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<blockquote data-quote="Water Bear" data-source="post: 8865218" data-attributes="member: 673826"><p>I'm in way out of my depth here, but that was an interesting question that made me think. Let's just imagine that all changes in air pressure travel at the local speed of sound. If you think about it the distance from the back of your woofer through the port to the front means that it'll take a while for changes on each side of the woofer to reach each other. When the woofer extends, the air is compressed in front of the woofer, that expands in a spherical wave, and the low pressure zone inside the box starts to draw in higher pressure air from the environment. But that low pressure region travels at the same speed as the compression wave. So it'll take a few...milliseconds or less or whatever for the low pressure effects to reach the front of the woofer, and by then the woofer has started to draw back. Time it all just right and you get resonance - the low pressure from the port reaches the woofer right when it is decompressing the cabine. All this happens in a spherically radiating pattern (reflecting off the cabin interior) so it's hard to describe exactly where the peaks and valleys of pressure happen, be that constructive or destructive interference. Compared to having two woofers right next to each other firing out of phase, the destructive effects would align along much more of the wave fronts much more of the time.</p><p></p><p>Anyway I'm just pondering the answer as I sit here in the crapper, using some basic mathematical knowledge and with very little engineering expertise, so I could be way off. Interesting question you asked though.</p></blockquote><p></p>
[QUOTE="Water Bear, post: 8865218, member: 673826"] I'm in way out of my depth here, but that was an interesting question that made me think. Let's just imagine that all changes in air pressure travel at the local speed of sound. If you think about it the distance from the back of your woofer through the port to the front means that it'll take a while for changes on each side of the woofer to reach each other. When the woofer extends, the air is compressed in front of the woofer, that expands in a spherical wave, and the low pressure zone inside the box starts to draw in higher pressure air from the environment. But that low pressure region travels at the same speed as the compression wave. So it'll take a few...milliseconds or less or whatever for the low pressure effects to reach the front of the woofer, and by then the woofer has started to draw back. Time it all just right and you get resonance - the low pressure from the port reaches the woofer right when it is decompressing the cabine. All this happens in a spherically radiating pattern (reflecting off the cabin interior) so it's hard to describe exactly where the peaks and valleys of pressure happen, be that constructive or destructive interference. Compared to having two woofers right next to each other firing out of phase, the destructive effects would align along much more of the wave fronts much more of the time. Anyway I'm just pondering the answer as I sit here in the crapper, using some basic mathematical knowledge and with very little engineering expertise, so I could be way off. Interesting question you asked though. [/QUOTE]
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