HOW TO CREATE BROADBAND ABSORBERS WITH ROCKWOOL: A STEP-BY-STEP GUIDE
Introduction
1 of 14 identical panels I made for my home studio, saving hundreds including the cost of tools- the electric stapler was the real MVP.
When it comes to sound design and home studios, a well-treated space is paramount for achieving professional-grade results. Broadband absorbers are crucial for managing sound reflections, reducing reverberation, and improving overall acoustic quality in the room. By absorbing a wide range of frequencies, these panels help create a more controlled and pleasant sound environment.
However, pre-made panels can be prohibitively expensive, and a DIY approach can provide a cost-effective solution for achieving professional-quality acoustic treatment that not only meet your acoustic requirements but also reflect your personal style and creativity.
For those embarking on a DIY project, Rockwool is a highly recommended material due to its exceptional acoustic properties. It provides even broadband absorption, is easy to handle, safe, cost-effective, and offers additional benefits such as fire resistance and moisture control. While fiberglass and other materials can also be effective for acoustic treatment, and will work pretty interchangeably with this guide, Rockwool was the best choice for my specific use case.
Fiberglass is a great absorber but can be more challenging to handle safely due to its tendency to shed fine particles, which can be irritating to the skin and lungs.
Rockwool is more user-friendly and easier to cut and shape without excessive dust.
Rockwool’s price and availability happened to be better at the time of my purchase, so it is important to keep that in mind as you design your own panels.
Creating your own broadband absorbers not only allows for significant cost savings—often exceeding 50% compared to pre-made panels—but also enables customization in terms of size, depth, shape, and aesthetics. This guide will walk you through the process of constructing broadband absorbers using Rockwool insulation.
Cost Considerations
Get the best bang for your buck with custom DIY panels.
Creating your own broadband absorbers with Rockwool is not only a rewarding DIY project but also a smart financial decision. Let's explore the cost savings you can expect by opting for a DIY approach compared to purchasing pre-made panels.
Cost of Pre-made Panels
Pre-made sound panels typically range from $50 to $150 per panel, depending on the brand, size, and quality.
Cost of DIY Rockwool Panels
Rockwool Insulation: A pack of rockwool insulation (e.g. Safe'n'Sound) costs around $50-$70 and can typically make 6-12 panels, depending on the size and thickness.
Fabric: Acoustically transparent fabric costs around $5-$20 per yard, and you might need 1-2 yards per panel.
Wood Frame: Wood for the frame might cost around $10-$20 per panel.
Additional Materials: Miscellaneous materials like adhesive, screws, and mounting hardware might add an extra $5-$10 per panel.
So, the total cost for a DIY panel typically comes in at well under $50, allowing you to better treat your space.
Materials and Tools Required
Materials
Try to find lumber that is not warped, as this will make squaring corners difficult.
Insulation batting: I used 3” deep, 15.25x47” Safe'n'Sound batting
Lumber: 4x1 planks allow internal space for the batting and a flush center brace
Acoustic Transparent (AT) fabric: I used Guilford of Maine (plus cheaper tulle backing fabric)
Wood screws
Corner brackets: Optional, for added stability.
Staples
Mounting hardware: French cleat recommended for secure and flush mounting
Stick-on foam bumpers: Optional, to prevent tilting/ vibrations
Tools
A speed square can help you achieve square corners quickly and easily.
Tape measure
Speed square
Pencil
Saw (jigsaw or circular saw)
Drill
Screwdriver
Fabric scissors
Staple gun (electric recommended)
Level
Safety equipment (gloves, mask, and goggles)
Planning and Measurements
Decide on the placement of your absorbers for optimal sound absorption. Prioritize key areas such as first reflection points, corners, and back walls. Consulting with acoustic treatment experts like GIK Acoustics, ATS Acoustics, or Acoustimac can provide valuable insights, as well as treatment options or mounting hardware that may be more difficult to DIY or source elsewhere.
Determine the size and quantity of absorbers needed based on your room's dimensions and acoustic requirements. For more information on this, check out my previous entries on mix room calibration part one and part two. Effective broadband absorbers typically combine a depth of Rockwool with an air gap to target specific frequencies, enhancing their efficiency. Utilize the "Product Data Sheet" or "Technical Data Sheet" for selecting your batting.
This document typically contains detailed information about the product's acoustic properties, such as its sound absorption coefficient, density, thickness, and other relevant specifications. You can usually find this sheet on the manufacturer's website or by contacting them directly.
Selecting Fabric
Burlap covered panels tend to look sloppy no matter how careful you are.
Choose a breathable AT fabric that allows sound to pass through, such as Guilford of Maine, which is specifically designed for acoustic treatments. When making your selection, look for the "Acoustic Performance Data Sheet" or "Acoustic Transparency Data Sheet." This document provides information on the fabric's acoustic properties, including its ability to allow sound to pass through while still providing adequate coverage for acoustic treatments. Alternatives like burlap or other heavy fabrics do not have this data and can often impair acoustic performance and durability. These fabrics will also not be as easy to tension correctly, leading to visual flaws.
Calculate the amount of fabric needed based on your panel dimensions and the width of the fabric roll. You may find certain orientations lead to less waste or fewer cuts.
In my case it was optimal to lay the long dimension of the panel across the width of the roll, where the only waste was at the top and bottom of the panel and could be left on the back without the need of additional cuts as this small bit of extra fabric would not be seen when mounted.
Cutting the Frame
Measure and mark the 4x1 lumber to match the internal dimensions of the Rockwool panels.
Arrange the cuts to minimize waste and avoid knots, which can weaken the structure.
Cut the lumber to size, ensuring precise measurements for a snug fit around the Rockwool without compressing the batting, as this will compromise the performance of the material.
In my case I needed 3 lengths of cuts: the long sides (2 per panel), the short sides (2 per panel), and the center brace (one per panel), which is shorter so that it may fit between the long sides and lays flush to the exterior edge of the frame.
Assembling the Frame
Align the corners of the cut lumber, using a speed square to ensure right angles.
You may wish to sand out any rough or uneven edges, especially if using alternative fabrics.
Drill pilot holes to prevent the wood from splitting, and join the pieces using screws—two per corner—leaving enough space along the edges for the staples.
For additional stability, consider reinforcing with metal corner brackets or scrap wood cut to triangles, the latter of which can help keep the batting in place.
Attach AT backing fabric (e.g., tulle) to the interior of the frame with staples to hold the Rockwool in place.
Preparing the Fabric for Rockwool
Cut the fabric to size, allowing some extra material for overlap—you want to avoid staples right on the edge of the fabric.
Lay the fabric flat, exterior side down.
At this point you may wish to apply a spray glue to the fabric where the batting will be placed, however with a wood frame design this shouldn't be necessary.
Handle the Rockwool carefully, wearing gloves and a mask to avoid skin irritation and inhalation of fibers.
Lay the Rockwool flat in the center of the fabric.
Attaching and Wrapping the Frame
Place the frame onto the Rockwool, with the backing side up, centered on the fabric.
Ensure the Rockwool is evenly distributed within the frame and is not being compressed or bunched up anywhere.
Begin stapling the fabric on each side of the center bracing, pulling it taut without overstretching.
Continue stapling evenly around the frame, spacing the staples about one staple width apart for even tension (electric staple gun highly recommended).
Work from the center outwards to maintain even tension and avoid waves or distortions in the fabric.
Begin by going from middle to right on one side, switching sides and going the full width from left to right, and finish with the first side going from the middle to the left end, ensuring it is even and taut as you go.
Fold and secure the corners neatly, tucking any excess fabric underneath for a clean finish. Ensure the corners are flat and uniform for the best appearance.
Uneven tension will be visible as waves or distortions in fabric thread/ texture/ design, but this should not have much effect on the acoustic performance of the panel. An even wrap is easier to accomplish with something purpose made such as Guilford of Maine than with alternatives like burlap.
Mounting the Absorbers
Install the mounting hardware, such as French cleats, on the wall and the back of the absorbers.
You will want a secure mounting option as the panels will typically exceed 5lbs, largely due to the weight of the frame.
Use a level and tape measure to ensure accurate placement.
Attach stick-on foam bumpers to the rear side of the corners of the panels to prevent tilting and vibrations, ensuring a secure and stable installation.
Conclusion
In the field of sound design, a well-treated space is crucial for achieving professional-grade results. Broadband absorbers crafted with Rockwool offer a rewarding DIY solution, enhancing your acoustic environment while providing customization and significant cost savings.
With careful planning and execution, your DIY broadband absorbers will transform your studio into a professional-grade acoustic space. Remember, a well-treated space not only improves sound quality but also fosters creativity and productivity in your work. Let your creativity shine through each step of the process, and enjoy the enhanced sound quality that your custom broadband absorbers bring.
Ready to elevate your project with expert sound design? Let's bring your vision to life! Explore my services or contact me today to discuss your project requirements. Thank you for visiting sameliaaudio.com. Stay tuned for more insights and analysis on cinematic storytelling through sound.