This project was intended to treat a medium size critical listening room.

 

Introduction

To make the better investment possible, it is necessary to study a few acoustics concepts that will determine which is the best option we have to treat our room.

Some of them are:

• Standing waves
• Understanding the frequency domain
• Air velocity vs air pressure in sound waves
• Air flow resistance

However, these concepts are exlained in depth with a practical approach in my project Acoustic treatment for a medium size room, (añadir link) which, in addition to these cocepts, it covers the decisions made to design these panels.

This article is a mere explanation of the structural design and manufacturing of the panels.

Design criteria

Once we have decided our needs based on the acoustic study we made previously, it is time to design the structure of our panels.

We will be making them out of wood, fabric and insulating material, because it is the easiest and cheapest way to do so.

The design proccess is commited to these criteria:

• Budget
• Placement
• Woodworking experience and workbench
• Material availability

Which are explained more deeply in the next lines:

Budget

First of all, and most important, the budget.

The first thing you want to cover is effectiveness, which is the cheapest property in DIY panels.

Once you have reached the budget thereshold of a functional panel, all the money goes into appearence and/or versatility.

If you plan to treat a small-medium sized room with the lowest budget possible without compromising the performance, you can make big improvements with 150$.

In my case, I had 350$ to spend, and I was looking for versatility and appearance too, because the panels were intended to be in my bedroom.

Placement

Basically, if you plan to put the wall, in a corner, or in the ceiling.

For wall mounted panels the best option is a rectangular panel. It is also the cheapest and simplest option in general.

For corner panels you can make triangular or trapezoidal panels. However, this is significantly more expensive and complicated. You can also use rectangular panels for this purpose, but they will have a worse performance/space ratio

For ceiling panels you will use the two options mentioned above, but you have to consider the strenghth of your ceiling. If you have a false ceiling like mine, you have to use lighter materials.

Woodworking experience and workbench

The more experience you have working with wood, the less money you spend and the better the result will be.

My advice here is to be cautious. If you don’t have that much experience, do not use wood thinner than 2cm. You will be fine with 3cm thickness pine wood.

Tool quality have also a huge impact in your work, and if I would have to recommend a tool for this project, it would be a torque adjustable drill with the possibility of putting a screwdriver head in it.

You will NEED an upholstery stapler to cover the insulating materials with fabric.

Material availability

Depending on where you live, you will have access to a different set of materials, specially when talking about insulating material.

Because of that, you have to do a little research about what suits you the best.

 

FINAL DECISION:

For my project, I decided to make trapezoidal panels for the corners and rectangular ones for the walls. These will have a high density material inside, because I have to move them quite often and I don’t have that much space in my car.

For the false ceiling I needed to do special panels with a lower density material and thinner wood.

I needed to cover low frequency waves, so I decided to use at least 2 layers of 4cm deep insulating material per panel.

I also made bigger panels that I don’t need to get out of the studio, so I will show also the process of making a huge bass absorber later.

Design process

Trapezoidal panels

To begin with the ddesign process, I did a simulation model to have a brief idea of what we can expect in terms of performance. I will be using a 8cm thickness layer of absorbing material which has an air flow resistivity of 22000 Pa*s/m^2.

I decided to build them with 1cm thick MDF wood because is more even than raw pine wood, which is important for the shape I wanted.

In my case, I didn’t have the tools I needed to make precise cuts on wood with that shape, so I decided to make a 3D CAD model in Google SkethUp and ask a professional to do the work for me.

3D Sketch:

The measurements are decided to match the size of the insulating material blocks as much as possible. It’s the best option to save work and money.

Insulating material inside the panels

Finally, I made a technical drawing with the information needed in order to cut the wood

MDF boards are sold in my local store with measurements of 244x144cm.

Considering that, we can make 4 panels out of one wood board, and there is not much difference in cutting 1 panel than cutting 4 of them, which makes it worth it.

Wood pieces measurements

Rectangular panels

These panels are actually very simple and cheap to make.

You can buy cheap wood planks to make the structure and put fabic on top of the entire panel, as shown in the next image.

Anyway, I wanted to make them with the same visual style of the trapezoidal ones.

To do them in that way, I decided to make them out of simple wood skirting boards and put the fabric inside the structure to let the wood cover the outer part of the panel.

Here is an example of what I had in mind (this commercial panel alone costs the same than the entire project)

Build proccess

Basically consist on three steps:

1. Structure construction
2. Insulation material filling
3. Covering with fabric

Trapezoidal panels

This was by far the most complicated structure to build. I do not recommend to do these panels if your time and experience is limited.

1. structure build

It is recommended to use long and thin screws, because the MDF wood is quite thin and fragile.

ALWAYS drill the wood before screwing

I also used wood glue between pieces to enforce the union.

Then I made a structure for the front cover.

These were actually very hard to make, because I didn’t have the best materials to do this kind of shape and I had to figure out a way to do so.

Finally, I painted them white.

2. Insulation material

As we can see, I had to cut a little to fill the entire panel.

3. Fabric cover

In this panel, I had to put fabric in the structure I made for that purpose, and then on the back of the panel.

Final result

 

Despite of the complexity of this build, I have to admit that the result is excellent.

I am happy that I built them, not only because they work as well as they look, but also because I got a lot of experience and learned not to do this anymore until I retire.