What do speakers do? They convert and drive the amplified signal to a soundwave and into yours – the listener’s – ears. And beyond. But how exactly does it do this? Well, there are a few different technologies at play (of course) but a crucial element is, of course: the driver.

But what does a driver actually do? How do they work? What are the different types and why do some speakers have more of them? Well, that’s what we’re here to answer today.

Let’s start from the top…

What do drivers do?

Basically, the drivers are the last piece in the hi-fi puzzle. The crowning glory. This is where the signal – perfected through the various phases of source to amplification (and the cabling in between) finished its journey and sends the soundwave exactly where you need it to go – to you. This makes them pretty damn important!

A driver is an individual transducer (i.e. a device that converts energy from one form into another – more on that shortly!) which takes an electric signal, and converts it into a soundwave. In the case of loudspeakers, the driver (which can be referred to – quite simply – as the ‘speaker’ in instances where it is used as a tertiary device – laptops, televisions and keyboards etc.), the speakers are mounted in enclosures (… cabinets) which provide acoustic isolation from interference from vibration.

How do they work?

Now, this can get pretty technical. But never the less, I’ll try to keep things simple. I already mentioned that a driver is a transducer that converts one type of energy (electrical – as provided by the amplifer) to another (sound energy).

For this particular transducer it does this through the use of an electromagnet which is called a voice coil – this is usually a tube of various types of material wrapped in a conductive wire – such as copper. When electrical current (i.e. the electrical impulses from the amplifier – communicated via a permanent magnet at the back of the driver) is applied to the wire in alternating phases, the tube gets a magnetic charge. This charge allows the voicecoil to move back and forth, which moves the speaker cone.

This movement – back and forth – of the speaker cone compresses the air, which travels through the air before arriving at your ear drum, causing it to move back and forth in a corresponding fashion. And that is how sound is made!

Now, onto the equally technical, but slightly more specific stuff.

The types of driver…

Drivers come in various shapes and sizes, all designed with a specific type of sound wave in mind. Materials and intricacies differ, but the major difference is the size of the cone: the larger the cone, the slower the movement. The slower the movement, the lower the frequency. The lower the frequency, the lower the sound, and vice versa for the higher frequencies.

Tweeter

Appropriately named (after the high-pitched frequencies of birds!), the tweeter is designed to provide the high audio frequencies (right up to the edge of human-hearing) typically from around 2,000 Hz to 20,000 Hz. There are varying types of tweeter – from cone to ribbon – but they all function as a diaphragm of sorts stretched over an electromagnet. These are the smallest of the speaker drivers, and will reproduce the likes of the cymbals.

Mid Range

Also known as the ‘squawker’ (because it deserves a cute nickname too!) the mid range is a medium-sized driver, intended to produce the frequencies from approximately 300 to 5000 Hz. It is called upon to provide the ‘most audible’ range of frequencies – i.e. what’s most familar to the human ear – the human voice, the guitar, the trumpet, the sax.

Woofer

So named for the low frequency sound of a dog barking (… you can probably see where this is going), the woofer produces most of the lower-level frequencies that remain audible to the human ear, between 40 and 20 Hz. These are the sounds akin to the bass guitar and the tuba.

But there is a way of getting a little lower still…

Sub Woofer

A relative newcomer (first appearing for commercial use in the early 1990’s) in the hi-fi realm, the subwoofer is a large woofer designed to produced the lowest frequencies, from 20 Hz and below. This is where your bass comes from. Typically, a subwoofer produces sound well below human hearing, so what you get with a sub, you feel rather than hear. These are the lowest rumbles of the pipe organ and the thumping bass of your edgier music collection.

And yes, there are a few hi-fi specific drivers too, for that all important sound stage.

Super Tweeter

A super-responsive breed of tweeter designed to step in when normal tweeters may reach levels of frequency which could produce distortion. Super tweeters help create the most realistic sound stage possible, by producing frequencies as high as 80 khz.

Rotary Woofer

Not all-that-common in commercial speakers (bu rather funky, none-the-less!) the rotary woofer utilises rotating blades – rotating at a constant speed – instead of a diaphram, alongside a conventional voice coil. The electromagnet then changes the pitch of the blades, which in turn produce the soundwave.

The Hi-Fi Stuff!

Drivers serve a few different functions, and can be used in a few different ways when it comes to sound reproduction.

Your main seperation in terms of the practical uses of drivers in speakers is between the two-way, and the three-way.

As you can see above, the two-way speaker combines a high frequency driver and a mid/low frequency driver in one enclosure, which typically involves a tweeter and a woofer.

The three-way speaker combines all three of the main driver types: a woofer, tweeter, and a mid-range. Depending on your budget, the three-way is considered more desirable, due to improved accuracy and dynamics. However, if your budget is at the lower end, a two-way is a more sensible option.

Sub woofers generally come into play as separates and very rarely feature in the same enclosures as other drivers. This is when the terms 2:1 (and the like) occur. A 2:1 system features two loudspeakers (rwo-way or three-way, of course) and a subwoofer, a 5:1 system (i.e. a surround sound system) features five speakers (with different frequency strengths) and a subwoofer, and the list goes on.

So, there you have it. Drivers in a nutshell! Now, this is a very simplified view, of course. But there will be more niched blogs to come as time goes on. In the meantime, if you have any questions about drivers (or speakers for that matter) then feel free to give us a shout! After all, it’s what we know best.