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What is nominal impedance?

Speaker impedance is an important characteristic to consider when choosing a sound system. Unfortunately, few amateur audiophiles are aware of what nominal impedance is, or even that it exists. Understanding what the impedance rating is and its impact on the quality of your equipment can give you a significant advantage when choosing your hi-fi or home theatre system.

Let Fillion’s experts help you learn about nominal impedance and its impact on your devices.

What is acoustic impedance?

When talking about acoustics, impedance describes the level of resistance of a device, such as wireless loudspeakers, to an audio signal emitted by a direct current source.

Acoustic impedance is calculated in Ohms (Ω). You can often find this symbol somewhere on the back of your equipment. Usually, a speaker will have an impedance of 4 or 8 Ohms.

This same resistance can be divided into two types: low and nominal. Low impedance is the lowest resistance of your device. Nominal impedance is the actual resistance of the device.

This means that a 4 Ohm speaker will need a power amplifier to produce more sound, whereas an 8 Ohm speaker will be able to produce the same volume of sound as a speaker and amplifier combined.

Can nominal impedance vary?

Yes. To understand why, you need to look at the nature of impedance itself. The resistance (or impedance) of a device results from the mechanical properties of the sound system, in particular, the membrane, the electronic filter and the load.

For example, the impedance will vary depending on whether your loudspeaker is protected by a cabinet. Any change in the volume of the air around the speaker causes a variation in the impedance curve, and in turn, will influence the sound quality at the level of the output of the amplifier.

This is why not all devices and sound systems have the same impedance. In fact, variations in air volume have as much to do with the manufacturing quality of the loudspeaker as with the type of current that passes through it: a direct current or an alternating current. This is why there is such a notable difference between Bose and Marantz speakers, for example.

Why is it important to choose the right nominal impedance rating?

Once you understand what the number on the back of your speaker means, here's why it's important to take it into account when choosing your hi-fi,stereo or sound system.

Maintaining speaker sound quality

When it comes to setting up your speakers, the impedance rating will indicate which receivers and transmitters are compatible. In other words, a loudspeaker and a power amplifier can be connected as long as their impedance is similar or complementary.

Note that connecting two devices with different impedance ratings can impact the quality of the sound emitted from the receiver. If you connect two incompatible devices, the sound will be distorted, which could affect the efficiency of your speaker. It may even produce no sound at all. The compatibility of your equipment is key to the quality of the sound.

The higher the impedance of the speaker, the more likely it is that the receiver's output interference will disappear. On the other hand, the lower the resistance, the more interference you will have, which will directly impact the quality of your listening experience.

More efficient energy use

If you connect incompatible devices, the resistance of one to the other will create a clash and damage them both.

To avoid this, you will need to increase or decrease the impedance of one or both devices. In these cases, your speaker will require more power, increasing the power consumption of your system.

Pairing the right devices will help you save trouble and power your system more efficiently.

What happens if the nominal impedance is not compatible?

As explained above, sometimes two devices do not have a compatible impedance rating. Here’s what you need to know for each possible circumstance.

An impedance rating that is too low

When the nominal impedance of your device is too low compared to the receiver, it will create sound distortion and interference.

This low impedance level also damages your equipment, and can even cause it to stop working completely.

An impedance rating that is too high

On the other hand, when the impedance is too high, above 16 Ohms, the amplifier will need a higher power output to compensate for the difference and generate sound from the speaker.

Making devices compatible

Audio equipment suppliers have found ways to bridge the gap between different impedance levels among your devices. Instead of selling a newly purchased device because it doesn’t match your sound system, you can now invest in specific boxes or cables that will allow you to adjust the nominal impedance of your devices and enjoy total immersion.

How to choose the right impedance rating?

Now that you understand why the impedance rating of your equipment is important, how do you choose the right one?

It is possible to do this yourself by looking at the impedance ratings of the devices you have selected, and creating a compatible system with no problems of sound distortion or interference.

If you would rather minimize the risk of making a mistake in your choice of equipment, we recommend that you seek the advice of a sound system expert who can guarantee the compatibility of your products.

Trust the experts at Fillion to choose the right impedance rating

The impedance rating of a device can be a complex concept to integrate into the selection of devices, and consumers often forget to consider it. However, ignoring this rating can have repercussions on the quality of your system and the sound it produces.

To avoid any unpleasant surprises and to help you enjoy the best possible sound experience, Fillion Électronique can provide help. Our experts will guide you in selecting compatible devices from our wide selection of speakers, amplifiers and home cinema systems. Contact us now or visit one of our stores in Montreal.

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