A practical space for recording or listening to music requires good acoustics. An essential part of this acoustic environment is the reduction of echoes or diffused sound. Sound diffusers represent an optimal solution for this challenge. These devices scatter the sound waves in different directions, reducing the distortion that echoes can cause. Due to their typically high prices, many sound enthusiasts resort to DIY sound diffusers. This article will teach you how to build a sound diffuser on a budget.
To get started, you’ll need some basic tools, including a saw, a measuring tape, a pencil, wood glue, sandpaper, a level, and clamps. Additionally, you’ll need the building materials: sound diffusing blocks (usually made from wood) and a plywood sheet for backing.
Choosing the Right Material
Raw wood is the most common material for DIY sound diffusers due to its affordability, ease of use, and efficient sound diffusion capabilities. Hardwoods like Oak, Mahogany, or Maple can provide stylish designs and are perfect for high frequency diffusion, whilst softwoods like Pine or Cedar can also be ideal for budget choices with similar acoustic properties.
Design Concepts
The design is equally as critical as the materials for your DIY sound diffuser. The Quadratic Residue Diffuser (QRD) and the Skyline Diffuser are among the most popular models.
A QRD consists of a series of wells of different depths, organized according to quadratic residue sequences. Sound waves penetrate these wells and scatter at varying depths, diffusing the sound.
Skyline diffusers, on the other hand, are modeled after the city skyline, hence the name. They have multiple blocks of different heights assembled randomly. The inconsistencies in block height create a more evenly distributed diffusion pattern across a wide frequency range.
Building a Quadratic Residue Diffuser (QRD)
To build a QRD, start by determining the well widths. The well width is usually linked to the highest frequency that the diffuser will affect. For a typical home recording studio targeting a highest frequency of around 4.5kHz, a width of 75mm works well.
Next, decide on the well depths. These should follow the quadratic residue sequence of a certain prime number. For instance, if we take the prime number 7, the residues of the squares from 1 to 6 (as 7 is our maximum) mod 7 give a sequence of 1, 4, 2, 2, 4, 1. Multiply these by a depth constant for simplicity – if we take our constant as 25mm, this would give us depths of 25mm, 100mm, 50mm, 50mm, 100mm, and 25mm.
Finally, lay out the plywood sheet on a flat surface, marking out the wells according to the calculated widths and depths, before cutting and assembling the wood pieces.
Building a Skyline Diffuser
The process for building a Skyline diffuser is somewhat less mathematically complex. Firstly, decide on the size of your blocks. Common dimensions range from 50mm to 150mm, with height variations leading to the eponymous ‘skyline’.
Once you have your blocks, organize them into a pattern. Many follow a random placement for simplicity, but guided randomness (avoiding long straight lines, for instance) can offer better diffusion.
Next, apply wood glue to each piece’s bottom and place it on the plywood sheet, pressing firmly. Use a level to check each row for evenness as you progress. Once all pieces are set, allow the glue to dry for 24 hours.
Finishing Touches
After assembling your diffuser panel, it’s time to add the finishing touches. Start by sanding the diffuser to a smooth finish, to prevent any injuries from splinters in the future. Next, apply a finish of your choice – this could be oil for a natural look, or paint for a more personalized touch.
Placement
Now that your sound diffuser is ready, it’s time to consider its placement. Sound diffusers should ideally be placed in locations where sound reflections are prevalent: for instance, on the rear and side walls and ceilings in a rectangular room. The ‘mirror trick’ – sitting in your listening position and having a friend move a mirror along the wall – can help identify where these early reflections occur.
Though building a sound diffuser from scratch might seem daunting, each phase of the project offers room for customization and fun while solving real-life acoustic issues. Whether it’s the QRD or the Skyline model, your DIY sound diffuser will not only improve the acoustics of your room but also impart a unique personality to your space. Dive in and explore the world of DIY sound diffusion today.
