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How does the size of a speaker affect its frequency responseFeatured science projectScience project video

Conclusion

The hypothesis that reducing the size of the speaker enclosure will cause the dB of some frequencies to be higher is proven to be true. 

With a  depth of  300mm the sound of speaker C  at  the 150Hz  frequency  was  6 times  louder than the sound level of the other speakers.

This type of air tight speaker enclosure is called a sealed enclosure. When the diaphragm of the speaker moves in, the air pressure will build up inside the speaker enclosure and push the diaphragm back out. Similarly if the diaphragm of the speaker moves out, the air pressure inside the enclosure will drop and pull the diaphragm back. This spring like effect will cause the sound  produced  to be more precise. However the audio electrical signal will need more boosting by the amplifier circuit.
 

Also consider

The experiment can also be done by checking the frequency response  using different types and thickness of wood for the enclosure.

This experiment can also be repeated using different sizes of speakers.
 

References

Speaker enclosure design - http://www.niksula.hut.fi/~mdobruck/siililand/mini/diy/alien/ice/speaker.html

How speakers work - http://electronics.howstuffworks.com/speaker9.htm
 

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Complexity level:
7
Project cost ($):
90
Time required:
2 days to prepare, 1 day for experiment
Material availability:
Easily found. May be purchased at a hardware store (eg. Home Depot)
Safety concerns:

None