We took a break from our discussion of resonance for last month’s NAMM review, so this month we’ll return to try and resolve the discussion by answering specific questions and add some additional context to the answers by discussing some of the issues I’ve encountered performing in various environments.
To briefly refresh our memories, resonance is a form of feedback. Resonance occurs at a specific resonant frequency. Every system — in our case, our guitars — has a frequency at which the system will oscillate at maximum amplitude with minimum external energy applied to the system. The key to this is that the energy has to be applied externally. Under normal conditions, the external energy comes from the player strumming, picking, or otherwise causing the strings or body to move. Acoustic guitars are designed to respond to multiple frequencies and resonate in accordance to the energy applied. However, the resonate frequency of the guitar is specific to whichever frequency causes the guitar to resonate with very little energy being applied. As we all have experienced, when we attempt to amplify our acoustic guitars, we need only be in the general vicinity of a sound source that is emitting that resonant frequency for our guitars to begin howling.
So, how do we amplify our guitars while preserving their tone and controlling unwanted resonance? The place to start is with the quality and type of pickup(s) that we use. As I’ve previously stated, the most common pickup system available now is an under-saddle piezo system with an onboard preamp/EQ. Right behind are soundhole mounted magnetic pickups. Some guitars are equipped with a hybrid system consisting of some combination of piezo, magnetic, or contact pickup, often in conjunction with an internally mounted microphone. We don’t always have a choice as to which pickup system to use. Most of the time we’re stuck with whichever system is already built into the guitar when we buy it. That’s not necessarily a bad thing, as hopefully the manufacturers of both the guitar and the pickup system paired them because they work well together. Here’s the catch: every pickup system that I am aware of is equally adept at amplifying its inherent sound as it is amplifying the sound of the guitar it is installed into. The trick is to dial in guitar tonalities while dialing out raw pickup tonalities. In worst case terms, piezo pickups sound plastic or quacky, magnetic pickups sound metallic, and internal mics sound boxy. Again, this is worst case — and usually associated with low-quality or poorly installed pickup systems — but varying performance conditions and environments can drive even the best system into a worst-case scenario.
Where to start? Get to know your guitar and pickup system. Practice with your guitar plugged in to a small PA (you do own a PA, don’t you?) amp, or whatever you have that you intend to use to amplify your guitar on a gig. Using the controls that you have on the guitar and amp/PA, learn what every knob and switch does and how it affects the tone of your guitar. Don’t be afraid to explore the extremes of the controls but be mindful that the old adage “less is more” will usually yield the best results. Find the blend between tone and resonance and learn where the “edges” are for volume levels and tonality. Also be aware that what the player hears is different from what the listener or a microphone hears. I tend to dial-in my tone based on that external (in-front) tone rather than what I expect to hear from my listening point behind my guitar, so it can sometimes help to have another competent player play your guitar while you listen to both the unamplified and amplified sound. This will give you an opportunity for a reality check so that you get a better idea what your rig really sounds like. Dial in what you think is your best sound and then listen from the other side of the microphone while someone plays your guitar. Be prepared for a few surprises. You may discover that what sounds good to you actually sounds quite different to the audience. Adjust accordingly. At many gigs, you’ll be plugged directly into the house PA and much of your guitar sound is at the discretion of the person running the house mixer. Hopefully you’ll have a monitor that is as least somewhat representative of the sound that is being sent to the house. Use this as your guide to adjust your sound. This is where knowing your guitar and its pickup system is most valuable because that will be your only access to the sound that you can control. Make sure that you can really hear the monitor and listen for detail in the sound. Monitors don’t have to be loud if you can hear enough detail to recognize your touch on the guitar.
Something to remember: body resonance is usually in the lower frequencies. This is where most feedback will occur. It’s very tempting — especially for solo performers — to boost the bass frequencies to make your guitar sound big but resist doing so. It really doesn’t sound as big as you think is does and will often make your voice sound thin in comparison. Some remaining thoughts — resonance can be induced by strong bass signals, by wind in outdoor environments, and low frequency non-musical sounds. Other environmental factors include big rooms, big stages with high ceilings, playing close to bandmates whose equipment generates strong low frequencies (bass guitar, electric guitar, drums), playing in a live room with lots of hard reflective surfaces or where there is a constant background noise (such as in a restaurant), and overly loud or improperly EQ’d monitor systems. Take your time and really listen to your environment — room, stage, monitors — and hear where your guitar will fit and which sounds will be most likely to cause problems for you. Whether you’re playing solo guitar or accompanying a voice, you need to make sure your guitar sounds its best in whichever environment you’re performing.
This is not the end-all, be-all treatise on resonance, but hopefully I have explained enough for you to have a better idea of what resonance is — how it happens, and how you can learn to control it. In future columns, I hope to detail some specific tools and devices — both electronic and passive — that you can use to your advantage. Until then, practice with your gear and get intimate with it. You can never be too prepared…
Need to know? Just ask… Charlie (firstname.lastname@example.org)