How to Match Speaker and Amplifier Correctly and How They Work Together
The job of a PA system (Public Address System) is to convert weak audio signals, such as those produced by vocals, into electrical signals, increase the amplitude of these signals, and then convert them back into much louder volume sound energy. A PA system consists of several components that are the work of the speaker to increase the amplitude of the audio signal and convert this signal back from electrical energy to sound energy.
If the amplifiers and speakers used in a particular PA system are not properly matched in terms of amplifier power output and speaker power ratings, speaker damage may result in costly repairs or even require speaker replacement. This article explains the basic theory behind speaker and amplifier ratings, why speaker damage occurs, and how to match amplifiers or speakers to produce the best possible sound quality and minimize the chance of speaker damage.
How Amps and Speakers Work Together
An audio signal amplifier accepts a small electrical signal and uses a series of transistors to ultimately reproduce the original voltage fluctuation but produce a much higher-power electrical signal. The speaker works on the principle of an electric motor, where electrical pulses from an amplifier are passed through a coil of wire that creates magnetic energy in the form of an electromagnet. This coil attracts or repels a second stationary magnet, causing the paper cone to vibrate, which then transfers energy to the surrounding air molecules to create sound.
How Are Speakers and Amplifiers Rated?
Both amplifiers and speakers are rated according to the power they can supply or their ability to cope with the power being supplied. Power is measured in watts (W) and is the rate at which energy which is measured in joules, is converted from one form to another. For example, 1 watts of power corresponds to 1 joule of energy converted per second and 10 watts of power corresponds to 10 joules of energy converted per second.
There are a number of methods used to describe the power of electrical signals, best used to evaluate the power of amplifiers and speakers.
Instantaneous Power: This refers to the power used at any given moment during operation, but it is not a useful metric for describing the performance of an amplifier or an amplifier because the power used to move the speaker cone in the complex way required is constantly changing rapidly.
Peak power: The maximum amount of instantaneous power present at the highest level of a signal. For amplifiers, peak power is useful for describing the maximum instantaneous limit of a function for sounds such as drum beats and bass notes. Amplifier peak power is limited by the available power supply, and signal distortion known as clipping occurs when the input level is increased beyond the point where the amplifier reaches the limit of the power supply.
In the case of a speaker driver, maximum power occurs at the point where the speaker cone reaches the front or rear point where damage can occur.
RMS or Average Power: This is a function of the maximum continuous average power output of an inherently undistorted signal for a given load impedance (in this case, the load is the speaker) and is the most consistent way to compare power levels between amplifiers and speakers.
Music or program output: Often used for loudspeaker ratings, this term is seldom used for speaker drivers to produce pure tones (average output is measured) instead of being used to reproduce sounds with a rapidly changing power distribution. It is a term coined by Music or program power that is said to be approximate twice the equivalent average power.
Why Speakers Fail
Speakers usually fail due to excessive power or a distorted signal fed from an amplifier. Heat is a by-product of the motor effect when sending electrical signals through a speaker coil, and if excessive power is sent to the speaker, the heat generated can damage or destroy the coil. Or, if driven to the point that a low-power amplifier can deliver, this "clipped" signal will produce excessively high frequencies that can burn up a tweeter or horn.
How to Match Your Amplifier and Speakers
When constructing a PA system, you may need to match amplifiers and speakers that are rated in different ways (eg amplifiers are rated for RMS Power and speakers are rated for Music Power).
A 100W per channel amplifier and a 100W RMS-rated speaker can be directly compared if both the amplifier and speaker are rated in terms of RMS power and are not likely to be overdriven. However, if you are using the system for dance music or heavy metal where the amplifier is overdriven and likely to clip, we recommend a speaker system rated at approximately twice the RMS of the amplifier.
If a speaker is rated in terms of music or program output, this is about twice its average or RMS power, and for low-level applications such as speech, the speaker should double the amplifier rating (e.g. 100W amp to 200W power). . speaker). For applications such as live or dance music where clipping can occur, a speaker driver at Program Power will need at least twice the amplifier RMS Power, potentially up to three times more for higher power applications.
Overall, the PA system must be designed so that the amplifier is not driven into clipping and the speakers are powerful enough to accept the constant power generated by the amplifier.