Ashly MQX-2310 manual Typical Applications, Design Theory

Operating Manual - MQX-2310, MQX-1310, and MQX-2150 Graphic Equalizer

7.TYPICAL APPLICATIONS

7.1General Tone Control

The graphic equalizer is a very useful device for general tone shaping because it is intuitive and easy to adjust. The visual reference provided by the slider posi- tion gives an approximate idea of the frequency response generated, with the lower frequencies on the left and higher frequencies on the right. To use the power of an equalizer effectively, you need to translate your idea of the tone you want to produce into a range of numerical frequencies. This is simple after a little practise. Here are a few references which are useful for starting points:

Very low bass (the “wind” in a kick drum, almost felt as much as heard -40Hz-80Hz.

The low register of a male voice - 200Hz

The low register of a female voice - 350Hz

Lower midrange (“warmth” frequencies) - 400Hz-1KHz

Upper midrange (“harshness”, snare drum “bite”, “hot” sound) -2.5KHz-4KHz.

Sibilance (“sss” sounds, cymbal “sizzle”) - 8KHz-

15KHz.

Try using these starting points as a guide when you want more or less of these types of sounds. Adjust by ear from there. It is always a good idea to remember that a little equalization usually works out much better than a lot, and that there are many audio problems which can not be solved with equalization alone.

7.2 Feedback Control

A graphic equalizer can be used to provide some control over moderate feedback problems, but does not have enough flexibility or resolution to handle severe situ- ations. You will achieve the best results when you can eliminate one or two feedback points by setting one or two sliders for no more than a 6dB cut. Often you can find a feedback point by boosting sliders in succession to determine which frequency ranges contain the feedback modes, and then cutting those ranges. Be very careful in this process to avoid explosive feedback and possible sys- tem and hearing damage! If you find feedback points with many equalizer bands, remember that cutting every band may not help (all you will do is reduce system gain).

The combination of a graphic equalizer for tone control and a parametric equalizer (such as the Ashly PQX-571 or PQX-572) for feedback control is highly recommended.

7.3 Console Channel Equalization

Many mixing consoles provide only simple equal- ization for individual channels. If your console has chan- nel inserts, you can patch your graphic equalizer into a channel that’s being used for something important and use it to tailor the sound of this channel exactly the way you want.

7.4 Large Room Equalization

Large rooms tend to suffer from multiple reflec- tions with long time delays, long reverberation times, and “ring-modes”, all of which lead to reduced intelligibility and a generally “muddy” sound. As sound travels long distances through the air, high frequencies are attenuated more than low frequencies. In general, large rooms ben- efit from some low frequency roll-off, high frequency boost, and attenuation of ring mode frequencies. As in the case of feedback control, a graphic equalizer can help reduce an isolated ring-mode or two, but a tunable nar- row-band equalizer such as a parametric is more effec- tive here.

8. DESIGN THEORY

While most graphic equalizers look very much the same, there are several important differences in the circuitry used to implement various designs.

Perhaps the major differences are in the filters. Some equalizers use a filter made of a capacitor, an in- ductor, and a resistor, or “RLC” filter. The advantage here is simplicity, but the real disadvantage is the induc- tor itself. An inductor is a coil of wire with a core of some sort. Inductors are susceptible to hum fields and they are large and expensive.

Other equalizers use the same basic approach, but replace the inductor with a “simulated inductor”, which is actually a circuit comprised of an amplifier, a capaci- tor, and a couple of resistors. This adds parts but is less expensive than a real inductor. The problem with this approach is that simulation is less than ideal; it produces an inductor with high resistive loss resulting in poor curve shape when used in a filter.

Another problem with “RLC” designs is that large capacitors must be used for the lower frequency filters, limiting the choice to large, expensive non-polar types or electrolytic capacitors with poor audio performance. Also,

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