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Low Earth Orbit
DIY Audio
No compromises front loaded double 18” cab
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<blockquote data-quote="Phil Graham" data-source="post: 131920" data-attributes="member: 430"><p>Re: No compromises front loaded double 18” cab</p><p></p><p></p><p></p><p>Luke,</p><p></p><p>Teflon will be a poor choice for your runners, though I appreciate the intent of what you are aiming to do. PTFE is very expensive and has dreadful impact resistance.</p><p></p><p>More affordable, better performing alternatives include:</p><p></p><ul> <li data-xf-list-type="ul">Ultrahigh molecular weight polyethylene (UHMW PE)</li> <li data-xf-list-type="ul">Polypropylene</li> <li data-xf-list-type="ul">Acrylonitrile Butadiene Styrene (ABS)</li> </ul><p></p><p>And a couple of more exotic plastics:</p><p></p><ul> <li data-xf-list-type="ul">Kydex (a fancy PVC)</li> <li data-xf-list-type="ul">Delrin 300CP</li> </ul><p></p><p>---</p><p></p><p><strong>Some pointers on box design:</strong></p><p></p><ol> <li data-xf-list-type="ol">The prediction programs are based on math designed to simulate the small signal performance of vented boxes. They will let you enter big values for things like input power, but you should not assume that their models scale up to high power performance in a linear fashion.</li> <li data-xf-list-type="ol">The port length prediction of these programs is rarely on point. Expect to have to make sawdust to confirm box tuning</li> <li data-xf-list-type="ol">High performance modern woofers have been squarely out-performing the ports in boxes for more than five years now. Further extracting performance from vented boxes is now in the realm of fluid mechanics.</li> <li data-xf-list-type="ol">One of the quickest way to make sure that your box is tuned how you intend is by looking at the impedance curve. <a href="http://www.parts-express.com/dayton-audio-dats-v2-audio-test-system--390-806" target="_blank">Parts Express sells a nice affordable tool for doing impedance sweeps.</a></li> <li data-xf-list-type="ol">People also look for the box tuning frequency by inputting tones to the driver and looking for the frequency where the cone moves the least. This is also a valid method, but has the potential caveat that the box's tuning frequency will tend to increase as the input level increase.</li> <li data-xf-list-type="ol">Driver parameters change with increased power input. The most obvious of these changes in the increase in voice coil resistance as it heats up. As Re increases, Qe increases proportionately, which means that the driver has less electrical damping. The boxes overall response will change as a result. You can't assume the pretty flat line in your simulation program will match the boxes performance in the middle of long day out on a gig.</li> </ol></blockquote><p></p>
[QUOTE="Phil Graham, post: 131920, member: 430"] Re: No compromises front loaded double 18” cab Luke, Teflon will be a poor choice for your runners, though I appreciate the intent of what you are aiming to do. PTFE is very expensive and has dreadful impact resistance. More affordable, better performing alternatives include: [LIST] [*]Ultrahigh molecular weight polyethylene (UHMW PE) [*]Polypropylene [*]Acrylonitrile Butadiene Styrene (ABS) [/LIST] And a couple of more exotic plastics: [LIST] [*]Kydex (a fancy PVC) [*]Delrin 300CP [/LIST] --- [B]Some pointers on box design:[/B] [LIST=1] [*]The prediction programs are based on math designed to simulate the small signal performance of vented boxes. They will let you enter big values for things like input power, but you should not assume that their models scale up to high power performance in a linear fashion. [*]The port length prediction of these programs is rarely on point. Expect to have to make sawdust to confirm box tuning [*]High performance modern woofers have been squarely out-performing the ports in boxes for more than five years now. Further extracting performance from vented boxes is now in the realm of fluid mechanics. [*]One of the quickest way to make sure that your box is tuned how you intend is by looking at the impedance curve. [URL="http://www.parts-express.com/dayton-audio-dats-v2-audio-test-system--390-806"]Parts Express sells a nice affordable tool for doing impedance sweeps.[/URL] [*]People also look for the box tuning frequency by inputting tones to the driver and looking for the frequency where the cone moves the least. This is also a valid method, but has the potential caveat that the box's tuning frequency will tend to increase as the input level increase. [*]Driver parameters change with increased power input. The most obvious of these changes in the increase in voice coil resistance as it heats up. As Re increases, Qe increases proportionately, which means that the driver has less electrical damping. The boxes overall response will change as a result. You can't assume the pretty flat line in your simulation program will match the boxes performance in the middle of long day out on a gig. [/LIST] [/QUOTE]
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No compromises front loaded double 18” cab
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