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<blockquote data-quote="bladebarrier" data-source="post: 6207807" data-attributes="member: 603808">Sealed boxes roll off at a lower rate than ported. Both can get very low, assuming the box size and tuning is designed to do so.Here&#039;s the problem.... Boxes in cars are small.... I know, it doesn&#039;t seem like it, but they are.Say it with me: &quot;car subs are in small boxes&quot;. I hope that doesn&#039;t sound rude, but always remember that mantra. Car speakers are all designed for small boxes, even the ones that seem to take big ones.Ok, so here&#039;s the issue. Cars boost bass because the car itself is small.It&#039;s called transfer function. That&#039;s why we can get great bass in a car. The speaker/enclosure is designed to be tiny compared to what it would need, in say, a large concert hall.So, the trick is that you can tune a box higher in a car, and still get solid bass, because the car boosts those notes.... Until you get really low. A 4th order box (vented) rolls off at 24db on the low end, but a 2nd ordered (sealed) rolls off at 12db. This is a factor of physics. If you want specifics as to how this works, I can shoot some links out, but essentially it has to do with dampening.It&#039;s also why amps have subsonic filters. You set your subsonic filter just below your tuning frequency to help avoid damaging your woofer. A sealed design doesn&#039;t need this. The excursion of the woofer stays steady with the frequency (though lower frequencies take more excursion no matter what, to produce the same db that humans hear), where a ported acts as if it isn&#039;t in a box at all, once it gets about a half octave below its&#039; tuning frequency. At that point, all dampening is lost, and you might as well be holding it in your hands, because the box isn&#039;t doing anything to resist the pressure and keep it moving linearly.</blockquote>

[QUOTE="bladebarrier, post: 6207807, member: 603808"] Sealed boxes roll off at a lower rate than ported. Both can get very low, assuming the box size and tuning is designed to do so. Here's the problem.... Boxes in cars are small.... I know, it doesn't seem like it, but they are. Say it with me: "car subs are in small boxes". I hope that doesn't sound rude, but always remember that mantra. Car speakers are all designed for small boxes, even the ones that seem to take big ones. Ok, so here's the issue. Cars boost bass because the car itself is small. It's called transfer function. That's why we can get great bass in a car. The speaker/enclosure is designed to be tiny compared to what it would need, in say, a large concert hall. So, the trick is that you can tune a box higher in a car, and still get solid bass, because the car boosts those notes.... Until you get really low. A 4th order box (vented) rolls off at 24db on the low end, but a 2nd ordered (sealed) rolls off at 12db. This is a factor of physics. If you want specifics as to how this works, I can shoot some links out, but essentially it has to do with dampening. It's also why amps have subsonic filters. You set your subsonic filter just below your tuning frequency to help avoid damaging your woofer. A sealed design doesn't need this. The excursion of the woofer stays steady with the frequency (though lower frequencies take more excursion no matter what, to produce the same db that humans hear), where a ported acts as if it isn't in a box at all, once it gets about a half octave below its' tuning frequency. At that point, all dampening is lost, and you might as well be holding it in your hands, because the box isn't doing anything to resist the pressure and keep it moving linearly. [/QUOTE]

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