When Designing, Selecting and Building a sound system there are a few question that need to be answered to be able to select the proper size system. Planning is a major factor with selecting you system. These questions include:
- Mobility – Will this be a permanent or a portable system?
- Venue Size – What’s will be the largest size of the room that this will be used in?
- Headcount – How Many People?
- Sound Level Requirements – How Loud Do You Need to Get?
- Budget – How much money do you have or can justify for this system?
Will this be install at one location and level it? Will this system be set up and torn down for every gig for each location? Manufacturers provide certain feathers that are directed for permanent installation while other features are provided for the mobility of a system to maximize their functionality. If the selection is portable, the flexibility in connections and convenience features like handles and carry bags are a must but the same time strive for simplicity and not complicate features.
Room size is a critical piece of information. The first focus in the length and width of the room but the ceiling height is also critical if it happens to be very high. This information is critical if you are using modeling software that is provided with some systems. This will allow you to better predict the response you can possibly get form you system. The size of the room, coupled with the surface hardness of the room will have an impacts on the the RT60 of the room. This is the reverberation time which is the time measured of how long the ringing in the room will last. One thing that is done upon the initial evaluation of a room is to clap the hand is done and then count then number of seconds that elapses that the echoes last. Less than two seconds is good but four or more seconds will impact your system and the design has to address this to be successful.
Defining your audience is one of the important items when putting a system together. The number of people and the distance from the speakers is a major issue. Human bodies provide a large dampening factor especially in the high frequency range. For the portable systems, you need to identify the maximum potential number of people that you will be required to serve. If this is a large variation in the number of people, it might be suggested to focus on more of a modular system where you may use a small number of speakers for a small group with an addition of 2 of 3 cabinet for a medium size group and then your complete system that will address the largest group you designed for. Now if you are going to address an outdoor application you have the temperature and humidity as well as the number of people.
Sound Level Requirements
All of the above have addressed a portion of the loudness requirement but you have to define the type of music you will be dealing with or playing. If the used of stage monitors are applied on the stage, this could add to the overall output of the system. Acoustic drums and live guitar amplifiers will require the system to be louder then these sources. The loudness also has an impact on the “BOOM” effect on the low frequencies. To make you aware, it costs more to generating low frequency then it does for mid and high frequencies. The reason for this is that it requires larger drivers and larger power amplifiers.
Distortion is not a friend. Distortion can make the best of system sound like one you purchased at a dollar store. Operating a system close to its edge or over its capabilities will end up costing you additional cash in blown drivers and overheated amplifiers.
A system designed to produce 90dB at 90 feet of clean sound, then required to produce only 90dB at 50 feet, will operate much better than a system designed for 90dB at 50 feet and then required to provide this same 90dB at 50 feet. This would be pushing your system to its limits.
This ratio is the number of suggested FOH cabinets per subwoofer.
- One subwoofer for every three FOH cabinets in lighter applications
- One subwoofer for every two FOH cabinets in heavier applications.
Please note that subwoofers on the ground are more efficient than ones that are flying in the air.
The first decision in the budgetary phase is what you are trying to accomplish. The amount of money spent here can make you sound fantastic or totally sound like crap. In fact, if you skimp on this, this could cost you even more money. This is a critical piece of the selection. Now, how much you can afford to spend on your system?
You cannot design and build a $1000 system and expect it to produce like a $5000 system. At the same time you cannot design a system for a mid-size club and use this same system in a small auditorium or for an outdoor function.
One aspect of this design is to start at the beginning to design your system as one that has flexibility and can be easily expandable with like kind and still look professional. You do not change cabinet designs midstream.
The best approach would be to plan for where you want to be in a couple of years and design your system for those requirements. This may be done by the purchase of better quality equipment or increase the power requirement of the system.