Ok well I have a few questions when it comes to the proper way to decide on the amount of port are that you should use when it comes to designing ported boxes and 4th order enclosures . I have been hearing mixed " opinions " when it comes to picking the amount of port area needed . The most common way I have heard about is staying in between 12 - 16 sq inches of port per cube. Which in my opinion is not a very accurate way to design an enclosure . The other way that have been told is that you adjust your port area according to the xmax or linear max on your woofer. Which sounds to be a more accurate way in to better suit a build. So if anyone knows the actual proper way to determine port are plz inform me.

Thank you ,

Christopher Murray

Welcome! Interesting question, I am tuned in

!

Yes the proper way is xmax and tune frequency.

http://www.carstereo.com/help/Articles.cfm?id=31

I would model the system and try to keep the port velocity to acceptable speeds.

You will have to search for what is considered acceptable, different numbers depending on different people.

Also keep you eye on whether it's measured in metric or standard in whatever program you're modeling the system in.

download WinISD, add a new driver, then under a new modeling project you can see the calculated vent mach.

Edited May 1, 201213 yr by stefanhinote

I wrote a basic article on designing an enclosure with a port: http://blog.stefanhi...rted-enclosure/

About half way it mentions port area and port speed, then links to: http://blog.stefanhi...ding-vent-mach/

With the formula shown, if your using multiple drivers, then multiply everything in the square root by the amount of drivers.

I also made an app that does the math for you, just plug in the T/S specs: http://portsgalore.s...om/?do=ventmach

Alternatively, and rather easily: download WinISD, add a new driver, then under a new modeling project you can see the calculated vent mach.

Hope that helps.

Nice website and calculator. However, when I calculated vent mach I get 0.11 while winISD gives me 0.04. I checked the T/S in winISD and they are correct. I wonder why there is a large discrepancy? Could winISD be that inaccurate?

On a side note, I used the minimum port area calculator, and for a 12" driver with 21mm Xmax and 31.5Hz tuning it recommends 4 x 4" aero ports. That doesn't even seem feasible to fit 4 x 4" tubes in a box for a single 12".

I am just trying to understand some of the calculations because I am currently trying to design a ported box.

I wrote a basic article on designing an enclosure with a port: http://blog.stefanhi...rted-enclosure/

About half way it mentions port area and port speed, then links to: http://blog.stefanhi...ding-vent-mach/

With the formula shown, if your using multiple drivers, then multiply everything in the square root by the amount of drivers.

I also made an app that does the math for you, just plug in the T/S specs: http://portsgalore.s...om/?do=ventmach

Alternatively, and rather easily: download WinISD, add a new driver, then under a new modeling project you can see the calculated vent mach.

Hope that helps.

Nice website and calculator. However, when I calculated vent mach I get 0.11 while winISD gives me 0.04. I checked the T/S in winISD and they are correct. I wonder why there is a large discrepancy? Could winISD be that inaccurate?

On a side note, I used the minimum port area calculator, and for a 12" driver with 21mm Xmax and 31.5Hz tuning it recommends 4 x 4" aero ports. That doesn't even seem feasible to fit 4 x 4" tubes in a box for a single 12".

I am just trying to understand some of the calculations because I am currently trying to design a ported box.

WinISD is accurate. What driver are you using, and how much power?

Edited May 1, 201213 yr by stefanhinote

WinISD is accurate. What driver are you using, and how much power?

IA Lethal Injection 12" D2, 750wrms, and I plugged in 29 for FS, 48 for VAS, 0.61 for QES, 31.5Hz tuning and 2 x 3" aero ports.

WinISD is accurate. What driver are you using, and how much power?

IA Lethal Injection 12" D2, 750wrms, and I plugged in 29 for FS, 48 for VAS, 0.61 for QES, 31.5Hz tuning and 2 x 3" aero ports.

Use WinISD, it calculates port area for multiple ports differently. I need to find why, and update my page.

4 4" ports is ludicrous.

I used a single 6" aero on mine and worked great.

I built a second enclosure with a slot port with similar PA and works great as well.

Duran posted this link awhile ago and is a great read on Ports.

http://www.bodziosoftware.com.au/PORTS.pdf

Well I just tried using http://www.carstereo.com/help/Articles.cfm?id=31 and its telling me to use 366.38 inches . What are they meaning by this ? Is this the recommendation towards the amount of port area ?

I don't know what you did.

I put in 1 12 22mm xmax 31.5hz and got 36.24.

And yes that is port area. Not to be confused with port area per square foot. That is the port area in relation to the enclosue size.

Ok well i put in the sub size (15) . Then I put in the amount of woofers (2) . Then I put in the xmax of my subs (40mm) . Then i put in the tuning which is 45 and it came up with that number

Ok well i put in the sub size (15) . Then I put in the amount of woofers (2) . Then I put in the xmax of my subs (40mm) . Then i put in the tuning which is 45 and it came up with that number

that 40mm xmax, is that total or each??

That is each