# box specific for spl comps..



## jukebox

hi guys, i would like some help with porting my box please, i hope this is the right section, well im sure the spl heads are frequenting here so i suppose it is..

sorry about the long post, but i wanted to add all relevant info in the first post, as the comp is this sunday and id need to get cracking with this... all help , info or advice is great, im a total noob at this... 

i have built the box to the biggest i could fit in my hatch
the box specs are, 

top depth is 260mm
bottom depth is 400mm
width is 935mm
height is 450mm

these are exteranl demensions, and im using 18mm mdf.. 
either side of the box can be used as the front, but the sloped side was designed to butt upto the rear seat, but it would be ok either way.....

the subs are jl audio, 12inch w3'v3-4ohm svc and i have 2 of them going in the box.. its one box, with no divider..

the amp is a jl audio 1000/1, it is a regulated power supply down to 11v... so it gets a constant 1000wrms...

how should i port this box, should i do slot ports, or round ones so i can try and tune it better later simply by shorting or lengthening the extendable sleeve around the actual port itself.. should i port out the top or front where the subs are mounted.. any help is very appreciated, the comp is this sunday so im pressed for time,lol.. 

so could some one tell me the measurements i need to use to do the ports please, either port design is fine by me... 

the car is a daihatsu charade 4 door hatch back.. im not sure if this is relevant, but i just hit 139.8 with two sealed boxes, they were 35 ltrs each, the peak frequency was 52 hz if that means anything for porting the box now..

thanks... BRAD.....


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## Oliver

Use WINISD or similar box building program to model your subs and design the best "ported" enclosure you can.

http://mobile.jlaudio.com/support_pages.php?page_id=165

port it tuned near your resonant frequency [ 45 - 48 hertz ].

keep the system as cool as possible until it is time to burp it [ don't play it until they have the mic in your vehicle ]

forum for SPL ~ http://forum.soundpressure.com/

G'luck !


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## Ed Lester

jukebox said:


> hi guys, i would like some help with porting my box please, i hope this is the right section, well im sure the spl heads are frequenting here so i suppose it is..
> 
> sorry about the long post, but i wanted to add all relevant info in the first post, as the comp is this sunday and id need to get cracking with this... all help , info or advice is great, im a total noob at this...
> 
> i have built the box to the biggest i could fit in my hatch
> the box specs are,
> 
> top depth is 260mm
> bottom depth is 400mm
> width is 935mm
> height is 450mm
> 
> these are exteranl demensions, and im using 18mm mdf..
> either side of the box can be used as the front, but the sloped side was designed to butt upto the rear seat, but it would be ok either way.....
> 
> the subs are jl audio, 12inch w3'v3-4ohm svc and i have 2 of them going in the box.. its one box, with no divider..
> 
> the amp is a jl audio 1000/1, it is a regulated power supply down to 11v... so it gets a constant 1000wrms...
> 
> how should i port this box, should i do slot ports, or round ones so i can try and tune it better later simply by shorting or lengthening the extendable sleeve around the actual port itself.. should i port out the top or front where the subs are mounted.. any help is very appreciated, the comp is this sunday so im pressed for time,lol..
> 
> so could some one tell me the measurements i need to use to do the ports please, either port design is fine by me...
> 
> the car is a daihatsu charade 4 door hatch back.. im not sure if this is relevant, but i just hit 139.8 with two sealed boxes, they were 35 ltrs each, the peak frequency was 52 hz if that means anything for porting the box now..
> 
> thanks... BRAD.....


is this car like yours?









if so, your box is not optimal for SPL.

the sub choice is not great for SPL but you can make them work.

First thing is that you want to do away with the slant. Then you want to fire the sub up. and since there is not much room between the back seat and the hatch, you want to fire the port up too.

you should do a rectangular box with the ports in the center of the subs.

Total box size shouldnt exceed 304.8mm from rear seat to hatch.
380mm in height.
and about 935mm in width is OK.

you may have to reduce internal volume when tuning for frequency.

Use at least 1, 8" flared round port. or a flared rectangular port in the middle.

With those subs, and that power, you can possibly achieve mid 145 dB on a Term lab meter.
If you did a 3000w or 4000w amp and louder subs like T3 TSS or DD 9900, then you may do 153 dB or higher.

I will post a pic of a Panda if I can find one, thats the style box you want.


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## jukebox

ok, thaks for that info, and the panda pic would be great....i was reading something about these cars the other day... it was about dd subs and herts subs,, and an argument between the two sales reps...lol... 

but i agree, the subs are far from good for spl, it is my daily driver, i will if i get hooked buy some better subs for this purpose, and my bro is a shop fitter so mdf is free, so i can build a new box easily if need be..

thanks for all the info so far, and any thing else you can add...

thanks


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## jukebox

its hard for me to measure the actual area i have to work in cos the ninstall is in, but a freind has an identical car so ill use his when i get a chance too.... but if i only go 380 high, i can get the 308.4 depth, and the width aswell.... so with those meaurements, and both subs facing up, ill port it in the centre, and use the port size you mentioned.. ill let you know how i go, and what db i hit..


oh and that car is not like mine, i think thats an earlier model charade, or a honda civic maybe...

BRAD....


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## Oliver

box for 2 ~ 12W3V3 4 ohm

with 8 inch round vent tuned to 45 hertz...

tuned to 45 Hz


liters 107.6


mm 18 thickness

mm 518 width

mm 807 heighth



mm 254 depth top

mm 407 depth bottom


mm 290 length of vent

mm 203 diameter of vent

vent mach 04


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## jukebox

IM SO SORRY MATE, I APPRECIATE THE NUMBERS YOUVE JUST SUPPLIED, BUT DUE TO RESTRICTIONS IN THE SPL COMPS, I CANT GO ABOVE WINDOW HEIGHT WITH MY BOX, IT MUST ALSO BE KEPT BEHIND THE REAR SEAT SO I CANT EVEN LEAN THE SEAT FORWARD AND BUILD A SQAURE BOX TO ALLOW FOR THE SLANTED REAR SEAT...

SO THAT HEIGHT WILL NOT WORK MATE, EVEN IF I SWITCHED THE WIDTH AND HEIGHTS AROUND I STILL WOULDNT GET AWAY WITH IT..

THAT WOULD MEAN ID BEING GOING INTO THE NXT CLASS, WHICH ALLOWS SEPERATE MONOS FOR EACH SUB, AND I THINK THERES A HEAP OF OTHER THINGS THAT DONT WORK IN MY FAVOUR..

SORRY, I REALLY APPRECIATE THAT, AND IT MAY COME IN HANDY ANY WAY, BUT I REALLY JUST NEED TO KNOW IF I CAN PORT THE DEMENSIONS IVE SUPPLIED... I KNOW ITS FAR FROM IDEAL, BUT ALL I CAN DO FOR THIS COMP..


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## Oliver

Updates ? Jukebox


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## tard

WIN ISD it's not worth a shiznit in the real world.

you should realistically achieve 145 on the TL with that amp and those subs. i've seen that done in a blazer with the same equip and the box wasn't even maximized.


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## Hispls

Can you extend ports outside the box above window-line? That could save you a cube inside the box.


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## jukebox

nah thats not allowed.. im thinking of buying 1 spurpose sub, making a box for that, and then running 1000rms on the 1 sub.... its win win... bigger box, lower class of comp, and more power to one sub


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## ChrisB

What about finding the resonant frequency of the vehicle that works best with cabin gain, tuning your port to that frequency, then burp a test tone at that particular frequency?

I remember before the days of the Termlab where people would build bandpass boxes that were tuned to the frequency that the old (AC??) mic was most sensitive to. I knew one local guy who designed several one note wonder bandpass boxes for the old school SPL competitions based on the fact that he knew what frequency to tune it at.


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## jukebox

yeah, ive been told that before... i suppose its a good idea... my car hit 139.8 with 2 sealed 12s, and 500rms on each sub..there jl audio w3s and they arent known for there spl numbers..lol.. i think i would have more trouble building the bandpass then the ported box,lol

so, anyways..

im hopeing to hit 145-ish with the right box and sub combo.. a freind hits 143db with the same subs in a station wagon with these subs, and a ported box, the box is 2 cubes each sub though and i dont really have room for that..

next time i have my subs out, or i at a wreckers, ill measure the exact room i have to build the biggest box possible and post the measurements.. the ones gave and the box i first built were estimates, i may be able to get another 10 ltrs of volume or more yet.. 

thanks for the reply/feedback.. much appreciated mate..


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