Sub Box Venting

First time of nthe forums... Found a TON of usefull info here!  Many thanx!

Well here's the backround.  I have a pair of X-Site 1000w RMS 12" Subs  I Presently have them in a Sealed box  I built and they sound pretty good.  But I would like to make a second box for use at the local car show which does some SPL contests.  Not planning on winning anything here, just trying to see what I am capable of getting these subs to do.  Currently in the sealed box we tested them to reach 123.7db using test tones.  I have a friend that builds boxes and uses a single 15 to reach numbers in the 147db range.  Now I know these most likely will never reach those numbers but he tells me to go with a vented box.  So, I look up the info on a vented box and find this: Airspace 2cu Ft,  Port 4"x8.5" long.  I showed him this and he says that is a ported box that a slotted vent would produce better numbers and I call the company to get the info.  They tell me there is no difference?  Anyways they gave me the same numbers from the book and my buddy says, that wouldn't work for my intentions.  Of course he says had I bought some Audiobahn's or MTX, etc I wouldn't be having this problem.  So my question is, how/where could I find or figure out how to make the box?  Another friend who I get most of my equipment from says to stop on by and we'll just try a few slotted vent boxes he has in the shop... But I would never know if I am getting close to a peak db with them?

Yeah that's why I am planning on building my own.  The sealed box sounds great, but I want to see what kind of SPL I can get out of those 2 12's  My buddy has a demo pair I can get as extras and if I can get the info on the speakers I may get them to try making one of those 6th boxes just for experimenting.  but for now I am trying to find the car resonance thing.  It sounds like that is where I should start

Yeah I am thinking of that exact box.... But I called Audiobahn (maker of xsite) and they were able to give me the following...

Qes: 0.57

Qms:4.93

Qts:0.51

Fs: 29.8

Vas: 74.6L

Mms:

BL: 8.623dm

fLe:

Cms:

Dd:

KLe:

Rms:

Le: 1.2mh

Re: 3.9

Sd: 483 cm^2

Xmax: 16mm

Xlim:

Hc:

Pe:

Hg:

no:

Znom:

USPL:

SPL:

So, according to the help file, alot of the numbers I am supposed to enter in WinISD are not given, although the final calculated numbers are.  I would not be too worried in a standard vented box, but with the 6th order I am a bit concerned about it pumpin out the right specs.  I guess MDF isn't that expensive I could always try it and see how it goes..... One other question about it..  I didn't notice a place to put size of mdf you are using into the calculations.  With a box that is appearently as Particulate as a 6th order, I am guessing I am on my own to figure out the amount of air space the MDF is taking up and add air space accordingly.  One other note I noticed aznboi talked about finding the resonate freq of my car.  How do I go about doing that?  Will that change greatly with a box installed in the trunk?

According to those parameters, that sub has an EBP of 52 and is an ideal candidate for a sealed enclosure.  But it's certainly worth modeling it out and perhaps building a trial box to see if you get the louder SPL you are looking for.

You will not likely get more specs than given already for that sub, but you can use the minimum Fs, Qes, Qms and Vas to work with in WinISD.  The fact that you have, also:  Bl, Xmax, Le, Sd, and Re is a plus.  You should be able to model it accurately as long as those numbers are fairly accurate for the particular sub you are working with.

Keep in mind that the program calculates net air space.  Think internal volume, not external size.

Use your current sub and sound system along with a test tone CD of frequencies stepped up through about 40 Hz to 80 Hz.  This is where cranking it up will come into play, so use some earplugs.  You'll find the most sympathetic resonance of the car will be strongest at one frequency, and you'll feel it in the car's sheet metal.  An SPL meter is a plus for figuring this out, too.