We all use loudspeakers to listen to music. But how many of us are familiar with its basic components? The subject covered in this article is important to both audio professionals and consumers as well. Hence, before you go out and buy those pair of speakers you’ve always wanted, better learn about the loudspeaker system design first!
There is quite a bit of material to cover, when it comes to explaining the various components of a loudspeaker. But you don’t have to worry too much, as I will only cover the basics that is necessary in giving you a good grasp of this subject. Find out how the various aspects of a loudspeaker’s design affects its overall quality. Ready to learn? Then let’s get on it!
Before you go hunting for a pair of loudspeakers that will fit your budget, you need to know that the transducer element of a speaker is not the only component that matters. Regardless of whether you are planning to use your speaker for professional applications, or just for casual listening, these are the various aspects that you should look out for:
- Horn loudspeakers
- Wiring connections
Every multi-driver loudspeaker will include this vital subsystem. The crossover is designed to separate the input audio signal into different frequency bands, before routing them to the relevant drivers. Every driver will only receive the signal that is within the frequency range that they are designed to handle, thus minimising distortion and interference between them.
A component made up of resistors, inductors, or non-polar capacitors, the passive crossover is essentially a carefully designed network of electronic parts. It is often placed between the power amplifier (that powers the drivers) and the speaker drivers themselves, to filter the amplifier’s signal into various frequency bands that are suitable for each individual driver.
Passive crossovers only require the audio signal itself, and no external power is needed. But it comes at a high cost, large components, and lack of circuitry adjustment options (due to limited options of high power level components etc.). The overall audio signal loss will also be high and the damping factor between the voice coil and the crossover will be reduced greatly.
The vast majority of low-powered and home stereo systems use passive crossovers that are typically installed inside the speaker enclosure itself. Similar to the driver components that they feed, passive crossovers have power handling limits, insertion losses (said to be 10%), and change the load seen by the amplifier. These factors are often of high concern to audiophiles and engineers.
Unlike its passive counterpart, an active crossover (also an electronic circuit) filters the signal into separate frequency bands before it goes into the power amplifier, thus requiring at least one power amplifier for each bandpass. Its possible for passive filtering to be used in the same way (before amplification), but it is a rare method, due to the lack of flexibility.
The method of filtering before amplification is known as bi-amping, tri-amping, quad-amping, and so on, depending on the number of amplifiers used. There are speakers that use both passive and active crossovers, for example, passive filtering between the mid and high-frequency drivers and active filtering between the low-frequency driver and the combined mid and high frequencies.
A simple active crossover circuit emulates a passive network’s response, but more complex circuits allow for a more elaborate audio attenuation. Some high-end active crossovers such as digital loudspeaker management systems, may have parameters for phase and time alignment between frequency bands, equalization, and dynamics (compression and limiting) control.
Unless you are an acoustical engineer wanting to build your own loudspeaker, this section is not very important to most audio practitioners and consumers. However, I would like to just give a basic overview on speaker enclosures, so that you will be better informed about the purpose it serves. After all, knowledge is power, don’t you agree?
Speaker drivers are often mounted in an enclosure, or cabinet. The enclosure prevents sound waves produced from the back of a driver from interfering with those from the front. Sound waves coming from the back are 180° out of phase with those projected forward, and will cause wave cancellations, thus greatly diminishing the level and quality of sound at low frequencies.
You may want to look out for design terms such as bass reflex, passive radiator, transmission line, etc. These enclosure types are built to alter the rear sound radiation, in order to allow it to constructively reinforce the sound emanating from the front of the speaker cone. They are often used to extend the driver’s effective low-frequency response and enhance its low-end output.
This type of speaker uses a shaped “waveguide” in front of or behind the driver to increase the directivity of the speaker and to convert a high pressure condition at the driver cone surface (with small diameter), to a low pressure condition at the horn’s mouth (with large diameter). As a result, the speaker’s sensitivity improves and the sound is focused over a more narrow area.
Speakers that are horn-loaded can reach the peak sensitivity of 110 dB at 2.83 volts (1 watt at 8 ohms) at a distance of 1 meter. This is a massive increase in output when compared to a speaker at 90 dB sensitivity. Horn speakers are very useful in applications that require high sound levels or in situations where amplifier power is limited.
Horn speakers are often used in sound reinforcement systems at live concert venues and in PA systems at schools (or other facilities). However, there are also audiophiles and other consumers who use them for home music and home theatre applications, due to their high sensitivity (even when driven by low-powered, consumer level power amplifiers).
Loudspeakers are generally connected to a signal source (for instance, to the audio amplifier or receiver) via two wiring points. In order to receive electrical audio signals through wire connections, the loudspeaker enclosure may be designed with binding posts, spring clips, or a panel-mount jack (depending on the make and model).
If you do not adhere to the proper electrical polarity (the “+” connector on the speaker should be connected to the “+” connector on the amplifier, and “−” to “−”), the loudspeakers will be “out of phase” or to be more accurate, “out of polarity”. Most speaker cables are usually marked in a way that one conductor of a pair can be distinguished from the other.
When loudspeakers are “out of phase”, the motion of one cone will be in the opposite direction of the other. More often than not, this causes monophonic audio elements within a stereo recording to be cancelled out, reduced in level, and made much harder to localize, all due to the sound waves destructively interfering with one another.
This cancellation effect is most noticeable at the low frequencies, which is a crucial frequency component for most types of music. Don’t worry too much if you have connected your speakers incorrectly, as it does not damage them. But your listening experience will definitely suffer greatly.
That is all folks! I hope you had a great time reading this article, and can now make a more informed decision when you are finally ready to buy a pair of speakers!
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