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Subs, what to do if you lack excursion?
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<blockquote data-quote="Art Welter" data-source="post: 91072" data-attributes="member: 52"><p>Re: Subs, what to do if you lack excursion?</p><p></p><p></p><p>Plenum is the fancy word for slot.</p><p>Make the plenum 3 inches wide, or 76 millimeters wide, whichever your preference ;^).</p><p>The depth of the port area should be as in the sim attached in post 13, the area should be four times for one cabinet of four times the volume with four speakers (approximately what you will have converting your existing cabinets).</p><p></p><p>If you divide the cabinet in four parts, each section would be ported as in the sim, using four 3 inch diameter tubes 9.4 inch long, or the rectangular equivalent in cross sectional area, about 28.26 square inches.</p><p>Making the plenum the full depth of the cabinet wastes a little bit of the valuable internal cabinet volume, which is already partially used up by speaker, plenum and port volume.</p><p>Ports closer to square than skinny will be more equivalent to round.</p><p></p><p>Rectangular ports will tune slightly lower than circular .</p><p>Round over the plenum and port exits to reduce chuffing noises</p><p></p><p>It is best to make the ports a bit long on the first cabinet, then cut them down until the desired Fb is reached.</p><p></p><p>You can determine Fb by running sine wave tones through the cabinet, the cones will move least at Fb. Put a white dot on the cone to make it easier to see the movement.</p><p></p><p>There are a number of on line port calculators you can use to determine the port size if you find that the internal cabinet volume differs much from the sim.</p><p>Since the small cabinet volume results in a non-flat alignment, you are free to choose the Fb, knowing the lower the Fb the less output at Fb the cabinet will have.</p></blockquote><p></p>
[QUOTE="Art Welter, post: 91072, member: 52"] Re: Subs, what to do if you lack excursion? Plenum is the fancy word for slot. Make the plenum 3 inches wide, or 76 millimeters wide, whichever your preference ;^). The depth of the port area should be as in the sim attached in post 13, the area should be four times for one cabinet of four times the volume with four speakers (approximately what you will have converting your existing cabinets). If you divide the cabinet in four parts, each section would be ported as in the sim, using four 3 inch diameter tubes 9.4 inch long, or the rectangular equivalent in cross sectional area, about 28.26 square inches. Making the plenum the full depth of the cabinet wastes a little bit of the valuable internal cabinet volume, which is already partially used up by speaker, plenum and port volume. Ports closer to square than skinny will be more equivalent to round. Rectangular ports will tune slightly lower than circular . Round over the plenum and port exits to reduce chuffing noises It is best to make the ports a bit long on the first cabinet, then cut them down until the desired Fb is reached. You can determine Fb by running sine wave tones through the cabinet, the cones will move least at Fb. Put a white dot on the cone to make it easier to see the movement. There are a number of on line port calculators you can use to determine the port size if you find that the internal cabinet volume differs much from the sim. Since the small cabinet volume results in a non-flat alignment, you are free to choose the Fb, knowing the lower the Fb the less output at Fb the cabinet will have. [/QUOTE]
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