Technical Description: Portable Bluetooth Speaker

By Sanbir Rahman

Engl 21007: Writing for Engineering

Professor Maryam Alikhani

The City College of New York

October 29, 2018

 

 

 

Table of Contents

1. Technical Poem…………………………………………………………………………………4
2. Introduction……………………………………………………………………………………5

III. Description of Parts…………………………………………………………………………..5

1. Outer Casing………………………………………………………………………………….6
2. Sound Driver…………………………………………………………………………………..7
3. Subwoofer…………………………………………………………………………………….7

VII. Power Cord………………………………………………………………………………….8

VIII. Battery………………………………………………………………………………………8

1. Printed Circuit Board (PCB)………………………………………………………………..9
2. Conclusion……………………………………………………………………………………10

References………………………………………………………………………………………….11

 

 

 

 

I. Technical Poem

 

My smooth chassis shrouds what lies within

Couplings and resistors are where my heart begins

Calibrate me to your ears’ content

Louder and louder till you relent

 

The voices echo through and reach you

With every track, I feel something new

Earth shattering, ground breaking

Bouncing to the rhythm you’re creating

 

Let me fill your soul with good vibrations

 

II. Introduction

A speaker is a transducer that vibrates the air to produce sound. It does this by converting electrical energy around it to kinetic energy (Millersound, p.1, n.d.). Speakers come in all shapes and sizes and they are characterized by their sound driver. The sound driver is what initially produces the sound and determines the ultimate quality of the sound. As an electromagnet powers the sound driver, the air around the speaker body begins to vibrate and audible sound is produced. The types of electronic loudspeakers include the tweeter which produces high-end frequencies from 2 to 20 kilohertz (kHz), the mid-range speaker which covers most frequencies attributed to instruments and the human voice from 5 to 300 kHz, the woofer which produces low frequencies from 1 to 40 kHz, and finally the subwoofer which produces the lowest frequencies from 0.02 to 0.2 kHz (Normandin, p. 2b, 2014).

Though the electronic loudspeaker is today’s staple in amplification, the horn was actually the earliest form of amplification. The idea of a metal horn producing sound eventually lead to the invention of the modern electrodynamic speaker by C.W. Rice and E.W. Kellogg in 1921 through the use of the newly developed electromagnet (Normandin, p. 2a, 2014). This was a revolutionary idea at the time when electricity was a novelty and experiments with it had just begun to take off. In the next sections, the parts of a type of portable subwoofer speaker will be described along with their functions.

 

III. Description of Parts

The type of speaker that will be discussed is a portable Bluetooth speaker with a passive subwoofer and a 5W sound driver. The outer casing is made of a hard plastic material and the overall dimensions of the speaker are 2.6 inches in width, length, and height. It is a lightweight speaker at approximately 9 ounces. There are openings for AUX cords, micro SD cards, and micro USB port for charging. The speaker can also function as an FM radio when the micro USB cable is plugged in and functions as an antenna. There is a button labeled “M” which changes the mode between Bluetooth, AUX-in, micro SD card, and FM radio next to the power switch. Inside the speaker, a printed circuit board (PCB) connects some of the components including the power cord, sound driver, the passive subwoofer, capacitors, battery and antenna. There are small metal slots placed on the board which hold the micro SD card slot, the AUX-in port, and the micro USB charging port.

Figure 1: Outer casing of portable speaker showcasing various ports and switches (Anker, n.d.)

 

IV. Outer Casing

This particular speaker is cylindrical in shape with a depression on the top to hold the speaker layer. The speaker layer has the company’s name on top surrounded by small holes to let sound out. It holds the three functional buttons in front: the “+”, the “-“, and the play button. These can also function as the seeking buttons when playing in FM radio mode. On the bottom of the device, there is a mode button and a power switch along with an AUX-in port, a micro USB port, and micro SD card slot.

 

Figure 2: Power cord, sound driver and subwoofer highlighted (FCC, 2016)

V. Sound Driver

The sound driver is what drives the speaker to vibrate the air and produce sound through the subwoofer. It is connected to the power cord and in this particular speaker it is a plastic covered ring electromagnet. It bounces as the magnetic force of the electromagnet, which is also known as the voice coil, converts an electrical current to sound waves (O’Neal, 2018).

 

VI. Subwoofer

The subwoofer is the diaphragm that emits the sound waves produced by the sound driver. In this particular speaker, the subwoofer is a black circular drum that looks kind of like an eardrum and contains a passive radiator. This allows the subwoofer to produce more bass output and limits port noise from the sound driver (Hicks, p.1, 2018). As the sound driver bounces, the subwoofer vibrates at the same frequency to emit a specific sound.

 

VII. Power Cord

The power cord is a small white box that couples a (+) red wire and a (-) black wire.   There is a socket that the power cord uses to connect a battery to the micro USB charging port on the PCB. It wraps around the sound driver and subwoofer setup and allows for the PCB to function properly.

Figure 3: The battery connected to the power cord (FCC, 2016)

 

VIII. Battery

The battery is a square pack that is covered by a yellow film and is connected to the power cord. The power cord supplies approximately five watts of power and 3.7 volts to the battery which stores the charge. One charge on this speaker lasts approximately fifteen hours of continuous use.

Figure 4: Close look of printed circuit board (PCB) (FCC, 2016)

 

IX. Printed Circuit Board (PCB)

The printed circuit board is located at the bottom of the speaker once it is disassembled. It contains many small parts and it looks like a small city from an aerial view. The smaller metal boxes are the capacitors which use small amounts of energy taken from the battery and stores them for later. The metal parts marked with blue pen are the micro SD slot and micro USB charging port. To the right of the parts is the AUX-in port and further down the mode button and power switch lay flush against the PCB. The PCB has an antenna at the bottom on top of a yellow section which is amplified when a micro USB is connected without a charging source. The antenna also allows devices to connect to the speaker through Bluetooth.

 

X. Conclusion

Speakers are used virtually everywhere sound is required from computers to PA systems. The modern loudspeakers are versatile enough to hit a wide range of frequencies depending on the situations. Most portable speakers are equipped with multiple ways of playing sounds such as the one discussed which had FM radio, a micro SD card slot, Bluetooth connection, and an AUX-in port. Passive radiators are taking speakers to another level as they produce virtually no noise and use less power than previous models of speakers. One day, speakers may even be force conservative and require less energy to power. This would certainly lower the cost of materials required to produce small-scale speakers like this one.

 

References

Anker. (n.d.). Soundcore Mini. Retrieved November 1, 2018, from https://www.anker.com/products/variant/soundcore-mini/A3101111

FCC. (2016, June 28). A3101 SoundCore mini Teardown Internal Photos Anker Technology Co., Limited. Retrieved October 31, 2018, from https://fccid.io/2AB7K-A3101/Internal-Photos/Internal-Photos-3049440

Hicks, J. (2018, April 30). The Science of Sound and Anatomy of a Speaker. Retrieved November 3, 2018, from https://www.aperionaudio.com/blogs/aperion-audio-blog/the-science-of-sound-and-anatomy-of-a-speaker

Millersound. (n.d.). Speaker Anatomy. Retrieved October 28, 2018, from http://www.millersound.net/speaker.htm

O’Neal, J. (2018, May 25). How speakers make sound. Retrieved November 1, 2018, from https://animagraffs.com/loudspeaker/

Normandin, S. (2014). History and Types of Loudspeakers. Retrieved November 4, 2018, from http://edisontechcenter.org/speakers.html