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Enclosure Design & Construction
Twin 18" PA-Sub 6th-Order Blowthrough in Trunk... Sanity Check.
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<blockquote data-quote="recon440" data-source="post: 8723992" data-attributes="member: 636364"><p>On the Hornresp sim the cross over point where the XLs start overtaking is at 35Hz on the above designs.</p><p></p><p>Out of curiosity I tweaked port lengths while keeping volumes the same and see how the B&Cs would do in each alignment:</p><p>- B&Cs using 30cm rear ports vs 20cm (black)</p><p>- B&Cs using 15cm front port vs 5cm (grey)</p><p></p><p>As you can see the output using the longer ports (black trace) give huge low-end gain at 30Hz at the expense of 3-5dB on the top end (40-100Hz). I don't usually play any modified music and prefer to get loud in the spectrum where typical music is mastered so I'm thinking I could be happy.</p><p></p><p>[ATTACH=full]24618[/ATTACH]</p><p></p><p></p><p>Fs on the B&Cs is 32Hz. When loaded into that alignment it brings the fundamental frequency up to 36Hz based on the length of the front port. If I lengthened the ports I can get effectively get the fundamental frequency all the way down to 20Hz if I wanted. At the end of the day in the case of these B&C drivers, on paper they have the best of both worlds with an xmax much higher than typical pro drivers with the higher efficiency which is surely beneficial >50Hz.</p><p></p><p>[URL unfurl="true"]https://www.bcspeakers.com/en/products/lf-driver/18-0/8/18sw115[/URL]</p><p></p><p>In terms of a simple bass reflex, B&C recommends a ported alignment 5.3CF tuned to 35Hz. Overall in the case of a 6th order the total net system volume will be ~10cf+ (depending on how tightly to the trunk I can build the front chamber "sleeve"). Generally in series 6th order, the low-tuned rear chamber is much smaller than the front chamber so I think in terms of the design objective this is well in the real of a useable volume (~40% of what would be recommended for a standard bass-reflex requirement). This will also the design constraint so that the rear chamber can actually be fit into the trunk in one piece... LOL</p></blockquote><p></p>
[QUOTE="recon440, post: 8723992, member: 636364"] On the Hornresp sim the cross over point where the XLs start overtaking is at 35Hz on the above designs. Out of curiosity I tweaked port lengths while keeping volumes the same and see how the B&Cs would do in each alignment: - B&Cs using 30cm rear ports vs 20cm (black) - B&Cs using 15cm front port vs 5cm (grey) As you can see the output using the longer ports (black trace) give huge low-end gain at 30Hz at the expense of 3-5dB on the top end (40-100Hz). I don't usually play any modified music and prefer to get loud in the spectrum where typical music is mastered so I'm thinking I could be happy. [ATTACH type="full" width="594px" alt="Capture.PNG"]24618[/ATTACH] Fs on the B&Cs is 32Hz. When loaded into that alignment it brings the fundamental frequency up to 36Hz based on the length of the front port. If I lengthened the ports I can get effectively get the fundamental frequency all the way down to 20Hz if I wanted. At the end of the day in the case of these B&C drivers, on paper they have the best of both worlds with an xmax much higher than typical pro drivers with the higher efficiency which is surely beneficial >50Hz. [URL unfurl="true"]https://www.bcspeakers.com/en/products/lf-driver/18-0/8/18sw115[/URL] In terms of a simple bass reflex, B&C recommends a ported alignment 5.3CF tuned to 35Hz. Overall in the case of a 6th order the total net system volume will be ~10cf+ (depending on how tightly to the trunk I can build the front chamber "sleeve"). Generally in series 6th order, the low-tuned rear chamber is much smaller than the front chamber so I think in terms of the design objective this is well in the real of a useable volume (~40% of what would be recommended for a standard bass-reflex requirement). This will also the design constraint so that the rear chamber can actually be fit into the trunk in one piece... LOL [/QUOTE]
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Twin 18" PA-Sub 6th-Order Blowthrough in Trunk... Sanity Check.
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