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Archive for the ‘Acoustics’ Category

Simple Salvaged Wood Diffusor

Thursday, June 13th, 2013

This week one of my neighbors left his unwanted Ikea bed frame in the alley. Among the parts of the bed was a set of SULTAN LADE slatted base. In other words: 20 3/4″ pine boards for free. Keep an eye out for these because they can be used for a ton of simple DIY projects.

IMG_2613With these, I decided to make some super simple diffusors to cover up the bare wall around the closet at the back of my studio. The goal was to use the least amount of materials, hardware and effort. This design accomplished that and I didn’t even need to use a saw.

Each diffusor is made of 5 boards in a wide V shape. I used extra boards to get the spacing right, then held it firm with a pair of C-Clamps while hammering. The clamps were a huge help to prevent the boards from shifting around. I had just enough nails of the right length to build two diffusors, I would have built 4 if I had more nails. These aren’t very heavy so for now I have them mounted with a single drywall screw and picture hanger.

I’m sure an expert will disagree with the design as an effective diffusor. QRDs these are not. However, just holding it to the wall I could hear it was doing something far better than a bare wall. Unpainted soft wood like pine is porous and I could hear it softening the highs a little. Not sure if it scatters the sound at all but surely it is doing something more than the drywall was. QRDs are complicated, heavy and extremely labor intensive to DIY.

There are two downsides to building with free/salvaged wood like this.
1 – needing to remove staples, screws or nails before you can build.
2 – Sometimes the wood is warped which is hard to fix.
These don’t sit as flush on the wall as I’d like because of some warping.

I’m undecided whether I will leave these natural or stain them. If you’re looking for a simple wood stain, vinegar and steel wool left in a jar for a few days will give you a nice grey aged fence/barn wood look. Toss coffee grinds in the jar too and you can get a pretty dark almost chocolate brown stain. Teas, cocoa or spices can give you different colors. Steep longer and apply repeatedly for darker color. Again, super simple and practically free, but also it doesn’t stink up your house for days with toxic fumes.

I have some more ideas for diffusors which I will explore at a later date. One idea is to use the curved SULTAN LUROY bed slats and symmetrically staggering them at a few different heights and depths. Would probably look really nice and modern in a live room especially behind a drum kit.

Have you made a DIY diffusor? I’d love to see it, leave a comment and link below.

Drum Kit isolation platform using tennis balls?

Friday, June 7th, 2013

I stumbled across this interesting construction diary of an impact isolation platform for Electronic Drums that uses a couple layers of MDF and tennis balls to float the kit. This is a genius idea and it came out looking great and probably very effective.

This looks like a very inexpensive and effective solution for acoustic drums or on a smaller scale, loud guitar amps or subwoofers. I wonder how ‘squishy’ it feels to walk on this, it might be a good non-permanent solution for floating a small live room, or at least a toddler bedroom.

Click this link to read the build instructions and discussion.


TED Talk: Why architects need to use their ears

Wednesday, January 23rd, 2013

Another great TED Talk by Julian Treasure (watch another, and another) about architecture, acoustics and education. I can certainly relate to this, my high school had terrible acoustics and the lecture rooms in my audio school were even worse!

Towards the end of the video Julian talks about the Sound Education seminars and the free app called Study with sounds designed to mask ambient noise, help focus, improve cognition and reduce fatigue.

Guest Post: Charcoal Based Low Frequency Absorption

Wednesday, June 13th, 2012

Mike Sorensen (@mikesorensen06) is a master cabinet maker, structural engineer and the author of the sound diffusion audio blog. I think you’ll find his research on activated carbon for acoustic absorption very interesting.

If you’re going to make a great recording you have to find a solution to the room acoustics. Like the black sheep of any family, room acoustics are somewhat left un-talked about given their unsexy nature. Yet they are key to helping you produce the best sound from your recordings whether in the live or listening room.
Some people think that throwing up a bit of foam here, dampening the sound there and generally shutting the door and turning off the extractor fan will do it but alas no. There is a big science that goes into it and I want to share some of my years of experience with you today so you can start to consider some of the treatments and how they work in conjunction with your studio space.

Diaphragmatic Absorbers
Diaphragmatic absorbers are powerful, low frequency, absorbing technologies. One must build a solid, sealed box that has a front wall that can “move” in reaction to sound pressure waves. This front wall movement slows the wave down, so that it can enter the inside of our sealed cabinet. Yes, the cabinet is sealed without any air holes. Low frequency waves that are 40 and 50 feet long do not care about some 1/4″ air holes in any type of absorber. With low frequencies we are dealing with waves of energy not rays.

Fixing Small Studio Acoustics Problems

Monday, August 15th, 2011

This weekend I moved my home studio from one room to another. From a nearly 200 square foot living room to a 100 square foot bedroom. It’s been a long time since I’ve thought about room acoustics and because this is a common situation for home studios, I thought I’d share my experience.
This article will help you understand and overcome the challenges of a dedicated studio in a small room. It will be most helpful to those with symmetrical rooms (no weird angles) and to those that don’t need all the usual bedroom stuff, at the very least it will be a starting point to making the best of the situation.

Corner bass trap and broadband absorbers plus foam above.

The Problems
Small rooms are more likely to have acoustic problems than larger ones, primarily flutter echo, room modes and early reflections that are too short. In my room, I knew there was a very bad flutter echo problem and room modes may be a problem but were predictable. The room is symmetrical which was an advantage the old room didn’t have. The measurements are approximately 11ft long x 9ft wide x 8ft tall. There is a door and a closet on the back wall and 6 x 4 window on the front wall.


The History of Echo (Echo) Chambers (Chambers)

Wednesday, February 2nd, 2011

This is a guest post from Geoffrey Granka of Fresh Produce Productions. Find him online at and @gmgranka on Twitter.

The invention of reverb itself is impossible to pin-point in time. Gregorian monks knew it sounded great and so does anybody who sings in the shower. As soon as recording started, it was natural to record music in its most pleasing setting. Early recording engineers followed music wherever it went, frequently ending up in spacious churches and music halls. When electronic recording began to gain ground over the phonograph, interns started complaining about hauling tube tape machines to every church in the city. Subsequently, marking the first and last time anybody listened to an intern, dedicated recording studios started being built to house the gargantuan, over-heating recording equipment.

When it came down to live rooms, flexibility was the biggest concern. An 80-piece orchestra sounded great in a room with a lengthy reverberation, but it was hardly desirable for a rock band. Specially made reverb chambers were developed using a send (called an echo send) from a console, the engineer could adjust how much signal would be sent to that chamber and what channel would receive the treatment.

Note: Most audio engineering text books will refer to “echo” as a small number of repeats, each discernible. This is a misnomer in the case of “echo” chambers. Most echo chambers provide reverb, which is usually accepted as thousands of repeats that are unable to be individually picked out by the human ear.

A view inside an Echo (or Reverb) Chamber

How It Worked:

The rooms were not nearly as large as you would expect (or as they sounded). Studio architects used what little trickery they had at their disposal to exaggerate the acoustics of what was often little more than a large pantry. Echo chambers would have shellac or tile on all surfaces of the room, much like a shower. The loudspeaker (playing what was being sent from the echo send on the console) would usually be placed not facing the room, but facing a reflective wall. This increased the reflections in the room, and also decreased the amount of direct signal that would be picked up by the microphone(s). In the early days of recording the echo chambers would be mono send, mono return.

Famous Examples:

Gold Star Studios is arguably the most famous example of a reverb chamber. Phil Spector made Gold Star his home while recording the early hits of his career, and its reverb chamber played a key role in Phil’s infamous Wall of Sound. If other studios included reverb chambers as fringe benefits, Gold Star included it as a downright necessity. A cramped room where elbow room amongst musicians was a legitimate concern, the reverb chamber was the saving grace. In a Mix Magazine article, Larry Lavine testifies to the speaker in the chamber being a cheap 8-inch speaker being picked up by an equally cheap ribbon microphone (bi-directional). The chambers were a mere 2×3 feet, but the cement lining did wonders to enlarge that. You can hear this reverb on The Ronettes’ Be My Baby, parts of Pet Sounds, and other staples of that era in recording.

Try getting away with a fart in this room.

EMI Studios (later Abbey Road Studios) was a studio complex built by a record label at a time when it was hard to imagine a better business model than recorded music. There were 3 reverb chambers built inside the complex, one for every studio live floor.

Capitol Studios, located in the basement of Capitol Tower, was the frat house of Frank Sinatra, The Beach Boys, and the equally charming Beastie Boys. Its four identical trapezoidal rooms were designed by musician cum technological-soothsayer Les Paul. The rooms were built using reinforced concrete and coated with metal lath and cement plaster on the interior. Even the ceilings were sloped to ofter flutter or standing waves.

Other Famous Reverb Chambers:

Motown Records’ Hitsville USA complex is rumored to have used a hole in the ceiling as a jerry-rigged echo chamber. This wasn’t a traditional reverb chamber, it wasn’t controlled from the board, adjusted by positioning mics to pick-up the desired amount of reverb.

Joe Meek, the English producer of the 1962 hit, Telstar was well-known for using cavities in his house, like beneath the stairs or in the bathroom, to supply the reverb he needed.

An example of a staircase reverb set-up

Build Your Own:

Dave Simons over at Electronic Musician wrote a great article on his experience building a reverb chamber in the basement of his home studio.
What are some reverb chambers that I left out? Do you have any favorite examples of reverb chambers?

Techniques for dealing with Phase

Thursday, July 16th, 2009

Phase is a constant concern for recording and mixing engineers. Problems with phase can ruin your music, they can be easily avoided or corrected, but first you need understand how these problems occur.
This guide will attempt to explain almost everything there is to know about phase, what it is, how it happens, what it can sound like and some techniques to deal with it.

What is phase?
I’m going to consult my Engineering school textbook Audio In Media for this.

The time relationship between two or more sounds reaching a microphone or signals in a circuit. When this time relationship is coincident, the sounds or signals are in phase and their amplitudes are additive. When this time relationship is not coincident, the sounds or signals are out of phase and their amplitudes are subtractive.

No wonder people are confused about phase. Even I got confused at that, looking up other entries on phase in the book were even worse. I guess I shouldn’t read books.

I’ll try to break it down more simply.