“How do I get my speakers to sound the loudest?” is a common question that gets asked by Audio/Video Enthusiasts. There are a lot of numbers that are thrown around when it comes to how to get the most out of your speaker setup. Terms like Resistance, Impedance, and Sensitivity are thrown around interchangeably, and leave the A/V enthusiast a little bewildered about their meaning. At Technospeak, here’s how we see it…
When it comes right down to it, all those rockin’ tunes you hear coming out of your speakers break down into electrons and electrical flow in the same way as the light allowing you to read this article. The relationship of electrons and their flow can be understood by Ohm’s Law which breaks down into Voltage, Current and Resistance.
Voltage is the potential for current to flow. It is not actually current flowing—just the potential. A great analogy is the water in your kitchen sink. There is always the potential for water to flow, however no water will flow until the faucet is turned on.
Current is the real “work” and refers to the density of electrons going past a point in time. Using the same water analogy, a 2-inch pipe has more water in it flowing past a point in time than a ½-inch pipe does.
Resistance is the resistance of Electricity to flow in a circuit. The more resistance in a circuit, the less current that flows through that circuit; the less the resistance in a circuit, the more current that flows through that circuit. Back to the water analogy one more time, ½-inch pipe with years of corrosion inside it will provide more resistance to water flowing through it than a ½-inch pipe that is brand new.
Ohm’s Law states that for a given Voltage (V), it is equal to the Current (I) multiplied by the Resistance(R). The equation for this relationship is V = I*R. This relationship was originally discovered for DC current, however, and all the amplifiers and speakers we care about run on AC current. In an AC circuit, resistance to the flow of electricity is referred to as Impedance (Z) instead of Resistance(R). For the purpose of this article, we will generalize that Impedance in an AC circuit is equivalent to Resistance in a DC circuit (in reality it is slightly different). As such in an AC circuit, our relationship still holds true and is written alternatively as V = I*Z.
Now back to speakers…
Typically you will read about speaker configurations in 4 ohms, 8 ohms or 16 ohms. These are Impedance values and are the resistances the amplifier has to overcome to produce sound energy. Usually Amplifiers are designed to run most efficiently at a given speaker Impedance value with a matched Voltage and Current value (to complete the equation V=I*Z that we learned above). At this point it is important to note that there is no difference in volume between a 4 ohm, 8 ohm and 16 ohm speaker AS LONG AS the amplifier powering these speakers is equipped with the proper Voltage and Current to handle each of these Impedances.
Speaker volume (loudness) comes into play by varying the Voltage/Current that is coming in to the speaker from the amplifier via the volume knob as well as the sensitivity of the speaker. Speaker Sensitivity is a measurement of the amount of sound output derived from a speaker with one watt of power from an amplifier measured 1 meter in front of the speaker. Thus, if two speakers are given the same watt of power from an identical amplifier and Speaker A has a higher sensitivity than Speaker B, Speaker A will be louder than Speaker B.
Given this, if you mismatch your Amplifier and speakers, you can have a similar feeling of your speakers becoming softer and louder. For example, if you put a 16 ohm speakers load on an Amplifier that is most efficiently run at 8 ohms, your volume may appear softer, but only because there is ½ the electrical current flow in to the speakers. Alternatively, if you put a 4 ohm speaker load on an Amplifier that is most efficiently run at 8 ohms, your volume may appear louder, but only because there is twice the amount of electrical current flow in the speakers.
Although Amplifier/speaker mismatch may seem like an Ok way to go for dialing in your volume level, it’s not. With too much resistance for your amplifier to overcome to produce sound energy in your speakers, your sound quality will manifest as flat and “tinny,” as an insufficient voltage/current value is reaching your speakers. With too little resistance for your amplifier to overcome to produce sound energy in your speakers, your speakers will receive too much of a current/voltage value and destroy the drivers. Additionally, the amplifier does not have enough resistance pushing against it to dissipate the heat generated from amplifying the speaker and it will destroy itself.
The most common scenario we see is not enough speaker resistance connected to an amplifier. This appears as multiple pairs of speakers in a house with only one amplifier to drive them that is not rated for that purpose. As more than 1 pair of speakers are added to the amplifier, the resistance of all the speakers in the circuit drops. When the resistance drops, too much current flows through the system and all speakers and the amp can get damaged and eventually destroyed.
What’s the main take-away? If you don’t properly match your amplifier and speakers and rely on input voltage/current and sensitivity to manager your volume, you run the likely risk of damaging or destroying your amplifier and your speakers.