building box for l7’s

looking for some suggestions on boxes, for 2 kicker L7 12's   they are dual 2 ohm.     This is going to be for SPL purposes only, if any of you know me you know I wouldnt run L7's on the street.

Again SPL only.     I am debating between seperate chambers or a large single chamber for both subs     Right now I am running thoughts of between 5-6cuft total.   This will include the port.    The 5 cu ft will have a port of 5x15x20   giving me a tuning of about 38hz.       I might raise the tuning a little, but the car we are using really likes low tuning for SPL.

Again any thoughts or suggestions would be great

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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place

Ahhh, the fesy. Low tuning? If i remember right, res freq was in the mid 50s on that. I beleive it got the nickname "Panda" from SPL compeditors. Anyways, i would go for around 5.5 cubes after displacement, do a common chamber box, use aeroports (or VERY smoothed and rounded slot port). Use 3/4" or 1" MDF with a layer or two of fiberglass resin. Dont fear aerodynamic bracing, as it makes the differance between winning and loosing ;)

Is this going to be for showing off or competing?

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04 dodge neon SXT
(2) Oz Audio Matrix Elite 12"s sealed in 4 cube fiberglass enclosure, powered by HiFonics BX1605D
Oz Audio Matrix 180cs 6.5" component set power by HiFonics ZX4000

this is going to be going into the civic for a few shows.    That car seams to like the low frequencys.

I was planning on a common chamber around the range you were talking 5-5.5 cu ft     More then likely going to go with a slot port, I will go with your suggestions of rounding the port, I have seen some increases that way, but where gonna test the box before then try again rounded.

We are going to go with 2 diffrent box designs.   One with subs and port up, the other with sub up port back.     having alot of trouble getting this car to get to the #'s we want to see

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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place

When you say your car likes lower numbers, what frequency are you talking about? Saying 38Hz tuning, im assuming 46-50Hz? How do you know what your car's resonant frequency is?

That would be where i would start first. It seems that you may be tunning too low. My neon has two peaks. First is at 48Hz, secondly at around 57Hz. Since it takes less power to play 57Hz, it would be wiser to tune to that. Also, a subwoofer responds MUCH louder when porting higher, so 57Hz would be ideal to produce my resonant frequency. so taken that example, id figure out your next best number and stick with it ;)

round the ports the best you can. More and more dBdrag compeditors are finding this out. Its like port+polishing your intake... smooth and no restriction. If you want to get REAL picky and get down to adding a few .1 Hz. fiberglass and do a smooth sand through out the entire box to make it smooth as possible inside so the turbulance is minimal. Just remember, aerodynamics inside the box is the key along with strength. If im to guess which would be loudest in your ford, i would say facing back with ports firing back as well... Im sure you can find a few SPL installs on sounddomain or termpro using your type of car and get some ideas.

Hope that helps.

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04 dodge neon SXT
(2) Oz Audio Matrix Elite 12"s sealed in 4 cube fiberglass enclosure, powered by HiFonics BX1605D
Oz Audio Matrix 180cs 6.5" component set power by HiFonics ZX4000

Again we are not using the ford for this project.      We are using the Civic Coupe.      Yes there are 2 peaks 42hz, and 54hz.      we have tested this numerous times using a 1 cuft sealed box and diffrent subs.      At 54hz we only hit .1db higher.     Yes a gain but not much.      We were tuning to 34-36 hz depending on the sub to hit our 42hz mark.     
with these subs it looks as we will be able to tune to about 38 hz to get around our 42hz in cab.    Only time will tell on this one.      Since you use a neon, what way do you fire your subs/ports.     
We have fired in before but the car didnt really resond well to that,    and finding that there is a sweet spot that when we back the box up towards the tail lights we can gain about .3db      so the new box will have to be moved back and forth to find the spot.
Should be interesting

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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place

coupe? There ya go!

so a trunk in other words. The best way to hit hard ON THE METER (definatly not to the ears/at the headrest) is to face them foreward and seal it off from the trunk. I, myself, have mine facing upward, in a sealed box as this is my SQ vehicle (until i can afford doing my SPL rig)....

www.sounddomain.com/id/nodestiny

Why are you trying to hit the lower 42Hz mark? Though with sealed boxes it will show with a .1 dB gain, thats not the point. goto www.linearteam.org and get WinISD. Get your subs programed into there, start a new project, select the sub, select quantity of 2, vented, and it will come up to the main screen. Then, pick home many cubes you have in your box. Tune on box to get its peak at 42Hz. Then, do everything again (start a new project, leave the 42Hz peak box open though) and with the new one, find the peak at 54Hz. Ill bet youll gain a good 3-4Db just by changing over your attemped frequency peak. If the point is just to bump to the meter, go for the higher tuning.

Just make sure that when you face the subs and port foreward, SEAL SEAL SEAL from the trunk. Seal off the best you can. There are trunker's hitting in the 150's doing this (of course, with a ton of power, but people with 2 10"s can do it).

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04 dodge neon SXT
(2) Oz Audio Matrix Elite 12"s sealed in 4 cube fiberglass enclosure, powered by HiFonics BX1605D
Oz Audio Matrix 180cs 6.5" component set power by HiFonics ZX4000

Jeff, any chance you can give up more room for the enclosure so that you can get it to 3.25 ft^3 plus port volume for each sub?  (...and rework the port size for two subs...)  This response shown in the Kicker MANUAL looks like a good one:

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Sure enough, L7s LOVE airspace. Biggest airspace hogs in terms of subwoofers that i have ever seen. The bigger the box you can get, the better. And as i have said, WinISD will help you model the box to get your best peak with whatever airspace you go with.

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04 dodge neon SXT
(2) Oz Audio Matrix Elite 12"s sealed in 4 cube fiberglass enclosure, powered by HiFonics BX1605D
Oz Audio Matrix 180cs 6.5" component set power by HiFonics ZX4000

Jeff, just for the helluvit I worked these subs up in Unibox and looked at different tuning freqs.  For what it's worth to you I'll post links to .gifs showing the response and port size for two subs in one chamber.  You would need to double check me, though.

Tuned at 40 Hz, slot port opening area 95 square inches, 16.33" long.  vb_response_kicker_l7_12_40hz.gif

Tuned to 45 Hz, slot port opening area 95", 11.2" long.  vb_response_kicker_l7_12_45hz.gif

Greatest SPL at 55 Hz, slot port opening area 95", 4.8" long.  vb_response_kicker_l7_12_55hz.gif

( When these charts show up, an icon will eventually appear at the bottom right to expand the image.  It will be clear to read then. )

These are all with a single chamber of 6.5 cubic feet net.  Single port, no port noise.  And I'm supposing that you will be wiring series/parallel.  Now if I can just figure out how or if I can adjust the db range of these graphs to go over 130 db we can see how loud it gets!

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

thanks steve I will get a chance to look at them tonight.    Its gonna be tricky. we are going to use 2 amps, one per sub.     Nodestiny   I think you underestimate me,    I have used WinISd for years.   The box will be ported, no SQ for these shows.   The reason I am not wanting to raise the tuning frequency is the last 2 sets of subs re ran at a high frequency, 56hz. were both damaged due to the port being so large it almost was operating free air.    Just need to spend alot of time testing and retesting       

the show is on the 12th so we still have a few weeks,   thanks for all the help you guys,   let me know if you have any other suggestions

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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place

That looks about like what I got with the 55 Hz tuning freq.  Big azz port opening...but that's for no noise at max SPL.  An alternative to that is to make the port opening smaller at 76 sq in and 3" long.  Will have some port noise but it might not be a big problem for SPL.  Those subs look like they really like that 50ish Hz tuning.

I am noticing in your graphs, even tuned to 55 hz it seams to peak still around 46-48, cant really see the gaph is topped out.    This would work about perfect beacuse it is inbetween our peaks in the vehicle...Very similar to the graphs I was using when we were using our 10 eclipses,   the peak for the sub was around 46hz and then in vehicle it peaked at about 52.     

Were u using the recomended airspace of 6.5 with a common chamber?     
I am liking that program, is it better in your oponion then WINISD?    Is it shareware?      

I am probably going to size down the port, port noise is not a big issue as long as it is not going to cause a large amount of interference with the reproduction of the tone,    I would rather go this route then use a large port and have another set of damaged subs.


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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place

Here's the link to Unibox https://www.pvconsultants.com/audio/boxmodel/unibox.htm  But you have to have Microsoft Excel installed on the computer because this program along with most of the others in the FRD Consortium use the .xls file which shares info between the programs using the Excel spreadsheet.  It's free.

I like the easy way you can enter parameters, and I especially like the graph displays.  My biggest problems with it is that the units of measurement (like cm^2 or liter) are fixed;  you can't just click on them to change them to inches or whatever like you can in WinISD Pro.  Another thing is the fixed graph.  It goes up to 1000 Hz and up to 130 db, and I can't find any way to change that.  A box's response will only affect frequencies below 1k anyway, so that part makes sense...but I'd like to be able to see a peak above 130 db.  WinISD allows you to change the graph to a higher peak to see the response.  I could probably just lower the wattage input and keep the peak on the graph...then just add 3 db per doubling of power, I suppose.  But I don't think that's an accurate way to do it when you're dealing with a port...

This program is pretty easy to use, so it's worth getting it.  I can enter data quicker in this than in WinISD.

I  want to look at your setup again now that I know you're using two amps.  I can't imagine you want to use a common chamber with two amps, but you're the expert.  I would play it safe and use two chambers, two ports.  If one amp or sub glitches at high db's, both subs will go, using one chamber.

Yeah, I was using 6.5 cu ft, one chamber, two subs 4 ohms each wired in parallel to 2 ohms for that with 1500 total watts.  But now I would look at it again using the parameters of each sub in parallel for 1 ohm, and look at each one individually.  But...I'm not sure of them because the parameters listed are for 2 ohm coils in series.  I'd like to know what they really are if you're going to be running these at 1 ohm.

...oh yeah, that's another thing I like better about WinISD...you can change to a rectangle port and the program will figure it for you, but with Unibox it gives you only the diameter of the port you have to get to eliminate noise.  So you have to do the change to a slotted by other means.  They both have their good points.  The last project I worked on I loaded it in both programs and worked it both ways.  Like, WinISD would immediately give me an answer for centimeters when all I had was inches and I could just enter that into Unibox...stuff like that.

But this conversion calculator helps out a lot, too.

I'd just want to know whether you intend on using one common chamber or two separate chambers/ports.  And the other thing I don't know about this sub is its RMS.  The parameters list 750 watts Pmax.  I wouldn't want to figure on a port size for that if the RMS is really 500 watts or something like that, because Unibox calls for "nominal power" when it figures how big the port diameter has to be.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

RMS power is 750 watts.   
The amps we are using are 2 kicker kx1200.1's   I think you might know where I going with this....Both of the amps will be strapped together with a 2 ohm load presented to the "amp/amps"     

Yes I know it could go bad if one sub dumps out. But I really think they will be fine as I have seen 1 sub running (2) crossfire 1000d amps, so I think they should handle the 1500each.

I would consider 2 chambers but this is already getting to be a very large box in a quite confined trunk, if push comes to shove, yes I can make it fit.    

I have seen these sub doing very well, and have been advised that they really like a common chamber.

Let me know what you come up with in the next few days, we are going to be doing a few tests over the weekend and I will let you know how they go.

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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place

OK, so that's the way I had it figured, then.  Each sub is wired to 4 ohms, the two are paralleled together to get 2 ohms.  The mono amps are strapped, receive the load of 2 ohms, and each amp outputs at its 1 ohm rating.  So there is at a minimum 1050 watts available to each sub (engine off) but you'll be adjusting so that the subs aren't overpowered.  So figuring 750 watts each, or a total 1500 watts, would be right.

Using the 76 sq in port opening with a 3" length, 55 Hz tuning, here is the graph:  vb_response_kicker_l7_12_sngl55.gif .......which appears the same as the other 55Hz graph, the difference being that the port opening is a little smaller.  A slot 5.5 X 14 or whatever fits.

From what I can understand with the info I have, the program says the max SPL at 1500 watts is 121.7 db.  The graph at the upper right says "response peak 011 db", so I'm guessing that's added to the 121.7 for a total of 132.7 db.  That would be my guess as to where the peak tops off in the graph.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Then, who knows what cabin gain will be, and who knows what power we will really run the subs at.      We will probably push them awfully hard.      test till clipping back down a good amount and fire! Lots of testing, Thats the only way to tell for sure.

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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place