Ready to venture into the dynamic realm of live sound production? Ready to have your ear drums damaged as a result of over-exposure to crappy, overwhelmingly loud club music? (okay, I’m exaggerating) Whatever the reason is, if you are seriously looking into a career in this business, then at the very least, you need to know what is a sound reinforcement system all about!
There are many things to cover when it comes to talking about this topic. As usual, this article is meant to give the new guy, a comprehensive understanding of the basic components that make up a sound reinforcement system. I will try to be as brief as possible while still covering important fundamental points. So let us start with the introduction!
What is it all about you ask? Well essentially, it is a combination of professional audio equipment such as microphones, signal processors, amplifiers, and loudspeakers that serves to amplify live or pre-recorded sounds and also distribute those sounds to a larger or more distant audience. On top of that, sound reinforcement systems are also used to enhance the sound coming from sources on stage, as opposed to just simply amplifying the sources unaltered.
The configuration of a sound reinforcement system may vary depending on the needs of an event, and at times may include hundreds of microphones, complex audio mixing and signal processing systems, tens of thousands of watts of amplifier power, and multiple loudspeaker arrays, all overseen by a team of audio engineers and technicians.
On the other end of the spectrum however, a sound reinforcement system can be as simple as just having a single microphone connected to an amplified loudspeaker for a singer-pianist playing in a jazz club. This stripped down version of the sound system is also known as a “Public Address” system or simply just “PA”. In both cases, these systems work to reinforce sound to make it louder and distribute it to a wider audience.
System Components – What do I need?
Unfortunately, we cannot afford to go into too much technical detail here as it will ultimately take a lifetime (Hey, I have a day job too you know?). But don’t worry, enough information will be covered here, to give you a decent grasp on what you need to know to start your very own live sound production. So, let’s look at the various components that you need:
- Input Transducers
- Mixing Consoles
- Signal Processors
- Power Amplifiers
- Output Transducers
Sound reinforcement always starts from the sound source (voice, instruments etc.). Hence, a plethora of different input transducers can be used in a sound reinforcement system to capture those sounds, with microphones being the most commonly used ones. Microphones can be classified according to their method of transduction, pickup (or polar) pattern or their functional application. Most microphones used in sound reinforcement are either dynamic or condenser microphones.
Other types of input transducers which you might find yourself using occasionally, includes magnetic pickups used in electric guitars (at times, acoustic) and electric basses, contact microphones used on stringed instruments, and piano and phonograph pickups (cartridges) used in record players.
Also, do take note that wireless technology has become increasingly popular in sound reinforcement, and are generally used for electric guitar, bass, and handheld microphones. This allows performers to move about on stage (or off stage) freely during the show or even go out into the audience for engagement, without worrying about tripping over cables and ending up disconnecting them from the system.
Mixing consoles are said to be “the heart of a sound reinforcement system”. Some people may disagree and argue that you do not need it in some cases. However, it is generally understood (at least among audio professionals) that the mixing console plays a pivotal role in any live show, even if it is just for a speech by a single speaker.
It provides the tools and functions for the professional operator to mix, equalize and add effects to sound sources. For different applications, the use of multiple consoles can be implemented within a single sound reinforcement system. However, for smaller scale venues (churches, pubs etc.), a single mixing console is often enough to meet the various audio requirements for live shows.
I strongly advise that you place the mixing console at a location where the operator can observe the performance on stage and hear the output of the loudspeaker system. You may realise that some venues with permanently built-in sound systems such as educational facilities and theatres, place the mixing console within an enclosed booth but this approach is more commonly applied for broadcast and recording applications. This type of configuration is quite rare and when it comes to live sound reproduction, as the engineer performs best when they can hear what the audience hears.
If you are thinking that signal processors are not relevant when it comes to smaller PA systems, think again. With more tech savvy audiences today, demanding higher quality of sound reproduction in live shows, even venues such as bars and clubs have their PA system fitted with features that were formerly only available on professional-level equipment. This includes:
- Noise Gates
- Feedback Suppressor
Equalizers are available in two types: “Graphic” and “Parametric”. A high-pass (low-cut) and/or low-pass (high-cut) filter may also be included. You would normally see “Parametric” equalizers built into each channel on mixing consoles (more obvious in analog consoles) and are also available as separate units. Parametric equalizers first became popular in the 1970s and have remained the program equalizer of choice for many engineers since then.
“Graphic” equalizers have faders (slide controls) which, as a whole, resemble a frequency response curve plotted on a graph. Audio engineering professionals typically use graphic equalizers with one-third octave frequency centers. These are typically used to equalize output signals going to the main loudspeaker system or the monitors on stage.
If you are constantly annoyed with the crackling voice of that Mariah Carey wannabe-singer when she is trying to hit those sky-high notes, then this piece of equipment is definitely for you.
Compressors are designed to manage the dynamic range of an audio signal. It accomplishes this by reducing the gain of a signal that is above a defined level (threshold) by a defined amount (ratio). Without this function, a signal that gets, say 10% louder as an input, will be 10% louder at the output. With the gain reduced, a signal that gets 10% louder at the input will be perhaps 3% louder at the output.
A “Noise Gate” allows a threshold to be set, where if it is quieter it will not let the signal pass and if it is louder it opens the gate. Its function is actually the exact opposite to that of a compressor. Noise gates are useful for microphones which will pick up background noise which is not needed, such as the hum of a miked electric guitar amplifier or the rustling of papers on a speaker’s podium.
You can also use noise gates to process the microphones placed near the drums of a drum kit in many hard rock and metal bands (even for other types of music too). Without a noise gate, the microphone for a specific instrument such as the kick drum, will pick up signal from nearby drums or cymbals. This is also known as the “bleeding effect“. Engineers often use noise gates for a “cleaner” and clearer mix.
Effects such as “reverberation” and “delay” are widely used in sound reinforcement systems to enhance the mix relative to the intended artistic or musical impact of the program material. Some examples of modulation effects includes flanger, phaser, and chorus which are also applied to some instruments.
The appropriate type, variation, and level of effects are subjective and is often decided by a production’s engineer, artist, or musical director. Reverb, for example, gives the effect of signals being present in anything from a small room to a massive stadium, or even in a space that doesn’t exist in the physical world. However audiences normally do not realise the effects of reverb as it often sounds more natural than if the signal was left dry.
A feedback suppressor is used to detect audio feedback and suppresses it by automatically inserting a notch filter into the signal path of the system, which prevents feedback “howls” from occurring. Not all engineers like the idea of using it, as it may be disruptive to their live mix (due to its nature of cutting down frequencies).
Okay, so you have all the secret ingredients to produce the perfect live mix. But do not forget one thing, you need an amplifier to get your awesome mix across to as many people as possible! (Unless you are working in a charity event for the hearing impaired, then it probably won’t matter)
Power amplifiers serves the function of boosting low-voltage level signals and provide electrical power to drive a loudspeaker. Every speaker requires power amplification of the low-level signal by an amplifier, even headphones. You will find that many audio amplifiers provides protection from over-driven signals, short circuits across the output, and excess temperature. A built-in limiter is often used to protect loudspeakers and amplifiers from overload.
Unlike most other sound reinforcement products, professional amplifiers are designed to be mounted within standard 19-inch racks. Most of power amplifiers feature internal fans to draw air across their heat sinks. Since they can, and do generate a significant amount of heat (after prolonged use), thermal dissipation is an important factor for you to consider when mounting amplifiers unto equipment racks.
You might also be interested in “active” loudspeakers, as they feature internally mounted amplifiers that have been selected by the manufacturer to be the best amplifier for use with the given loudspeaker.
Finally, the audience and performers are going to hear the final live mix (either FOH or Monitor mix) through “output transducers”. Let’s look at some of the most commonly used ones:
- Main Loudspeakers
- Monitor Loudspeakers
- In-Ear Monitors
If you are on a tight budget or just working within a small area, you can look into PA loudspeakers that have a single full-range loudspeaker driver, housed in a suitable enclosure.
Sound reinforcement systems that are more elaborate (normally for bigger live productions), may incorporate separate loudspeaker drivers (in separate enclosures) to produce low, middle, and high-frequency sounds respectively. This configuration often requires a crossover network to route the different frequencies to the appropriate drivers.
I highly recommend (if you are just starting out) that you look into companies that are making lightweight, portable speaker systems for small venues that route the low-frequency parts of the music (electric bass, bass drum, etc.) to a powered subwoofer. When the low-frequencies are routed to a separate amplifier and subwoofer, it results in a substantial improvement to the bass-response of the system.
The overall clarity of the mix may also be enhanced this way, as low-frequency sounds (which takes a great deal of power to amplify) can take a disproportionate amount of the sound system’s power if only a single amplifier is used for the entire sound spectrum.
Also famously known as the ‘foldback’ loudspeakers, these are actually speaker cabinets which are positioned on stage to allow performers to hear their singing or playing (or whatever audio feeds that are coming from the monitor mixing console). Hence, due to its function, monitor speakers are always pointed towards a performer or a section of the stage.
The performers will hear a different mix of vocals or instruments than the mix that is sent to the main loudspeaker system. You will notice that monitor loudspeaker cabinets are often designed in a wedge shape, allowing the output to be directed upwards towards the performer when set on the floor of the stage. These speakers are usually designed in a two-way, dual driver fashion, with a speaker cone and a horn, as monitor loudspeakers need to be smaller to save space on stage.
These loudspeakers do not take up as much power and volume as the main loudspeakers, as they only need to project sound towards a few people who are, often times, within close proximity to the loudspeaker. You might be interested in loudspeakers that are designed for use either as a main speaker of a small PA system, or as a monitor loudspeaker.
Also, many manufacturers today, produce powered monitor speakers (often called active speakers), which contain an integrated amplifier for convenience.
These are essentially headphones that have been designed to be used as monitors by live performers. You can find them in “universal fit” or “custom fit” design. The universal fit in-ears, features rubber or foam tips that can be inserted into virtually anybody’s ear.
The custom fit versions are created based on an impression of the customer’s ear that has been made by an audiologist. Take note that in-ear monitors are generally used in conjunction with a wireless transmitting system, as this allows the performer to move around on stage freely, while maintaining their monitor mix.
Isolation is key in the design of an in-ear monitor, meaning that the monitor engineer can produce a much more accurate and balanced mix for the performer. In-ear monitors allows each performer to receive their own customized mix (similar with monitor speakers) and not have it interfering with other musician’s monitor mix.
However, a major downside of this isolation is that the performer will not be able to hear the crowd or other performers on stage that do not have microphones (e.g., a bass player). Hence, in larger productions, this issue is resolved by setting up a pair of microphones on each side of the stage facing the audience that will then be mixed into the in-ear monitor sends.
Phew! That was a long one was it? I really hope you find this article useful. We’ve gone through all the major components in a live sound reinforcement system and I will definitely go into more detail with each of them in the future.
Thanks for reading and do leave comments or questions below!