Free Box Plans (again)

[Omarvelous 10+ year member]

12" XXX !!!!!!! YEAAAAA!!!!!!!!!!!

Ported.....2 x 3" Diameter Flared Ports

 

[smullen 10+ year member]

12" XXX !!!!!!! YEAAAAA!!!!!!!!!!!
Ported.....2 x 3" Diameter Flared Ports

Yea I wanna see one for 12" XXXs too...

Vented for SQL....

 

[davidfre21 5,000+ posts]

how bout a box for a new B2 1.5cube tuned to like 28hz

 

[Bill T. 10+ year member]

Lone - I was looking at your design for a XXX15".. and was wondering why you didnt use a lot of port area? And what is the gain you came up with?

Thanks,

Bill T.

 

[LoneRanger 10+ year member]

Bill: the port area for a 15 in an SQ "daily use" setup is usually best around 36-40 square inches. gain is minimal for the same reason. when you build a box for listening pleasure, you want to keep the response curve as flat as possible. those nice spikes you get from adding port area cause the box to be peaky and innacurate.

as for the rest of you, i'm not drawing any more free plans this week so it's pointless to keep on voting. however, if you'd like to get a head start on next week's voting you can head over to ssaudio.com's forum (the gnome audio part, of course) and throw me some ideas.

 

[smullen 10+ year member]

Bill: the port area for a 15 in an SQ "daily use" setup is usually best around 36-40 square inches. gain is minimal for the same reason. when you build a box for listening pleasure, you want to keep the response curve as flat as possible. those nice spikes you get from adding port area cause the box to be peaky and innacurate.
as for the rest of you, i'm not drawing any more free plans this week so it's pointless to keep on voting. however, if you'd like to get a head start on next week's voting you can head over to ssaudio.com's forum (the gnome audio part, of course) and throw me some ideas.

I know this is gonna sound dumb, but how do you calculate a 36-40 square inches of port area? Not how did you find out how much was needed, but after you had that how do you figure the actual port size? 12x3=36 or 4x10=40, then thats just the mouth of the vent, how do you know how deep to make it? like it could be 12"w X 3"H X 12" D too???

what would be the measurements on 300sq" of port area in a huge box?

 

[LoneRanger 10+ year member]

I know this is gonna sound dumb, but how do you calculate a 36-40 square inches of port area? Not how did you find out how much was needed, but after you had that how do you figure the actual port size? 12x3=36 or 4x10=40, then thats just the mouth of the vent, how do you know how deep to make it? like it could be 12"w X 3"H X 12" D too???
what would be the measurements on 300sq" of port area in a huge box?

port area is figured exactly how you described: Length * Width. A port that is 12" x 3" would have a surface area of 36 square inches. The depth of the port is directly proportional to the desired tuning frequency and surface area of the port. I don't know the equation off the top of my head (used to, but then I got lazy and started using CAD), but there's no need to worry your pretty little head over such things when bcae1.com gives you all those nice java calculators for free //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Bill T. 10+ year member]

Actually, bcae1.com doesnt explain the tuning frequency in relation to the port length and surface area. And the calculator they do have to calculate tuning freq doesnt work right. It always gives lengths under 5"... unless its user error.

If you could find that equation, that would be great. I have a few plans for my next box, including a SS box.

smullen - port area is always measured in square/inches and its almost always at the exit point (correct me if Im wrong)

Bill T.

 

[smullen 10+ year member]

smullen - port area is always measured in square/inches and its almost always at the exit point (correct me if Im wrong)

Bill T.

Yea I guess, I asked my question wrong again... I knew how to find square area just BxH=square, but I get how to get the length of the vent is the one I never understand...

 

[Bill T. 10+ year member]

Thats the equation we speak of. Lone has the goods... we must get it at all costs!

Bill T.

 

[djvi0lent 10+ year member]

Hey LoneRanger, the RE HC 12 box plans you submitted.. what is the box tuned to, and how many cubes is it before/after port displacement??

 

[ShRapNeR 10+ year member]

Dd 9512

*************

 

[Benny212 10+ year member]

Yea I guess, I asked my question wrong again... I knew how to find square area just BxH=square, but I get how to get the length of the vent is the one I never understand...

the equation your lookin for is

(tuning frequency)=.159(sqr root of (area of port*1.84*10^8)/(volume of box*(length of port+(.823*sqr root of area of port))))

plug in your values for tuning frequency, area of port and box volume and you can solve for length of port. If you want that equation but cleaned up a little go to

http://www.jlaudio.com/tutorials/ports/index.html