Nearly every live sound system uses an equalizer between the mixer and the power amplifiers. The setting and adjustments have less to do with the tonal shaping of the mix and more to do with compensating for room acoustics. Each room colors the sounds that happen within its walls. These acoustic colorations can adversely affect the live sound in several ways, as they hold the potential to:
The proper use an excellent 31 band graphic equalizer, used in conjunction with a real-time analyzer, can solve many system equalization problems.
Most modern mixer provide ample equalization control. However, each device offer a sonic ingredient that adds character and personality. Outboard equalizers can help the sound operator shape the mix into something that is just a little more exciting and unique than it might without them.
Certain equalizers, such as the Focus-rite Red series, Tube Tech PE1-C, or virtually any equalizer made by solid state logic, Neve, Pultec, or Universal audio has helped shape the sound of modern music recording also, to build a mix that resembles the original recordings, it is helpful to have access to these tools.
Practically speaking, most sound operators can't justify spending the amount of money it would take to have several of these classic devices available in the rack. However, a single prudent perusal eBay and of online merchants could provide one processor that could help add a world-class character and personality to the single most apparent sound in the mix, which is almost always the lead vocal. Aside from systemwide applications, equalizers are usually patched into the insert of one channel at a time.
This is called a graphic equalizer because it is the most visually graphic of all equalizers and it is obvious at a glance, which frequencies you've boosted or cut.
A graphic equalizer isn't appropriate to include in the channels of a mixer, simply because of the space required to contain 10 or more sliders, but it is a standard type of outboard EQ. The graphic EQs that we use in sound reinforcement have 10, 31 or sometimes 15 individual sliders that each cut or boost a set frequency with a set bandwidth. The bandwidth on a 10-band graphic is one octave while that on a 31-band graphic is one third of an octave.
Graphic equalizers were very popular in the studio a number of years ago. Today, graphic equalizers are used mostly in live sound reinforcement applications because they are convenient and very visual, and they well in conjunction with acoustical measurement devices. It is typical for a traditional sound system design to include a 31-band equalizer between the main output and the house amplifier inputs.
A shelving EQ leaves all frequencies flat to a certain point, then turns all frequencies above or below that point down or up at a rate specified in dB per octave. As with high and low pass filters, shelving equalizers roll off the highs or lows, at a slope between 6 and 12 dB per octave; however, pass the slope, all frequencies remain boosted or cut to the end of the frequency spectrum.
shelving equalizers are a convenient way to add air (the high frequencies we can't necessarily hear as much as feed) to a mix. Simply sweep the cutoff frequency into the highs, above 12 kHz or so and raise the shelf slightly. This is a common technique, especially with the advent of the ultra quiet gear available today.
This is the most flexible type of EQ. It operates just like a sweepable EQ, but gives you one other control called the bandwidth or Q.
With the bandwidth control, it is possible to choose either to boost a large range of frequencies or a very specific range of frequencies. For example, you might boost a four-octave band centered at 1000 Hz, or you might cut a very narrow band of frequencies, a quarter of an octave wide, centered at 1000 Hz. With a tool like this, you can create sonic pieces that fit together like a glove.
Parametric equalizers are a great addition to any mixer. They are readily available in outboard configuration, and most expansive consoles provide built-in parametric equalization.
A lot of mixers have sweepable EQ which is also known as the semi-parametric EQ. These equalizer dramatically increases the flexibility of sound shaping. There are two controls per sweepable band:
mixers with sweepable EQ typically have three separate bands on each channel: one for highs, one for mids, and one for lows. Sometimes the highs and the lows are fixed frequency equalizers but the mids are always sweepable.
Software-based equalizers emulate each type of hardware EQ. Many contain identical controls and even emulate the look and feel of highly respected classic equipment. Additionally, several software based equalizers offer all the features we've discussed, all in one equalizer, in fact, most offer multiple option at each band.
Equalizing circuitry does affect the sound of the source. There are equalizers that sound good and equalizers that don't sound good. The quality, manufacturer, and design of any audio tool matters. Always listen to your music with or without the equalizer; be very discerning. It's better to avoid EQ rather than use an EQ with lots of flexibility and a crummy sound. Well respected outboard gear gets that way because it works well and sounds good. Value reputation, yet always assess for yourself. It's up to you to listen and select the equipment that works for you.
Even with the multitude of available equalizers, don't use EQ first to shape your sounds. First get as close to the sound you want using mic choice and mic technique then use EQ if it's necessary.
