BeAlLsTaR13
10+ year member
CarAudio.com Veteran
mines 60 square inches of port with 4.0 cu ft. tuned to 35hz... but thats for 2 12" subs
general rule is at least 15 sq inches of port area per cubic foot
Buck
5,000+ posts
little alien on campus
That should be fine. A big port imo would be best for SPL.
bigger/better to a point, after that it will be just negative, many decrease their dbs when they go with to big area, the box will have to much efficiency and the sub will not handle the power, just like when you put a sub open air,
i would say that is to much portarea for a single 12"
go with a 6" aero and you will see 150dbs //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif
the smaller the port to faster it will compress. I have software that can model that and you can literally watch your dB's drop as you make the port smaller (keeping the tuning the same) under high voltage. You really want as big of a port as possible.
sjobas,
what you are suggesting is completely incorrect, What happens as you increase the port area is these guys don't re-measure the impedance of their system and they miss the tuning and bottom out their driver. You need to always burp at the coupling region where the drive pulls the maximum amount of current from the amp and the back EMF drops to its absolute minimum. This is actually not the most efficient point of the system, in terms of power / SPL, but it IS the most efficient point in terms of active driver displacement vs SPL and because the xmax is always the limit for short term burps - we must burp through a port.
using a port calculating software just based off length, area and volume is inaccurate, and especially inaccurate, and for high voltage where you see potential port compression in conjunction with driver non-linearity which both alter the impedance of the system and push the tuning higher. As you increase the power to your driver, you actually the raising the tuning of the system in most cases. So what also could have happened is these guys you speak of increase teh port area and then re-burped at the same power level as before. Perhaps before they compensated for this shifting and perhaps in the new system, it did not shift as much so they were above tuning and they could bottom out. In ether case, if you're not on the ball with 5000 or so watts, you could really damage your driver.
Now, about port compression vs non port compression - as you reduce the port area for a given high voltage what you are doing electrically is reducing the impedance generated from the resonance of the port - if you continue this trend and make the port smaller and smaller then the system slowly becomes a 2nd order system and the port pretty much no longer makes any SPL - meaning you have a sealed system. So what you suggested about a port too big really make no sense at all and quite the opposite is true.
If i was competing with a 12, i might even try 100 square inches, and i would probably do a more elaborate system than a standard 4th order, possible a 6th or 8th and maybe even couple that to a horn that phases my front and rear waves.
sjobas,
what you are suggesting is completely incorrect, What happens as you increase the port area is these guys don't re-measure the impedance of their system and they miss the tuning and bottom out their driver. You need to always burp at the coupling region where the drive pulls the maximum amount of current from the amp and the back EMF drops to its absolute minimum. This is actually not the most efficient point of the system, in terms of power / SPL, but it IS the most efficient point in terms of active driver displacement vs SPL and because the xmax is always the limit for short term burps - we must burp through a port.
using a port calculating software just based off length, area and volume is inaccurate, and especially inaccurate, and for high voltage where you see potential port compression in conjunction with driver non-linearity which both alter the impedance of the system and push the tuning higher. As you increase the power to your driver, you actually the raising the tuning of the system in most cases. So what also could have happened is these guys you speak of increase teh port area and then re-burped at the same power level as before. Perhaps before they compensated for this shifting and perhaps in the new system, it did not shift as much so they were above tuning and they could bottom out. In ether case, if you're not on the ball with 5000 or so watts, you could really damage your driver.
Now, about port compression vs non port compression - as you reduce the port area for a given high voltage what you are doing electrically is reducing the impedance generated from the resonance of the port - if you continue this trend and make the port smaller and smaller then the system slowly becomes a 2nd order system and the port pretty much no longer makes any SPL - meaning you have a sealed system. So what you suggested about a port too big really make no sense at all and quite the opposite is true.
If i was competing with a 12, i might even try 100 square inches, and i would probably do a more elaborate system than a standard 4th order, possible a 6th or 8th and maybe even couple that to a horn that phases my front and rear waves.
strange, ive heard that from many that competes, and many was thinking same " more port must means more dbz" but they went the wrong way.. and i have never seen any with like 3 and a half 6" aeros for a single 12" sub, that must be crazy in a ordinary ported..
Supergumby5000
5,000+ posts
Project: F350 begins...
I wish i had the problem of having too MUCH port area //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif
sounds like a good problem to have, lol
sounds like a good problem to have, lol
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