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Low Earth Orbit
DIY Audio
60 Degree DIY Mid Hi - AKA PM60
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<blockquote data-quote="Max Warasila" data-source="post: 212896" data-attributes="member: 3845"><p>Oh, and Rodger - I do have a few specific technical notes to add that didn't really fit the narrative of my previous post.</p><ol> <li data-xf-list-type="ol">I did not include recommendations for the rear angles because there is no good way of cutting the angles ahead of time before assembly. The multiple compound angles required is nearly impossible with even the more advanced tooling I had access to at the time. Without the scale of many boxes, I felt it was better to simply leave out the compound angles and stick to a simple angle. Also it made the math easier!</li> <li data-xf-list-type="ol">I did, however, consider the lines that would be formed by cutting those angles and made sure it was still possible without cutting into areas where handles/drivers were attached. I think you've noticed that my box has less space in the rear to put these angles, and that's true! The angles created when splaying would be tighter from the perspective of the rear of the box. However, because the entire assembly is slightly more compact (and trust me - there's not more than a cm left to squeeze in any direction) relative to the front of the box you actually get closer horn placement and the drivers (which impacts the effective acoustic center) are also closer together. So no worries there!<br /> <br /> (For additional salt ? - this was a change that came about as a result of moving to the PM90 platform. The concern over ensuring that both horns fit led me to push the envelope on how tight the internal chamber could be. Again, another undocumented improvement over the original PM60 pdf drawings.)</li> <li data-xf-list-type="ol">Normally the most effective way to brace the internal chamber would have been to tie the centers of the two side walls together. Unfortunately, there's a horn in the way - oops! That main brace is a result of this, and while it may be tempting to just drop the connections between the side, they provide more benefit than any other part of the bracing plan. This same concept is true regarding the horn bracing.</li> <li data-xf-list-type="ol">While we're talking about the internal chamber - <em>damping material is not optional!!! </em>IMO, it is necessary to get the apparent volume of the chamber high enough and the tuning consistent between the two different horns (which take up very slightly different spaces and volumes of the chamber). If I were to have built these, I suspect I would have very slightly different tunings between the interchangeable horns.</li> </ol><p>Please let me know if you have any other specific questions either here or in a PM. Like I said, there's two years of work into those drawings, and I've learned a hell of a lot since I worked on this cabinet. I simply can't write down all of that in a few forum posts. Luckily I keep notes more often now to help with this sort of thing in the future.</p></blockquote><p></p>
[QUOTE="Max Warasila, post: 212896, member: 3845"] Oh, and Rodger - I do have a few specific technical notes to add that didn't really fit the narrative of my previous post. [LIST=1] [*]I did not include recommendations for the rear angles because there is no good way of cutting the angles ahead of time before assembly. The multiple compound angles required is nearly impossible with even the more advanced tooling I had access to at the time. Without the scale of many boxes, I felt it was better to simply leave out the compound angles and stick to a simple angle. Also it made the math easier! [*]I did, however, consider the lines that would be formed by cutting those angles and made sure it was still possible without cutting into areas where handles/drivers were attached. I think you've noticed that my box has less space in the rear to put these angles, and that's true! The angles created when splaying would be tighter from the perspective of the rear of the box. However, because the entire assembly is slightly more compact (and trust me - there's not more than a cm left to squeeze in any direction) relative to the front of the box you actually get closer horn placement and the drivers (which impacts the effective acoustic center) are also closer together. So no worries there! (For additional salt ? - this was a change that came about as a result of moving to the PM90 platform. The concern over ensuring that both horns fit led me to push the envelope on how tight the internal chamber could be. Again, another undocumented improvement over the original PM60 pdf drawings.) [*]Normally the most effective way to brace the internal chamber would have been to tie the centers of the two side walls together. Unfortunately, there's a horn in the way - oops! That main brace is a result of this, and while it may be tempting to just drop the connections between the side, they provide more benefit than any other part of the bracing plan. This same concept is true regarding the horn bracing. [*]While we're talking about the internal chamber - [I]damping material is not optional!!! [/I]IMO, it is necessary to get the apparent volume of the chamber high enough and the tuning consistent between the two different horns (which take up very slightly different spaces and volumes of the chamber). If I were to have built these, I suspect I would have very slightly different tunings between the interchangeable horns. [/LIST] Please let me know if you have any other specific questions either here or in a PM. Like I said, there's two years of work into those drawings, and I've learned a hell of a lot since I worked on this cabinet. I simply can't write down all of that in a few forum posts. Luckily I keep notes more often now to help with this sort of thing in the future. [/QUOTE]
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