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<blockquote data-quote="Rawr-DQ" data-source="post: 807433" data-attributes="member: 558585"><p>To be more specific about the "bad" waves I was talking about, here:</p><p></p><p>Avoiding Standing Waves</p><p></p><p>Most boxes are roughly shoebox or rectangular in shape. Technically speaking, this is a square prism. Unfortunately, these box shapes have a built-in flaw: box shapes with two or more sets of parallel sides will be prone to a phenomenon called “standing” waves. Standing waves are sound waves that reflect back and forth between two parallel sides inside the box. The frequency of a standing wave will have a wavelength equal to twice the distance between the two sides. For example, if two parallel walls are 24 inches (61 cm) apart, the standing wave that will develop between them will have a wavelength of 48 inches (122 cm). This corresponds to approximately 283 Hz. You can use the wavelength calculator to convert from the wavelength to the frequency.</p><p></p><p>A cube is generally a bad box shape since all of its parallel sides are equidistant. This means that all the standings waves inside the box will have the same frequency and will sum together, making them louder. This reduces the fidelity of the loudspeaker. But all is not lost if you really like the cube shape because there are ways to overcome standing wave problems. Here are a few suggestions:</p><p></p><p>• Add damping to the interior of the box. Bear in mind, that most of the commonly-used absorption materials have poor absorption coefficients at low frequencies. If your box is large, you should probably calculate the frequencies of the standing waves and check the absorption coefficients at those frequencies for the damping material you plan to use.</p><p></p><p>• Add one or more angled walls to the interior of the box. In this way, the outside of the box still has parallel walls, but the inside does not. These walls must be rigid and either have openings or be short in one dimension so that air can flow around them without any restrictions. Without parallel walls, standing waves will not develop.</p><p></p><p>• The frequencies of the standing waves can be spread apart so they do not sum together. It uses a 1.62 : 1 : 0.62 ratio between its three dimensions (height, width, depth) to spread apart the frequencies of the standing waves.</p><p></p><p>• Pick a box shape without parallel sides"</p></blockquote><p></p>
[QUOTE="Rawr-DQ, post: 807433, member: 558585"] To be more specific about the "bad" waves I was talking about, here: Avoiding Standing Waves Most boxes are roughly shoebox or rectangular in shape. Technically speaking, this is a square prism. Unfortunately, these box shapes have a built-in flaw: box shapes with two or more sets of parallel sides will be prone to a phenomenon called “standing” waves. Standing waves are sound waves that reflect back and forth between two parallel sides inside the box. The frequency of a standing wave will have a wavelength equal to twice the distance between the two sides. For example, if two parallel walls are 24 inches (61 cm) apart, the standing wave that will develop between them will have a wavelength of 48 inches (122 cm). This corresponds to approximately 283 Hz. You can use the wavelength calculator to convert from the wavelength to the frequency. A cube is generally a bad box shape since all of its parallel sides are equidistant. This means that all the standings waves inside the box will have the same frequency and will sum together, making them louder. This reduces the fidelity of the loudspeaker. But all is not lost if you really like the cube shape because there are ways to overcome standing wave problems. Here are a few suggestions: • Add damping to the interior of the box. Bear in mind, that most of the commonly-used absorption materials have poor absorption coefficients at low frequencies. If your box is large, you should probably calculate the frequencies of the standing waves and check the absorption coefficients at those frequencies for the damping material you plan to use. • Add one or more angled walls to the interior of the box. In this way, the outside of the box still has parallel walls, but the inside does not. These walls must be rigid and either have openings or be short in one dimension so that air can flow around them without any restrictions. Without parallel walls, standing waves will not develop. • The frequencies of the standing waves can be spread apart so they do not sum together. It uses a 1.62 : 1 : 0.62 ratio between its three dimensions (height, width, depth) to spread apart the frequencies of the standing waves. • Pick a box shape without parallel sides" [/QUOTE]
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