If you’re looking to improve the sound quality of your PA system, you may be wondering what a speaker compression driver is.
In this article, we will explain what they are and how they work. We’ll also discuss some of the benefits of using compression drivers in your PA system.
A speaker compression driver is a specialised type of loudspeaker where the air moved by the speaker diaphragm moves through channel regions that are much smaller than the diaphragm area. Hence, we get greater air compression.
There are several benefits to using compression drivers in your PA system, and understanding how they work can be a great benefit for loudspeaker designers.
In this article I will cover:
- What is a compression driver?
- Is a compression driver a tweeter?
- How does a speaker compression driver work?
- What are the types of compression drivers?
- Can you use a compression driver without a horn?
- How do you install a compression driver?
What Is A Compression Driver?
A compression driver is a type of speaker, where the air movement generated by the speaker diaphragm component is compressed into smaller air channels. This is because the area of the diaphragm radiating surface is far greater than the throat or phase plug channels through which the sound will travel.
The output of a compression driver is attached to a horn, which helps to radiate the sound to the audience.
How Does A Speaker Compression Driver Work?
Just like conventional speaker design, the compression driver contains a small diaphragm that is attached to a voice coil.
When electricity is applied to the voice coil, it creates a magnetic field. This magnetic field interacts with the diaphragm, causing it to vibrate. The vibrations of the diaphragm create sound waves that are amplified by the compression driver.
What makes a speaker compression driver different from regular speakers, such as tweeters, is the internal design and structure of the speaker.
Although compression drivers generate sound in a traditional way through a voice coil and magnet assembly, how the air travels through the speaker and into a horn is different.
Unlike traditional speakers, where a diaphragm must move air in free space, in a compression driver, the air being moved is compressed and cannot escape easily.
Instead of just a diaphragm, which is a solid coupled to air, we have a diaphragm, which is a solid coupled to air, which is coupled to more air in the compression chamber and phase plug design.
This results in a diaphragm, moving air, which moves even more air.
Air moving air is a very efficient design.
As a result, the movement of the diaphragm in a compression driver is far more efficient at moving air and, as a result, creating sound at high frequency.
Below is a cross-section image of a compression driver design. This is a conventual design and is used widely in the audio industry. [source]
There are a few different types of speaker compression designs, for example:
A forward radiating design, where the radiating diaphragm surface that moves air and makes the sound is on the opposite side of the diaphragm to where the voice coil is attached.
A conventional design where the voice coil is attached to the radiating side of the diaphragm and moves air from the underside of the dome of the diaphragm through a phase plug assembly design to the driver exit.
Speaker compression driver design is complex, with great care being taken by audio industry experts to design the right size channel apertures through which sound will travel through the compression driver to the horn.
Is A Compression Driver A Tweeter?
No, a compression driver is not a tweeter.
A tweeter is a type of speaker that is used to produce high-frequency sounds. A compression driver is also a type of speaker that is used to produce high-frequency sounds. However, the two types of speakers are not the same.
Compression drivers are designed to produce very high-quality sound. They are also very efficient, which means that they don’t require a lot of power to produce a loud sound.
Tweeters, on the other hand, are not as efficient and require more power to produce the same volume of sound.
The fundamental design between tweeters and compression drivers is different.
As mentioned previously, a dome tweeter will just move air in free space. However, a compression driver will move air in a compressed air chamber, which results in the movement of more air as the air tries to escape and exits the driver.
What Are The Benefits Of Compression Drivers?
Speaker compression drivers have some significant benefits, including:
1. Greater Sensitivity
In general, speaker compression drivers are very sensitive and efficient. They can reproduce high frequencies very accurately without using a significant amount of power.
As a result, we can get greater dynamics and better sound reproduction than most dome tweeters.
In general, we get higher sound output for a given input power.
2. Directivity
A speaker compression driver is used with a horn. A great compression driver/horn design combo allows for better sound directivity.
This is particularly important in venues such as cinemas where you want to ensure that the sound is distributed equally over the audience. A compression driver and horn can achieve this.
3. Better Sound
This is tied into sensitivity, but overall you can get better sound clarity, realism and dynamics with a good horn and compression driver design.
When you go to the cinema, that loud, clear and effortless sound is the result of compression drivers.
4. Excellent Power Handling
When it comes to efficiency and power handling, speaker compression drivers knock it out of the park.
This has a major impact on the sound, as greater power handling results in higher volume.
Can You Use A Compression Driver Without A Horn?
A horn is a device that directs acoustic energy. As sound waves exit the speaker compression driver, the horn will extend and direct that energy.
It is possible to use a compression driver without a horn. However; it is not recommended to do so. Compression drivers are designed to be used with horns, therefore, removing the horn reduces the acoustic load, which will result in greater excursion of the speaker diaphragm.
The diaphragm of a compression driver without a horn will move a lot more, as it does not have the acoustic load of the horn.
Some care must be taken if using a compression driver without a horn, as you will be using it outside of its design parameters. As a result, the diaphragm could be displaced too much and result in compression driver damage.
In addition, you will lose the directivity that the horn offers.
How Do You Install A Compression Driver?
Generally, compression drivers come in two types of design, which will determine how you attach them to a horn.
1. Screw Fitting
The most common type of compression driver fitting is using screws.
This design consists of two or four screws (depending on the size of the compression driver) to which you attach the horn.
Below is an image of a standard speaker compression driver with screw fitments. This compression driver design fixes to the horn using screw inserts on the face of the compression driver.
2. Screw-In Fitting
The second most common type of speaker compression driver design with an alternative horn mounting is the “screw-in” design.
This speaker compression driver has a threaded boss which screws into a mating horn.
Final Thoughts
Speaker compression drivers offer a number of benefits over traditional dome tweeters, including greater sensitivity, directivity, sound quality and power handling.
The design of a speaker compression driver is fundamentally different to that of a dome tweeter. Many design aspects can affect the performance of a speaker compression driver from the choice of materials to the geometry design of the internal air channels.
While it is possible to use a compression driver without a horn, it is not recommended, as the results will not be as good.
If you are looking for an excellent way to improve your sound system’s performance, consider investing in a speaker compression driver.