Sound is a difficult science to perfect because of its subjective nature. For people with substantial home theaters or entertainment systems for watching TV, movies and listening to music, tweaking and refining the sound setup is often the most difficult aspect of creating the ideal listening experience.
Part of what sets these special setups apart from standard in-TV speakers is the inclusion of subwoofers as a part of the audio arrangement. These produce the low-end and bass in shows and music that help simulate a studio or theater experience. But because of the strength and pervasive nature of low-frequency sound waves, subwoofers can cause bothersome vibrations that distract listeners and muddle sound. Bass can gather in corners of rooms and also sound “boomy” when a subwoofer is placed on the floor.
Fortunately, there is a way to combat the problems subwoofers present in a sound setup and maximize their qualities without any of the issues. That solution is decoupling.
By separating the subwoofer from the building structure, whether it is a floor or shelf, there is no bond to produce room vibrations as the woofer fires. This is exactly what a decoupler does; breaks the bond between the woofer and surface by serving as an intermediary damping agent. The vibrations a subwoofer can create aren’t just an issue for getting the best sound out of your speakers. These vibrations easily travel through solid surfaces in a building like the floors and walls and can be a major source of irritation for other members of your home or those sharing an apartment complex. Even if you don’t have any issues with the sound of your audio setup, a single decoupler can go a long way in keeping neighbors happy.
Many companies sell pre-made decouplers, sometimes called isolators. These are a great way to quickly solve sound issues you are experiencing, but for people who have a little time and want to save money, building your own decouplers is surprisingly easy.
On a basic level, a decoupler is nothing more than a solid surface resting atop open-cell foam. In a pinch, people have even paired sponges and books to create a makeshift speaker decoupler. But for a more professional appearance, there are some specific materials you will want to stick to.
The woofer platform in a DIY decoupler is best made from medium-density fiberboard (MDF). This is a much sturdier product than plywood and also non-resonant, an important quality in a sound treatment product. For optimal balance and aesthetics, the MDF surface should be no smaller than the widest dimensions of the woofer’s base. Sometimes speakers have feet that aren’t on the outer perimeter of the box, and only building to those dimensions can make for a decoupler that isn’t as stable as it should be. If cutting the board yourself, it’s also important to wear eye protection, as well as a mask or respirator since the material generates a fine dust when cut. Always refer to product-specific safety and handling guidelines before starting projects.
The base of a decoupler is where you get your vibration-reduction. Open-cell foam provides a substance that absorbs the vibrations before they have an opportunity to reach the floor and walls.
Some people have used simple packaging foam or old mattress remnants, which can work, but it’s important to remember that these pieces of cheap, old or damaged foam are supporting electronic equipment that may have cost thousands of dollars. To produce the best performance, as well as the necessary stability and strength, brand-new foam is always suggested. There are many varieties of foam with different firmness levels as well, and it’s important to get foam rated as firm. Firmness is measured by Indentation Load Deflection (ILD), and values in the 50s, 60s and 70s will offer a firm foam that is strong enough to support the weight of a subwoofer and stable enough to minimize rocking if it’s bumped. Contacting a foam manufacturer or retailer and explaining your project can help you get the right foam type.
Bonding the two materials is the last step, and it plays a major role. For the sake of stability, the foam shouldn’t be more than two or three inches tall, as that’s enough material to absorb vibrations without making the decoupling pad unstable. Foam should also be trimmed into smaller pieces so the MDF isn’t resting on a solid slab. The smaller the footprint of the decoupler, the less contact with the floor and the more difficult it is for vibrations to escape. One smart design is to cut rectangular blocks and glue them to the MDF in each corner, perpendicular to each other. A short end will always face a wide end in this design, giving sufficient stability while minimizing materials. Use spray adhesive designed for use in open-cell polyurethane foam projects and you will have a sound treatment product that makes your listening experience much more enjoyable.
Whether you decide to purchase a decoupling pad or make your own, they are the single best way to cut down on vibrations and improve the sound quality of your sound system.