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
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:
- 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.
- 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.
- 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:
- Found relatively inexpensive, good choral, microphones
- Have a mixer with spare channels, monitors and house speakers
- Are able to store them compactly and deploy them quickly
- 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
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
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.
- 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
- 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
Steps to creating an upper choral shell
- String fishing line through the sheets so they can be adjustably curved and un-curved
- Apply Velcro so that the sheets can be reversibly linked together
- Create an easily-assembled batten
- Apply Velcro to the batten and sheets so that your batten can stick tightly to the sheets
- Put together the whole shell assembly
- “Flying” the assembly, either from the ground, or from the stage rigging
- 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.
- Put some holes in the sheets: 2" from the top, 6" and 36" from the corner. Use a 1/32" bit.
String fishing lines through the holes.
Tie the lines snugly in the back – suggest using needle-nosed pliers and a barrel knot.
- Make Velcro tabs to allow the fishing line to curve the Coroplast as desired:
- Put a Velcro hook tab on the line
- 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
- 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.
Step 2: Apply Velcro so that the sheets can be reversibly stuck together
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.
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.
- Check that the pieces are the same length, all 8’ long and sound.
- Mark off 6” from the end.
- Overlap the wood pieces, offset by 6", as shown, to make an “L” beam.
- Be aware that the 3-D shape you are making has a handedness – make them all with the same overlap shape!
- Lay a line of glue down on the join; this will make the L-beam quite strong
- Nail or screw the pieces together enough to hold snugly together until the glue dries, and so that you can work with the batten
- Make the batten end-stubs – take one batten and cut it in half at the exact middle these will be the end
- Fit the batten sections together, overlapping the 6” offset sections, as shown to the right.
- Note that you will have 2 end pieces that are not interchangeable;: there will be a stage-left and a stage-right version.
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
- 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.
- Lay the sheets on the ground.
- 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.
- Put the batten on the sheets, sticking the Velcro on the batten to the sheet.
- 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
- Lift up the assembly.
- 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
- Detach the choral shell from the rigging – several people may be needed. Hold up the unit by the batten, with the sheets upright
- Un-curve the sheets
- 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)
- Pull one sheet at a time from the batten
- When all sheets have been pulled off, put the batten on the floor
- Unscrew the sections of batten, but don’t unscrew the screws all the way out; leave them for the next assembly
- 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.
- If you have a 4-row or five-row setup, the 3 upper rows should hear each other noticeably better.
- The director should hear the group better: he/she will stop bugging you to sing louder.
- 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.
- 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.
- As a consequence of point 4 above, the black choral shell seems to make the room more cosy.
- As a consequence of all these "little" improvements, you should sing better; more in pitch; more in sync, with less strain.
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
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.