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mendon mafia
05-01-2009, 12:57 AM
So i found this calculator for minimum vent area:

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

How accurate is this calculator? anyone use it before?

I used it for my 12" alphas (assuming ~25mm xmax, not sure what it really is) and it gave me a number of almost 50 inches of area per sub for minimum!

I was planning on using about 50-60 inches for each sub but i thought i was going big.

most people use 16 inches per cube right? by that formula i only need 32 inches each but i wanted to go bigger for more spl and sq (less vent noise) but if 50 is the real minimum i should use then i may go even bigger possibly 60-70 inches for each sub. but i dont want to go so big that the subs are basically in free air.

DBBOOM
05-01-2009, 01:03 AM
It's only as accurate as the info entered. I've used it many times with good results, but i entered the actual Xmax.

mendon mafia
05-01-2009, 09:32 AM
well the x max value on rd's website is only 16 mm. i know for sure the sub moves farther than that on 2kw. its got a long *** coil thats why i assumed 25 mm. my old sx's were 22mm and these alphas are only more bad ***.

even using 16mm i still come out with 32 inches per sub which would e exactly following the 16 inches per cube rule.

mazdakid
05-01-2009, 10:49 AM
What's wrong with the 16 per cube? Usually people try to get 12-16 per cube, so you'll have more than enough port area

Immacomputer
05-01-2009, 11:09 AM
well the x max value on rd's website is only 16 mm. i know for sure the sub moves farther than that on 2kw. its got a long *** coil thats why i assumed 25 mm. my old sx's were 22mm and these alphas are only more bad ***.

even using 16mm i still come out with 32 inches per sub which would e exactly following the 16 inches per cube rule.

Xmax is NOT the same thing as max throw. Their calculator is pretty useless for determining port area. The enclosure design (and port profile), power used, and motor strength are far more useful in deciding port area than xmax. The port will have the most noise (and the most movement) around tuning and the sub should not be anywhere near xmax or xmech (what you're describing) around tuning unless you're running a ridiculous amount of power. And if you are approaching xmech around tuning, you're going to rip the sub apart above tuning.

The 12-16/cubic foot rule is equally as retarded but for the most part, it will keep vent velocities low enough to be noise free. The alphas should be fine with about 30-35 in^2 of port area.

mendon mafia
05-01-2009, 03:44 PM
Xmax is NOT the same thing as max throw. Their calculator is pretty useless for determining port area. The enclosure design (and port profile), power used, and motor strength are far more useful in deciding port area than xmax. The port will have the most noise (and the most movement) around tuning and the sub should not be anywhere near xmax or xmech (what you're describing) around tuning unless you're running a ridiculous amount of power. And if you are approaching xmech around tuning, you're going to rip the sub apart above tuning.

The 12-16/cubic foot rule is equally as retarded but for the most part, it will keep vent velocities low enough to be noise free. The alphas should be fine with about 30-35 in^2 of port area.

thanks a lot! Great info!

im gonna shoot for 60 inches of port area, 2 cubes net and 35 hz for each sub then.

SicAudio
05-02-2009, 04:35 PM
he just told you that 30-35 is more than enough and your still going to double it?

mmouse57
05-02-2009, 07:08 PM
Its not very good i used winisd for a box i made for 3 w78 jl's tuned at 33ghz and ended up wiht a port tuned that was 19.25in long via winisd i then in car tuned the port and found for 33hz i needed 21.125in port length.

with the parameters entered in that proggy for same speakers/tuning freq and port size they state 15.5in long which would have tuned my box to like 40hz so i deff would not use that

mendon mafia
05-02-2009, 08:41 PM
he just told you that 30-35 is more than enough and your still going to double it?

More port = more output. As long as it not to big. i dont think 60 will be to big but i dont know for sure. my friend runs a single 10 that has more port area than cone area and it gets mad loud on only 90 watts he swears to make the port as large as possible.

mendon mafia
05-02-2009, 08:43 PM
Its not very good i used winisd for a box i made for 3 w78 jl's tuned at 33ghz and ended up wiht a port tuned that was 19.25in long via winisd i then in car tuned the port and found for 33hz i needed 21.125in port length.

with the parameters entered in that proggy for same speakers/tuning freq and port size they state 15.5in long which would have tuned my box to like 40hz so i deff would not use that

that program accounts for slot ports which are shorter than normal ports. winisd does not.

im not using it for the tuning/length anyways. im using it just for port area.

dappa5
05-02-2009, 10:24 PM
dude srry it took me so long to get this to you http://sketchup.google.com/3dwarehouse/details?mid=e12ab4c2b399f57753e3b43bd47066d4
it is 2+ ft3 before port and sub displacement I only made it with 40 in 2 per enclosure but you could bump it a little (like 3" totaling 48 in2) too much will take away from volume (bad) since it's my math I wouldn't garantee it but this set up should be tuned around 37-38 hz:D:D:D:D

p s real simple to build too :crazy::crazy: