I want to go ahead and put two subwoofers of the same make/model into a ported box. Do I calculate the port of the enclosure the same as for a single subwoofer, except for the obvious increase in enclosure volume considering there are 2 subwoofers. Or is there some other things I have to consider for this to be right? thanks
The port size will be the same as it depends only on the size of the enclosure. However with two subs sharing the same airspace you can more easily have issues with port noise as the amount of air being moved is doubled. Use the largest diameter port you can make work in your enclosure.
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Support the12volt.comIs there a specific formula for finding the minimum port diameter?
Yes. This from the Subwoofer DIY Page:
Minimum Port Diameter
To calculate the minimum diameter of the port required to prevent port noises, you will also need to know the following:
Xmax = maximum linear displacement (mm)
Dia = Effective diameter of driver (cm)
Np = number of ports
Calculate the minimum port diameter from the following equations:
Sd = pi*(Dia/100)^2/4
Vd = Sd*Xmax/1000
Dmin = 100*(20.3*(Vd^2/Fb)^0.25)/Np^.5
where,
Dmin = minimum port diameter (cm)
Note: You CAN use ports that have a smaller diameter than that given by the equation above, especially if the ports are flared at both ends. However, at higher volumes, you may notice some port noise caused by the air rushing through the ports.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Me and Jethro Clampett would have to stick our brains together and cipher for pert' near a coon's age to come up with an answer using those formulas.
If that math hurts your head like it does mine, here are easier ways to find the answer.
1. The manufacturers of some reputable subs will give you that information in the manual in the section that describes recommended enclosures.
2. There are online calculators that have formulae plugged in that will do the math for you.
https://www.carstereo.com/help2/Articles.cfm?id=31
https://www.mhsoft.nl/spk_calc.asp
3. There are box-building software programs that will enable you to see a graphic representation of port noise with a given opening size and power applied. See the featured sticky subject on WinISD above for info on two such programs that are free to use.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
stevdart wrote:
Me and Jethro Clampett would have to stick our brains together and cipher for pert' near a coon's age to come up with an answer using those formulas.
If that math hurts your head like it does mine, here are easier ways to find the answer.
1. The manufacturers of some reputable subs will give you that information in the manual in the section that describes recommended enclosures.
2. There are online calculators that have formulae plugged in that will do the math for you.
https://www.carstereo.com/help2/Articles.cfm?id=31
https://www.mhsoft.nl/spk_calc.asp
3. There are box-building software programs that will enable you to see a graphic representation of port noise with a given opening size and power applied. See the featured sticky subject on WinISD above for info on two such programs that are free to use.
The second link does it work for me (https://www.mhsoft.nl.spk_calc.asp), is it working for you guys?, or is it just me?
It's not up right now. The first link will give you a good calc. And, actually, I use a lot of the calcs in the second link but I'm not sure if it has a min. port diameter calc included.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.