Economic condensers for Church choir?

[Bobby1note]

Originally Posted by joeguam

Here's a picture of the choir setup and the way I positioned the condenser today:

http://m.flickr.com/lightbox?id=8480187119

And here's the layout of the altar with the PA's behind the mics up against the wall:

http://m.flickr.com/lightbox?id=8481279000

Thanks so much!

...
Joe

OK Joe,

those pics help somewhat. Lemme get this straight; the bank of chairs against the wall, are the seats for the choir? They stand while singing I presume???? If the mic-stand you used was adequate for todays' service, you don't need a new mic stand. As long as there's not too much angle in the boom, you should be fine, but, you might want to add some weight to the base,,,, just in case.(for stability) As long as the boom is fairly vertical, the stand will be less prone to tipping.

Now, just to be clear, the mic should be placed two feet in front of the front row, and no higher than 2 feet above the head of the tallest singer, and aimed at the second row. If you're happy with your present set-up, that's fine too.

Now, you have an issue with "noise" from some of your mics? All mics will have a certain level of self-noise, and this will be especially true of cheap poorly designed mics. What are the chances that you're noise issue though, is related to the gain-structure of those mic channels??? Chances are this is your main issue, and that your channel gain is not set high enough above the noise-floor of the mixer. Is it possible that someone was turning gain down, to avoid feedback? If so, raise the channel gain, but pull back the channel fader. The fader doesn't have to be at "unity", if the mic output is "hot".

What mixer are you using? and,,,,, do you have a graphic equalizer at your disposal?

Now, your feedback issue I presume, is happening at the alter??? The pulpit???? Are those the only locations you're getting feedback? Can you describe the sound of that feedback? Are they high,, piercing squeaks? Steady-state, or intermittent? The placement of the speakers is a definite problem, but if they're not flexible in allowing you to move the speakers, maybe we can pull a lil' trick on the speakers.

[krisls]

Might I just chime in here and say that even if this is not my world and I doubt I will ever be in this situation.... Well threads like this are just inherently interesting and it is good to learn stuff just because.

Cool beans guys

Kris

[joeguam]

Oh man Bobby, in the midst of worrying about the feedback so much, I totally forgot the basics of sound engineering! You're totally right that the "noise" might possibly be from the gain. Because all the feedback previously with TWO condensers and 3 dynamics all for the same three rows of choir singers (crazy huh?!!! not my setup, I just started playing in this church about 6 months ago), I used to level the condensers by setting the faders to unity, increase the gain until I got feedback, and then turned it back a little. It was the only way I could get it to its highest point with no feedback.

The feedback is coming from the 2 Mackie SRM450's you see in the picture against the wall behind the altar. It definitely high piercing and only coming from the condenser. What tricks do you have to help this?

The board the church has is a Mackie CFX14, so yes, there is a graphical EQ available which I use to test the levels when I solo each track. Now that I changed the mic position and configuration, I'm definitely going to relevel the channels from scratch again and see if this alleviates the "noise".

Oh, and as far as the boom stand I'm using, that's one of my personal stands that I use for gigs. I'm looking into upgrading and just donating it to the church. If I upgrade, I'm going to get a much more sturdy base as I hang both my Taylor GA and ukulele on the mic stand when I do solo gigs with my loop pedal. Definitely looking into your suggestions - but they're not cheap! Haha! Thanks again Bobby!

Kris, just more reason why AGF is so amazing. I just make sure to "pay it forward" and help out wherever I can on here.

...
Joe

[Bobby1note]

Joe,

Thanks for that info. That mixers' built-in GEQ is all you have, correct? You don't have a 31-band GEQ??? The mixers' EQ is very limiting, to say the least, but maybe we can do something there. I need more "specific" info however.

First, when I asked where the feedback is coming from, I meant which mic (or mics) are feeding back? Yes, you hear it in the speakers,,, but that's not where the feedback is occurring. I'd need to know "how and why" the feedback is occurring, and since I can't hear it for myself, I'll need you to describe exactly what's happening,,,"when" it's happening,,,, and what it sounds like. Feedback, is the result of excess gain,,,, and that doesn't necessarily mean the channels "gain" setting. We can reduce gain at the mic itself, by a simple repositioning of the mic,,, or the speakers,,,, or both. We need to identify which mics are feeding back.

Now, I realize that you're now using far fewer mics than before; did this reduce any of your feedback issues yesterday? (I suspect that it didn't, but I hope I'm wrong) Is the feedback occurring when the music is happening,,, or when the preacher is speaking???? When the feedback occurs, is it an intermittent VERY high-pitched squeak, or is it a slowly increasing howl? How have you been dealing with, or reducing that feedback as it happens?

I don't know your mixer, but, do you have channel mutes that you can engage, when a specific mic is not being used? If not, the fader on that channel should be pulled back,,, at least until we nail down precisely where and why the feedback is occurring.

Are you currently applying any EQ at the channel-strips???? In a "live" situation, you must never use "additive" EQ,,,, subtract only. Why? Because EQ is like "volume controls" for certain frequency bands. (hi, mids,and lows). At the start of a "show",,,,iIf you optimize your channels' gain-structure to "max-output-before-feedback" when EQ is flat,,,,, and then you boost EQ while performing,,,, you increase the gain of that channel-strip,,, and presto,, you've just crossed the feedback threshold. If you want to add, that's fine, but cut the fader first,,, by a few dB's,,, then add EQ by the same amount.

Let's leave it there for now, and let me know the specifics of your feedback.

[ljguitar]

Originally Posted by joeguam

Oh man Bobby, in the midst of worrying about the feedback so much, I totally forgot the basics of sound engineering!

Hi Joe...

Yes, you did kind of forget...is that arrangement of speakers and mics set in cement, or can you change things?

Unless you move the mics in front and above the first row, and aim them at the middle of the group you will not be picking up the entire choir. With the setup as pictured, even if you move the mics above and in front of the choir as pictured, you are only ever be able to use enough mic for minimal reinforcing of the sound.

Where you have your main speakers is at issue with the choir mic placement (I'm assuming the main speakers are the ones at the back of the platform) . No mic in the world I'm familiar with is going to survive not skirting the edge of feedback with your current setup as pictured. So be sure you kill the choir mics in those under-balcony speakers which I assume are choir monitors.

Your main speakers need to be much higher in the room, (woofer 8-10 feet off the ground) and if you are going to situate the choir under that balcony, the mains need to be further forward...well in front of the choir (toward the congregation).

Hope you get it all worked out. My initial assessment is you may not need new mics at all.

[tomana]

good stuff, thanks

[leonard d rock]

thanks guys, i'm learning a lot here. i never thought 2 mics for 30 people would be enough. there's a guy in my school who is in charge of the mic'ing the university choir and he has 6 condensers in front at mouth level and 2 pencil mics overhead for 15 people and you still couldn't hear them. they bring their own PA system (JBL eons and Behringer mixer) and still they cannot be heard. so proper placement is just the key: distance, height and tilt of the mic and the 3:1 rule. wow!
i may be handling a church group in the future and this will come in handy. thanks again

[Bobby1note]

Originally Posted by leonard d rock

thanks guys, i'm learning a lot here. i never thought 2 mics for 30 people would be enough. there's a guy in my school who is in charge of the mic'ing the university choir and he has 6 condensers in front at mouth level and 2 pencil mics overhead for 15 people and you still couldn't hear them. they bring their own PA system (JBL eons and Behringer mixer) and still they cannot be heard. so proper placement is just the key: distance, height and tilt of the mic and the 3:1 rule. wow!
i may be handling a church group in the future and this will come in handy. thanks again

He's probably experiencing phase cancellation issues, due to certain frequencies arriving at the front mics at different times, and cancelling each other out. (front row, 2nd row, 3rd row of choir). He's also probably experiencing some serious comb-filtering. The proper set-up is a great example of "less is more".

[tomana]

this might be of help regarding placement, etc

http://www.shureasia.com/support_dow...s-basics/choir

[leonard d rock]

Originally Posted by Bobby1note

He's probably experiencing phase cancellation issues, due to certain frequencies arriving at the front mics at different times, and cancelling each other out. (front row, 2nd row, 3rd row of choir). He's also probably experiencing some serious comb-filtering. The proper set-up is a great example of "less is more".

yes, less is more. can you please give a simple explanation of phase cancellation, comb filter and speakers in or out of phase with each other? ( sorry to op, not meant to hijack thread.mods please do the necessary changes if needed) thanks to all.

btw, that guy in my schools, prosound experience is live band sound, probably used to close micking everything

[joeguam]

Bobby & Larry, thanks for all the info. Sorry it's taking a while to respond, been working on my display case/wall cabinet build all day. I have responses to all your questions and additional information that I'll add tomorrow.

Thanks again so much, I can't express how much of a blessing you folks and the AGF have been with this regard! The best part, as Larry mentioned, is I might have the mics I need!

...
Joe

[Bobby1note]

Originally Posted by leonard d rock

yes, less is more. can you please give a simple explanation of phase cancellation, comb filter and speakers in or out of phase with each other? ( sorry to op, not meant to hijack thread.mods please do the necessary changes if needed) thanks to all.

btw, that guy in my schools, prosound experience is live band sound, probably used to close micking everything

Phase cancellation occurs when two identical frequencies of opposite phase, arrive at the same time. The frequencies will cancel each other out. Here's an image that illustrates it. There are three diagrams, and the top and middle sound waves are identical, but out of phase to each other. The bottom graph with the red line, shows the frequencies laid over each other,,, cancelling each other out. The result is silencing of that frequency.

Speakers that are out of phase will produce the same result, which is mostly heard in the low-frequency range. The speakers will usually sound very "thin".
There's also a time-alignment component, where two perfectly in-phase speakers can be out of phase at certain wavelengths, due to their relative placements to each other., and the location of the listener.

http://www.google.ca/imgres?imgurl=h...QEwBA&dur=1711

Here's a detailed explanation; I haven't read this, but I'm sure it'll explain it well. They also touch on "comb-filtering"

http://www.soundonsound.com/sos/apr0...emystified.htm

[leonard d rock]

Originally Posted by Bobby1note

Phase cancellation occurs when two identical frequencies of opposite phase, arrive at the same time. The frequencies will cancel each other out. Here's an image that illustrates it. There are three diagrams, and the top and middle sound waves are identical, but out of phase to each other. The bottom graph with the red line, shows the frequencies laid over each other,,, cancelling each other out. The result is silencing of that frequency.

Speakers that are out of phase will produce the same result, which is mostly heard in the low-frequency range. The speakers will usually sound very "thin".
There's also a time-alignment component, where two perfectly in-phase speakers can be out of phase at certain wavelengths, due to their relative placements to each other., and the location of the listener.

http://www.google.ca/imgres?imgurl=h...QEwBA&dur=1711

Here's a detailed explanation; I haven't read this, but I'm sure it'll explain it well. They also touch on "comb-filtering"

http://www.soundonsound.com/sos/apr0...emystified.htm

thank you very much

[Bobby1note]

You're very welcome Leonard,,, my pleasure.

[joeguam]

Bobby, the mixer's GEQ is all I have, but it's not the full 31-band. Here's a picture of the board we have in our Church (but we have the 14 channels and not the 12):

EDIT: Instead of inserting the image, here's the link: http://www.mackie.com/products/cfx12...12mkII-top.jpg

As you can see, there's a stereo GEQ for the main output but not for the individual channels. Any tricks we can use with this GEQ?

I'm sure the feedback is coming from each of the condensers WITH THE FORMER mic positions. Remember, formerly, we had 3 dynamics in the front row, the two condensers in the second row and none in the last row. The reason for this is that the choir members get shy and don't want to sit in the front row. Thus, to get them closer to the condensers (I usually mute the dynamics if no one sits in front of them), I moved the condensers closer to them instead of the other way around. Well, when setting the gain, I used to solo the condensers and bring the level up to the correct setting with all the other inputs (dynamics, piano, etc.). However, as soon as I unmute the condensers - instant feedback! So, as a result, I had to resort to setting the levels for all other inputs EXCEPT the condensers, then unmute everything and SLOWLY increase the gain of the condensers until I hear the feedback SLOWLY starting - then I hit mute real quick and bring the gain back just a bit. This way, I was sure to have the gain as high as possible before the feedback threshold. Now, with the single condenser configuration, I'm able to get the gain up a little higher, but still have to level it the same way (just a few notches back from the feedback starting).

I know the solution to all of this is to MOVE THE SRM450 MAINS FORWARD OF THE MICROPHONE - believe me, I've about had a stroke trying to explain this to the admin folks. I also know from experience that the ideal position of the mains should be UP HIGHER AND ANGLED DOWNWARD so as to promote as equal a distance as possible from the speaker to the first row as compared to the last row. There's a ledge just above the choir (no balcony) that would be much better, however, they don't want to block the artwork. We don't have the funds to install ceiling brackets either. When I offered to move the speakers on top of the ledge, I also volunteered to do all the soldering to splice their XLR cables so they could reach that distance. I make my own TRS and XLR cables so this is not a problem, but it's just been an uphill battle.

The fewer mic configurations (just 1 to be exact) has greatly reduced the feedback - but it's not where it's full potential should be. Meaning, the condenser levels should be set with the input meter equal to all other inputs so there's a balance in the mix and this is not the case. For the condenser, I just have a flat EQ (i.e. all knobs pointing in the 12-o'clock position). If you look closely in the picture, there's a satellite speaker directly above the soundboard - I immediately climbed up and disconnected the wire from the back of this speaker a couple of months ago as this was providing a direct return of the output right back into the condensers! The feedback is slow growing. Normally, I sit out the entrance hymn while my fiance plays the piano, just so I can level the condenser. Once I get this set, I usually don't have anymore feedback problems - unless the priest decides to get excited and raise his voice in the mic. Then, I jump out of my seat and run (yes, I said RUN) to the mixer to turn it down. That's another issue, as you see in the picture that I sit and read the music behind my fiance at the grand piano - AND THE MIXER IS ABOUT 30-40 FEET AWAY! This is another thing that the admin folks will not let me move! UGH! So, I had to purchase the LR Baggs Venue DI (which I love BTW!) just so I can send my instrument signal all the way to the board.

Anyways, if you have anymore suggestions, please let me know. Right now, the sound is average, much better than it was before I came into the picture, but it could be much, much better. I'm still going to lobby to get the mains put on the ledge but if not, I'll have to just make due. Would you believe that before I started playing for this church, they only used the baby grand piano DURING POWER OUTAGES and the only piano sound came out of the speakers under the clavinova which was set at a 98% level each time? So the congregation heard a very loud piano source only coming from the front-right of the church. Since I've mic'ed up the grand with a simple SM58, my fiance LOVES playing the ivory keys much more than the plastics on the clavinova.


Larry, I was sure to kill that under balcony/ledge speaker as it's not a choir monitor, its actually a satellite speaker for the altar mics (yes, they configured the altar mic's on a different mix from the choir). I'm trying to get the main PA's repositioned, but you're right, I don't think I need new mics. We definitely could use an upgrade from the old Audix condensers we have but that's a separate issue.


I'm going to follow your suggestions and see if raising the MAIN FADER to back off the CHANNEL GAIN on the condenser will help. We play the 10:30AM on Sunday's here on Guam so that will be Saturday out there in the mainland. I'll update this thread and let you know what happens.

Thanks again so much everyone. The motivation that all this is for the Lord, Our Father, keeps me going despite the obstacles. I truly believe those of you here on the AGF are a blessing.

Cheers!

...
Joe