Speaker Impedance Calculator-Calculate Speaker Impedance For Free

Speaker Impedance Calculator
Speaker OHM Calculator

This calculator tends to calculate nominal impedance that can be created with various combinations of wiring speakers together that differs. Please take note that this calculator should not be taken as a real-life situation calculation. The impedance, in reality, should be affected by various factors such as coil temperature and it should vary with frequency.

How To Use:

  • Give Speaker 01 Ohm To The Text Box
  • Give Speaker 02 Ohm To The Text Box
  • Get Result (That’s It)

For Serial Speaker

Speaker 01
Speaker 02

Your Speaker Impedance is 


For Parallel Speaker

Speaker 01
Speaker 02

Your Speaker Impedance is 


Speaker Impedance: What is it?

Curious about how much current flows through your speaker at a given or certain voltage? Well, that is what impedance basically tells you. Let’s assume for example a 10 volts signal shows on your amplifier, this can produce 2 amps of current through the speaker. Now, if the voltage doubles to 20 volts, the current will definitely double also. What you will get is quadruple the power, and this is because of the power = voltage x current (2×2 = 4).

A speaker with low impedance can accept more power. An example is that a 5-ohm speaker will attract more power from your higher amplifier than a speaker with 10 ohms, which is twice as much.

With this being said, most people however always have the issue of how to combine various speakers effectively and safely, and also avoid blowing either the speakers or amplifier.

Ohm: What is it?

Ohm has its symbol as “Ω” and it is a unit of impedance. Curious about what then is impedance? The impedance is defined as the measure of something that restricts the easy flow of current present in an electric circuit, of course, you know that in this case, we are talking about the speaker.

Impedance and its Basics

An electric circuit that involves of a bulb should consist of a power source and a light bulb. The flow of electrons is inbound in the circuit and this can be said to be a circuit.

The voltage is being produced by a power source that pushes the electrons around the circuit. The bulb acts as the resistance in the circuit. This grabs the current and converts it into light and heat energy. This resistance or bulb impedes the flow of current in a circuit. In the case you add another bulb to this in a series connection, it will reduce the brightness of these bulbs by half, and this is because the voltage is being utilized by two separate bulbs. But, when the bulbs are connected in a parallel manner, its brightness stays the same in both bulbs, also with the voltage. (You should note that the current changes (halves) in this case).

Now you can convert this series/parallel example or fact to speakers. If connected in series, voltage is being shared, but if connected in parallel, the voltage it draws remains the same. However, current needs more in this case to sustain the connected bulbs, and its power source in this case which is the amplifier needs to work more.

The relationship between current, resistance and voltage can be called Ohm’s law, which states that Voltage = Current x Resistance or represented as V = IR.

In AC circuits like the audio system, its resistance is called “Impedance”.

Note: You can’t really saw these terms because resistance and reactance are being contained in Impedance (reactance always varies with frequency) although this can be ignored by just calculating the impedance of speaker setups.

Now you have an equation to work the impedance out, very simple. This can be used to get the sum load impedance of the amplifier. R = V/I – this is what a speakers impedance calculator would ensure you do.

The Speaker Impedance Calculation Law

There are generally 2 ways to connect speakers; parallel and series.
R = R1 + R2 (Serial connection)
1/R = 1/R1 + 1/R2 (Parallel connection)

Speakers connected in series requires the impedance to be added.

For speakers connected in Parallel impedance, the sum is the impedance of 1 speaker divided by the number of speakers.

In the situation you have some speakers connected in series while still having others connected in parallel, it is recommended you split the problem into different parts. First determine the parallel impedance, then add the series speakers’ impedance.

Example: If you have one 4 ohm and two 8 ohm speakers, and your amplifier is rated to carry loads of 4 to 16 ohms. What will you do in this case? Let’s divulge into some examples.

If we parallel the two speakers of 8 ohms, and that of 4 ohms which is just one. Adding the 4 ohms speaker (series connected) will result in 4 + 4 = 8 ohms total. Great for your amplifier.

However, you can alternatively parallel one 8 and one 4, it will give a 2.7 ohms (from the example above). Then connect in series the other 8 and you will have 2.7 + 8 = 10.7 ohms. Also superb for your amplifier.

And about paralleling all 3 speakers? The 8 ohms speakers (that is two in number). That together in parallel connection with the 4 ohms will give you a 2 ohms total, which is bad for your amplifier.

Talking about quad speaker cabinets, in a case all speakers have the same impedance (8 ohms for example), it is recommended that you connect the double sets in parallel, then connect those in speakers series to actualize back at the speaker impedance matching that you started with.

Power Ratings

There is a fact when trying to connect multiple speakers. If there are two speakers in series, the speaker with higher impedance will take more power.

Example: A 4-ohm speaker and an 8-ohm speaker connected in series, it’s power shared or utilized is proportional to the resistance; this means that the 8-ohm speaker would take in twice the power of its 4-ohm speaker partner.

However, if there are two speakers connected in parallel, the speaker with the higher impedance will take up less power. Example: An 8-ohm speaker and a 4-ohm speaker connected in parallel, it’s power distributed are inversely proportional to the resistance, which means that the 8-ohm speaker will absorb the power (half the power) of the 4-ohm speaker.

You have to take note of this because if for example, the speakers mentioned above have the same power rating, say 50 watts, one of the speakers will tend to absorb more power, this will make the combination of both speakers power rating not to be 100 watts. This will put one of the speakers at a risk of failure.

Quality vs. Impedance

Most curious minds have researched about the quality of a speaker to its relation to impedance. The brief answer is: No. Top quality speakers are produced every day over the different range of impedances. The impedance of a speaker only denotes how to use your speaker to full power; using an amplifier with a corresponding output impedance.

Most Effective Ohms for Speakers?

Tower and bookshelf speakers are mostly rated 6- ohms or 8- ohms. If a speaker impedance rating is 4-ohms, that speaker is typically a high-end, audiophile speaker that needs an amplifier that has the ability to provide more power.

This is just a simple fact. A loudspeaker producer will likely build a 4-ohm speaker be he knows what type of amplifier would be needed for it to get the appropriate sound. However, with a lower impedance range, it opens up for different choices and designs.

Most people would prefer a 6-ohm or 8-ohm speaker because these kinds of speakers are well suited for most AV receivers.

This shouldn’t be taken as a final statement, of course, a loudspeaker receives plenty more than its impedance rating. However, there are indicators you should take note of when aiming to grasp the impedance ratings and amplifiers, although a speaker impedance calculator can help you solve a headache.

Speaker Impedance: How to Measure it

There are two methods that are being used to measure speaker impedance; Quick estimate and Accurate Measurement.

The measurement of a speakers resistance towards an alternating current is called the speaker’s impedance.

If the impedance is low, the speakers would tend to draw in more current from its amplifier. In the case that the impedance is too high for the amplifier, it’s dynamic range and volume would suffer.

However, if the impedance is too low, the amplifier can destroy itself because it will be trying to produce more power. If you are curious about how to test speaker impedance, you can test it with a multimeter. But for a more accurate testing, some specialized tools are needed.

First Method: Quick Estimate

You should check the label for its nominal impedance rating. Most top speaker manufacturing companies do list an impedance rating on the packaging, sometimes on the label. This rating is usually denoted in 4, 8 or 16 ohms. For typical audio ranges, this is usually an estimate for them. Their frequency usually takes place at frequencies such as between 250 and 400 Hz.

Its main impedance is normally close to these values within these ranges, as you increase its frequency, it rises slowly. However, below this range, the impedance changes quickly, reaching the resonant frequency of the speaker.

Most manufacturers opt for listing the actual measured impedance for a specifically listed impedance.

A typical example of what these frequencies mean can be seen in most bass tracks, which are in-between 90 and 200 Hz, while the chest thumping sub bass can go as low as 20 Hz. For the midrange, that is voices and non-percussion instruments cover 250 Hz to 2k Hz.

How to Measure Speaker Impedance with a Multimeter

A multimeter is a device that measures resistance by sending out a small DC current. But, impedance has a quality of AC circuits, this device won’t direct measure impedance.

This approach, however, will only get you close enough to home audio setups, a 4 ohm and an 8-ohm speaker can be distinguished this way. Apply the lowest setting for resistance. A 200Ω for most multimeters, a 20Ω multimeter may give more accurate results though.

When there is only one setting for resistance, the multimeter features auto-ranging and will locate the correct range automatically.

Note: The voice coil of a speaker can be demagogue if there is too much DC current. It is a low risk though since many multimeters are configured to produce only a small amount of current. This a suitable answer to the question of how to test the speaker impedance.

How to Determine Speaker Impedance?

How to calculate speaker impedance? Read the following points below;

  • The speaker needs to be removed from its cabinet, but if a loose speaker with no speaker box, then you have nothing to do here.
  • Power shouldn’t run to the speaker else it would ruin all measurements, and worse, fry your multimeter, cut off all to the speaker. But don’t disconnect any wire connected to the speaker cone.
  • Next to do here is to connect your multimeter leads to your speaker terminals. You should take a keener look at the terminals to ascertain which is negative and which is positive. There is often a plus and minus sign denoting these. The multimeters red probe should be connected to the positive side, while the black probe to the negative side.
  • The impedance should be estimated from the resistance. Normally, the resistance should be read from about 15% lesser than its nominal impedance on the label. Example: it is a normal occurrence that an 8-ohm speaker should have a resistance between 7 or 6 ohms.
  • Most loudspeakers possess a nominal impedance of 4, 8 or 16 ohms. So unless you have a strange result, it is totally safe to assume that your speaker possesses one of these impedance values for pairing it with an amplifier. This also should answer the question of how to match speaker impedance with the amplifier.

Second Method: Accurate Measurement

You’ll need a tool that can generate a sine wave. Since a speaker’s impedance varies with different frequencies, you will need a tool that will ensure that you send out a sine wave at any given or set frequency.

The best option for this is an audio frequency oscillator. Although any function generator or signal generator would work with a sine wave, however, some models will give us inaccurate results due to a poor sine wave or changing voltages.

If you’re a newbie to all these kinds of stuff or DIY electronics, it is recommended that you consider audio testing tools that can be used with a computer. These can be less accurate too, but at least newbies would find the auto-generated data a relief.

The too should be connected to an amplifier input. Locate its power on the amp label in watts RMS. Higher power amplifiers tend to give more accurate measurements using this test.

The amplifier should be set to a low voltage. This test is a standard test for low voltages. The gain on your amplifier should be lowered with a voltmeter set to AC voltage should be connected to the amplifiers output terminals. The voltmeter should read about 0.5 and 1 V, but if sensitive tools are not readily available for you, just set it to not more than 10 volts.

There are amplifiers that give you inconsistent voltage at low frequencies, and this is a known source of inaccuracy in this test. Make sure you check the voltmeter to ensure that the voltage stays constant as frequency adjustment is done by you using the sine generator.

We recommend that you use a high-quality multimeter because the less expensive ones tend to give off a less accurate result.
Select a resistor with high value. You can locate the power rating (in watts RM) nearest to your amplifier on our list below.

Select your resistor in accordance with the recommended resistance, also you can select a higher wattage rating or the listed wattage rating. It doesn’t necessarily need to be exact, though it shouldn’t be too high, because it might disrupt the test, while too low will result in a less accurate result.

100W amp: 2.7k Ω resistor rated to 0.50W
90W amp: 2.4k Ω, 0.50W
65W amp: 2.2k Ω, 0.50W
50W amp: 1.8k Ω, 0.50W
40W amp: 1.6k Ω, 0.25W
30W amp: 1.5k Ω, 0.25W
20W amp: 1.2k Ω, 0.25W

Take a measurement of the correct resistance of your resistor. This might be different from a printed resistance, put down on paper its measured value.

The speaker and resistor should be connected in series. Then link the speaker to the amplifier, leaving the resistor between them. This will ensure a constant source will be powering the speaker.

The speaker should be kept in a place with no obstructions. Factors such as reflected sound or wind can disrupt this test. In a windless area, place the speaker cone up. If high accuracy is your aim, the speaker should be enclosed to an open frame, with no objects in about 2ft from it.

Then you can now sum up the current using Ohm’s law. (I = V/R or current = voltage/resistance). Write down your calculation for the current and write down your answer. For R, you can use the resistors measured resistance.

Example: A resistor with a 1430 ohms measured resistance, it’s voltage source is 10 volts, calculating the current I = 10/1430 = 1/143 amps.

The frequency should be adjusted to locate the resonance peak. Your sine wave generator should be set to frequency situated at the upper or middle range of the speakers aimed at use.

Now, place an alternating current voltmeter on the speaker. You can use a 100 Hz which is for bass units. Reduce the frequency to about 5 Hz at a given time, do this until you see a sharp rise in the voltage. Now play with the frequency back and forth until you locate the frequency with the highest voltage. This is called the speaker’s resonance frequency in “free air”; any surrounding object or enclosure will tend to change this.

An oscilloscope can also be used in place of the voltmeter, but you will have to locate the voltage in relation to the greatest amplitude.

Next, the impedance at resonance should be calculated. In Ohm’s law, the impedance Z could be substituted for resistance. That is calculated Z = V/I to determine the impedance at the resonance frequency. The result should be the highest impedance your speaker will come across in its intended audio range.

Example: I = 1/123 amps and voltmeter measures 0.05 volts, Z should be Z = (0.05)/(123) = 6.15 ohms.

Finally, you calculate to determine the impedance for some other frequencies. This is also how to calculate the speaker impedance across its aimed frequency range. The sine wave should be increased in small increments.

Take a record of each frequency, and utilize the same calculation (Z = V/I) to determine the impedance of your speakers at each frequency. However, once you get away from from the resonance, you might find the second peak.