Audio processing encompasses many types of product. Here you can buy graphic equalisers, crossovers, speaker management systems and feedback reducers. You can take a view on what you need to achieve and select the product best suited to perform the task.
A graphic equaliser is a relatively straight forward piece of equipment, but can often resolve annoying imbalances in the audio sound spectrum. If you choose 15 or 31 band graphics it is easy to smoothly correct any peaks in frequency response or compensate for poor or challenging building acoustics.
Active crossovers are often a necessary part of any large PA system. As powers increase its becomes increasingly difficult to make passive crossovers that perform correctly, these are crossovers that are internal to the speaker cabinet. Active crossovers split the audio signal into frequency bands before the power amplifiers and then channel the respective bass, middle and top frequencies through the power amplifiers and into the speakers. This has a number of benefits, but primarily it gives you complete control over all crossover frequencies and often allows you to select what style of filter is used, so you can set up a system to suit your loudspeakers and make fine adjustments it to suit individual venues.
Speaker management systems include a variety of functions often with built-in crossovers, parametric graphic equalisers, time delay and limiters and or compressors. Generally speaker management systems have remote access via a computer link, so it is easier to set all the parameters before performances. You can then store the information for later recall, so after collecting a number of common set-ups one can often be recalled and just modified slightly for the current situation. With the large combination of functions it is possible to finely tune a PA system, setting crossover frequencies, time delays, compression characteristics and other functions. As you can see from this, using one of these devices eliminates the need for separate crossovers, graphics and so on, but speaker management systems are more expensive of course.
Feedback reducers or feedback killers can be a big help when, despite your best efforts with microphone and speaker positioning, feedback or howl-round persists. By placing the feedback killer in the appropriate stage of the system, often fairly early on in the audio chain, you can reduce the feedback effect significantly. The devices have minimal effect on the overall audio signal and use ultra-sharp filters to achieve the benefit.