In a prior article, I mentioned the ways of getting a good acoustic guitar sound through the different types of sound amplification (built-in guitar amp, sound hole pickup, and instrument microphone. In this article, I'll be turning to equalization.
Please note that some of this information is targetted to first-time sound operators, such as the HPF usage. My point is to show how simple it can be to EQ a basic guitar sound.
First things, first…on each channel on the mixer you should find a button, typically near the top, that cuts all low-end frequencies below 80 Hz. This high-pass filter (HPF) might appear as a button with a label of "/80." Press this button (turn on the HPF) so that all frequencies below 80 Hz are cut. Some HPF's run at /100 Hz. These frequencies can muddy the sound of the guitar – give it a rumble quality that is not good.
The HPF option might be used for sounds that aren't focused in the bass range. Those using that range include true bass vocalists, bass guitar, kick drum, electronic keyboard due to range of sounds, and the drum's floor tom. Given time, you'll find sometimes HPF is needed and sometimes it's not. If this is all new to you, start with using the HPF option on.
Now with the lowest of low's out of the way (no tax-collector jokes, please), let's look at the guitar channel's EQ. Slowly cut the low frequency knob until you get a clear sound. While the guitar does have a large octave range, it's just not a bass-heavy instrument. However, because of the 6th and 5th strings being "bass-ier," you can boost the EQ in the 150 Hz range by a few dB's. Test this yourself to find the sound you like.
The following breaks the EQ'ing down into several frequency ranges. Digital work stations can work within the different frequencies. However, the basic channel EQ'ing with only 3-4 knobs will not give the same level of control. Therefore, apply these as they fit best to your situation.
The 150-300 Hz range can be used to beef-up the tone of the guitar but as mentioned, it's easy to get muddy again so only boost frequencies in this area if it clearly improves the sound.
The 300-600 Hz range can be boosted if you have a thin sounding guitar.
The 600-800 Hz range is your meaty mid-range sound. Cut this if necessary to give better tone and better distinguish from other instruments.
Jumping to the 1-3.5 kHz range, these frequencies can push the guitar to the front of the sound mix and effect note definition. Boost these frequencies when looking at fingerpicking-style guitar and guitar riffs.
The 3.5 kHz to 12 kHz range is all about the sparkle. This range adds brilliance and can make the guitar jump out. This range can be further broken down into 3.5-5, 5-8, and 8-12 kHz. Start at the 3.5 to 5 kHz range for adding that sparkle to the acoustic guitar. If you want more, jump to the next range and boost a little there.
Remember that you might be mixing against other instruments that might have their foundational sounds in one of the above ranges. In those cases, you can either boost or cut one instrument's range over the others so the two instruments sound distinctly different instead of stepping on each other.
The guitar is an instrument that produces a wide range of frequencies and depending on properties such as brand of strings, brand of guitar, and type of wood used in the guitar, the overall sound can vary greatly. By default, a great sounding guitar sounds great without the equalization…alone. But when you place that same instrument in a realm with other instruments such as the piano, bass, and violin, equalization is very important not just in bringing out the best in the instrument so everyone can hear, but with blending and setting in its proper place with the other instruments.
For a quick re-cap of those frequencies….
1. Turn on the HPF to drop those low frequencies.
2. 150-300 Hz can be boosted for warmth.
3. 500-800 Hz can be boosted or cut for tone.
4. 1-3.5 kHz can be boosted for single-note playing (fingerpicking and lead lines).
5. 3.5+ Can be boosted for sparkle and brilliance – yes, kind of like a diamond.
Once your comfortable with the guitar EQ process, experiment with the HPF on and off and experiment with other EQ settings.
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I'm Chris Huff and I've been working behind a mixer for over twenty years. Since 2008, I've been helping other sound techs learn all about the art of church audio through behindthemixer.com.
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Hello, great blog!
I agree with most of what you describe, but I wouldn’t automatically put the HPF in for an acoustic guitar. The bottom E string played open is 82Hz, on a desk with a 100Hz HPF this will be down considerably more than 3dB at 80. Assuming you have a low shelf fixed EQ at 60Hz, you may be able to fatten up the bottom end again, compensating for the upper edge of the HPF whilst still filtering out the sub content. Experimentation (it takes only seconds) during a sound check is all that’s needed.
I also think it’s worth mentioning that the fundamental frequencies of a 6 string guitar are between 80Hz and 1KHz (that’s from bottom E, open, to a high b (b6) on the top E string), anything above this is harmonics. So though you may be able to get a guitar sounding audible by boosting outside of this range the ‘musicality’ of the instrument can only be manipulated in the sub-1kHz range.
I also think it really depends on context and what purpose in the mix the guitar is serving. If it’s playing mainly rhythm parts and is accompanied by a full band with bass guitar, drums, keys etc then it’d be perfectly acceptable and probably beneficial to take out some bottom-end from the guitar and boost in the high-mid area and seat it in the mix volume-wise so that it’s just audible, it’s there primarily to add texture to the sound. If however the line-up is lead acoustic guitar and a single female vocal you’ll want to milk the guitar for everything it’s got, probably boost the bass (without HPF) and boost the very top to ‘sparkle’ it up nicely, may add some reverb to it or maybe even a sub-harmonic processor. But you’d want the vocal to occupy the high-mid space and almost certainly wouldn’t boost in that region (unless it was a very deficient pick-up).
Sorry that ended up being a bit long!
cheers :)
Thomas
Excellent information especially regarding sonic space. JB said it like this once; make a small band sound big (greater sonic space). With a larger band, the sonic range per instrument will probably need to be tighter so it doesn’t blend so much with other instruments that it sounds like they just all bled together.
Yes. We almost always use the HPF cut to prevent a boomy acoustic guitar. My personal preference is to cut problem frequencies rather than boost preferred ones. I often will pull down the 300-2k which tends to clean up rhythm guitar and give it some gentle character. A notch filter is also very useful on acoustic. Every soundboard tonewood has a resonant frequency (mine is Ab) that will tend to resonate or feedback easily. With a notch filter you can pull down a very specific note or group of notes to eliminate this resonance when everyone is playing at volume.
thanks for sharing..
I have 30 yrs experience as guitarist, performer, worship leader, and sound engineer. I can tell you that a huge percentage of the time you will find that acoustic guitars with transducers as pickups will sound nasty if you boost the hi-mids (3.5k to 6k)…. in fact I find that on almost every acoustic I have used or recorded or done live sound for, adding the ‘sparkle’ in about 10k to 12k range and cutting the hi mids and a very slight boost at about 800 cleans it up and makes it smooth and yet clear. It is almost always true that using HPF is best. Even if the low E string is 3db down, it is very likely that the pre-amp in the guitar has a boost or a built in slope in the preamp that brings the lows up by about 2 db anyway. It is important that the HPF cuts the lows BEFORE the signal passes through the mixer channel, so that it can run cleaner and not risk distortion in th elow end. If you do that and need to add a little lows back in this is better way to get it thicker, and claner for the preanmplification in the mixer…
I can also suggest a careful use of compressor/limiter on acoustic guitar. Some of the acoustic amps like the Fender Acoustisonic that I use have this built in. It means the guitar can be fairly strong and defined for fingerpicking and softer bits, but protected and controlled in the more dramatic adn aggressive strumming. Set compresser to create 5db of gain reduction at the hardest hits, and a release time of about 250ms. You may find as I have that this also prevents blowing tweeters and horns so often. take carre and God bless — Barry