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Author Topic: Mic in a bell tower?  (Read 6465 times)

AlaunPederson

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Mic in a bell tower?
« on: March 26, 2010, 11:27:36 pm »

My family built a new church next to the old one.  The old church contains the bell which was restored at great expense and time.. only now you can't hear it inside the new church.  They don't want an electronic bell system, they want to hear the original bell that they all worked on.

The thought is to put a gated microphone in the old bell tower and feed it to the sound sytem at the new church.  There's already low voltage conduit run underground between the 2 buildings.

The tower is protected from rain but it does get very cold up there.  Has anyone put a mic in a bell tower?  Isn't it a bit loud?  Do you hear the mechanical parts moving? Would an SM58 stand up to the freeze/thaw and moisture?

Could you get away with running mic level cable for 400' or would it be better to place a preamp in the old church and send line level signal over the long distance?

Thanks for any input-  

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Tom Young

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Re: Mic in a bell tower?
« Reply #1 on: March 29, 2010, 07:10:47 pm »

Wow. These are either small, not very loud bells or you did a magnificent job of acoustically isolating the inside of the new church  Wink

In theory this could be done. This is one of the few applications where a PZM microphone (Crown Audio) might do the best job. Tuck it under anything that protects it from the elements while keeping it close to the source(s). You can even wrap it in thin plastic (saran wrap) and, because you are likely to need to EQ it anyways, you can probably get good sound. Make sure the PZM is on a large surface (or in the corner of 2-3 roof surfaces) so it will reinforce lower frequencies.  You can read about how a PZM functions at Crown's website.

400' cable length is a bit long but it could work. Try it first and then see if you need to preamplify it from nearby and send line-level the rest of the way. The better the cable (very good shield, twisted pair, larger gauge conductors, not Canare star-quad), the lower your (resistive) losses, HF roll-off and the lowest amount of noise will be picked up.

Applying a gate will be tricky. This mic will be exposed to wind which can trigger the gate. The sustain of the bells may get clipped-off. If the bells are rung at different levels, the gate settings may not work for all these levels.

Definitley have a good compressor-limiter on this signal. As well as flexible (multiband parametric) EQ and a good high-pass filter. And don't forget about phantom power.

BTW - an SM58 would work. Wrap it in the thin plastic. It is not as good a solution as it will have less output than the (condenser) PZM and it will be more susceptible to wind-induced noise (rumble) due to its cardioid characteristics.

HTH
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Brian Ehlers

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Re: Mic in a bell tower?
« Reply #2 on: March 30, 2010, 12:36:37 pm »

There's another consideration which, unfortunately, contradicts some of Tom's excellent suggestions.  If you mount a microphone near the bell, you will get a very "direct" sound from it -- a sound which is not at all what you are used to hearing from further away.  Up close you will hear a much sharper sound from the clapper and mechanical noises from the mechanisms (bearings; rope, if human operated; motor if automated?).  You will also hear nothing but the bell.  A listener on the ground 100 feet away hears pleasing echoes from the ground, buildings and other nearby objects.

All of which means you might want to place the mic further away from the bell, or plan on running the feed through an effects processor to add some reverb.  If you want to play with this ahead of time, perhaps you can place a wireless mic in the bell tower and receive the signal in your new sanctuary.

My church no longer uses its bell to call the neighbors to church on Sundays but reserves it for special occassions.  It is not uncommon for a bride to ask that it be rung at the end of a wedding ceremony.  Even though the bell is in a tower attached to the sanctuary, it is difficult to hear inside.  So I open a few windows, place a mic near one of them, and crank it through the PA system.  No one is the wiser.
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Tom Young

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Re: Mic in a bell tower?
« Reply #3 on: March 30, 2010, 06:27:10 pm »

Quote:

 If you mount a microphone near the bell, you will get a very "direct" sound from it -- a sound which is not at all what you are used to hearing from further away. Up close you will hear a much sharper sound from the clapper and mechanical noises from the mechanisms (bearings; rope, if human operated; motor if automated?). You will also hear nothing but the bell. A listener on the ground 100 feet away hears pleasing echoes from the ground, buildings and other nearby objects.


I agree that a microphone that is placed where it needs to be, both due to available architectural elements and for weather protection, will also pick up mechanical noises. But I intuitively do not think the levels of these are anything close to those of the rung bell(s). Can you provide a more detailed explanation of (or elaborate on) this ?

Perhaps you can point me towards any published papers or articles that discuss acoustic reflections/reverberation and their impact on church bells ?

While clearly a church bell-tower in midtown Manhattan benefits to some degree from the acoustic reinforcement provided by adjacent, taller buildings..... I suspect that country churches with very low-elevation adjacent buildings (if present) exhibit very little, if any, perceived or measureable acoustic reinforcement and including from the ground. That is to say: other than boundary reinforcement, which is not perceived as distinct reflections.

Audible 1st and 2nd order reflections could certainly exist when further away from both source and reflecting surfaces, depending on where the listener is. But this is not what I think you are referring to and which would be noticed if absent (because the bell(s) is mic'd).

What reverberation does a bell listener experience, other than within the church itself and provided it is large enough and capable of producing a reverberant field ?

Perhaps I am uninformed about all this. Educate me.
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AlaunPederson

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Re: Mic in a bell tower?
« Reply #4 on: March 31, 2010, 12:21:15 am »

Thanks for the input!  

I see Crown also makes a weather-resistant boundary mic, the PZM-11LLWR. Even fits in an electrical box. That's handy.  I might give that a try if there are no spare mics around the church.  I plan on the location that's most out of the wind, along with a windscreen.

As far as reverb,  I agree this might produce a more dry sound than we are used to.   After all, our only experience with church bells is being at least 50-100 feet away.  While a country church doesnt have the builidngs of lower Manhattan, it still has trees (usually) and some small buildings around.

I think trees are underrated for their reflective qualities.  Example-  deer hunting season in farm country.  Large, flat fields are punctuated by clearly defined sections of woods. High powered rifles produce some fantastic reflections off the trees.  Many times you can hear gunshots bouncing off treelines 2 miles away and more.  A gunshot out in a field sounds drastically different than inside the woods.  The trees have a huge effect on the perceived sound.  Even though each branch and leaf presents a small area, there are so many of them that the sum is large.

Of course a church bell is not as loud as a rifle, and it's a longer duration sound.  We may not be as acutely aware where each reflection is coming from, but I'm willing to bet the bell is loud enough so the trees and houses in a small town make a difference in what we expect a bell to sound like.

I should make some recordings and compare the sound in the bell tower with that from the parking lot.  Will post here.
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Brian Ehlers

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Re: Mic in a bell tower?
« Reply #5 on: March 31, 2010, 01:03:30 pm »

That would be great -- to hear level-matched recordings from both locations.  You could then play those recordings in your sanctuary to see how they sound in there.  Sounds like a fun project.

Tom, I certainly don't think you're uninformed, and I'll admit my post is based on conjecture, not experience.  Though I will say that at my own church the bell makes all sorts of creaking and rope-rubbing noises when nearby which you can't hear from any distance.

I guess I'm thinking about how much ANY instrument sounds different when you stick your ear, or a mic, up close than when you back off a ways and let the sound "develop."  It's not just reverberation, and it's not just mechanical noises like fingers on strings and valves on woodwinds.  The entire harmonic structure is different when you get too close.  Even in a live situation, I'd rather mic a cello from four feet away than one foot (given enough gain-before-feedback).  Same for a good vocalist.  I'm thinking the same thing will apply with a church bell.  So what's the "right" distance from which to mic a big bell?  Beats me.
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Frank DeWitt

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Re: Mic in a bell tower?
« Reply #6 on: March 31, 2010, 02:26:35 pm »

I don't know how to mic a large bell, but I do know a bit about what it sounds like up there.

I have repaired a few tower clocks and rebuilt a Carillon system.  In both cases you want to run the bell through all of it's possible cases so you can watch and make sure everything is just right before you leave.  (It is a long climb)

Two things strike you right away.
1.  They aren't real loud.  I don't know why or how but I am a person who carries ear protection and uses it at about 100 dB  I have never been tempted to use it in a bell tower.  The sound is pure and wonderful but not overpowering.  Not like having your head in front of the mains in a church.

2.  You can hear all the stuff that makes the bell ring.  Now admittedly I was up there to make that stuff work so I was listening for it but You can pick it out both before the bell rings and even during the ringing. Humans have a tremendous dynamic range so I don't know how a mic would "here" what I heard.

Based on my experience in a bell tower, not my experience as a sound guy My first thought would be to mic a room below the bell

Often there is a room that is one floor up from most of the building and in the steeple.  It is useless and empty and might be a good spot.  My next choice would be to try in the steeple as far as I could get from the bell and still be undercover

I would not rule out placing a mic in a garage or other uninsulated out building. Just go around and listen and see what sounds good.

I like the idea of a listening test first followed by a test with a wireless mic.

Dick Rees

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Re: Mic in a bell tower?
« Reply #7 on: March 31, 2010, 04:58:49 pm »

Frank is headed in the right direction.  Consider the listening position folks previously occupied.  That's what they're asking to hear.  Finding a position for the mic that gives that sound will probably be satisfactory.
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Jonathan Johnson

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Re: Mic in a bell tower?
« Reply #8 on: April 04, 2010, 11:59:25 pm »

I don't have any experience with bells, but there are a few things that this thread has made me think about.

First, the noise of the mechanical action shouldn't be a problem. While it's certainly audible in the tower and not on the ground, remember that the sound of the bells will be much louder in the tower than on the ground, too. We simply hear the mechanical noise more because our hearing naturally "compresses," allowing us to pick up faint sounds in between very loud sounds. The ratio of desired to undesired sound should be about the same whether you are in the tower or on the ground, unless your mic is closer to the mechanical action than the bell. On the other hand, since low-frequency tones tend to propagate differently from high-frequency tones, there likely will be some noticeable effect. Nevertheless, a close-miked bell will have less gain applied, which will cut the mechanical noise to some degree.

As for the sound of the bell being different due to reflections and propagation differences, perhaps you could mount a hypercardioid or shotgun mic on the new church building, aimed at the bell tower. This would allow you to pick up the bell sounds from a more natural location, while rejecting most of the ambient noise: dogs barking, trucks downshifting on the highway, etc.

Frank, you mention you don't use hearing protection in a bell tower. Have you ever taken any SPL readings up there? You might be surprised. (I might be surprised. Maybe it's not as loud as I suspect.) As humans, we can tolerate pure, clean tones at much higher SPLs than distorted sound. Poor sound systems can be very fatiguing to listen to, even at low SPLs. Even so, hearing damage can occur from listening to pure, clean tones at high SPLs.
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Tom Young

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Re: Mic in a bell tower?
« Reply #9 on: April 07, 2010, 07:04:45 am »

Quote:

As for the sound of the bell being different due to reflections and propagation differences, perhaps you could mount a hypercardioid or shotgun mic on the new church building, aimed at the bell tower. This would allow you to pick up the bell sounds from a more natural location, while rejecting most of the ambient noise: dogs barking, trucks downshifting on the highway, etc.


How will such a mic work as far as being exposed to the elements ? How well will a shotgun mic work as far as its increased susceptibility to wind noise ?
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Re: Mic in a bell tower?
« Reply #9 on: April 07, 2010, 07:04:45 am »


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