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Question on How to Measure Port length-2 diff. designs
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<blockquote data-quote="Immacomputer" data-source="post: 2726194" data-attributes="member: 570419"><p>Well that was a grade "A" answer... You basically defined my question with your answer.</p><p></p><p>And nice random about the sub strokes and end correction only being used by one way of the stroke... where do you get this stuff?</p><p></p><p>Why don't you do some reading on what a ported enclosure really is.</p><p></p><p><a href="http://www.audioholics.com/education/acoustics-principles/helmholtz-resonant-absorber" target="_blank">http://www.audioholics.com/education/acoustics-principles/helmholtz-resonant-absorber</a></p><p></p><p>After you read that, take a look here:</p><p></p><p><a href="http://en.wikibooks.org/wiki/Acoustics/Bass-Reflex_Enclosure_Design" target="_blank">http://en.wikibooks.org/wiki/Acoustics/Bass-Reflex_Enclosure_Design</a></p><p></p><p>Then, you might want to swing by JL's site as well:</p><p></p><p><a href="http://mobile.jlaudio.com/support_pages.php?page_id=165" target="_blank">http://mobile.jlaudio.com/support_pages.php?page_id=165</a></p><p></p><p>Do you know what all of those sites have in common? They all factor end correction as part of the port. By part of the port, they mean the air mass in the end correction is part of the total air mass in the port. The reason you don't count that as net volume is because that mass of air is NOT being compressed but rather, it resonates. The net volume of air is doing the compression and expansion and that is what drives the port into resonance. How can this mass of air act like net volume and port volume at the same time? It can't and it doesn't.</p><p></p><p>Subs do not have eyes; they just feel the enclosure volume. We have eyes and when we look at a port, we can see the wood blocking the air. We can't see the end correction of the port but the sub does. The sub can feel the entire column of air that is the port and in that column of air, is the small amount of port that was added due to end correction.</p><p></p><p>I know it's hard to admit when you're wrong, especially when you have been building and designing enclosures for a long time. But I'm sorry, you're wrong in this case. It won't make much of a difference but it is something to calculate in on future designs.</p></blockquote><p></p>
[QUOTE="Immacomputer, post: 2726194, member: 570419"] Well that was a grade "A" answer... You basically defined my question with your answer. And nice random about the sub strokes and end correction only being used by one way of the stroke... where do you get this stuff? Why don't you do some reading on what a ported enclosure really is. [URL="http://www.audioholics.com/education/acoustics-principles/helmholtz-resonant-absorber"]http://www.audioholics.com/education/acoustics-principles/helmholtz-resonant-absorber[/URL] After you read that, take a look here: [URL="http://en.wikibooks.org/wiki/Acoustics/Bass-Reflex_Enclosure_Design"]http://en.wikibooks.org/wiki/Acoustics/Bass-Reflex_Enclosure_Design[/URL] Then, you might want to swing by JL's site as well: [URL="http://mobile.jlaudio.com/support_pages.php?page_id=165"]http://mobile.jlaudio.com/support_pages.php?page_id=165[/URL] Do you know what all of those sites have in common? They all factor end correction as part of the port. By part of the port, they mean the air mass in the end correction is part of the total air mass in the port. The reason you don't count that as net volume is because that mass of air is NOT being compressed but rather, it resonates. The net volume of air is doing the compression and expansion and that is what drives the port into resonance. How can this mass of air act like net volume and port volume at the same time? It can't and it doesn't. Subs do not have eyes; they just feel the enclosure volume. We have eyes and when we look at a port, we can see the wood blocking the air. We can't see the end correction of the port but the sub does. The sub can feel the entire column of air that is the port and in that column of air, is the small amount of port that was added due to end correction. I know it's hard to admit when you're wrong, especially when you have been building and designing enclosures for a long time. But I'm sorry, you're wrong in this case. It won't make much of a difference but it is something to calculate in on future designs. [/QUOTE]
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