Know The Difference
Speakers come in several types and it is important to know the difference between them. There are situations that make different kinds desirable and knowing which ones to use and when is a skill that it is worth developing. In order to do that you will need some background information which it is my intention to provide. You will of course need to use your ears when you are making any audio decision. No book (or blog) will be able to get a good sound for you, no matter how much jargon they use.
Speaking of jargon, lets agree on some terminology. The word speaker is a shortened version of loud speaker (or "loudspeaker", you will find that many terms in any technical subject are simply lazy, and possibly not any easier to type for the trouble). This can refer to the electrical component itself or the entire unit including the cabinet and any electrical connectors, depending on who you ask. It is the latter that we will use it to mean here as in a normal situation it would be very foolish to bring just a cone with some wires poking out of it. however this would not be entirely unheard of. Audio engineers may fit unenclosed loudspeakers into bespoke hidden sound systems. Such systems are seen (or not) and indeed heard in department stores and supermarkets. Normally you will be working with more conventional modular enclosed speakers. While on the subject of speaker cabinets it is worth thinking about size and shape. Speakers with a large cone are usually louder and give better bass reproduction but require extensive transport arrangements, i.e. a van. Modern acoustic engineering has led to the development of small speakers that deliver a big sound. these are well worth looking into.
Most speakers are constructed with a metal basket. At the back end is a powerful magnet shaped in such a way so that a coil can move forth and back inside the magnet, moving a paper cone along with it as it does so. The electromagnetic action of the coil when an audio signal of sufficient voltage is supplied to it is such that it will cause the cone to move in conjunction with the voltage of the signal. This movement pressurises the air in front of and behind the cone. The pressure waves caused by the movement of the cone are experienced by anyone nearby as sound.
Whats In The Box
The basic types of loud speaker cone are the high range or tweeter, the mid range and the woofer. The tweeter is the smallest and it is specially made to reproduce high frequencies. Sometimes the tweeter is referred to as the horn, because it is a piezoelectric transducer fitted into a plastic horn shaped assembly which works in a different way to the cone and coil speakers we most commonly see. As its name suggests the mid range reproduces the mid range frequencies and at is usually the middle size speaker in a cabinet and the woofer is the largest and produces the bass frequencies. There is another type of loud speaker that is the sub woofer. These are usually quite large so that they can produce the frequencies desired although recent developments in speaker enclosure design have enabled smaller models that perform well.
Pay Attention To This Bit
let me add at this point, DO NOT connect your home Hi-Fi speakers to PA system amplifiers. they will probably be overloaded and become damaged or even blow. If you want to hear a live mix through such speakers you will need an amplifier that is designed to give them at the correct level. Then again, it is your stuff and absolutely not my fault if you break it.
A normal passive speaker is the first type of electrical arrangement that we will look at because it is the cheapest and most common type you may encounter. It must be said that they are widely used in industry as they do sound very good. They have one input that delivers an amplified signal to one or more loudspeakers inside the cabinet. They are passive, which is an electrical term that means that they do not require their own power supply. The power that drives the speakers comes from the signal that is sent to it. For this reason passive speakers require an amplifier to produce the signal which runs them. We will return to the subject of amplifiers. Speakers with an input and an output may be linked together in a daisy chain style. This sends the signal from the amplifier along to more speakers but can lower it if too many speakers are linked. This technique is useful for overcoming echo problems in big rooms.
Passive speakers can be configured to use signals from more than one amplifier. some cabinets will have two or more inputs that are linked to a single loudspeaker within the cabinet. Needless to say more than one amplifier will be required to run this arrangement, which has a special name, bi-amping. A bi-amped speaker can be used to increase the sound quality that you can get by giving you more control over the overall sound. The amplifiers can be used in conjunction with a device called a crossover, which sends different frequency ranges from a signal into two or more output signals with differing frequency ranges. these differing signals are then amplified before being sent to the speaker. Some crossovers require power and are therefore known as active crossovers, while others do not and are referred to as passive crossovers. Obviously bi-amping is more expensive than using a single amplifier but it will come in useful for large setups involving lots of signals, as frequencies can be divided between suitable cones. Sometimes bi-amped systems are referred to as integrated active systems.
If you do not want a huge pile of bulky equipment but still need to get the power that can be achieved with having many amps there is always the powered speaker option. Speakers that require their own power supply do so because they have their own amplifier on board. This means that they can be fed an unamplified signal directly from a mixer. They are generally more expensive than other speakers but this is justifiable because of their more complex construction, and good deals are available for second hand units, just make sure that you have tested it first. Good music shops will let you do this. If a store will not allow this then the likelihood is that they are selling broken gear. Do not buy from them.
powered speakers come in two flavours between which the difference is subtle, but never the less it should be understood. The term powered speaker could mean that the enclosure contains a power amplifier and a passive crossover or in the type known as an active powered speaker there could be an active crossover that then goes to separate amplifiers which are individually connected to each speaker.
Studio monitors, which are very precisely engineered speakers that give excellent sound quality are usually powered, but different models may use either or a combination of the above configurations. Of course there is disagreement as to which particular models are the best. It is usually a good bet to get a set that can handle a balanced signal, as the nature of that kind of signal disallows distortion to a certain extent.
There are advantages and disadvantages to choosing and using any equipment and speakers and it should be apparent that powered speakers will be heavier than passive ones because of the built in equipment. They also require power which will naturally cause a need for more power cables, and therefore health and safety becomes more interesting. They will give more dynamic range than a normal passive speaker but they could be equalled by a bi-amped speaker. Powered speakers can simplify the process of achieving good quality sound by removing the need to set equaliser levels on crossovers and amplifier output levels such as in a bi-amped system, as the manufacturer has built this functionality in and optimised it already.
Well I think that we may have scratched the surface but before I go, I would like to give you something to play with, because I am nice. But I must warn you I take no responsibility for your actions, passive loudspeakers can be used as a dynamic microphone. It is up to you to discover whether or not they should be, take care.