big panic when a man came to the sound desk and demanded I turn them off. It seems that there was a National Bowls Championship on the bowling greens, two or three hundred metres away - and they'd gone home, locking up - but leaving their sound system on. Trouble was it was on the same channel as Bobby Ball - so everything he said was broadcast to everyone on the promenade! This was his own system, on channel 70. Swapping to one of my 'more private' ones on 69 solved the problem for the second half of the show.

Channel 70 is bad news!

July 30th, 2010, 07:43 AM	#1
Rob Harlan Regular Crew Join Date: Jan 2010 Location: UK Posts: 62	Wireless mic questions Re: wireless lav tie-clip mic on groom during ceremony - a couple of recent issues:- 1] After testing in church before the ceremony, all sounded good through the camera headphones. Camera input levels were set as normal. I was away from headphones for a while, until the bride had arrived down the aisle. Upon plugging back in at the beginning of the service... aural chaos: a squelchy, clipped, nasty sound from the Reverend. He was using a radio lapel mic of his own, which probably wasn't turned on (or nearby) when I made the initial test. After some flapping with my mic receiver (moving the thing around, adjusting the aerials, taking mic plug out and back in, switching mic off and on, treble checking the audio levels etc) it looked like I was stuck with this problem so I quickly switched to my only alternative at the moment which is my shotgun microphone. Not ideal but after holding its own during the Reverend's bits, I tried the wireless mic in again one more time and mercifully the 'interference' had passed. My wireless mic system is a mains powered unit, and I connect through the 3.5mm jack to the camera. Also I have a rather skinny 3.5mm jack in/out extension lead connecting it to the camera (so I can have some flexibility of movement with the receiver plugged into the mains). Question: is it likely my lack of XLR connection could have contributed to the initial audio fuzz? I have recorded services when the Reverend has a radio mic before with no issues - but perhaps my luck had run out using the 3.5mm mic jack method? Or would an XLR have made little or no difference to this situation? I have 4 'channels' on my radio mic transmitter/receiver, but even if I changed channel on my receiver I would not have been able to reach the groom once the ceremony started to change his trasmitter to the corresponding channel. 2] Editing some ceremonies, I notice when scrutinising the radio mic audio that in some locations there seems to be a little 'background fuzz' rears its head when the officiant speaks. By this I mean that although the voice recording seems well balanced, loud and quite clear, I can however sometimes detect a faint 'mushiness' in the background of the louder voices - as if something, perhaps a 'digital' symptom of some sort, is attacking the clarity of the spoken words. This seems to come in especially when the officiant (usually the loudest at the ceremony) speaks, and goes away when his/her sentence is over. This issue doesn't strike me as 'interference', because I can only sense it when someone is actually speaking - i.e. when the mic has 'work to do' I suppose. My radio mic is UHF by the way. The issue is not noticeable on normal listening, but when I am sound editing with the headphones on and look for it, I can hear it. Anyone well versed in wireless sound recording then: could the 3.5mm jack connections (rather than XLR) and/or thin extension wire I'm using be a cause of any of these issues? Is upgrading to the popular Sennheiser kits a must, or will I likely encounter the same problems? Thanks for any advice.

July 30th, 2010, 07:01 PM	#2
Chris Harding Inner Circle Join Date: Jul 2009 Location: Perth, Western Australia Posts: 8,441	Hi Rob I think that using a mains based unit is the start of your issues as it will certainly not be designed for wedding video at all. I personally use Azden UHF pairs which have never given me an issue but even with the correct units there is no guarantee that you will always have perfect reception. You cannot control external sources!!! If you are going the radio mic route then choose a pro unit with the receiver on your camera and all on battery. Don't be tempted into the cheap UHF sets from Asia...they seldom work correctly so choose a brand name that is made for the job. You might also want to consider dropping a Zoom H2 into the groom's pocket which will be virtually safe from any influences ..however you will have to sync the audio in post!!! Chris

July 30th, 2010, 09:56 PM	#3
Philip Howells Trustee Join Date: Jan 2009 Location: Manchester UK Posts: 1,212	Rob, I think we need considerably more details than you've provided - not least whether the officiant's radio mic was on the same or near frequency. Personally I'd never consider jacks of any sort - not only is the connection not secure but the actual contact area in the connection is a small point, a minute part of the metal surface. One tiny bit of dirt in the wrong place and you're sunk. In contrast XLRs lock and each pin is grasped by its socket. Like Chris I'd never use any mains unit at a wedding - you never know what else is on the ring and in the UK at least it avoids you being asked by an officious Heath and Safety person to see your PAT testing certificate. I've even seen a Registrar put on her H&S hat and demand the hotel disconnect and remove an intriguing array of mains adapters and extensions supplying power to a critical display. If the answers you get here aren't very helpful you might try posting a similar but different question in the sound section of this forum. There are some very clever people there.

July 31st, 2010, 09:40 AM	#4
Rob Harlan Regular Crew Join Date: Jan 2010 Location: UK Posts: 62	My wireless mics do not seem to display frequency, they simply have 4 options for channels. Next time I will ask the officiant to switch on his own mic while I run pre-ceremony test, and change the channels on transmitter and receiver if there are issues. I'll also buy a jack to XLR lead which I think will help. I guess I will upgrade to one of the battery-powered Sennheisers shortly - about six times as expensive as my current wireless setup, but if they are more reliable performers all round then I suppose a wise investment.

July 31st, 2010, 10:06 AM	#5
Paul R Johnson Inner Circle Join Date: Nov 2005 Location: Lowestoft - UK Posts: 4,044	The clue here is 4 channels. You have a consumer intended, license free system that gives you a one in four chance of being on the same channel as the vicar! (Assuming he has the same kit). These frequencies in channel 70 are not suitable for interference free use in an unknown environment, and from 2012 will be even worse, as all the users of lower channels suddenly get cellphone interference, and shift up into an already busy slot. There is no problem whatsoever with using mains powered receivers - the only downside is the cable. If you have the gain set so that levels do not exceed the maximum the camera input can handle without distortion, then the problem you found is most likely to be intermodulation from an adjacent frequency - this can be a mild burble, or a nasty distortion but doesn't sound like the distortion you get when accidentally driving an input too hard. Connectors can fall out (with non-locking jacks), or even get bent if the cables are tugged - but if you've got suitable cables and can manage them properly, I'd be happy using them. Mains receivers are also usually diversity - making drop outs less likely - only expensive radio systems that work on batteries have this feature. Cheaper ones don't! Cheap radio systems are like balancing on a high wire - at some point, you'll fall off! Cheap ones often have good performance, and sound quite good, lulling you into a false sense of security. It's really common for me to have to provide alternate radio kit when visiting people's kit misbehaves - almost every week a piece of nice, expensive radio kit makes nasty noises - and it's far simpler to be able to just hand them something else that I know will work. I did a Cannon & Ball show in a big theatre at the seaside. During the show, a big panic when a man came to the sound desk and demanded I turn them off. It seems that there was a National Bowls Championship on the bowling greens, two or three hundred metres away - and they'd gone home, locking up - but leaving their sound system on. Trouble was it was on the same channel as Bobby Ball - so everything he said was broadcast to everyone on the promenade! This was his own system, on channel 70. Swapping to one of my 'more private' ones on 69 solved the problem for the second half of the show. Channel 70 is bad news!