Why do speakers have ohms

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.

Well, what if the speakers have different impedances? Like an 8 ohm cabinet and a 4 ohm cabinet? The same method can be used. To make it simpler, remember that impedance was a physical property that doesn't depend on the voltage.

The speaker has the same impedance whether the source is 10 volts or 1 volt. So let's use 1 volt to make it simpler. Both together draw 0. Notice that the total is less than the lowest value speaker. While the calculations may seem complicated, examination of the results above reveals some patterns that make things much easier.

First, if all speakers or cabinets have the same impedance ratings, the total impedance can be found by using the impedance value of one speaker and dividing that by the total number of speakers. If you go back to our example of 8 ohm speakers, we found that a single speaker had a total impedance of 8 ohms duh What happens with 5, 6, or more speakers?

Second, the relationship between typical speaker impedance ratings allows for some equivalents when mixing different ratings. A single 4 ohm speaker is the equivalent of two 8 ohm speakers in parallel. So a 4 ohm speaker combined with an 8 ohm speaker would have the same total impedance as three 8 ohm speakers in parallel.

See if you can figure out the equivalents for a 4, 8 and 16 ohm speaker combination. So, if you see a speaker jack labeled "Minimum Load 4 ohms", that means you can connect up to two 8 ohm speakers or a single 4 ohm speaker to that jack. What if the jack label says "Minimum 2 ohms"? If you are mixing speakers with different impedance ratings, be sure to check the total impedance using the rules above to be certain the total is within the limits of the amplifier. Solid state amps typically have a 'minimum load impedance' indicated near the speaker terminals, and the total speaker impedance must be equal to or greater than that value.

Tube amplifiers typically have a switch on the back to adjust for the speaker load impedance. Tube amps have different output characteristics than solid state amplifiers, and too low a load impedance will not normally damage them, but the total output will become weaker and muddy. So too little load impedance is still undesirable. Too high a load impedance on a tube amp can cause high voltages inside the amp that can damage power output tubes or the output transformer.

So, how do you tell what the impedance of a speaker is? On most cabinets, it should be printed on a label next to the jack. If the speaker is visible, it may be printed on the speaker label or stamped on the frame or magnet.

To measure the true impedance of a speaker or cabinet requires a rather complex procedure involving signal generators, power amplifiers and high frequency AC voltmeters. However, with raw speakers and many cabinets, the ohmmeter function of a digital multimeter can help you identify what the impedance of the speaker should be.

So, a 4 ohm speaker will typically measure about 2. Another thing As mentioned, applying a voltage across the voice coil will induce a magnetic field in the coil, which causes it to move. This is how speakers ultimately work as transducers. The opposite is also true. Moving the voice coil within a magnetic field will induce a voltage across the coil. This voltage is in opposition to the voltage that would cause the coil to move. This is called back electromotive force. At the resonant frequency, the speaker driver will want to vibrate freely, which causes an increase in back EMF and, therefore, an increase in impedance.

This may cause several spikes in the overall impedance of the speaker. Oftentimes these peaks are damped or tuned in the speaker design to help achieve a smoother impedance graph. Inductive reactance is a property of an AC circuit like a voice coil in a speaker driver that opposes the change in current. Reactance is similar to resistance in the fact that it is measured in ohms.

Notice the difference in the definitions: reactance opposes the change in the electrical current while resistance opposes the current itself. Both reactance and resistance are factors that make up the overall impedance of a speaker driver. The hertz values represent cycles per second.

We know that the current of higher frequency signals changes direction more times per second than lower frequency signals. The reactance of a voice coil, therefore, opposes higher frequencies more than it opposes lower frequencies.

Now imagine having multiple drivers within a single speaker unit. Most loudspeakers are designed with at least 2 drivers a woofer and tweeter , and many are designed with more. As we can imagine, each driver will have its own effect on the overall impedance of the speaker unit.

This can cause several peaks in the overall impedance that coincide with the resonance frequency of each driver. Note that crossovers are used to send specific frequency bands to the drivers that will best reproduce them. Therefore, the increase in high-frequency impedance due to inductive reactance will likely only be a result of the tweeter as no high-frequencies will be sent to the midrange speakers or woofers.

Note that each driver may also have a different nominal impedance, which may dramatically alter the overall impedance graph. A speaker enclosure improves the performance of a speaker by effectively blocking off the rearward out-of-phase sound waves from the speaker driver. The resonance s of a speaker enclosure, like the resonance of the speaker driver, affects the impedance of the overall speaker unit.

The driver will oscillate more easily at the resonant frequency of the enclosure and, therefore, more back EMF will be produced in the voice coil. The enclosure resonance is often, but not always, below the driver resonance.

The peaks in impedance due to the enclosure and the driver resonances coincide with their respective resonant frequencies. For more information on speaker enclosures, check out my article Why Do Loudspeakers Need Enclosures? There are plenty of stereo amplifiers on the market with multiple channels that can connect to multiple speakers.

Generally, these distinct channels act as multiple single connections between the amp and a speaker. There are two methods of connecting multiple speakers to a single amplifier channel:. This is because, when connecting multiple speakers to a single amplifier channel, we must look at the total load impedance of the circuit. This is not technically correct but will allow for an easy and intuitive understanding.

This is for good reason since the overwhelming majority of speakers utilize these types of drivers. However, there are certainly other speaker driver types worth considering when thinking of speaker impedance. Electrostatic loudspeakers tend to have low inputs impedance.

The impedance graphs of electrostatic speakers do change with frequency due to the capacitive nature of the driver but do not present overly sharp spikes, as do moving-coil drivers. The Magnepan 1. Air motion transformers are the ribbon-diaphragm speaker transducers.

These driver types work tremendously well as tweeters. The impedance graphs of air motion transformers, however, are much flatter with significantly less variation. This is due to the lack of an enclosure and a typical resonant frequency well below the audible range of sound.

To learn more about the various speaker transducer types, check out my article What Are Speaker Drivers? How do audio power amplifiers work? The role of the audio power amplifier is to amplify line level signals at its input from audio players to a speaker level signal at its output to drive speakers.

It does so with energy from the power mains that effectively powers the vacuum tube or transistor-based amplification circuit. Power amps are different from microphone preamps and headphone amps. How many watts is a good speaker? The best wattage power handling rating of a speaker depends on the power output of the amplifier that is driving the speaker. Mismatching speakers and amps can lead to poor signal output, distortion, and even blow-out. With so many loudspeakers on the market, purchasing the best speaker s for your applications can be rather daunting.

Check it out for help in determining your next speaker acquisition. He's an audio engineer by trade and works on contract in his home country of Canada.

When not blogging on MNM, he's likely hiking outdoors and blogging at Hikers' Movement hikersmovement. Check out his Pond5 and AudioJungle accounts. Boiling water is usually associated with cooking or blanching.

You will probably not hear the phrase "boiling strings" very often in everyday lingo. Why do guitarists and bassists boil their Think of the speaker as a pipe. The audio signal —your music—acts as the water flowing through the pipe. The bigger the pipe, the more easily water can flow through it. Bigger pipes also handle more volume of flowing water. A speaker with a lower impedance is like a bigger pipe in that it lets more electrical signal through and allows it to flow more easily.

As a result, you see amplifiers that are rated to deliver watts at 8 ohms impedance or or watts at 4 ohms impedance. The lower the impedance, the more easily electricity the signal or music flows through the speaker. A lot of amplifiers aren't designed to work with 4-ohm speakers.

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.