1. Loud speaker directivity Enroll no. 130470111041 Name: Valambhia celeste

2. Why investigate loudspeakers? Most important link in the audio chain Last piece of equipment audio signal passes through Many variables in loudspeakers; permanent magnet, size and weight, material of cone, size and type of enclosure, etc. TheToneChamber.com

3. How speakers work Voice coil (electromagnet) is positioned in constant magnetic field from permanent magnet Current across voice coil constantly changes, changing the magnetic field polarity and strength causing the voice coil and diaphragm to move Cross-section of typical loudspeaker

4. Loudspeaker analogous circuit Using electrical components to model the mechanical components of the loudspeaker, further work must be done to accurately calculate these using data collected

5. Low distortion power amplifier No audio amplifiers readily available in lab Need to amplify signal from function generator to power loudspeaker Building amp using widely available LM3875 chip amp Constant voltage source, typical for powering speakers Component going into amplifier

6. Amplifier pictures

7. Data acquisition technique for measuring electromagnetic properties of loudspeaker Based on UIUC Physics 498POM PC-Based Pickup Impedance Measuring System

8. Complex pressure p and particle velocity u measurements Acoustic measurements will be taken at the same time as electromagnetic measurements

9. Impedance and Power Electrical Impedance (Ohms,  e ) Electrical Power (W) Radiation Impedance (Pa-s/m   ac ) Acoustic Intensity (W/m 2 )

10. Phase sensitive equipment SR830 Dual-Channel DSP lock-in amplifiers

11. The Speaker Italian Jensen C12N Ceramic magnet 12”, 8  50 watt rated power Designed to emulate American made Jensens from the 1960s

12. Apparatus Took measurements 3 ways: in free air, on baffle board, in speaker cabinet Microphones are on movable arms controlled by computer program Current and voltage cables attached underneath Foam sound absorbers used under speaker to prevent reflections Setup with speaker on baffle board

13. Speaker Cabinet Designed and built by Steve Errede, based on Marshall 1965B 4  10 straight speaker cabinet Sound absorptive material placed in cabinet behind speaker