What Does a Passive Radiator do in Speakers?

A passive radiator enhances low frequencies (bass) in small sound systems. It is similar to a speaker/driver but does not have a voice coil or magnet to produce sound. The passive radiator moves with the movement of drivers/speakers and thus enhances bass like a port on the speaker enclosure.

However, a passive radiator does not fit for larger sound systems. It only works best for compact enclosures and also protects you from unnecessary noise produced by the ported enclosure.

Today in this blog, we will discuss all the important things that you should know about passive radiators including their function, importance, pros, cons, and their difference from ported designs.

So, let’s dive in and discuss all these things one by one.

What is a passive radiator?

A passive radiator also known as a drone cone is just like a speaker installed in the enclosure but does not have have voice coil or magnet and does not require any connection to work. It moves with the air pressure created by the active speaker or subwoofer.

You may know about ported systems in which a port is made in the speaker enclosure for air movement; a passive radiator plays the role of this port but keeps the enclosure fully closed and does not create noise. However, ported systems are large and come with a woofer that draws power and delivers powerful output.

It is used in compact enclosures, computer speakers, and Bluetooth speakers because they enhance the bass while taking a little space. Their resonance frequency is determined by the mass and springiness of air in the enclosure. So, you can tune a passive radiator by increasing or decreasing its size according to the system requirements.

For this purpose, you can use our passive radiator calculator. It will help you determine the size, mass, and all other important factors of passive radiator according to your system.

What does a passive radiator do?

The basic purpose of a passive radiator is to enhance the low frequencies (bass) while taking minimum space or resources in the enclosure.

It moves with the motion of the active driver (speaker or subwoofer) and creates a richer immersive sound experience. Distortion is also decreased when a passive radiator is installed because it reduces the motion of the active driver at increased volumes.

When active driver moves back and forth, an air pressure is created and the passive radiator resonates with the active driver. It creates additional waves that enhance the bass of the system. However, it is crucial to design and install the passive radiator properly. Otherwise, it may lead to a distorted sound.

Importance of a passive radiator

Passive radiators have great importance in small enclosures, Bluetooth speakers, and computer speakers. Since these speaker systems have a limited space, it is not possible to add active woofers which are larger in size. So, here passive radiators perform the function of an active woofer by enhancing bass.

The resonant frequency of the passive radiator is matched with the lows of active speaker resulting in enhanced bass.

That’s why passive radiators are of great importance for many sound systems: they enhance the bass to create a fully immersive and rich audio experience while keeping the system compact. They work perfectly with active speakers and provide a better sound experience without requiring additional power.

You can read comprehensive research by Small and Hurlburt on the analysis and design of passive radiators in loudspeaker setups.

Pros and Cons of a Passive Radiator

Like everything in the world has plus and minus points, so does the passive radiator. Here are some notable pros and cons of a passive radiator.

Pros

• Enhanced bass without adding an extra woofer
• The enclosure remains fully sealed
• Provides a beautiful design as a passive radiator looks like a speaker from the outside
• It prevents the noise usually created by a ported design
• You can tune the resonant frequency according to your system
• Using a radiator keeps the system compact; it saves space while still providing better bass

Cons

• A passive radiator is only suitable for smaller systems like computer or Bluetooth speakers and is not recommended for larger speaker setups
• The design sometimes is complex and if handled carelessly it can distort at increased volumes
• Passive radiators are good but can’t give you results like an active driver. So, if you want really good sound, using an active driver can provide much better experience

Passive Radiators vs Ported Systems

Whenever you decide to set up the speakers, you may think if you should go for a passive radiator or ported setup. So, let’s break it down and make choice easier for you.

If you are setting up a large sound system, then you will go for a ported system because passive radiators are designed to work well with smaller setups and Bluetooth speakers.

A passive radiator surely looks great and provides a beautiful design but it does not deliver much power. It provides good bass but can’t beat a ported system. However, for small and portable setups, passive radiators are best to use.

In terms of budget, passive radiators are comparatively affordable. So, it depends on your budget, space, audio needs, and personal preferences whether you should go for a passive radiator or ported system.

Wrapping up

I have explained in detail what a passive radiator does in a speaker system. Hopefully, you will have a clear idea of its function, importance, and pros and cons. I also compared it with the ported system to help you decide which one you should choose.

The function of passive radiator is described in detail but choosing it depends on your setup requirements, budget, and personal preferences. Let me know about your opinion in the comments section.