Trouble with sound system - boom mics are picking up "organ"
  • Hi everyone, I'm a college student at Virginia Tech and I'm new to directing our church choir. Given that we are a Catholic Campus Ministry, we are at liberty of the school in terms of the spaces that we are given for Mass. We currently hold Mass in a small chapel.

    We've had problems with our choir boom mics (2 of them) picking up the sounds of the (electronic) organ and causing major feedback, primarily due to the location of the choir. Here's a diagram of our setup:

    A couple of things to note:
    1) Since the chapel isn't our space, and we only rent it from the school on Sundays, we have to use a portable sound system (aka, nothing is wired into the ambo or anything else). For the choir, we use 2 boom mics - one for the altos and tenors, and one for the sopranos and basses (as shown on the diagram). We also use one dynamic mic for the director (me), one dynamic mic for the ambo (lectors and cantor), and the wireless priest mic.

    2) I know that people may suggest that we just don't use any mics for the choir. This unfortunately is NOT an option because the chapel ceiling is not high in any way, and we are stuck in a corner of the chapel, so our sound doesn't go anywhere. For the words to be made out by the congregation, the choir needs to be mic'd up.

    3) Not only are we stuck in a corner of the chapel, but we are also directly next to the organ's speakers. The organist and more organ speakers are all the way across the chapel, so he has to look over the alter to see me give cues and cutoffs.

    4) We cannot move out of our general area, because if we go anywhere else, we will be in the way of those who receive communion.

    5) The reason I have the tenors and altos against the wall (as demonstrated in the diagram) is that we figure we could cut the lower register from that microphone using an equalizer to avoid organ feedback. If we flipped and had the basses against the wall, and then cut out the lower register, their parts wouldn't be picked up. However, the mic picks up the organ anyways, causing feedback regardless of how we change the equalizer.

    So, we don't have a lot to work with. If you have any ideas that we could do to alter the direction of the mic next to the organ without messing anything else up, that would be great. Or, maybe if you know of anything else we can do, please let me know. This has been an issue for as long as we've used this space and the organ.
  • CharlesW
    Posts: 11,835
    So are you picking up the organ speakers from the side or from the back? Can you identify which are causing you problems?
  • Schönbergian
    Posts: 1,063
    You could try narrower (i.e. hypercardioid) microphones placed at an angle away from the organ speakers.
    Thanked by 1CharlesW
  • CharlesW
    Posts: 11,835
    Some mics have an adjustment to shut off one side to pick up from the other direction. If you find that a particular speaker is causing your problems, you might determine if that speaker could be turned off during your mass. It's difficult to suggest solutions for a place you have never been.
  • Are your boom microphones placed more in front of or above your choir? Perhaps try placing them in a position that is more above them with the mics pointed down, and see if that helps. Feedback was a perennial problem in my current parish until we installed a new sound system several years ago, and by design, the mics that originate from our choir space do not sound through the speaker that is closest to and slightly behind our space which was the cause of our problems. We have not had any issues since.
    Thanked by 1tomjaw
  • GambaGamba
    Posts: 514

    First of all – God bless you in your ministry!

    Second – in re your point 2 – why not fix the choir’s singing? It’s an impossible technical situation to remedy. If the choir can hear the organ, that means that mics that can pick up the choir will also be picking up the organ. [Apart from individual mics for each singer, with heavy compression, in which case you cease to have real choral singing] there is no way to somehow pick up and amplify sounds coming out of singers’ mouths, without also picking up the sounds going into their ears a few inches away. Just reduce the volume of the organ at the amps, or keep the swell box shut, improve the diction and projection of the singers, don’t mic the director or cantor, and you’ll be fine. There’s no reason to mic up singers in a small room. Let the sound be naturally vibrant, even if it’s gentle, not artificially earth-shaking.
    Thanked by 1tomjaw
  • Carol
    Posts: 805
    The only thing not mentioned by someone else that might work would be those plexiglass partitions that you sometimes see around the drum kit in a rock band. I have no idea if it would help and it would be ugly, but I figured I'd mention it anyway. It sounds like a difficult situation, for sure.
  • ServiamScores
    Posts: 2,362
    I can think of a few things to try:

    More directional mics aimed down at the choir as hcmusicguy suggests.
    If it's truly "boomy" then it's likely that what is being amplified are likely the pedal tones (and perhaps lower-to-mid manuals at 8' pitch). You can set a high-pass filter on your mics at the mixer level to cut everything below, say, 80hz which is fairly common. Your best basses are not singing in the lower pedal octaves, so the mics can be told to ignore that part of the spectrum and not reproduce it. This will greatly ease the strain on your speakers, no doubt. Similarly, a soprano only sings up to about 1100hz-ish, so you could do a low-pass filter to get rid of everything above that so the mixtures and overtones of the organ are ignored too.

    From an audio mixing website:
    Bass: 75 – 300 Hz
    Baritone: 100 – 400 Hz
    Tenor: 135 – 500 Hz
    Alto: 180 – 700 Hz
    Soprano 250 – 1100 Hz

    That means you only need the mics to pic up 75-1100 hz. Everything above and below can be cut via high/low pass filters and the sound of the singers shouldn't suffer. Low C of a pedal 16' is 32hz, so you'd be cutting out quite a few of the low notes that tend to make speakers boom.

    EDIT: a.) I see I didn't initially process the fact that you've already been applying filters and it hasn't helped, b.) Gamba is right, I'm sure, that 1100 would be way to low a cut off.
  • ServiamScores
    Posts: 2,362
    Having googled your chapel, the only other thing I could suggest is moving down the side aisle away from the speakers so the effect isn't quite so pronounced. If it were me, I'd likely sing in the other side aisle to better communicate with the organist and stand a little ways down. It's a terribly intimate space, so you're close to the people either way. I'd guess that if you sang further down the aisle and more into the room, you might not need mics anyway, apart from, perhaps, the first refrain of the psalm by a cantor.
    Thanked by 1Gamba
  • GambaGamba
    Posts: 514
    @ServiamScores I agree about a lo-pass filter and you are right about the frequencies of the fundamentals of the pitches a choir produces, but if you roll everything off above 1100hz, the text will be unintelligible.

    The energy of the vowels primarily lies in the range 250 – 2,000 Hz and that of voiced consonants (b, d, m etc.) in the range 250 – 4,000 Hz.

    Unvoiced consonants (f, s, t etc.) vary considerably in strength and lie in the frequency range 2,000 – 8,000 Hz.

    To be able to understand speech clearly, it is therefore important to have good hearing across the entire range of frequencies from 125 – 8,000 Hz, but especially in the range of the unvoiced consonants.

    And then also the overtones of the singers will be lost and the sound will be rather dull and flat.
    Thanked by 1ServiamScores
  • Richard MixRichard Mix
    Posts: 2,646
    I'm feeling grateful I lack the experience to give the kind of advice requested, but from a distant perspective
    4) We cannot move out of our general area, because if we go anywhere else, we will be in the way of those who receive communion.

    Singers do have legs, and it might be better to be near the console most of the time. At St David's Communion is always sung by a single cantor while the choir receives before returning to the front pews.
  • ServiamScores
    Posts: 2,362
    TBH, the space is so small, I find it odd that mics are even required. Granted, I'm not there, but I cantor without a mic in a space that is 3-4x bigger than that (communion antiphons anyway; I do use a mic for the psalm). It appears to have plenty of hard surfaces; is it an oddly dead space or something?