This is probably the primary reason I prefer acoustic guitars to electrics. There's no doubt that certain types of wood lend themselves to superior sounding electrics but for the most part the tonality and overall sound of an electric comes from those electromagnets we know as pick-ups. With acoustic guitars it's all about resonance and complexity of sound generated by the wood. Volume does play into it to a certain degree, that is, certain types of wood will produce more volume. What most players want though is that certain something that in their opinion defines the sound a good quality acoustic guitar.
Construction techniques have a lot to do with it but today I'm just talking about wood. First of all, some guitars are made of composites (or fancy plywood, if you will) and some are made of all solid wood. Some, like the Yamaha that I often use for teaching have a solid top and composite sides and back. It is generally accepted that an all solid wood guitar will sound better than a composite one and I believe that is true, most of the time. However - and that Yamaha is a good example - sometimes one that uses composites can sound very good. There are even a few makers who are making quite expensive all graphite guitars that supposedly sound great. I can't testify to that as I've never heard or played one. Then of course there are those curiosities from Ovation, which have the rounded plastic backs. These guitars sound pretty good. I once briefly owned one of the fancier Ovations, an Adamas model that was exceptionally nice. For some reason, about the only place you'll see them used these days is by singers in Irish pubs. I have no idea why.
The two primary woods used to make the bodies of acoustic guitars are rosewood and mahogany. I've owned many of each variety and I would never suggest that one is better than the other, although fine quality rosewood guitars are always more expensive than mahogany ones. What they are is different. Rosewood (and we're talking solid woods now, not composites) usually has a richer, more complex sound with nice overtones that leans more toward the bass end in terms of resonance. A well-aged rosewood guitar by one of the major manufacturers can almost take your breath away as it vibrates against you as you play. Unfortunately, it is rare to find a rosewood guitar that has a treble end that can match the bass end in resonance. This is just the nature of the wood, and can be mitigated somewhat by playing a guitar with a slightly smaller body so the bass end isn't boomy (see previous blog for more on that). Rosewood is also radically affected by relative humidity and the weather. Even a nice rosewood guitar will often sound dull and lifeless in the humidity of summer, only to come back to life in the dryness of winter. But be careful! Too much dryness (relative humidity of less than 40%) can lead to cracks, warping and worse.
Mahogany back and sides on an acoustic steel string guitar usually produces a less complex, "woody" tone, which in the larger bodied instruments is great for strumming. There is more even tone in mahogany, compared to rosewood. That is, from bass to mids to treble, no area to tonality sticks out. Recording engineers like this because it makes equalization and compression a lot easier to use. And the treble end is often nice and crisp, which in the smaller body sizes results in guitars that are wonderful for finger-style playing. The down side of mahogany is that, again compared to rosewood, it often has less volume and sustain and overtones/complexity just don't happen very often.
Now, having said all this, there are of course exceptions. This gets back to me first point - that wood is a living thing. I've played very expensive rosewood guitars that sounded like someone stuffed them with old socks, and I've played a couple mahogany guitars that absolutely shimmered in tone and sustained an unbelievably long time. These are exceptions however.
Other woods are used for the back and sides of some guitars, the most common being maple and recently, koa. Maple is great for strumming with its punchy, percussive sound but maple usually has not much volume and almost no resonance or sustain. Koa, which originally almost always came from Hawaii is a beautiful wood - it looks almost three dimensional when it is finished in gloss. It sounds very much like mahogany to my ears.
What about the tops and necks? Probably 95% of the acoustic guitars produced today have spruce tops, either solid (best!) or composite. It is much, much important that the top of any guitar be made of solid wood simply because it will transmit vibration far better than composite and result in better sound. There are many grades of spruce with most of it coming from Canada or Alaska (Sitka spruce) and some very expensive guitars are made with what is called Adirondack or Red Spruce (produced from Maine to New York State to the Carolinas) and the obscenely expensive Italian or German spruce. You'll find plenty of debate about the relative merits of each. The main reason spruce is so common is that it is readily available, reasonably durable and easy to work with, and it sounds good. Cedar and mahogany are used less commonly and they both sound good but tend to be quieter than spruce and cedar is very soft so scratches and even cracks can happen very easily.
Necks are almost always made of mahogany but that may be changing. Honduran mahogany is the most desirable type but as it becomes rarer due to over harvesting it is becoming cost prohibitive for some makers. Even Martin has turned to "select hardwood" (a dense, heavy variety of cedar) for many of their less expensive models. The Chinese companies are using mahogany from the Far East and while it seems to be acceptable now, it will be interesting to see if those guitars are more prone to warped necks a couple decades from now.
Other woods show up in guitar construction, especially ebony for fingerboards and bridges. It not only makes for a great sound due to its heavy, dense nature, a black ebony fingerboard with nice mother-of-pearl inlay is a true thing of beauty.
A moment ago I mentioned decades - and this is something that all guitarists have to also consider: how the passage of time will affect various woods. Not unlike fine wine, premium wood in guitars can and usually does change and the sound grows more complex as time passes. This is one reason that so-called "vintage" guitars (the subject of my next blog entry) bring such high prices. Guitarists call it "opening up" and it can take as little as ten year or less, but usually a guitar needs to be 30, 40 or even 50 years old before it reaches its potential, sound-wise. But remember - as I keep saying, wood is a living thing and sometimes a guitar will sound absolutely excellent withing six months or can sound dull and uninteresting even after sixty years.
If you really want to drool and explore the complexity of fine woods in guitars, visit The Guitar Emporium in Lexington, MA, or if you're going to New York, stop by Mandolin Brothers in Staten Island. Spend a couple hours trying as many guitars as you can and I promise you will be amazed. Just leave that credit card home or you may find yourself going home with a new member of your musical family!
Thanks for reading and as always, I welcome questions, opinions and input.
October 22, 2010