The fifth week of the engineering design project was mostly spent waiting for materials to come in so construction on the speaker enclosures could begin.  During this waiting time, it was decided to do more extensive research to help clear up some loose ends and bolster the final report.  To begin, the team looked into the golden ratio for speaker cabinet size and found that the ratio is with respect to the sides, not the size of the speaker.  For example if the front of an enclosure is 6 inches wide, the box would be 9.6 inches tall and 3.6 inches deep, even if the speaker is 3 inches deep.  Also, the team looked into more information about what the golden ratio actually does.  This ratio helps to dampen standing waves in a speaker cabinet.  These standing waves are the opposite of what comes out the front of the speaker.  If positive and negative waves meet, they will cancel each other out, this is destructive interference.  Therefore, being able to eliminate these waves is vital.

Destructive Interference

When two waves interfere, the sum of their amplitudes determines the new wave's shape.  The amplitude of a wave is its maximum amount of displacement from its position at rest to its crest (the uppermost part of a wave).  When two waves are 180 degrees out of phase, phase denotes a particular point in the cycle of a wave,  the crest of one wave is at the same point as the trough (the lowermost part of a wave) of the other.  Since these two amplitudes are opposite of each other, one being positive and the other being negative, when they add together the sum is 0.  Therefore the two waves cancel each other out.

This is not the only measure the team took to create destructive interference between these waves.  More research was also done with respect to the materials.  This research includes how the properties of the materials that were researched will affect the sound produced by the speaker.  The goal of a speaker is to eliminate the standing waves produced by the speaker.  It does this in two ways; through dampening and resisting resonance.  The properties that affect the dampening a material creates are density and stiffness.  Density because the more material that is between one and the speaker, the less one is going to hear.  Stiffness affects the dampening in a different way.  This property is slightly more subjective than density is, but still important.  If a material is very stiff, it will allow the waves inside the cabinet to bounce off of it nearly unchanged, which will then redirect it to another wall of the cabinet.  This becomes a problem because the number of waves inside the cabinet rise quickly as they bounce off the walls instead of being absorbed.  To absorb the sound waves, the enclosure is going to have to be soft.  If the enclosure is soft though it will be susceptible to resonance.  Resonance is when the walls of the cabinet move, making their own sound.  This is caused by the material being flexible.  Unfortunately, being flexible is the opposite of being stiff.  So for the material a good compromise between stiffness and flexibility is needed to try  and dampen, as well as not resonate.  It is the design groups belief that oak wood and MDF are good candidates for these properties.