ported or sealed

i have two 12inch kicker comp vr in a sealed box. each speaker sits in 3cu.ft. seperate chambers. my question is this should i leave  the speakers in a sealed box or should i vent them. i'm looking for spl. if i port them what size vent and length should it be. and what would be the ideal tunning frequency of that particular box. each kicker is getting about 300 watts rms at 4 ohms. via two coustic amp 460s. an amp for each speaker. any imput or comments is greatly appreciated. thank you.gcorrea

http://www.diysubwoofers.org has a lot of information re: port calculations and the positives / negatives of porting.  There are also a variety of enclosure design programs available on the web that allow you to plug in your speaker's t/s parameters and see the resulting frequency response curve for a given box / port design.  I've personally never built one a ported box, so that's all the help I can offer.  Good luck!New Project: 2003 Pathfinder

After a little investigation, on a 12 in Kicker Comp VR,   I found that you're making a ported box will be one helluva fun chore.....Kicker doesn't recommend the standard PVC type port box, but a slotted port box.....fun fun....    Here are the dimensions kicker recommends building your "VENTED" box;

Compact (minimum enclosure volume): 1.75 cu/ft; 2.5" x 12.5" port opening; 20" port depth

SQ (maximum enclosure volume): 2.25 cu/ft; 3" x 12.5" port opening; 20.5" port depth

Now those are some hefty ports....

As for sound:    ported boxes aren't ideal for listening to Black Sabbath's greatest hits.   I have a ported box now,  and it's perfect for listening to lil' john and waking the neighbors,  but if you want all around performance, stick with the sealed box......to my ears, it gives off a better quality sound, for all sorts of music tastes........plus the bass is a lot sharper.

Also, usually subs in ported boxes need lower power amps.....or problems may arrise.........so i read.....

~wayland

Oh, don't let me forget,     kicker also thinks the IDEAL size for a SEALED enclosure is 1 cubic foot,   although they have sizes as large as 4.6 cubic feet listed too.........~wayland

i've been able to down size my box to 2.53 cubic feet. thats including displacement for a 2.5 inch port and the speaker itself. using the port calculator a port 2.5inches by 7.578 inches long should give me a tunning frequency of 25 hertz. i'll wait a while for some comments and some more advice before i start cutting any port holes on the box. thanks for taking time in answering my questions.gcorrea

You can port the enclosure any way you see fit. There is no differance in slot porting or PVC porting. For an enclosure program I would reccomend the freeware WinISD Pro at www.linearteam.org . It is not the very best program, but it is close, it is free, and it is simple enough for new users. As far as porting the driver, I like to use the drivers QTS to make that determination. QTS takes both driver motor strength and the suspension into account. QTS levels of at or below .45 can be ported safely. The motor needs to be strong to overcome the massive pressures in a ported enclosure. As far as a ported driver not doing well with Sabbath, or not being sharp... I would suggest you have not heard a properly designed ported enclosure. I am willing to bet you my Brahma in it's ported enclosure is quicker, and more tonally correct than any sealed driver you have ever heard, aside from maybe a 10W7 which will be s shade quicker. My music of choice includes old school hard rock and metal. It is actually more of the job of the components to be "sharp" anyways. Punch is midbass, not subbass.

No. It will suffer terribly in a ported enclosure. It will have no bottom end. The motor is simply not strong enough to overcome the suspension and the enclosure's internal pressures.. You need to realise the pressures in a ported enclosure can reach 2 times the pressure of a sealed enclosure at the tuning frequency of the enclosure. At this point, the woofer and incoming air at the port are 180 degrees out of phase. What that means is, the air is coming into the enclosure creating pressure, at the same time the woofer is moving inward adding pressure to that already pressurized air To make this long story short, I highly reccomend against it.