How do I make my own soundboard sound?
A soundboard is a thin wooden board inside the body of stringed instruments that vibrates to amplify the sound. The purpose of the soundboard is to transmit the vibrations from the strings through the bridge to create an audible soundwave. A well-constructed soundboard can produce a rich, warm tone. In this article, we’ll cover how to make your own custom soundboard from choosing materials to installation and testing the final sound.
Choosing Your Material
The type of wood you choose for your soundboard will greatly impact the tone and quality of sound that your instrument produces. Soundboards are traditionally made from either hardwoods or softwoods, with each having their own characteristics.
Hardwoods like maple, rosewood and mahogany are generally heavier and denser than softwoods. This density helps hardwood soundboards produce a rich, full tone with good sustain. However, the extra density can also make them more brittle. Hardwoods also tend to emphasize the treble frequencies.
Softwoods like spruce, cedar, and redwood are lighter and more flexible. Their lower density allows them to vibrate freely, resulting in excellent resonance. Softwoods generally produce a warm, mellow tone with a strong midrange. They also tend to have a quicker response than hardwoods. The downside is that softwoods can be more delicate and prone to warping.
When it comes to thickness, soundboards are typically between 1/4″ to 1/2″ thick. Thinner soundboards are more responsive, allowing them to easily transfer string vibrations into audible sound. However, they provide less structural support. Thicker soundboards offer more stability and volume, but the additional mass dampens vibration.
The optimal thickness depends on your instrument and sonic goals. But in general, aim for the lower end of the thickness range unless extra support is needed. Remember that the properties of the wood matter more than thickness when it comes to tone.
Shaping and Cutting
Cutting out the soundboard blank accurately is one of the most important steps in building an acoustic guitar. Having the proper tools and technique is essential to get clean cuts and avoid tear-out or splintering of the wood grain.
For cutting the soundboard, you’ll need a bandsaw or scroll saw to do the initial shaping. Make sure the blade is sharp and has fine teeth to get smooth cuts in the spruce or cedar wood typically used. Go slowly and don’t force the saw through the cut. Let the blade do the work.
You’ll also need a bench hook to securely hold the wood as you cut. Line up your cutting marks accurately before starting. Climb cut up into the line rather than down into it to avoid splintering on the underside [1]. Maintain consistent blade motion without twisting and rotate the wood itself along the cut rather than the saw [2]. Periodically back the blade out to clear sawdust.
For final shaping, chisels and planes allow precision removal of wood right up to the line. Sandpaper and files can aid cleanup of any small irregularities prior to the final sanding and sealing steps.
Installing the Bridge
Proper bridge placement is critical for achieving optimal sound and playability on your homemade soundboard guitar. The bridge should be positioned based on the scale length – the vibrating length of the strings from the nut to the bridge saddles. For a standard 25.5″ scale length, the bridge should be placed about 14-20mm from the bottom of the lower bout (Cannonguitars, 2022).
When you’ve determined the ideal bridge location, mark the center line and use a straight edge to draw your bridge placement lines. Apply some glue to the underside of the bridge and clamp it in place along the lines. Titebond original wood glue or hide glue are good options. Allow the glue to cure fully before proceeding (Fuelrocks, 2022).
Bracing
The braces inside an acoustic guitar serve a crucial role in determining the sound quality and volume the guitar is able to produce. While there are several bracing patterns, the most common is X-bracing. This involves gluing strips of wood in an X shape on the inside of the guitar top below the soundhole.
X-bracing helps transfer and spread out the vibrations from the strings across the entire soundboard. The braces divide the top into smaller sections that can each freely vibrate. Without proper bracing, the soundboard would be prone to cracking and warping under the string tension.
There are variations on X-bracing with different bracing heights and scalloped braces to fine tune the flexibility and vibration. Lighter bracing patterns tend to produce brighter, livelier tones while heavier bracing can give a stronger midrange and bass response. The choice of wood used for the braces also impacts the sound.
Gluing the braces properly is critical. This involves carefully aligning the joint where the X meets, ensuring strong adhesion over the entire bracing surface, and clamping until the glue has fully cured. Proper bracing installation takes craftsmanship, patience, and an understanding of how the bracing interacts with the top to produce the desired acoustic properties.
Sanding and Sealing
Proper sanding is crucial for getting a smooth finish on the soundboard. Start with a coarse grit sandpaper like 80 or 100 to level and shape the soundboard, then work up through the grits to 220 or 320 for a very smooth surface. Be careful when sanding not to overdo it in any one spot which can create uneven spots or dips in the wood. Apply even pressure and work in the direction of the grain.
After sanding, it’s important to seal the wood before applying finish coats. Sealing will help fill in pores and prepare the surface. A common choice is a 2 lb cut of dewaxed shellac. Apply a thin coat with a rag or brush, let it soak in for 5-10 minutes, then wipe off any excess. Allow to fully dry before sanding lightly with 400 grit sandpaper. The shellac will help prevent the soft texture of the spruce from getting fuzzy when finish is applied. [1]
Finishing
The finish applied to the soundboard is crucial for protecting the wood and enhancing the guitar’s tone. There are several common types of finishes used for acoustic guitar soundboards:
Polyurethane lacquers provide a thick, plastic-like coating that is highly protective. However, some argue it dampens vibrations and harms tone. According to Acoustic Music (https://acousticmusic.org/research/guitar-information/guitar-finishes/), polyurethane lacquer is a popular choice for the back and sides but not recommended for soundboards.
Nitrocellulose lacquers are thinner and allow more vibration. Premier Guitar (https://www.premierguitar.com/acoustic-soundboard-guitar-finishes-and-care-101) states nitrocellulose lacquer is one of the most common finishes for acoustics. It provides some protection while retaining resonance.
Shellac is a natural finish made from resin. It allows optimal vibration but requires more maintenance. Some luthiers still use shellac for its traditional look and sound.
The application process involves sanding, staining if desired, spraying on multiple thin coats of lacquer, and buffing. Proper finishing requires a clean workspace, safety equipment, and expertise in the spraying technique.
Installing the Soundboard
Once the guitar body is fully assembled and finished, you’re ready to install the soundboard. This process involves carefully gluing the soundboard to the guitar’s top and applying pressure with clamps while the glue dries.
Start by applying a thin layer of wood glue to the top inside edge of the guitar body. Use a glue with high shear strength like Titebond or Gorilla wood glue. Spread the glue evenly using a foam brush or spatula. You don’t need a lot of glue, just an even thin coat.
Next, position the soundboard precisely where you want it to sit. Line it up evenly with the edges of the guitar top. Then, gently press it into place. Use a soft rubber mallet or hammer with a block of wood to evenly tap the soundboard into the glue. Apply firm but not excessive force.
With the soundboard positioned, place clamps evenly along the edges. This is a key step to ensure proper glue adhesion. Use several small C-clamps, applying steady even clamping pressure. Wipe away any excess glue squeeze-out. Allow the glue to fully cure based on the manufacturer’s recommendations, usually 24 hours.
Once cured, remove the clamps. The soundboard should now be securely glued in place, adding resonance and projection to the guitar. At this stage, your instrument is nearly complete. Next you’ll string it up and fine-tune to achieve the desired sound.
Testing the Sound
Once the soundboard is installed, it’s important to test the sound quality and make any necessary adjustments. There are a few common methods for testing an acoustic guitar soundboard:
Tap Testing – This involves tapping on different areas of the soundboard with your finger or a small mallet and listening to the tone produced. This allows you to identify any “dead spots” that don’t resonate well. These may need to be sanded down or have braces adjusted.
Frequency Response Testing – Using an electronic tuner, play each string open while fretting the 12th fret. This should produce the same tone an octave higher. If notes sound discordant, the soundboard may need adjustments. A guitar pickup can also be used with software to analyze frequency response.1
Deflection Testing – Push down lightly on the soundboard between braces while playing a note. If the pitch dramatically increases as you push, the braces may be too stiff. Sanding braces can adjust the flexibility and improve sound.
Listening Tests – The most important test is to simply play the guitar and listen critically to the tone. Focus on sustain, richness, volume and tonal balance across the strings. Make small adjustments until the desired sound is achieved.
Conclusion
Making your own soundboard can be a very rewarding and personalized way to craft an acoustic instrument that suits your tastes and playing style. With the right preparation, tools, and techniques, you can create a high-quality soundboard from scratch.
In summary, take your time selecting the perfect piece of wood, and make sure to cut, shape, brace, seal, and finish it properly. Installing the bridge and strings is the final step before you can start enjoying your custom soundboard’s unique voice.
Some final words of advice: have patience through each step of the process, work carefully and deliberately, and don’t be afraid to make tweaks until you achieve the sound you’re looking for. With persistence and care, you’ll have an amazing one-of-a-kind instrument to enjoy for years to come.
