Acoustic Soundboard: You Can’t Always Get What You Want
Larry Fishman talks about the virtual impossibility of using amplification to exactly replicate the sound of acoustic guitars.
In my past few columns, I've traced some of the historical approaches to amplifying acoustic instruments. I've also gone over the design philosophy behind some of the more common approaches, with a deeper look at the technical details of several currently available pickup designs. At this point, I think it might be useful to step back and consider what this is really all about.
Why do we want to amplify an acoustic instrument in the first place? After all, these instruments already are amplifiers on their own. Their original design intent was to mechanically amplify and enhance the sound generated by a tensioned string when plucked, bowed, or hammered-on so that that resulting sound could be heard at a reasonable volume in an intimate setting.
You're in luck if that's all you want to do with an acoustic guitar. Simply pick out an instrument that responds comfortably to your touch and is pleasing to your ear, invite some friends over to your house, and make some music! This is one of the rare cases where your wants and needs are in almost perfect alignment. You want this particular instrument because of its aesthetics, feel, and pleasing sound, and it's already loud enough on its own to fulfill the need to be comfortably heard in an intimate setting.
The trouble starts when we need an acoustic instrument to perform in an environment that requires it to produce much a higher SPL (sound pressure level) than it was originally designed to produce. Be it a local bar with the band in the corner, a sports stadium, or a converted warehouse, these gigging situations obviously require more than what's needed for the back porch or an acoustically pristine concert hall—the same need that spurred the invention of the electric guitar.
With the development of new sensors, electrical amplifying systems, and digital signal processors, we've fortunately seen some major advancements over the past 30 years in the pursuit of enhancing the SPL potential of acoustic instruments. Today's acoustic guitars can hold their own volume-wise, in any venue. But I caution you: Once we ask an acoustic instrument to perform at these “unnatural volumes," the wants and needs equation becomes much more complicated.
In my work, be it at my place of business, a customer's guitar factory, a concert venue, a night club, a music store, a recording session, a social gathering, or crawling through countless web forums on acoustic amplification, I listen to or directly talk to hundreds (if not thousands) of acoustic instrumentalists each year. The comments and conversations surrounding acoustic amplification range from the sublime to the ridiculous. There is little general consensus regarding the best amplification approach, but there are always steadfast advocates with regard to the benefits of one piece of gear verses another. I do, however, find a common thread in many of these discussions that poses a real dilemma.
For a typical example that illustrates my point, a local singer-songwriter was visiting our facility a few months ago. She was there to have a meeting with our artist-relations guy and discuss amplification gear for a new guitar she had just purchased.
After I was introduced to her and we spent some time talking about what was going on with her career, I asked her what type of gear she had in mind. She told me that she really loved the sound of her new guitar and wanted something that would give her more volume onstage, but would still “sound just like my guitar, only louder." I told her the only way I could help was to recommend a set of heavier-gauge strings. That wasn't what she was expecting to hear. When I continued that I was afraid I couldn't get her what she wanted—and neither could anyone else—she didn't say anything and looked at me like I had three heads.
Herein lies the rub: There is no way to raise the volume of an acoustic instrument by using electronics to make it louder onstage and project better into a room, yet still produce a sound “just like my guitar, only louder." There is no pickup, microphone, amplifier, or loudspeaker combination that can accomplish this, no matter how well designed, sophisticated, or expensive they might be. The real issue is based on the way our ears and brain sense and interpret sound.
Over the course of my next few columns, I'll discuss some techniques and examples that should shed some light on this subject. We'll then investigate if what you think you want is actually what you need to get the job done. Until then!