posted
Hey dukk or anyone can you give me the formula on how to get what a port is tuned at. Right now I have 2 ports going into 1 box with 2 10's does that change the formula now with 2 ports? Thanks
posted
If you have a spec for 1 sub in a box with 1 port and then double the box volume and add another sub and port (so now everything is doubled) then it should be no problem.
I'll look for that formula, it's in my car I think........
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Lord Dukk The Big Show The Dukk says: Know your bass: PORT your damn box!! Have HoleSaw, Will Travel!
posted
How accurate are these formulas. I tried to do some reverse calculation with the specs that came with my subs and I am getting number that seem to be way off. Like box sizes at 4.3cu. ft. compared to the 1.25cu.ft. the book has or port length of 40 compared to 10.24. Or are these real generic in nature and not taking in some factors that the companies are.
posted
Vega Vega 104 (10") box vol= 1.25 port dia.=3 port length= 10.27 displacement of driver= .07cu.ft. tuning freq.=35Hz This should be all the stuff you need for the formula dukk has.
posted
Well Using Dukks Formula.... ******************************************** Port length = [(8466.4 * R^2) / (Vb * Fb^2)] - (1.463 * R) ********************************************
8466.4 * 1.5^2 is 19049.4
Divide that by: (Vb * Fb^2) 1.18 * 35^2 is 1445.5
19049.4 / 1445.5 is 13.1784158
Subtract the last part: (1.463 * R) 1.463 * 1.5 is 2.1945
And you should get 13.1784158 - 2.1945 = 10.9839 inches long for a port length.
Which is about right. You have to remember their is some play in the numbers do to the bracing volume not being accounted for the speaker manuf. gives you room for that which you are not putting in the formula. You can if you want to. Just subtract it with the speaker displacement. You will get slightly different numbers depending on how you round the decimal.
Anyway my guess is that you used 3 as the R number insted of 1.5
Hope this all helped.....
------------------ ******************* Founder: Street Sounds Car Audio Club ******************* If It Don't Read 150+ it Ain't Loud......
[This message has been edited by audioextreme (edited 06-18-99).]
Posts: 289 | From: Howell, MI | Registered: May 1999
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posted
The Av is the cross sectional area of the port. And Lv is the length of the port.
Dukks Formula is a lot harder to goof up.
It is my experience that when you get radicals and powers people punch them in wrong. And get confused...
And you asked about using multiple ports. In your case do as dukk said.
If you ever want to use lets say two ports for each sub. Then do the following for each sub. If you want to use 2 ports cut the volume in half. Three ports cut the box volume into three and so on. You will notice that the more ports you add the length gets longer this is to account for frictional losses. Many free programs just use the total area of the multiple ports and the overall box volume which is incorrect...
------------------ ******************* Founder: Street Sounds Car Audio Club ******************* If It Don't Read 150+ it Ain't Loud......
[This message has been edited by audioextreme (edited 06-19-99).]
Posts: 289 | From: Howell, MI | Registered: May 1999
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