Posts Tagged ‘easy’

So today I hung around after a music history exam to do help a friend do all the sound/roadie work for the performance exams, he certainly manages to do a lot of different things at once.

1. The Setup

First we had to get in contact with whoever was performing and asked them what was on stage and what would be miked. We set up 3-4 mics for the first couple of exams even though we knew we probably wouldn’t need them, it was a just in case. Most of the exams just required lugging gear on and off, and some slight monitoring on the piano (which was normally the only thing miked). However, some exams wanted more miked, the most intense being a guy singing/playing piano or playing a leslie organ (alternated between songs), a small choir, a lead vocalist, a guitarist, a bassist and a drummer. The organ, all the vocals (choir of six had 1 mic between 2) and the piano (bass but was muted as it didn’t need any reinforcing) were miked. Everything had 58s on it except the piano which had a dynamic mic I can’t recall on it. 2 foldback wedges were run out the front daisy chained, also. This set up (including the instruments) had to be completed in a little over 30 min. This was the biggest challenge and the reason for not using more interesting mics/setup.

I found during this that the most important part of the speedy setup is to try and neaten mic cables as you’re running them, rather than afterward and ALWAYS try to work from left to right. Because without time to do a labelling system, and without an incredible memory, this will be your saviour. Keep gaffa tape with you if you can, so that you don’t have to go find it when you want to tape something, and you can do some of the taping while you go.

Also, without a sound check or any way for the performers to let you know if theres anything they want in their foldback there isn’t much you can do other than guess, but there are some things you can listen for that may help. If a singer seems to be a little pitchy, especially if they are a singer who is normally very good, chances are it’s because they can’t hear themselves. With all other instruments (and also singers as well), listen to hear how tight the timing is. If they fall behind then catch themselves back up a few times (or push ahead and pull back) then they probably can’t hear either. Drummers in particular have a tendency to push tempo when they can’t hear, however if they aren’t particularly brilliant drummers they may just not really be listening.

As for the actual mixing of this gig, it was mostly level riding, boosts for solos, a little EQ to tidy it up, nothing too fancy, a little bit of reverb as well, all on a basic yamaha mixer.

2. The audio CD and DVD of performance

While all this is going on, a spaced pair of matched cardioid condensers are set up on a high pole in the middle of the audience (everything run neatly so that it only takes up the space of one chair) to record the whole thing, running to the stage multicore and back to a separate digital mixer with a reverb effect on it to enhance the room a little. This signal is then sent to a Tascam CD Burner and a HD video camera running to a DVD burner. This CD and DVD is burnt/ripped/copied/backedup in numerous ways for numerous people and for the Cons achieves.

That’s a little for one person to do for almost 12 hours a day 6 days a week during exam week.

Build a Triffusor

Materials (per triffusor):

  • 2x equilaterally triangular pieces of MDF wood
  • 2x rectangular pieces of MDF wood (width same as trianglar side)
  • 1x rectangular piece of MDF wood slightly shorter and thinner than other pieces
  • Acoustic foam rectangle the size of the 2 larger pieces of MDF wood
  • 5 long thin pieces of any kind of wood to be placed on one side for diffusion
  • A decent number of screws and some PVA glue (and some contact glue, though PVA will work)
  • Saw(s) and miter box (if cutting any of the wood yourself)
  • (Optional) beading for the edges


Attached larger pieces of MDF wood to two sides of one of the triangle. PVA glued, and then screwed them together.  Attached other triangle to other end of the rectangular MDF wood in the same way.

Used contact glue to attach acoustic foam to one side of the triangular prism.

Put smaller wood rectangle where third side of triangle would go and push it in so that it sits further back than the other sides.

Place long thin strips of wood against the side with the deeper wall and glue

Acoustic Properties:

–       Reflective side: The reflective side is smooth wood, allowing the sound to bounce off easily, creating direct reflections.

–       Absorptive side: The side with the acoustic foam is designed to absorb sound. When the sound hits the acoustic foam it enters any tiny gaps in the foam and bounces around inside it so many times that barely any of the sound manages to get reflected, most of it dies within the foam.

–       Diffusive side: The side with the further back wood and strips of thin wood running up and down it is designed to diffuse any sound that hits it. Either before or after the sound hits the back panel, much of it will reflect off the strips causing it to be reflecting off to the sides, known as being ‘diffused’, often used to stop early reflections from causing phase cancelation without killing the reflections all together and risking deadening the room too much.

Personal Uses:

  1. In parts of my room there are cupboards and dressers that would cause unusual reflections, reflective side could be placed in front of these to give more direct reflections.
  2. Diffusive or absorptive side could be placed at the back of my room where the first direct reflections would occur to send them in different directions of absorb them to reduce possible comb filtering in the listening position.
  3. Absorptive side could be placed facing out of the corners and be used as a bass trap.

Evaluation: Overall, each of the triffusor’s sides has the acoustic properties they were designed to have, and the triffusor itself is very sturdy and solid. If building more, the only thing I would do differently is take more time perfecting some of the measurements in attempt to get that really neat and tidy, professional look.

The backboard for the diffusive panels had some bend in it after being placed in too tight. The diffusive panels needed holding screws to hold it in place till the glue dried and keep the bend in the backboard down, and some of the panels started bending too so I had to use some tech screws to hold them too.

Turns out one of the easiest ways to cut acoustic foam in a straight, relatively smooth line is to mark out the cut with a pen, use a piece of wood as a guide and cute with a bread knife.

The point of building a triffusor was to have adjustable room acoustics, absorption, diffusion or reflection, depending on what I need, at the moment I’m wondering whether absorption in the corners as bass traps or diffusion in the speakers first reflection points is best. Since I’ll have some left over foam I’m thinking maybe put that in the corners to absorb bass and diffuse the early reflections, either than or put it along the back wall and absorb early reflections, then absorptive side of triffusors in the corners and absorb that too (my room isn’t particularly acoustically awesome)

Bought and cut panels for diffusive side today. Note to self: if a board has to fit between 2 others, get 1mm more cut off than you will need in theory, just to be safe. Bought some acoustic foam too, that stuff is great and really not that expensive for a large amount.

My audio and sound obsessed uncle arrived today. We started chatting pretty quickly and he told me about his current projects for building speaker cabinets and different combinations of drivers, tweeters and horns. He talked about woofer horns and how they throw the sound better. He also showed me some models of some old JBL speakers hes trying to build/model and gave me a very large collection of info on a lot of audio topics, in particular speaker designs. Will keep you updated on what it says when I start reading!

So I’ve never really had much experience experimenting with acoustics, and decided to ask my recording and sound reinforcement lecturer what I might be able to do for one of my projects for the class that would allow me to learn more. He suggested that maybe I should build a trifussor. For those of you who don’t know (which is probably most) a trifussor is a triangular prism with a diffusive surface on one side, a reflective surface on another and an absorptive side on the last. I have no carpentry experience as well as no acoustical experience but decided to give it a go anyway. So I picked up some medium density fiber wood from my local hardware saw, asked my dad to find me his drop saw and together we started cutting, gluing and screwing the wood together into the shape of a triangular prism. So far so good, and all thats left to do is attach the diffusive panels and the absorption material and I will have my very own pair of DIY trifussors.