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Does port area Matter?


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So..... a big giant port will raise my F3 of the enclosure? Because that does not sound desirable... I know you guys are giving excellent info, but is there any physics behind it to prove any of the lore stated above? Most of all... will it even make a noticeable difference when applied to a real world scenario?

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When will people stop worrying about box size vs. port area????!!!!!

I would really like to hear your thoughts about this if you have a min...pm me if you want :drinks:

I have posted it many times as have many other people. Port size is related to the Vd of the driver and the tuning frequency (actually air velocity through the port). The amount of power can also come into play, but is hard to factor in without modeling the enclosure, since large enclosures allow for more driver excursion with less power.

I guess some people could argue that the driver will have less excursion in a smaller box, so less port area would be required, but that is the same situation as going by how much power will be used. Unless you know it is a situation where the driver will be limited from using its full range of excursion, the port should not be undersized based on box volume or power applied.

I always ask people this question:

If I have some cheapo 18" driver with low excursion capabilities on 100 watts in 6 cuft tuned to 32 Hz, why would it need the same amount of port area as an 18" high excurision driver on thousands of watts in the same 6 cuft tuned to 32 Hz. And I am not saying it can't, it just does not need it.

Current system:

1997 Blazer - (4) Customer Fi NEO subs with (8) American Bass Elite 2800.1s

Previous systems:

2000 Suburban - (4) BTL 15's and (4) IA 40.1's = 157.7 dB at 37 Hz.

1992 Astro Van - (6) BTL 15's and (6) IA 40.1's = 159.7 dB at 43 Hz.

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It also effects the roll off and peak of the enclosure.

15cuft small port may have a +3db @40hz and F3@28hz

15cuft large port may have a +6db @40hz and F3@35hz

This is purely hypothetical but you get what I mean.

-Drew

I always love this example.

If the boxes are the same NET volume, and the tuning is the same, the change seen in output and peaks is caused by an undersized port not operating correctly. There is not something magical that causes large CORRECTLY designed ports to have a different F3 and peak.

Current system:

1997 Blazer - (4) Customer Fi NEO subs with (8) American Bass Elite 2800.1s

Previous systems:

2000 Suburban - (4) BTL 15's and (4) IA 40.1's = 157.7 dB at 37 Hz.

1992 Astro Van - (6) BTL 15's and (6) IA 40.1's = 159.7 dB at 43 Hz.

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I ran 4 15" BTLs in 11.7 cuft with 386 sqin of port tuned to 34 Hz.

155+ playing music down to 30 Hz. 157 peak from 37 to 43 Hz. Designed to play music and played music like crazy. . .

http://s183.photobucket.com/albums/x24/bkolfo4/?action=view&current=MVI_0950.mp4

Current system:

1997 Blazer - (4) Customer Fi NEO subs with (8) American Bass Elite 2800.1s

Previous systems:

2000 Suburban - (4) BTL 15's and (4) IA 40.1's = 157.7 dB at 37 Hz.

1992 Astro Van - (6) BTL 15's and (6) IA 40.1's = 159.7 dB at 43 Hz.

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Ive not had much luck with tuning .... Last box I did was 6 American Bass dx 12's in 11.9 net internal tuned 33hz with 174in2 or port area and it simply would not play anything under 35 without losing all efficiency. Given the subs are low excursion, low BL, and average F3..... Seems like it should have been able to play lower. Not to get off topic though. How do you design your enclosure to play in certain frequency ranges if so many things change from paper to real life application?

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