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Old 05-17-2011, 01:36 AM
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Default Question about port length on 4th order bandpass

So I have tried to find this out, but don't understand it. I have read that to tune the 4th order it depends on the port length in the ported chamber. The concern I have is that so many bandpass walls I see the port length is so short and no where near how long it would seem like it needs to be to be tuned so low. Thinking of doing a 4th order bp wall with my 4 18's and the ported chamber is looking like it will come out to about 22cubes and I want it tuned to 45hz, but it says that it would need to be around 10" in length with a 450" port. Keep seeing people say that the port length in a BP should be like 6" maximum and I just don't get how I can make mine so short and still keep the tuning down.
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Old 05-17-2011, 02:00 AM
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6" maximum? No, that's wrong.

Just make it whatever it needs to be. I think you know this but 4th orders ported chambers are tuned a lot higher than just a ported enclosure.
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Old 05-17-2011, 02:33 AM
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Originally Posted by jt_buck View Post
6" maximum? No, that's wrong.

Just make it whatever it needs to be. I think you know this but 4th orders ported chambers are tuned a lot higher than just a ported enclosure.
Ok, I mean I know alot of people just talk online without actually knowing much, but then on some builds i've seen the port is HUGE and there is hardly no length at all so was confused.

And yea I know about the tuning...low end monster hopefully
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Old 05-17-2011, 02:40 AM
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You can get some ideas based on other builds, but you have to keep in mind there is no general rules that apply- like you have to make it what it needs to be to work.

Plus I've designed a few enclosures, tell you that you make that port however long you need to achieve tuning. And yes, 45 hz should play low.
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Old 05-17-2011, 05:38 AM
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450" of port is pretty big for 22 cubes, based on what woofer configs would fit that airspace. Then 45hz is a pretty low tuning for a 4th order as well so you have both of those working to long port length.

what kinda cone area?
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Old 05-17-2011, 10:08 AM
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Quote:
Originally Posted by profundus-sanus View Post
450" of port is pretty big for 22 cubes, based on what woofer configs would fit that airspace. Then 45hz is a pretty low tuning for a 4th order as well so you have both of those working to long port length.

what kinda cone area?
Well 450" is only 20.45" of port area per cube of ported space. Few other box designers said 18-25 for bp's so thought it'd be about right.
Cone area is 4 18" IA death penalties so 1,017.
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