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<blockquote data-quote="brian84corvette" data-source="post: 8333929" data-attributes="member: 586635">4th order advantage - properly designed / setup and installed in its car environment it can be as loud as ported or louder sometimes but play a larger bandwith before loosing output.&nbsp; usualy and octave below and above its &quot;tuning&quot;octave = double or half of the frequency.&nbsp; &nbsp;&nbsp; so if your 4th order setup is tuned at say 40hz&nbsp; then it should play from 20hz to 80 hz fairly well..&nbsp;&nbsp; unless your sub you use is not designed to play that high so that needs to be acounted for in your sub choice and box designing theory.4th order is not so much a set in stone mathmatical fourmua to put x and y together in your viechle and end up with spectacular results.&nbsp; it may take some tinkering - re engineering port design or chamber size.some general guidelines to look in to about ratio.&nbsp;&nbsp; the sealed side vs the ported side air space.1 to 1 ratio - is as loud as sealed box&nbsp; no real gain or use of having this ratio...2 to 1 ratio - can be as loud as a ported box in the same aplication...&nbsp;&nbsp; again no real advantage3 to 1 ratio louder than ported box because of the gain you can recieve in the larger ported section of the enclosure.going larger than 5 to 1 ratio starts realey eating up your usable frequency range and is more geared twards spl competion one note wonder viechles&nbsp; that play insanely loud in a small range of hzim an 18&quot; sub guy.&nbsp;&nbsp; my collection has nine right now.&nbsp;&nbsp; loved my re sx 18&quot; old style&nbsp;&nbsp; they lived in slot ported boxes and always made a ruckus in any viechle ive had.&nbsp; &nbsp; &nbsp;&nbsp; the biggest concern about 4th order single reflex bandpas style box is size it takes to properly do it - and also how it fits in to your viechle placment of the port sub ext...&nbsp;&nbsp; all factor in&nbsp; &nbsp; &nbsp; if its just too much to fit - its not worth building it smaller than neededi just built a old box suburban 4th using six 18s - in a 3:1 ratio using the truck as my structure to build as big as humanly possible inside my viechle.detailed build with lotts of pix in the build log section here of it - ghetto blaster build for cheap</blockquote>

[QUOTE="brian84corvette, post: 8333929, member: 586635"] 4th order advantage - properly designed / setup and installed in its car environment it can be as loud as ported or louder sometimes but play a larger bandwith before loosing output. usualy and octave below and above its "tuning" octave = double or half of the frequency. so if your 4th order setup is tuned at say 40hz then it should play from 20hz to 80 hz fairly well.. unless your sub you use is not designed to play that high so that needs to be acounted for in your sub choice and box designing theory. 4th order is not so much a set in stone mathmatical fourmua to put x and y together in your viechle and end up with spectacular results. it may take some tinkering - re engineering port design or chamber size. some general guidelines to look in to about ratio. the sealed side vs the ported side air space. 1 to 1 ratio - is as loud as sealed box no real gain or use of having this ratio... 2 to 1 ratio - can be as loud as a ported box in the same aplication... again no real advantage 3 to 1 ratio louder than ported box because of the gain you can recieve in the larger ported section of the enclosure. going larger than 5 to 1 ratio starts realey eating up your usable frequency range and is more geared twards spl competion one note wonder viechles that play insanely loud in a small range of hz im an 18" sub guy. my collection has nine right now. loved my re sx 18" old style they lived in slot ported boxes and always made a ruckus in any viechle ive had. the biggest concern about 4th order single reflex bandpas style box is size it takes to properly do it - and also how it fits in to your viechle placment of the port sub ext... all factor in if its just too much to fit - its not worth building it smaller than needed i just built a old box suburban 4th using six 18s - in a 3:1 ratio using the truck as my structure to build as big as humanly possible inside my viechle. detailed build with lotts of pix in the build log section here of it - ghetto blaster build for cheap [/QUOTE]

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