UNDERSTANDING SPEAKER SYSTEMS

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When you visit the pro audio department at your favorite music store and look at all the pretty speaker cabinets, it's very difficult to know what the best choice is for your situation. They all look great and they all look like they should sound good. However, they don't all sound the same, and they definitely don't all sound good. In addition, some of them won't last very long under any intense usage. It is your job as an astute sound operator to learn enough about loudspeakers to develop an intelligent opinion about how they might fit into your system.
In this article we will look at a few different aspects of loudspeakers;

• Commercially built cabinets (enclosures)

• Crossover configurations

• speaker impedance

• components

Commercially built cabinets :-

For majority of applications, commercially built speaker enclosures are capable of providing excellent audio. There are several manufacturers that offer excellent products. In audio production the brand name means alot as a product with an excellent reputation and critical acclaim is worth considering.
An off brand (one that you haven't heard of before and that has an unrealistically low price) is rarely a good deal in the Long run. There's a reason why this products are inexpensive, and it's not that the manufacturers just aren't interested in making a profit, but it's usually because the components are poorly constructed, lightweight, and unreliable.
A reputable manufacturer with an excellent track record in the industry will almost always provide a superior product, excellent technical support, and a respectable warranty. In system development, it is tempting to save money on speaker cabinets or components so that there's extra money left for other less critical devices. That strategy is Ill-advised.
Each cabinet offers a list of features and selling points such as:

• Size

• Cosmetic appeal

• Ability to handle power

• Type of components

• Built-in electronics

• Acoustical design

• Rigging points

• manufacturer reputation

• Durability

• Warranty

• Impedance etc.

These are all important considerations, but there are two considerations that must be met before any others.

• Does it sound good?

• Will it last a long time?

Even if you're designing a system from reputable manufacturers, you must listen to several cabinets to find the ones that fit your taste.

The cone speaker

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It is instructive to understand the coin speaker and its components. A moving coil microphone and a cone speaker operate according to the same principle. At the core of the both devices is a coil of copper wire suspended around a magnet. In a microphone, acoustic audio waveforms vibrate the diaphragm connected to the copper coil, which cause a variance in the status of the magnet, which moves the speaker cone which is the source of the audio signal.
In a speaker, the electrical signals from the power amplifier continuously vary the electromagnet at the core of the speaker, causing movement of the coil around the magnet and the attached speaker cone. This is the source of the variations in air pressure that we perceive as sound.

Crossover configurations

speaker cabinets typically contain components that reproduce specific frequency bands, ranging from the lowest frequencies to the highest. In addition, many systems are designed to include multiple speaker cabinets that each cover a specified frequency band from lowest to highest.
The full-range audio signal is spilt into frequency bands by an electronic circuit called the crossover. Typically crossovers divide the audio into two, three, or four bands and each band is sent to a component (or components) in a cabinet or in a large system, to a separate cabinets optimized for a certain band.
Using a crossover typically produces the best sound quality, but it must be adjusted correctly for the system components.

The two major types of crossovers are the;

• Passive crossover

• Active crossover

Passive crossover :-

This type of crossover is typically built into the cabinet and receives a full range signal from the power amplifier. High-pass, low-pass, and band-pass filters divide the frequency spectrum for delivery to the target components.
Passive crossovers don't require electrical power to operate as they are merely circuit that filter out specified frequency bands.

Active crossover :-

An active crossover receives a line level signal either from the mixer or In-line processor. Active crossovers require electrical current to operate and the filter included in the active crossover are typically adjustable and accurate. These valuable tools is what helps the system designer adjust the size and strength of each band.

Analog and digital crossovers

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Many great systems have been built around high-quality analog crossovers while the modern systems often take advantage of digital crossovers and the additional flexibility they offer. The digital filters are very precise, plus the A/D converter take the analog signal into the digital domain. Once the signal has been digitized, it is very easy to include access to digital signal processing such as compression, limiting, and time alignment. The processing can be applied separately to each band before returning to the analog domain through each channels D/A converter.

most digital crossover systems, such as dbx Drive Rack and the BSS Sound web, provide the ultimate in system control, feeding multiple bands and channels simultaneously with high-quality and precisely processed audio.

Full-range cabinets :-

Full-range cabinets use passive crossovers to distribute the incoming power signal to the individual components. Some speaker components act as full-range devices, but they are rarely used in high quality professional sound systems.
Many cabinets also accept a full-range powered signal and passes same through a passive crossover, while at the same time offering access to the individual components in the cabinet directly, bypassing the passive crossover. This affords the sound operator the opportunity to divide the frequency spectrum through an outboard active crossover, then route the specific bands through separate power amplifiers which are then connected to the individual components.

N/B: This typically creates a two or three way system from a full-range cabinet.

Two-way cabinets:-

Two-way cabinets, traditionally is referred to as bi-amplified, contain components that are optimized for two specific frequency bands: highs and lows. The components determine the exact crossover frequencies. A two way system is better than a full-range system, but it isn't the optimum in most circumstances. The high frequency drivers require less amplification then the low frequency drivers also, a two way system can adequately separate the highs, but the remaining band is so broad that it becomes inefficient as it tries to simultaneously push the mids and lows through the same component.
Two way system works fairly well in a studio monitor application where the speakers are within about one meter if the listeners ears, but in a live application, a three or four way system will provide superior sound quality.

Three-way cabinets :-

Three way systems are capable of providing excellent sound. High quality components combined with excellent power amplifiers should faithfully reproduce a good audio source. Three way cabinets provide access to components that are designed to reproduce highs, mids, and lows. Sometimes the low frequency components are unduly stressed as they attempted to reproduce the low-mid, bass, and sub-bass at the same time.
Depending on the style of music and the desired sound pressure level, a three way system could provide perfectly acceptable or woefully marginal results. It's really all about the sub-bass frequencies below about 100 Hz. These frequencies require the most power to accurately reproduce and they are the most adversely affected by the three-way design.

Four-way systems :-

Four-way systems typically add one or two subwoofers to a three-way system. The addition of components capable of receiving the sub-bass frequencies along with sufficiently powerful amplifiers provides a noticeable increase in the sub-bass frequency content. At the same time, removing the sub-bass frequencies from the components that handle the low-mid and low frequencies radically increases their efficiency.
Most professional system use this configuration, while some split the frequency spectrum into more than four bands.

Four bands with intelligently chosen crossover frequencies and ample power can adequately represent a well mixed, full-range audio source.

Thanks for reading!

Reference

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