What happens if speaker impedance is too low

Ohm's Law states: In an electrical circuit, current flow is directly proportional to voltage and inversely proportional to impedance. Mathematically, this becomes: Current in amperes equals voltage in volts divided by impedance in ohms. So increasing the voltage increased the current. If the voltage decreases back to 10 volts, the current will decrease back to 1. Now, if our amplifier with 10 volts output is connected to a 4 ohm speaker, the lower impedance will allow more current to flow.

Finally, if we can measure or in some other way determine the amount of current being drawn from the amplifier, we can calculate the value of the load impedance using Ohm's Law. We will use this shortly to figure out what happens when we connect several speakers to the output of an amplifier.

The formula for this is: Impedance in ohms equals Voltage in volts divided by Current in amperes. Also connect the black terminal of the amp to the black or '-' terminal of the speaker.

If you feed a pure tone through the amp so that it delivers 10 volts to the speaker, the current flow through the speaker as we saw above should be 1.

The first thing to understand is that the voltage output from the amplifier does not change. In reality, it might drop just a hair, but for this discussion let's assume a perfect amplifier. So it's still 10 volts AC. And since each speaker is connected directly to the amp's output terminals, each speaker will receive 10 volts from the amplifier.

As we saw earlier, if 10 volts is applied to an 8 ohm speaker, it will draw a current of 1. And if each speaker needs 1. If you add a third speaker, it will also draw another 1. If you keep adding speakers, at some point the speakers will demand more current than the amplifier can deliver, and it gives up its smoke and dies. Too many loads is an overload. See importance 1, above. Now, we are ready for impedance. As we said earlier, if you know the voltage and can figure the total current, you can calculate the total impedance of all the speakers together by dividing the voltage by the total current.

A single speaker is simple: 10 volts divided by 1. Remember that two 8 ohm speakers would draw a total of 2. So 10 volts divided by 2. What about 3 speakers that draw 3. Four speakers that draw 5 amperes from a 10 volt source have a total impedance of 10 volts divided by 5 amperes which equals 2 ohms. As more speakers are added, each one draws additional current from the 10 volt source, so there must be less total restriction of current. Using the pipe analogy, you can put a bigger pipe in, but it'll only carry more water audio if you have a pump amplifier powerful enough to provide the extra flow of water.

Using lower-ohm speakers without equipment that can support them may cause you to turn the amplifier all the way up, which can damage the equipment. Using mismatched speakers and amplifiers can cause problems when the receiver or amplifier is not up to the task. Take almost any modern speaker and connect it to any modern amplifier , and you'll have more than enough volume for your living room. So, what's the advantage of a 4-ohm speaker versus a 6-ohm or 8-ohm speaker?

Not a lot—just that low impedance sometimes indicates the amount of fine-tuning the engineers did when they designed the speaker. The impedance of a speaker changes as the sound goes up and down in pitch or frequency. For example, at 41 hertz the lowest note on a standard bass guitar , the impedance of a speaker might be 10 ohms. At 2, hertz the upper range of a violin , the impedance might be just 3 ohms. The impedance specification seen on a speaker is just a rough average.

Some of the more exacting speaker engineers like to even out the impedance of speakers for consistent sound throughout the whole audio range. Just as someone might sand a piece of wood to remove the high ridges of grain, a speaker engineer might use electrical circuitry to flatten the areas of high impedance. This extra attention is why 4-ohm speakers are common in high-end audio but rare in mass-market audio. Before you buy a 4-ohm speaker, make sure the amplifier or receiver can handle it.

It may not be clear, but if the amplifier or receiver manufacturer publishes power ratings in both 8 and 4 ohms, you're safe. A relatively inexpensive receiver might not be the best match for 4-ohm speakers. It might function OK at low volume, but crank it up, and the amplifier might not have the power to feed the speaker.

The receiver may shut itself off temporarily, or you may burn up the receiver. Some amplifiers and receivers feature an impedance switch on the back that you can use to switch between ohm settings. The problem with using this switch is that impedance is not a flat setting, it is a curve that varies. Send a private message to paulj. Send a private message to lucpes. Find More Posts by lucpes. Find More Posts by Frank Berry.

Quote: Originally posted by paulj Yes, but isn't the 4 ohm impedance of the speakers i8n danger of damaging the amps, which can only handle 6 - 16 ohms? Send a private message to boholm. Send a private message to kelticwizard. Find More Posts by kelticwizard. Send a private message to 5th element.

Find More Posts by 5th element. Posting Rules. Similar Threads. Impedance ratio and T-amps. Op amps: output impedance and load resistance. When we talk about the impedance of a speaker, most of the time people are referring to the range of the speaker assigned to categories like 2 ohms, 4 ohms, 8 ohms, and so on. This is how we match speakers to a car or home amplifier, radio, and so on. When a musical signal made up of alternating current is applied to a speaker it generates magnetic fields as current flows through the tightly wound wire coil.

Interestingly enough, a coil of wire develops magnetic fields that resist the flow of the current resistance, also called reactance in this case. Similarly, many other electrical components like motors deal with the same electrical resistance as alternating current AC is applied. You may remember this kind of math from trigonometry class.

You can find this by squaring each and then taking the square root of the two numbers added together. Just like any other device connected to an electrical power source, the speaker impedance will determine how much or how little current a home or car receiver, amplifier, etc will produce. The speaker impedance also affects how some speaker components such as speaker crossovers behave too.

You can connect a higher speaker impedance in most cases without any problems at least not major ones. A radio, home or car amplifier, etc will still produce sound and run at normal or low temperatures. Car stereos or amps, for example, have to work with lower voltages than home stereos so they need a lower impedance 4 ohm speaker typically to produce more power.

Home stereos, on the other hand, have higher voltage available and can use a higher speaker impedance 8 ohms, typically.