Tone Talk: Factors that Determine the Sound of an Acoustic Guitar

You know, every once in a while I find myself at a local music shop just killing some time and for some reason, I always end up going towards the acoustic guitar room. And being the avid tech guy that I am – along with all things music in general of course – I also spend a lot of time at big electronics stores such as Best Buy. Although I’m not sure if this is true for the rest of the country but down here in Southern California, Best Buy has added a music gear section to their store. Yes, a big pain for any impatient friend that goes in there with me indeed. Anyways, as I make my way through the store in the need for a memory card or what have you, I again find myself having to make a trip to the acoustic guitar room but getting more to my point, it seems like no matter what store’s acoustic room I’m at, I almost always hear some random customer asking one of the sales associates – the oddly termed “pros” – the same question; what’s the difference between these two acoustic guitars? Usually these customers are wondering why a similar sized guitar is priced more so than another even if they’re from the same manufacturer. As I listened to the explanation being given by one of these “pros” (that could have easily just been cashiers who just happened to like music) I felt the need to make sure our own guests here at ProAudioLand didn’t encounter the same problem of simply being uninformed about the deeper aspects of the acoustic guitar because trust me – just ask most any musician – just because someone works at the music department doesn’t mean they always know what they’re talking about.

With that said, I’d like to take the time today and further explore the differences between acoustic guitars; not just what causes the differences in price but more importantly, factors that directly affect the instrument’s tonal qualities and characteristics. Sounds good? Well then, let’s get going!



Size Matters

The first big difference that you will find with acoustic guitars – besides the pricing – is their size. While there truly aren’t any official set standards when it comes to typifying the size of an acoustic guitar, most musicians usually refer to the sizes of very notable instruments as a base point for comparing. Among these notable guitars used for size reference are those made by Martin – which makes sense since the company pretty much pioneered the modern steel string acoustic guitar. As far as a “normal” sized acoustic goes, most will agree that the 000-Martin fits the bill and the Dreadnaught would easily be considered a large. And of course, a “Mini Martin” would clock in as the small size. While there are certainly tons of different sizes between, above and below these three – for the sake of comparing inherent tonal qualities and size – let’s keep it simple with just smaller and larger.

The common accepted view on the impact of size to the tonal qualities of an acoustic guitar will tell you that the smaller the body the more treble response and brightness the instrument will have while the larger you go will give more potential for bass response.  Also, most people will expect large guitars to have a pretty “big” sound while they expect the smaller ones to have more diminished tone. Knowing these two qualities of size, you would assume that the bigger body should produce higher volume response as compared to the smaller one, right? Well, not exactly. Interestingly enough, the smaller body sized guitar can achieve some disproportionally and surprisingly loud volumes. Not only that, smaller body types usually have a much more balanced range of bass and treble frequencies as well. This becomes especially important when considering using an acoustic guitar on stage. Without having the extra bass and “woofiness” of the larger body, a smaller guitar will be able to handle feedback a lot better during a live performance. And when take into consideration that in a studio setting it’s much easier to add bass than to remove it, you can safely assume that a smaller guitar will most likely give you a cleaner recording over a larger one.


The Choice of Wood

Did you know that the type of wood used in an acoustic guitar is responsible for more than just looks and strength? Depending on what kind of sound you would like and how you tend to play, choosing the right tonewood for your acoustic guitar can either give you exactly what you need or fight against you. A guitarist that uses a lot of finger-picking techniques for example will want to choose a wood that works best with that delicate style of playing instead of a wood that requires a pick to be used in order to get the instrument to fully resonate. Not only that, but you have to take into consideration the choice of wood for each individual part of the acoustic.

Taking into consideration the techniques used by luthiers themselves, it is believed that the choice of the wood for the top is the single most important factor in how the guitar will ultimately sound like. From there, the back, sides and neck are the next important in that order as far as overall tonality is concerned. The choice of woods for other parts of the guitar such as the bridge, fretboard, binding and bracing can also either enhance or dilute the tonal characteristics of the other woods used in the acoustic but they don’t play a major role in defining the ultimate sound of the instrument. But don’t forget, the choice in wood is only responsible for certain traits of a guitars tone. Things such as design, build quality and – as we learned earlier – size of the acoustic also add up towards a certain end result in tone. Still though, the choice in wood is usually the base factor is creating an acoustic guitar with a specific sound and purpose. Let’s now take a look at some of the different types of wood used.

Spruce is pretty much the standard when it comes to wood chosen for the top of the guitar due to its high rigidity and its lightweight characteristics which makes it perfect for high velocity sound. Also, the Sitka spruce in particular has a power direct tone that tends to keep its clarity even when played with force. Cedar is also a popular top wood used mainly for its balanced warm sound. Finger pickers in particular are fond of cedar for its characteristically quick and rich response to lighter playing styles. Compared to other woods, guitars made with Mahogany tops tend to have a relatively low response rate, a good amount of density and low overtone. This creates a strong punchy sound that is favored by country blues players. When used for the sides of back of the guitar, Mahogany has relatively high velocity of sound, which adds a lot to the overtone coloration. Maple on the other hand tends to be much more acoustically transparent. This is due to the wood’s lower response rate and high internal damping which ultimately – when used for the back or sides of the guitar – allows the tonal characteristic of the top wood to be heard without any added coloration. And finally, Rosewood is used for its high response rate and excellent range of overtones. Not only that, it is also prized for its strength and complexity in the bottom end and an overall darkness of tone in the rest of the range. Other characteristics such as strong mids and highs also contribute to the richness of coloration in the upper registers.


Other Important Factors

Besides the wood, body style and size, there are a few more things that can add to the tonal characteristics of the instrument such as the choice of strings. In general, lighter strings – which are under less tension than medium strings – not only bend easier and are lighter to the touch, but they often help create a warmer sound as well. Medium strings on the other hand are much punchier and can produce a bit more volume. Also, we can’t talk about strings without mentioning the scale length of a guitar’s fretboard. Most acoustic guitars will either have a short (24.9") or long scale (25.4") fretboard and as far as tone is concerned, it affects the tension of the strings (which as we just learned ends up altering the instruments sound). This ultimately means that even with light strings, the higher degree of tension produced by the long scale fretboard will have much more punch than those same light strings on a short scale. The same is true with medium gauge strings. So essentially, the longer the scale length, the more tension the strings will be under, the punchier – and louder – the result.


Well, that’s all the time we have today but hopefully you will take all this into consideration the next time you’re in the market for a brand new acoustic axe but in the meantime, how about some healthy browsing through our acoustic guitar section here at ProAudioLand? Remember, we offer the best gear at the best prices, guaranteed!

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