MusicScienceGuy

Choral shells - Making a curved, floating sound reflector

Choral shells: Improving the sound of your choir through means fair or foul.  Part 2 of 3

Wherein I pass on a bit of hard-won lore

Background

In a posting a few years back, I explained how constructing choral shells helped my show chorus. We found the shells helped our choir better hear their mates on the risers. We think they also project a clearer sound to our audience.

Here, at long last, are three postings explaining how to build the shells we made.   Here are  the posting contents:

1. Making a choral shell out of your riser
   Recommended first step: easy to do, actually speeds your riser setup, and looks very professional. We set ours up at every performance. Details are given in this posting.
   
   
2. Making an upper choral shell – this posting
   This exotic-looking setup gives a pure, unified choral sound.
   Downside: it’s more work to build and set up. However, you may try out a small version to see if it is effective and practical for your group. Herein I give a design for a small, 16-foot shell that can be expanded, and hint at how to build a smaller, quartet-sized one.
    
3. Simulating a choral shell with choral microphones – a planned posting
   The Maple Leaf Singers switched to this (and dropped the upper choral shell) because we:
   1. Found relatively inexpensive, good choral, microphones
   2. Have a mixer with spare channels, monitors and house speakers 
   3. Are able to store them compactly and deploy them quickly
   4. Can dynamically adjust our sound while performing; our technician can, for example, boost a section’s sound to balance the sound

 

Making an upper choral shell for the upper-riser singers
or a small group of singers or players

Overview

  The plastic sheet material used to make signs (brand name Coroplast [I actually used Hi-Core]) is inexpensive, reflects sound surprisingly well, is light and easily curved. Better yet, it can be quickly curved with invisible fishing line into a focused sound reflector and un-curved in an instant for storage.

So far, so good. The only trick then, is to get this big reflector into place behind the performers and eliminate any features that might distract the audience.

 

 

Right: Instant sound reflector.  Thin white strings and a red plastic sheet were used to create this small demo.

 

 

 

     First, we need to join sheets together. Luckily, plastic sheets can be easily and temporarily stuck together with “hook and loop fastener” a.k.a. Velcro. to make bigger structures. 

 

Right: This stuff has very high sheer strength: even with just 4 square inches of Velcro, I could not pull the two sheets apart.

 

 

To allow the upper shell to be held up behind the performers, a light wooden brace (batten) is added and attached to the plastic with yet more Velcro. The batten can be suspended from the stage rigging, or held up by microphone stands or a purpose-built stand. Below is the way the first, experimental section looked in my living room, suspended from the high ceiling. [To the side is my long-suffering wife, who is wisely ignoring the whole process]

 

and here's how it looks assembled on stage.

How does the upper shell help?

The lower shell described in this post  benefits the singers and audience in several ways, but much sound is still lost.

Adding an curved upper shell further increases sound between performers, sends sound to the audience, and more audience sound comes back to the performers.

As an added bonus, the upper choral shell's clean white panels look good.

Downsides to the upper shell:

• Quite vulnerable to being knocked over by a breeze, so can’t be used outdoor
• Plastic sheets are translucent, so some stage lighting will shine through.
• Takes appreciable extra time to setup, unlike the riser-covering shell described in the previous posting.

What’s needed to create a 16-foot shell

We need a system that can be easily set up in just minutes, yet can be collapsed and
stored easily. 

I’ll show you how to use a pair of 8’ X 4’panels, making a 16-foot reflector shell.  to see how if you like the effect.

This design can be easily extended to 20, 24, 28 or 32 feet as shown below.  We even tried a double-level shell.

Material

• About 2 packs of  white 15' X 2“ wide 'industrial' Velcro (or equivalent)              $ 46
  Note: the hook and loop structure varies - stick with a single brand.
• White Coroplast or equivalent 4’ X 8’  sheets,  2 sheets                                            $ 36
• The strongest fishing line you can find – 40 lb test or so.                                        $  10
• 4 sanded 8’ X 1” x 3/4” wood slats - check for straightness  $1.60 ea.                   $    8
• Box of #8  1-1/2”   wood screws                                                                                      $   11
• Some 1 ¼” nails
• Bottle of white glue to re-enforce the batten                                                                $    5
• Red and Black Felt making pens
•  * prices at my local hardware store                                                 Total Cost:  ~$115

Tools

• Sharp utility knife to cut plastic –optional
• Scissors to cut tape
• 4’ straight-edge and measuring tape
• Cloths and strong grease-removing cleanser for cleaning Coroplast plastic sheets
• Cordless drills with drill bits to drill holes in batten for screws, and to drill in the screws
• drill bits: 1/8" bit to pre-drill h0les for #10 screws and a 1/32"  bit  for fishing-line holes

Procedure overview

Steps to creating an upper choral shell

1. String fishing line through the sheets so they can be adjustably curved and un-curved
2. Apply Velcro so that the sheets can be reversibly linked together
3. Create an easily-assembled batten
4. Apply Velcro to the batten and sheets so that your batten can stick tightly to the sheets
5. Put together the whole shell assembly
6. “Flying” the assembly, either from the ground, or from the stage rigging
7. Mark the assembly for easy rebuild, then disassemble and store it

Step 1: Set up the sheets to be reversibly and adjustably curved

[] Here we just put some holes in the sheets, put fishing lines through the holes, tying the lines snugly, and then set up Velcro tabs to allow the fishing line to curve the Coroplast as desired.

1. Put some holes in the sheets: 2" from the top, 6" and 36" from the corner. Use a 1/32"  bit.
   
   
   
   
2. 
   String fishing lines through the holes.
   
   
   
   
   
   
3. 
   Tie the lines snugly in the back – suggest using needle-nosed pliers and a barrel knot.
   
   
   
   
   
   
4. Make Velcro tabs to allow the fishing line to curve the Coroplast as desired:
   
   
   
   
   
   
   
   
   
   
   
   
5. Put a Velcro hook tab on the line
   
   
   
   
   
   
6. Clean off the sheet where the Velcro will go, then place a strip of loop tab on the sheet in the right spot to curve the sheet
   
   
   
   
7. Adjust the curve: with a partner at the other end of a sheet, curve the sheet to the right amount, and make sure there are strips of loop Velcro in the right place to curve the sheet evenly.
   
   
   

You will have a sheet that can be adjustably bent.
(Don't bend it too much!: it will crease permanently).

Step 2: Apply Velcro so that the sheets can be reversibly stuck together

Put the sheets on clean ground, face-down, so that you are working on the back side of the sheets

Cut 6” strips of 2” wide white “loop” Velcro, apply in three points: top, middle and bottom sides. The intent is to use the Velcro to pull the adjoining sheets together tightly at the critical top, middle and bottom edges.

Cut 6” long strips of Velcro hook-side tape and do not take off the backing. These strips will be used to pull the sheets together. Stick them on the look Velcro on the sheets for storage.

Put the sheets aside temporarily.

Step 3: Create an easily-assembled batten

The batten is assembled from two pieces of wood, offset by 6”, this makes for a very light, straight (the two pieces can straighten each other) wooden back that can easily be screwed into adjacent sections, using the 6” overlap.

Making a batten section

Here's the steps to make a section.

1. Check that the pieces are the same length, all 8’ long and sound. 
   
   
2. Mark off 6” from the end.
   
   
3. Overlap the wood pieces, offset by 6", as shown, to make an “L” beam.
4. Be aware that the 3-D shape you are making has a handedness – make them all with the same overlap shape!
   
   
5. Lay a line of glue down on the join; this will make the L-beam quite strong
   
   
6. Nail or screw the pieces together enough to hold snugly together until the glue dries, and so that you can work with the batten
   
   
7. Make the batten end-stubs – take one batten and cut it in half at the exact middle these will be the end
   
   
8. Fit the batten sections together, overlapping the 6” offset sections, as shown to the right.
   
   
9. Note that you will have 2 end pieces that are not interchangeable;: there will be a stage-left and a stage-right version.
   
   
   
   
   
   
   
   
   
   
10. 
    Drill screw-holes in the 6” overlap section, so that they can be screwed together.
    
    I made a piece of wood with pre-drilled holes, used it as a drilling guide to make sure all the screw holes were in identical places, so the battens were inter-changeable. The guide also saved time measuring and marking drill holes.
    
    

Joining the batten sections together

1. After all this setup, the battens can be screwed together in just minutes.

Step 4: Apply Velcro to the batten and sheets so that your batten can be reversibly stuck to the sheets

Lay the sheets together, ends aligned, face-down on the clean ground – you will be kneeling on the sheets.

Put the batten together and determine on the sheets where it will run. I suggest 2/3rds of the way: 32" from the bottom. Mark a line to follow, and put 6” strips of loop Velcro on the sheet every 2’ along the line. Put the complementary hook Velcro on the batten in matching points. Trim off any extra Velcro from the batten.

Drill 3/8” holes in the batten top-bar, so that suspension wires and hooks can be run through the batten.

Step 5: Assemble the  whole shell assembly

To assemble the choral shell – several people needed.

1. Lay the sheets on the ground.
   
   
2. Take the 12” “hook” strips you previously prepared and stick them to straddle the gap between sheets, over the loop Velcro placed on the top, middle and bottom edges. Pull the hook tape tight. The sheets should be held together without a gap.
   
   
3. Put the batten on the sheets, sticking the Velcro on the batten to the sheet.
   
   
4. Important! – Get a black and red permanent maker and mark all screw-points in red circles and the placement in black letters;
           e.g.  “Stage Left”, “Section A1”, “A1 to A2 join”, “Section A2””, “Stage Right”

==> Make sure anyone in the chorus can re-assemble the shell.

 Try it out

1. Lift up the assembly.
2. Pull on the fishing line tabs to curve the sheets, and adjust the curve until you are happy.

Congratulations – your upper choral shell is ready to fly.

 Step 6A: “Fly” the assembly – from the ground

You should be able to suspend the choral shell assembly using 2 microphone stands for each section.  Put a 1" hook about 18' from the ends of the batten sections, and  arrange something in the top of the microphone stand to hook into. I used tape. It was inelegant, but worked.

Each microphone stand needs a heavy weight, ideally a theatre saddlebag, to hold it in place.

Step 6B: Or “fly” the assembly – From the stage rigging

Safety first – check with your stage hands and follow their advice.  They may want to be doubly safe and screw the shell to it's batten. You may want to bring some white tape to cover the screws.

Step 7: Disassemble and store the upper choral shell

1. Detach the choral shell from the rigging – several people may be needed. Hold up the unit by the batten, with the sheets upright
2. Un-curve the sheets
3. Pull off the velcro that binds one sheet to the adjacent sheet (store this velcro by sticking it to the left end of each sheet)
4. Pull one sheet at a time from the batten
5. When all sheets have been pulled off, put the batten on the floor  
6. Unscrew the sections of batten, but don’t unscrew the screws all the way out; leave them for the next assembly
7. Tape the batten together with duct tape or bungee cord for carrying and storage

 So how does it SOUND?

Here’s a rough list to what to expect, sound-wise.

1. If you have a 4-row or five-row setup, the 3 upper rows should hear each other noticeably better.  
2. The director should hear the group better: he/she will stop bugging you to sing louder.
3. The biggest effect we noticed was the people on each end could hear each other, e.g. our altos could hear our sopranos and vice-versa.  Not surprising: this upper choral shell roughly doubles again the sound energy going from end to end on the risers.
4. For the audience, the sound should not seem that much louder as clearer. the direct improvement should be just noticeable.  As with adding the lower shell, the choral shell will stop sound leaking back-stage, and creating a muddy reflection off the back of the theatre. The two effects combined should make a significant difference.
5. As a consequence of point 4 above, the black choral shell seems to make the room more cosy.
6. As a consequence of all these "little" improvements, you should sing better; more in pitch; more in sync, with less strain.

Contact Me

I hope this helps your chorus.  If it does, please let us know.  Comments are appreciated.
If it does not, then we really need to know!  Please send details to MusicScienceGuy.

For more about the Maple Leaf Singers, you are welcome to visit our site: www.MapleLeafSingers.com

 

 Addendum

Making an 8-foot shell - a piece of cake.

If you have just a quartet, a single-sheet shell, with an upper and lower sections should do the trick. With a single sheet, you don’t need a batten, just a sheet that can be curved as described in the “Set up the sheets to be reversibly and adjustably curved” section below.  You then need to suspend it and use Velcro to fasten the upper sheet to the lower. 

Another, probably better way, would be to place the sections on end - then they can rest on the ground, and will be more stable.

I used 2 sturdy microphone stands for this demo.  Note the weight I put on the legs.

Related articles

Choral shells - Making your riser into a choral shell

Choral shells - Making your riser into a choral shell

Improving the sound of your choir through means fair or foul                Part 1 of 3

In a posting long ago, I explained how we of the Maple Leaf Singers made choral shells to help us  better hear our riser-mates, and project a clearer sound to our audience.  Here, at long last, are details on how to do make your own.

I have broken this advice into three parts:

1. Making a choral shell out of your risers; this posting.
   This is the recommended first step: it’s easy to do, actually speeds your riser setup, and looks very professional. See below for the details.
   
   
2. Making an upper choral shell. See Here 
   This is more exotic, but is possible to try out a small version to see if it is effective for your group.
   
   
3. Simulating a choral shell with choral mikes. (another planned posting)
   We (The Maple Leaf Singers) switched to this technique because :
       1)  Very good choral mics recently became available at a reasonable price
       2) They are more portable than choral shells and can be set up in minutes, in many venues
       3) Our sound can be dynamically adjusted during a performance
   
   

 How to make your choir’s risers into a choral shell

A choral shell covers our riser

"Choral-shelling" a riser is easy to do, actually speeds your riser setup (if you currently use black curtains), and the clean black panels look quite spiffy, as show on the right and above.

This change is also quite easy to try out before committing:

• Buy 4 plastic sheets when you have an on-riser practice;
• Put them on the riser and try songs or phrases with or without the sheets leaning on the risers
• If you  don't like the effect, or don't hear much difference, take the sheets back

What’s needed to cover a thirty-foot (7 - 8 sections) riser

Material

• About 45 feet of black, 3/4“ wide Velcro (or equivalent), sticky-back,              $75
• Black Coroplast or equivalent 4’ X 8’  sheets,  qty 4                                            $100
• Optional: if you have a end-railings (We made ours) get an extra sheet
• 45 feet of high-quality 3/4” black vinyl tape, e.g. 3M                                            $30
• 10 feet of duct tape (optional: to mark back of plastic sheet)                                 $5
• Optional: more sheets & tape for the riser-steps                      Total Cost:  ~$200-$250

Tools

• Sharp utility knife to cut plastic
• Scissors to cut tape
• 4’ straight-edge and measuring tape
• Cloths and strong grease-removing  cleanser for cleaning the risers and plastic sheets

Procedure

The plastic sheets go on the inside of the riser railing, not behind. As sheets can overlap we don’t need an exact fit. The reflecting sheets are stuck to the riser with Velcro. Here's how to set it up:

1. Set up full riser.
   
   
2. Prepare and apply Velcro tape to inside of riser railings.
   
   
   1.  Clean off, with strong detergent, the
      upper bar of the riser railings, on the inside (forward-facing side); it will likely have a bit of grease from hands or manufacture 
      
      
   2. Apply the soft-feeling loop side Velcro tape to the railing, pressing down firmly for several seconds.  It should lock in place like it has been glued. 
      
      Why put the loop-side on the railing?: it feels a lot better than the "hook" side.
      
      
3. Cut, prepare and trim black plastic sheets
   
   
   1. Put a plastic sheet on the riser and check how high you want it to come up  – we chose about an inch higher. Note: we put the raw panels up and came to a consensus; this approach worked well.
   2. Trim the sheets to this height.
      I think we trimmed off 5” or so,
      ending up 43” high. 
      Save the trimmed plastic – it may be useful for covering the steps.
   3. Take the black vinyl tape and tape along and over the edge that you want to be the top edge to smooth it. The top riser people will thank you: the idea is to prevent “paper” cuts.
   4. Cut the sheets exactly in half: 4’ wide, so that the sheets can be stacked, carried and stored.
   5. The corners will be sharp! Trim off round these corners a half-inch or so with a knife or scissors and put a bit of tape over them.
      
      
4. Prepare and apply Velcro tape to sheets.
   1. Rest the sheets on the riser railing, top up, and decide which side will be the front.
      (Often there will be marks or price & UPC labels on one side).
   2. The sheets may be dusty and may have grease on them. Clean off the dust and grease at the height of the Velcro strip that you have put on the riser.
   3. Cut up the “hook” side (prickly feeling) Velcro tape into squares (long strips are not needed), and apply to the plastic sheet, back side,  at the same height as the velcro on the railing, pressing the  velcro onto the plastic firmly for several seconds.  It should lock in place tightly.
      I suggest that you put the squares in about 1 inch in from the edge, one in the centre and two midway between the centre and the edge squares, You don’t need a lot of Velcro; if you use too much the plastic panels will be too hard to pull off the risers.
   4. Cut squares of the loop Velcro and apply two squares on the front side of the panels, at the same spot as the two velcro squares near the edge on the back side.
      These extra squares are so that the plastic panels stack and stick together and are easy to carry and store; without this modification, the sheets slide like a deck of Teflon-coated cards.
      
      
5. Make the sheets easy to orient and mount
   
   
   1. Finally, mark the back top of the panels with two 10”-long strips of duct tape arranged in the shape of an upside-down “V” (it will point out the top end). This shaves seconds off of riser setup time.
      
      
      
      
      
6. Test it out.
   1. The appearance should be good
      
   2. It should be faster to put up the sheets that it was to put up black curtains.
      
      
   3. Last of all, try out a few songs with and without the panels in place.
   4.  Acoustically there should be a fairly slight to modest improvement for the top risers, more for the middle risers and more yet for the bottom riser and floor singers. Sound travels around people better than one would think.
      
      
   5. I’d love it if someone could enlist a test “audience” to see what the change in sound is like. Ideally, blindfold the testers, but I expect this is asking for too much scientific rigor :) .
      
      
7. More: if you have end-railings (we made a pair) add plastic sheets to them too. They are more work to cut out but the effect is strong (think of them as sound-mirrors); creating an effect like adding 3 to 6 extra singers.

Adding panels to the steps

A surprising amount of recoverable sound escapes through the riser steps, as shown right.

This is a lot of lost sound, equivalent to a couple of 4X8' sheets!  Further, sound lost under the steps is not lost, it bounces off the walls farther back in your venue and muddies the sound.
  
For this reason, and because putting those little curtains on the steps is a time-consuming pain, I recommend also putting sheets over the gaps between steps.  About 2-3 extra panels are needed.

As you might expect, this is very similar to putting plastic sheets to the rise railings, with some important differences:

• It’s important to never introduce a tripping hazard:
  panels must never stick  up above the step and ideally should be ½ inch below the step level
  
  
•  The panels must be cut to 4 different lengths, to match the riser widths at each level.
• Make sure the corners are well rounded and the panels have no rough spots.
• Make a couple of extra step cover panels for each size; this removes the need to hunt for the last matching panel. 
• Use blue vinyl tape (easy for the mounting person to see) to round the top of the panels. The blue is not visible from the audience, but is easy to position correctly.

It’s not hard to mount the panels on the matching riser steps, but it requires a bit of practice. You need a set of applicators that know what to do and can train newbies.

Introducing the new choral shell

The first time you introduce the panels, have everyone practice once before a show.
The application technique is not hard to learn, but requires practice without a deadline.

The applicators must be told that the panels have to match the steps.
(It’s surprising how many people take a long time to notice the size differences; those that don’t get very confused and frustrated).

The applicators must be aware of the importance of keeping the top edge of the panel below the step.

Safety first

A designated riser setup safety person should double-check the risers to make sure everything is set up, especially that the step-panels do not stick up above the step.

Once everyone was in the habit of setting up the shell, we found it was quick and easy.

Results

After all that work, you'll receive the biggest un-compliment of all; your audience won't notice any of your handiwork. It should be totally "part of the background".

Here’s a rough list to what to expect, sound-wise.

1. If you have a 4-row or five-row setup, the lower rows should hear each other noticeably better.  
   
   
2. The director should hear the lower riser people better: whatever groups are on the top level will be asked to sing louder
   
   
3. The biggest effect we noticed was the people on each end could hear each other, e.g. our altos could hear our sopranos and vice-versa.  Not surprising: this choral shell roughly doubles the sound energy going from end to end on the risers.
   
   
4. For the audience, the sound should not seem that much louder - the direct improvement should be just noticeable.  However, the choral shell will stop sound leaking back-stage, and creating a muddy reflection off the back of the theatre. The two effects combined should make a difference.
   
   
5. As a consequence of point 4 above, the black choral shell seems to reduce the variation in the quality of the performance venue: a poor venue does not sound as bad to us.
   
   
6. As a consequence of all these "little" improvements, you should sing better; more in pitch; more in sync, with less strain.

Contact Me

I hope this helps your chorus.  If it does, please let us know.  Comments are appreciated.
If it does not, then we really need to know!  Please send details to MusicScienceGuy.

For more about the Maple Leaf Singers, you are welcome to visit our site: www.MapleLeafSingers.com