An equalizer (EQ) is a filter that allows you to adjust the level of a frequency, or range of frequencies, of a human voice audio signal. In its simplest form, an EQ will let you turn the treble and bass up or down, allowing you to adjust the coloration of your transmit or receive audio. Equalization is a sophisticated art. Good equalization is something to strive for.

The parametric EQ

The parametric EQ and semi-parametric EQ are the most common equalizers found because they offer continuous control over all parameters. A parametric EQ offers continuous control over the audio signal’s frequency content, which is divided into several bands of frequencies (most commonly three to seven bands).  A fully parametric EQ offers control over the bandwidth (basically, the range of frequencies affected), the center frequency of the band, and the level (boost/cut) of the designated frequency band. It also offers separate control over the Q, which is the ratio of the center frequency to the bandwidth. A semi-parametric EQ provides control over most of these parameters but the Q is fixed.

Q is the ratio of center frequency to bandwidth, and if the center frequency is fixed, then bandwidth is inversely proportional to Q—meaning that as you raise the Q, you narrow the bandwidth. In fully parametric EQs, you have continuous bandwidth control and/or continuous Q control, which allows you to attenuate or boost a very narrow or wide range of frequencies.

A narrow bandwidth (higher Q) has obvious benefits for removing unpleasant tones. Let’s say you have a particularly annoying nasal quality to your audio.  With a very narrow bandwidth, you can isolate this one frequency (usually around 650) and remove, or reject, it. This type of narrowband-reject filter is also known as a notch filter. By notching out the offending frequency, you can remove the problem without removing the instrument from the mix. A narrow bandwidth is also useful in boosting pleasant tones as well.

A broad bandwidth accentuates or attenuates a larger band of frequencies. The broad and narrow bandwidths (high and low Q) are usually used in conjunction with one another to achieve the desired effect.

A shelving EQ attenuates or boosts frequencies above or below a specified cutoff point. Shelving equalizers come in two different varieties: high-pass and low-pass.

Low-pass shelving filters pass all frequencies below the specified cutoff frequency while attenuating all the frequencies above it. A high-pass filter does the opposite: passing all frequencies above the specified cut-off frequency while attenuating everything below.

Graphic EQ

A graphic EQ is a multiband equalizer that uses sliders to adjust the amplitude for each frequency band. It gets its name from the positions of the sliders, which graphically display the resulting frequency-response curve. The center frequency and bandwidth are fixed; the level (amplitude) for each band is the only adjustable parameter.

Graphic EQs are generally used to fine-tune the overall mix for a particular room. For instance, if you are mixing in a “dead” room, you may want to boost high frequencies and roll off some of the lows. If you are mixing in a “live” room, you might need to lower the high-midrange and highest frequencies. In general, you should not make drastic amplitude adjustments to any particular frequency bands. Instead, make smaller, incremental adjustments over a wider spectrum to round out your final mix. To assist you with these adjustments, here is an overview of which frequencies affect different sound characteristics:

Sub-Bass (16 Hz to 60 Hz). The lowest of these bass frequencies are felt, rather than heard, as with freeway rumbling or an earthquake. These frequencies give your mix a sense of power even when they only occur occasionally. However, overemphasizing frequencies in this range will result in a muddy mix.

Bass (60 Hz to 250 Hz). Because this range contains the fundamental notes of the rhythm section, any EQ changes will affect the balance of your mix, making it fat or thin. Too much emphasis will make for a boomy mix.

Mids (250 Hz to 2 kHz). In general, you will want to emphasize the lower portion of this range and deemphasize the upper portion. Boosting the range from 250 Hz to 500 Hz will accent ambiance in the studio and will add clarity to bass and lower frequency instruments. The range between 500 Hz and 2 kHz can make midrange instruments (guitar, snare, saxophone, etc.) “honky,” and too much boost between 1 kHz and 2 kHz can make your mix sound thin or “tinny.”

High Mids (2 kHz to 4 kHz). High mids are responsible for the projection of the midrange.  It gives sparkle to your audio but can easily tear if overdone.

Setting up your EQ  (starting points) 

 
 
Often misunderstood by Hams, equalizers (EQ) are the bread and butter of good transmit audio reinforcement.  As such, knowing how to properly EQ is one of the most critical tasks to master.   From correcting problems and enhancing your sound to adding cohesion to your voice, there’s a lot you can accomplish with proper equalization.   Here are eight EQ tips that might help achieve your audio goals.
 
Focus on the inherent uniqueness of your voice
 
While equalization can do wonders for individual tracks, it’s important to consider the bigger picture every time you reach for the EQ. As a strategy, you’re far better off EQing for the primary purpose of creating a cleaner, clearer, and overall better-sounding sound to those who hear you on the ham bands.
 
Filter Judiciously
 
One of the easiest ways you can clear up your mix and reclaim a large amount of wasted headroom is by applying a highpass (low-cut) filter since extremely low voice frequencies do not contribute to effective, clearn and pleasant sounding transmit audio. 
 
Cut First, Boost Second
 
Before you boost what you want to hear, cut out what you don’t want to hear. The best reason for doing this is to remove problem frequencies from your particular voice profile. Once you achieve this goal, you’ll find you often don’t need to boost much else.  Many hams will resist doing this for the commonly held belief that "more is better".
 
Boost only as necessary and always with care
 
As you adjust the EQ, you’ll notice that frequency boosts are significantly easier to hear than cuts. This phenomenon causes many hams to boost frequencies they want to bring out, rather than to cut problem frequencies. There are two major issues associated with doing this. First, if you boost at 3kHz to achieve greater presence, your audio will likely become harsh and cutting. The other problem is that if you boost all of the frequencies around a problem frequency rather than simply cutting the problem frequency (like boosting the extreme lows, upper midrange, and high end instead of just cutting the lower-mid which is really the issue), you can easily overload the EQ gain stage and introduce distortion that you may not initially notice.
 
Understand the frequency spectrum of your voice

Your vocal tone needs to be as perfect as possible. That’s because as humans, we can’t help but scrutinize what we hear in an extremely critical manner. Trouble is that hams often disagree with what constitutes ideal sounding transmit audio.  So, develop your own style as you see fit but try to avoid unpolished or harsh sounding audio that will likely annoy and distract your listeners.  Here are a few suggestions for properly EQing your voice:

  • Body (200–500Hz)

    This frequency range is where muddiness lives, but it’s also where the warmth of your voice comes from. If your vocals sound mushy, try cutting low frequencies in this range. If your vocals are clear but lacking warmth, try boosting in this range.

  • Nasal (1-1.5kHz)

    Almost universally, 1-3kHz is where the nasal frequencies lie. Try cutting somewhere within this frequency range. Don’t go overboard though.

  • Presence (1.5 to 3kHz)

    When it comes to intelligibility, presence is absolutely critical but be careful boosting too much as this can render your vocals harsh and jarring.

EQ with Your Ears 

It is important to point out that the best tools you have for EQing are your ears. You can memorize tables of important frequencies for all kinds of instruments and applications, but the most important thing is that your voice sounds great. The best way to evaluate your sound is to listen to yourself from your rig's built-in monitor or, better yet, on air from a separate receiver, perhaps an sdr.

 

The bottom line for EQing your voice is to find the biggest offender and fix that first. Then, boost sparingly to polish the results.  If this technique fails, then consider reevaluating the quality of your microphone and the correctness of audio level settings in the audio chain.   Remember that an EQ can't fix poor unprocessed input.   So before you resort to the EQ, listen closely to that input to avoid falling victim to the "Garbage in... garbage out" syndrome.