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How does a 4th order bandpass work?
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<blockquote data-quote="mat3833" data-source="post: 8792442" data-attributes="member: 587645"><p>4th orders are really simple when you think of them as 2 seperate enclosures. I'm going to WAY over simplify here, but this is a pretty solid base level example. </p><p></p><p>Speakers produce 2 pressure waves 180 degrees out of phase with each other. A sealed enclosure just traps one of those waves so it can't cancel out the other and boom, you got sound. The low-end of a sealed enclosure tapers off at about 6 decibels per octave. </p><p></p><p>A ported enclosure traps one of the waves, but also adds a secondary chamber that acts like an additional driver at a specific frequency and gives you a boost around that frequency. This enclosure type is making the normally unwanted "rear wave" useful and getting some output from it, usually a +3 decibel gain. The downside is that below that frequency, your speaker is essentially playing without an enclosure. The low end of a ported enclosure rolls off MUCH steeper, usually between 18 and 24 decibels per octave. </p><p></p><p>Now, a 4th order basically utilizes the benefits of both designs. You have the sealed section which let's you play really low and not exceed your speakers mechanical limits, and you have a port that gives you a boost in output. In this case, the "rear wave" is trapped in the sealed section, and the "front wave" is playing through a port. From the ported enclosure example, you know that below a ports tuning frequency it basically acts like a big hole and does nothing. But the closer you get to the ports tuning, the more output "boost" you get. Generally you can expect a +6 dB gain over a small window, usually an octave; for example from 30hz to 60hz. However, above that frequency, your output drops off just like in a ported enclosure. </p><p></p><p>Matt</p></blockquote><p></p>
[QUOTE="mat3833, post: 8792442, member: 587645"] 4th orders are really simple when you think of them as 2 seperate enclosures. I'm going to WAY over simplify here, but this is a pretty solid base level example. Speakers produce 2 pressure waves 180 degrees out of phase with each other. A sealed enclosure just traps one of those waves so it can't cancel out the other and boom, you got sound. The low-end of a sealed enclosure tapers off at about 6 decibels per octave. A ported enclosure traps one of the waves, but also adds a secondary chamber that acts like an additional driver at a specific frequency and gives you a boost around that frequency. This enclosure type is making the normally unwanted "rear wave" useful and getting some output from it, usually a +3 decibel gain. The downside is that below that frequency, your speaker is essentially playing without an enclosure. The low end of a ported enclosure rolls off MUCH steeper, usually between 18 and 24 decibels per octave. Now, a 4th order basically utilizes the benefits of both designs. You have the sealed section which let's you play really low and not exceed your speakers mechanical limits, and you have a port that gives you a boost in output. In this case, the "rear wave" is trapped in the sealed section, and the "front wave" is playing through a port. From the ported enclosure example, you know that below a ports tuning frequency it basically acts like a big hole and does nothing. But the closer you get to the ports tuning, the more output "boost" you get. Generally you can expect a +6 dB gain over a small window, usually an octave; for example from 30hz to 60hz. However, above that frequency, your output drops off just like in a ported enclosure. Matt [/QUOTE]
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How does a 4th order bandpass work?
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