SPEAKER CABINET DESIGNPROJECT No. 83

Student Name: Murunga M Albert

Reg. No: F17/2130/2004

Supervisor: Mr. Ogaba

Examiner: Mr. Darmadhikary

The Outline Of The Presentation

1. Project objectives 2. Introduction and background3. Design4. Results5. Cost analysis6. Conclusion7. Questions

PROJECT OBJECTIVES1. To study the existing speakers in the market and establish

the following; Ø Power of speaker.Ø Internal volume of cabinet for speaker system

2. To develop a relationship between input electrical power into speaker system and internal volume of the cabinet.

3. Study three cabinets of the following specifications and compare their performance :

Ø Stiff box (approximately 70.7% of Normal volume).Ø Normal boxØ Oversize box(141%of Normal box)

Introduction and Theoretical background

Ø A speaker cabinet is an enclosure which covers the speaker drives and the crossovers. it removes the waves emanating from the back o f the speaker drive. It does this by providing acoustical resistance.

Ø Cabinets can be classified into two main groups closed and vented cabinets.

Ø Much has already been done by big companies like Sony and Pioneer. But they do not give their design formulas to the public.

The Design

In the design of the cabinets there are important factors to consider on:

Consideration on speaker drives are: • Band width or frequency response• Distortion of the signals • Efficiency of the speaker drive• Power handling and impedance

Consideration on speaker cabinetsCabinets/enclosures can vibrate and thus distort the input signal if the following measures are not taken care of:• Speaker cabinet mass loading• Speaker cabinet material• Loudspeaker box shape• Loudspeaker dampening

The Design Equations• The volume of the cabinet is expressed as follows;

• Then Vas is expressed as:

• The efficiency of the speaker is expressed as;

• Therefore the speaker cabinet volume as a function of the electrical power of the cabinet is given as:

0a r

e r

PP

η =

a sb

VVα

=

8 32.7 10ar es

bs er

P QVf Pα−

×=

× × × ×

08 32 .7 0 1 0

e sa s

s

QVf

η−=

×

Results WinISD test of Pioneer TX-120 (50 W) drive (woofer) in different

cabinet volumes.

Volume(liters) Qtc Lower cutoff frequency

0.60 2.30 202.22

2.10 1.30 125.05

0.75 94.56

17.50(optimum volume)

0.71 94.56

0.67 94.56

40.30 0.63 95.63

12.40(17.50 2)÷

24.80(17.50 2)×

Graphical Representation

Optimum Volume response.

Restricted volume response

A relaxed volume response

The Experimental Circuit

ResultsWoofer outside cabinet Response.

Frequency(Hz) Source voltage (V)

Load voltage (milivolts)

Log of frequency

50 1 7 1.7100 1 16 2.0500 1 15 2.71000 1 8 3.05000 1 11 3.710000 1 16 4.015000 1 22 4.220000 1 24 4.3

Woofer in the cabinet Response

Frequency(Hz) Source voltage (V)

Load voltage (milivolts)

Log of frequency

50 1 28 1.7100 1 28 2.0500 1 28 2.71000 1 32 3.05000 1 36 3.710000 1 28 4.015000 1 24 4.220000 1 24 4.3

WOOFER OPEN

0

5

10

15

20

25

30

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

LOG OF FR EQU EN C Y

Series1

Graphical representation of woofer response (without cabinet)

Graphical representation of woofer enclosedWOOFER IN CABINET

0

5

10

15

20

25

30

35

40

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

LOG OF FREQUENCY

Ser ies1

Cost AnalysisMy Design

Item Cost in KshsWoofer(30 to 50 watts) 400

Midrange 1000

Tweeter 200

Crossover 500

Other costs 1500

Total costs 3600

Cost of equivalent systems.

system Cost in KshsPioneer 12000Sony 8000Cheapest in Kenya market.

5000

Outline

Using Golden ratio where; H:W:D are related as follows2.618:1.618:1.000. the sketch of the cabinet shapeAnd it’s dimensions was as follows.

CONCLUSION

ØThe objectives of the project was achieved through study, design and the analysis of the speaker cabinet.ØThrough the project I was able to put what

I got in class into practical.ØSoftware can be built to use the design

equation derived to make it easy for the design.

THANK YOU