Notts Makers Club: Building Your Own Speaker

Does the idea of owning a speaker sound conventional to you? Well, how about the idea of owning a Bluetooth speaker that’s specially built and customised by yourself? Inspired by a Year 2 module in Electrical & Electronic Engineering, project leader Ivan Chiang Yik Hoe and his team decided to conduct a series of workshops in hopes of providing an avenue for students from different faculties to expose themselves to new experiences.

Organised by the Notts Makers Club, the workshop lasted for two days from the 11th to the 12th of November. Participants had to solder components together, assemble them in a wooden casing, and then customise the casing with their own designs. Therefore, participants sought out to free their creative minds.

Participants soldering the components for the speaker at the outdoor cafeteria.

According to Ivan,

The motive behind this project is to provide an opportunity for everyone on campus to experience the kind of projects Electrical and Electronic Engineering students do.

Now, enough of event reporting. Let’s move on to the technical part, shall we? Basically, for a speaker to produce sound, it would need to receive audio signals. What are audio signals, then? Audio signals are a type of electrical signal that convey information to the speakers in order to produce sound. Here comes another interesting question: how do we hear sound?

Sound is produced by the vibrations of particles in the air. Our eardrums will then process the different vibrations, otherwise known as rarefactions and compressions, to recognise the information conveyed. Similarly, how a speaker produces sound is that as the electrical signal passes through it, its diaphragm will vibrate back and forth to produce sound.

How a loudspeaker works. (Source: explainthatstuff.com)

A typical audio signal that has varying amplitudes causes the diaphragm to vibrate back and forth due to different polarity. (Source: HowToForge)

Now that we know an audio signal causes the speakers to produce sound, you may wonder, is that all we need? Just a signal? Technically speaking, the audio signals that we receive are often not strong enough to power drivers (in this case the speakers). Therefore, the solution to this problem is to include an amplifier. The name of it is self-explanatory–it helps to amplify a signal. Once the input signals are amplified, it can then be fed to the speakers in order to produce sound.

An amplifier also needs a power source. A rechargeable battery powers the amplifier so that the speaker can be recharged once it runs out of battery. As the name suggests, this is a Bluetooth speaker. Thus, a Bluetooth module is used to receive audio signals transmitted from either a laptop, phone, or another electronic device.

An example of a Class A amplifier amplifying an audio signal.

In the workshop, a class D amplifier was used as it has a very high efficiency, ranging from 95%-99%. A Class A amplifier is regarded as the best class as it has a low signal distortion and the highest linearity among all the classes. The downside is that it has an extremely low efficiency as the transistor is always turned ON in the circuit. In simple terms, it is desirable for the transistor to be in an OFF state when not needed in use. This is to ensure that it does not consume power, which affects efficiency. A Class D amplifier has a relatively low signal distortion. It is not as low as a Class A, but it has a higher efficiency, hence a compromise has to be made.

The participants claimed that they had a great time exposing themselves to something which they are not used to and it was an eye-opening experience.

Laila AlQirim, a Business student who participated in the workshop, had this to say:

I am a business student and I have never understood what an Electrical and Electronic Engineer does. This was really a good opportunity for me to try out different things.

Laila’s speaker design.

Overall, it was a successful project and hopefully there will be more interesting workshops to come!

Participants and the organisers posing for a group photograph after the workshop.

 

Article and photographs by Kelvin Wong

West Malaysian spirit of magniloquence, periphrasis and procrastination. I have half a mind...

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