I'm helping to set up an audio system for a small church. How small? Try 36' x 32' with about twenty people in the pews. Good audio is important, as some of the members are elderly and wear hearing aids. The church is in a spec of a town about 30 miles from the mouth of the Columbia River.

I've got the back end taken care of. I picked up a (well) powered mixer, two 12" Yamaha PA speakers and stands for cheap from craigslist. Feedback is not an issue as the only right angles in the room are from floor to wall. Acoustically, the place rocks, and the twelves are perfectly sized for the space and intended use.

Last weekend, I borrowed a Shure SLX wireless system with a cardioid lav. The SLX is not adequate for video work, but is somewhat adequate for live audio. (Too much hiss, too little high end.)

I learned some things though. I had placed the mic too close to the mouth. The pastor (a woman with a not-too-deep, not-too high voice) would go back and forth between addressing the congregation and reading. Thankfully, I was mixing live. When she looked down at the text, I dropped the mix by 9dB or so. When she looked up, the fader went back up. At times it was comical the way I mimicked her head movements. I felt like a marionette in reverse.

The other thing I learned was that I needed to bring the volume back down when she sings, as she is a strong soprano. And I needed to mute the audio during private conversations.

Given that I'm not a member of the church, and they have no resident audio engineers or mixers, I need to get her a system that she can manage solo.

I'm looking for the following:
* A good sounding lav (omni) that's inexpensive
* It can be wired to keep cost down and quality up
* It should sound good with a female voice
* It should allow some self control of the volume - full, -6dB (or so, for singing), and mute.

I've been eying the AT803b, which is wired, but it doesn't include any volume control. I would have her mount it at least eight inches below her chin.

I've also considered an over-the-ear type of mic for consistent placement, but the feedback risk is so low, that I don't think this is necessary, and, if cheap, it might overload during singing.

In either case, she would still need a volume control to go between speech and song. Is there a dirt cheap, passive, inline volume control or pad that I could hook between the battery box and the cable to the mixer? And remember, this isn't for film. Reliability is important. Audiophile sound is not.

Any recommendations are welcome. Thanks!

I suspect she won't remember to fiddle with settings depending on what she's doing.

Just wondering if you wouldn't be better off with a dynamic mic of some kind mounted in a fixed position. because I suspect she'll be able to adjust gain naturally by moving closer or further away when she hears herself getting too soft or too loud.

Just a thought FWIW

I suspect she won't remember to fiddle with settings depending on what she's doing.

I agree. She'll need to learn after making some mistakes - especially muting for private conversations. She got quick feedback when she sang and it was too loud, but it's easy to forget you're mic'd when speaking softly.

Just wondering if you wouldn't be better off with a dynamic mic of some kind mounted in a fixed position.

She has a fixed, dynamic mic, but she's an unfixed, dynamic person. :) She moves around a lot during the service. And during communion, she needs both hands free. They have a wireless dynamic as well that they pass around to the congregation when they speak.

She really needs a body or head mounted mic. Wireless is best, but wired is acceptable to keep costs down.

Funny how reality always sets in and disrupts our best laid plans!

I don't know if the Sennheiser Freeports are still available where you are and (big caveat) whether the frequencies are still OK for you to use (it's hard enough to keep up with the proposed changes to the PMSE spectrum over here) but I chose two of these systems for our church's audio system to replace ageing VHF mics

Pros:
UHF
diversity
cheap
omni mic
reliable when correctly fitted
easy to set up
levels easily adjustable on RX

Cons:
only 4 selectable channels
sometimes starts up with a panic-inducing noise (sounds like incipient feedback howl but isn't. Could be the "dynamic processor" starting up - less than 1 second to settle)
No easily accessible adjustments on TX (screwdriver required)
Pre-emptive battery replacements required (we do ours after ~ 3 hours' use to be safe)
Battery failure mode intrusive (BUMP off BUMP back on BUMP off BUMP back on - you get the idea)

USA link at Sennheiser USA - Wireless Mics, freePORT, Wireless Microphone Systems - Private Audio (http://www.sennheiserusa.com/private_microphones_wireless_021001)

User's guide downloadable (pdf) at top RH corner Product downloads

*In our church*, if the preacher doesn't want to be heard singing, he just switches the bodypack off and puts it back on just as the singing finishes.

The Freeport frequencies would probably work, given that the location is quite rural. The problem is that it doesn't solve the local volume problem, and is more expensive than a wired unit.

I can get the AT803b new for about $150, while the Freeport prices look to be $350 or so.

What I really need is an XLR inline passive volume control or switchable pad. I'd rather buy than build. Another option would be a similar lav to the AT803b that includes a level control on the battery pack.

I know of no transmitter that has an easy to get at and adj. level control.
Maybe you could use this Rapco in-line variable pad w/mute, but then you would need a battery-powered lav with an XLR, and attach some kind of belt clip..


Rapco Variable Pad with Mute Audio Signal Conversion at Markertek.com (http://www.markertek.com/Audio-Equipment/Audio-Signal-Conversion/Rapco/CVPBLOX.xhtml)

Thanks Rick! I've ordered the variable pad, the AT803b and parts for cables.

I'll review the variable pad after I get a chance to test it out. People often discuss needing a pad here, but we're often unsure of the impedance and how much attenuation is really needed. The variable pad could be a nice solution for just hooking it up and dialing it in as needed to get the job done. If you want, you could measure the settings, reverse engineer the values, and solder up or buy a comparable fixed pad for extended use.

I spend and awful lot of time with radio systems for live work, and when you are dealing with radio systems that give mobility, then any attempt at auto operation is futile. As you found, riding the fader to give the correct level is just how it is. Getting rid of the cardioid will easily level out the volume issues when heads turn, but also cuts down volume before feedback. As the typical transmitter pack provides polarising voltage up the cable, you cannot use any form of in-line attenuator, and although most packs have a sensitivity setting, it's not meant for continuous use. If you made up a cable remote volume, that could work, but if you have a volume cable, you may as well have used a cable mic in the first place.

A proper stage style headset mic would be pretty good sounding, as it could be got in close to the mouth, but then the person speaking has no way of controlling volume - with a lav, at least they could, if necessaary, shield the mic for a little privacy - accepting that this often is the trip that starts feedback.

As far as I'm aware, nobody produces a piece of kit to give control like this. You will only get good results with a human on the fader. It does strike me that even if the speaker could operate volume, then it would go wrong because their mind will be on what they are saying - expecting them to also consider volume will compromise what they do.

In the churches I visit where systems are setup and left, the sound is always poor, as they are set to allow people to walk anywhere without the system taking off - meaning they can simply use the pack switch to turn it on and off. They ignore the suddenly booming, suddenly inaudible audio that is a result.

Great points, Paul. Yeah, operating solo is far from ideal, but it's the reality.

I think the AT803b and the attenuator can work reasonably well. The church is nearly feedback proof, so the omni mic can be mounted far enough from the mouth to be reasonably consistent. The pastor won't be mixing, per se, but will simply go full bore for speech, down to a set level for singing, and mute when not addressing the congregation. She can always ask the members if the overall levels are good and adjust the channel at the board.

There's no doubt that she'll struggle with operator error at times, and she'll improve over time. It will still be a huge improvement over their previous setup.

I use one of these in such situations:

APHEX Systems 320A Compellor (http://www.aphex.com/320A.htm)

Set and forget, never messes up, very transparent considering what it does.

This combines a leveling amplifier, compressor, peak limiter, and has an idle gain setting (which they call a gate, but it is not a gate) so it will not pump.

Lots of radio stations use them.

You might also want to look at something like this for set and forget situations:

http://www.symetrixaudio.com/index.php?Show=14&Show1=&Show2=467

-MD

Mike,

Those solutions look killer. Unfortunately, they are *way* out of budget, which was $400 for everything. I got the powered mixer (12-inputs - ready for live music - EQ, feedback finder, and 2x300W), two 12" two-way speakers and stands for exactly $400. The mic, cables and volume control are out of the pastors pocket, and they belong to her. (It's her first year. She's likely to move around.)

I'm definitely keeping those model numbers for reference though. They could be handy for a higher profile, set-and-forget situation...

Mike,

Those solutions look killer. Unfortunately, they are *way* out of budget, which was $400 for everything.

OK, looks like she will need to learn a little about audio then. ;-)

The variable pad looks like it should work. There are several possible pitfalls in the design of this that may cause problems. If it has problems, let me know, and I will show you how to design a proper one for that mic that will also allow though the phantom power.

Maybe I should do a post on how to design pads, since this seems to come up frequently?

-MD

A pad thread would be really valuable, and might even become a sticky. That's the kind of general knowledge that never becomes obsolete.

I'm an EE with a fair amount of analog design under my belt, and a soldering iron at the ready. If the Rapco has problems, I won't be shy at all about leveraging the case and connectors with a modified circuit.

I'm an EE with a fair amount of analog design under my belt, and a soldering iron at the ready. If the Rapco has problems, I won't be shy at all about leveraging the case and connectors with a modified circuit.

Sorry, I didn't know you had an EE - you hardly need my help to design a pad! Hope you did not take that wrong, I was just responding to your earlier comment about 'but we're often unsure of the impedance and how much attenuation is really needed'. I can answer those questions.

I am entirely self taught (since my first vacuum tube volt meter in 1959), but have done a good deal of audio design and have many years of practical experience specifically in pro audio.

I still agree such a thread would be useful, I was thinking something along the lines of 'How to make passive audio pads and mixers'

So the question is - shall I start it or do you want to? (to avoid duplication)

-Mike

So the question is - shall I start it or do you want to? (to avoid duplication)

Go for it. I've got too many minutes of picture to compose to over the next few days...

...Maybe you could use this Rapco in-line variable pad w/mute, but then you would need a battery-powered lav with an XLR, and attach some kind of belt clip..

Rapco Variable Pad with Mute Audio Signal Conversion at Markertek.com (http://www.markertek.com/Audio-Equipment/Audio-Signal-Conversion/Rapco/CVPBLOX.xhtml)

So, I've received the AT803, built the cables and have the Rapco CVPBLOX...

The good news is that when the Rapco is at full volume, you can pull/push the knob and mute with only a slight signal bounce. It's usable.

The bad news is that when the Rapco is at less than full volume, the signal bounce is loud - lots of boom and click.

The other bad news is that the potentiometer is noisy. I shouldn't be surprised, as it's on a mic with -40dB or so sensitivity. It's okay when untouched, but you can hear the pot sweep as you turn it. At least it's mostly hiss, rather than crackle.

The Rapco is better suited for a line-level signal than a mic signal, and might even be too noisy at line level.

We will try the mic out in the church tomorrow...

The bad news is that when the Rapco is at less than full volume, the signal bounce is loud - lots of boom and click.

The other bad news is that the potentiometer is noisy. I shouldn't be surprised, as it's on a mic with -40dB or so sensitivity. It's okay when untouched, but you can hear the pot sweep as you turn it. At least it's mostly hiss, rather than crackle.


That is a phantom power mic, may I safely assume that you are not using that, and are using the battery instead? And if you are using the battery, I wonder if that mic could be putting some dc on its outputs.

It sounds like there is DC across the pot to me.

There are pots in mic preamps, they do not HAVE to be noisy.

Perhaps isolate both sides of the pot with caps and bleeder resistors. And a much higher value resistor right across the pot.

-Mike

Buy a cheap mic splitter transformer. Normally these have a primary conncted to the mic, and two secondaries to go to two different mic preamps.

Connect the mic to the primary as normal. Connect your mic preamp to the first secondary as normal.

To the second secondary, connect a pot roughly equal to the imput impedance of your mic preamp (about 2400 Ohms) in series with a 300 Ohm or so resistor (to protect the mic output from what could be a virtual AC short). You could also put a switch across the pot for mute.

This would guarantee no DC across the pot, maintain the CMRR, and probably provide noiseless operation. The only danger might be the load on the mic output, I would check its rating and adjust the fixed resistor to protect it - the voltage and current levels are so very very low it is hard to imagine them blowing an output stage, but better safe than sorry. It probably does not have to allow the mic output to go completely to zero, which would be safer.

I have not tried this, try it at your own risk. Just another idea that is very inexpensive.

-Mike

Thanks Mike,

Yes, I had phantom on during my test on my mixer. At the church, phantom was off, and it worked great. The potentiometer is still a bit dirty, but usable.

Previously, I had used a borrowed cardioid lav and had mounted it too high on the shirt. With the AT803 omni mounted a bit lower, it worked well even with the look-up-look-down while speaking from notes. Sure, it gets louder when she looks down, but her direct voice projects less, so things balance out.

I had to get a bit more aggressive on EQ cuts to nip all of the feedback, and in the end there was no resonance at all, and everything we clearly understandable, if not as flat as I'd like. My original plan was to buy components, including a 31-octave EQ. Instead, I got a great deal on a powered mixer with speakers and cables that I just couldn't pass up, but the EQ is only 7-band.

Anyway, thanks everybody for your help!