Design And Construction Of A Sound Powered Lectern Lectern/Podium

TABLE OF CONTENTS

Numbers                                                    Title                                                                   Page DECLARATION                                                                                                 i

ABSTRACT                                                                                                         ii

ACKNOWLEDGEMENT                                                                                 iii

DEDICATION                                                                                                     iv

CHAPTER ONE: INTRODUCTION                                                                               1-4

 

1.0.	Background of study	1
1.1.	Problem statement	2
1.2.	General Objectives	2
1.3.	Specific Objectives	2
1.4.	Scope of study	3
1.5.	Significance of study	3
1.6.	Organization of Chapter	4
1.7.	Limitations	4
CHAPTER	TWO: LITERATURE REVIEW	6-17
2.0.	Lectern	6
2.1.	Applications of lecterns	7
2.2.	Sound Powered lecterns	10
2.2.1.	SL400 – Sound Powered Lectern	13
2.2.2.	SL370 Table Top Sound Lectern	15
2.2.3.	The Executive Sound Column Lectern	17
CHAPTER	THREE: METHODOLOGY	20-32
3.1.	Materials	20
3.1.1.	JRC4558	20
3.1.2.	Mid-Range PC Board Relays	21
3.1.3.	C945 NPN Transistor	21
3.1.4.	Cordless Microphone Module	22
3.2.	Designing	23
3.2.1.	Designing of System Device Block Diagram	23

 

3.2.2.	Design of System Device Circuit	24
3.3	Construction	25
3.3.1.	Construction of the Class AB Power Amplifier	25
3.3.2.	Split Power Supply	27
3.3.3.	Tone Control Circuit.	28
3.3.4.	Four Channel Audio Mixer	29
3.4.	Mode of operation of system device	31
3.5	System Design	31
3.5.1	System Device Block Diagram	31
3.5.2.	System device circuit	32
3.5.3	System Development	32
CHAPTER	FOUR: RESULTS AND DISCUSSION	35-41
4.0.	Characteristics of Sound	35
4.0.1.	Noise Level and Sound Pressure Level (SPL)	35
4.0.2.	Sound Pressure Level Decreases with Distance	35
4.0.3.	Sound Reverberation and Absorption	36
4.1.	Discussion	37
4.2.	Costs Benefits Analysis	38
4.2.1	Material list	37
4.2.2	Labour cost	41
CHAPTER	FIVE: CONCLUSION AND RECOMMENDATION	42
5.0	Conclusion	42
5.1	Recommendations	42

 

REFEREENCES                                                                                                                  43

GLOSSARY                                                                                                                          45

LIST OF TABLES                                                                                                                46

LIST OF FIGURES                                                                                                              47

 

CHAPTER ONE

INTRODUCTION

• Background of study

Sound powered lectern is a handcrafted lectern constructed by using the finest solid hardwoods and artificial leather. The reading lectern is wide and deep providing over 12² inches of usable surface. The sound powered lectern is used for voice reinforcement in conference and meeting rooms, auditoriums, churches, hotels, motels, schools, meeting halls, etc. Sound reinforcement system is the combination of microphones, signal processors, amplifiers, and loudspeakers that makes live or pre-recorded sounds louder and may also distribute those sounds to a larger or more distant audience [1].

A sound reinforcement system is also used to enhance the sound of the sources on a stage. A sound reinforcement system may be very complex, including hundreds of microphones, complex audio mixing and signal processing systems, tens of thousands of watts of amplifier power, and multiple loudspeaker arrays, all overseen by a team of audio engineers and technicians. On the other hand, a sound reinforcement system can be as simple as a small public address (PA) system, consisting of a single microphone connected to an amplified loudspeaker. In both cases, these systems reinforce sound to make it louder or distribute it to a wider audience.

The result is superb voice reproduction with a minimum of reverberation. Additional features include: unidirectional dynamic microphone, shock-mount holder for the microphone, input for

second microphone, output for tape or external PA system, output for external speaker, speech equalizer with switch, auxiliary input, volume and tone controls [2].

A sound lectern would effectively cover audiences of 2500 or more indoor. Lecterns used in academia generally in seminar rooms and lecture theatres may have certain features that common lecterns lack, based on the technological sophistication of the venue. Lecterns of this sort are generally attached or integrated into a large desk, as the amount of support material tends to be larger in academic contexts than in straightforward public talks. In a church, the lectern is  usually the stand on which the Bible rests and from which the “lessons” (reading from Scripture) are read during the service. The lessons may be read or chanted by a priest, deacon, minister, or layperson, depending upon the liturgical traditions of the community. The lectern is normally set in front of the pew, so that the reader or speaker faces the congregation [3].

• Problem Statement

Imaging the stress and complexity of setting up loudspeakers, amplifier and microphones with limited time. One can imagine the stress that it entails, especially with the margin of error being large enough to cause misconnection that could lead to damage of the system. Lectern in these modern days in almost every auditorium has one way or the other become a necessity as it serves as a slim table besides which a group of people could be addressed from. The powered lectern combines the whole setup into one unit which makes it convenient to be fixed anywhere public address and lecterns are needed.

• General Objectives

The general objective of this project is to design and construct a sound powered lectern with a wireless microphone.

• Specific Objectives

Specifically, the system device would be able to:

• Produce sound for in-and-out door
• Scope of study

Audio sources like dynamic microphones, MP3, Compact Disc players are considered based on their decibel and impedance and a 3 channel audio mixer is designed. The channels are well labeled for clarity of sources which require pre-amplification. The JRC4558 dual Operational amplifier is used to design a number class ‘A’ amplifiers which is used to balance sound levels. Active high and low filters are used as equalization of sound to improve on the frequency response of the signal from the mixing stage before further amplified by the class ‘AB’ power amplifier to the loud speakers. The input connectors would be mounted on the front panel and then connected to the three audio channel mixer. The mixer would source its power from  the split power supply via a 12volts regulator. The output of the mixer would directly be amplified by an inbuilt class ‘AB’ power amplifier. The loudspeakers are arranged in a format that ensures that the total impedance is between 4-16 ohms.

• Significance of study

The significance of this project are as follows:

• Accessible shelves inside a lectern allow for the convenient storage of lecturers’ pointers, papers, and laptop computers while keeping the paraphernalia out of sight until it’s ready for
• Swift set-up requiring little or no expertise in setting
• Built-in storage space gives the presenter and the presentation space a more professional look.
• It has a 50 Watt inbuilt
• It has an LED Light for
• It is designed to support an Anti-shock with gooseneck microphone holder for unidirectional Dynamic microphone.
• It has a Mic/Aux Volume, Speech Filter and Tone
• It has two 6’’ loudspeakers with connection for External Speaker
• Organization of the Study

Chapter one gives a background of the study and introduces the subject matter of the project. It also explains the purpose and objectives of the present work. Chapter Two explains the literature of the work and give some of the information already existing. Chapter three is titled Methodology, it introduces and informs the reader on the components used, method of design, construction, development and implementation of the prototype. Chapter four captures the system device test results and discussions. The project ends with chapter five where a final conclusion on the entire project is made and recommendations for further work.

• Limitations

Basic limitation of the construction of this project is that:

• Quality of electrical and electronics components in terms of its
• The cost of producing a single unit of this project is relatively expensive since the prices of electronics components are cheaper when bought in a high
• Inadequate time and the high outages of power also amount in many challenges in coming out with a much more refined
• The difficulties involved in getting the major components from class A source was very difficult because all the companies who manufactures these components do not sell components in small quantities and it was very hectic getting all these