# L7 cutom box



## scrappy (Jun 30, 2002)

I have 2 12" L7 subs, I bought a pre made box the shop that sold it to me syas it is ok but Ive been told the port is tuned to high. How do I know if it is or isnt? Can I tune the port of the box I already have or build a new one. What about tuning the port if I build a new one? thanks for the help


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## sr20dem0n (Mar 19, 2003)

There's no real way to tune a prebuilt box to a lower frequency. If the box was tuned too low you could shorten the port a bit and raise it up, but there's no effective way to lengthen the port inside a box that's already built.

Best bet is to build a new one, I would go for 2-3cf per sub depending on how much power you have and a tuning frequency of 30-35 depending on what you're looking for out of the subs.


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## scrappy (Jun 30, 2002)

how do I know when i have it tuned to 30-35. I have a 1200 watt kicker amp. Ive never bilt a box before and I dont want to get it wrong> My first set of l7 blew so I have the redesigned model now and dont want them to bnlow to


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## sr20dem0n (Mar 19, 2003)

There are programs online that will tell you the tuning frequency based on the size of the box and the size/length of the port. Those are the easiest to use, the hardest part is coming up with a box shape and size that fits all these requirements and also fits into the back of your car. Honestly I doubt you'd get a 4cf 30hz box in your trunk, maybe 35hz, but that's pushing it (higher tuning = shorter port = less of the box's space taken up so the box can be smaller).

If you want to try it out, WinISD is a pretty good one to get started. Don't pay attention to the frequency response, power ratings, max spl, and all the other crap it tells you because once you stick it in a car EVERYTHING changes. But it is pretty accurate for box calculations (tuning frequency, port lengths, etc), which makes it a handy tool.
http://www.linearteam.org/winisd.html


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## scrappy (Jun 30, 2002)

ok thanks for the help Im going to check into the program right now


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## Zac (Mar 10, 2004)

I was running a single 12L74 off of a 1450 watt KX1200.1 @ 2 ohms on a prefab vented kicker box and I blew my first one (luckily Kicker is great on warranties and they helped me out a lot). The new designs do not differ much from second generation. I recenty found I most likely blew the sub because of a poor break in and a rather high bass boost setting. DO NOT crank these subs for 2 weeks, they for some reason are picky about the break in. Your box, especially if vented, better be big and thick. These subs need BIG room to be loud and clear. I am guessing you have the KX1200.1 and it is a damn powerful amp and the best bang for buck ever made in an amp. You will also want to update the battery and a cap and alternator or a combo. I am now rocking an Optima Yellow Top, 1 farad cap and a soon 200 AMP alternator.


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## sr20dem0n (Mar 19, 2003)

Both of you probably blew your subs because you let them unload with full power going to them. Prefab boxes are tuned high, and when the subs play below tuning they behave like they aren't in a box at all (like they're in complete freeair). If you're still sending them the same amount of power as before, the excursion will increase dramatically and can easily blow the sub. Well when the box is tuned high, half the signal going to the sub is below tuning, and will quickly blow the sub. This is why subsonic filters were created, even though people seem to not want to use them....


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## Zac (Mar 10, 2004)

The box I use was built specefically for the sub.


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## sr20dem0n (Mar 19, 2003)

That doesn't take away from the fact that it was tuned high and you apparently had no subsonic filter. I could have the manufacturer of my sub build me a custom ported box specifically for my sub, but that doesn't mean it won't unload below tuning, ALL subs will do that in ANY ported box.


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## Zac (Mar 10, 2004)

sr20dem0n said:


> That doesn't take away from the fact that it was tuned high and you apparently had no subsonic filter. I could have the manufacturer of my sub build me a custom ported box specifically for my sub, but that doesn't mean it won't unload below tuning, ALL subs will do that in ANY ported box.


I did not know that. I forget what my box was tuned to but it was rather high for a subwoofer box.


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## new94 (Jan 9, 2004)

I have 2-12" Alpine Sub's that are in sealed boxe'sat the moment, one box is mounted to the driver's side fender and the other is anchored down against the back seat facing the rear of course. I made both boxes approx. 1.5cf according to what i was told from a few guy's, is this acceptable for 12's in a selaed enclosure? It sound's good but i don't want to overheat them and/or blow them due insufficient air space, can a dual bandpass fit in a B13 Sentra and if so would it be worth losing the room?


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## scrappy (Jun 30, 2002)

So with the subsonic filter on would I need to build a new box. 

I already have a 1 farad cap and a yellow top battery.


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## Chicago Tony (Apr 15, 2003)

I believe the Kicker 1200.1 has a subsonic filter make sure its on. I have noticed that most prefab boxes are to small for the L7's. They like medium to large vented boxes to make them breathe. I am running a 12 L7 in a 2.5^3 tuned to 38 hz. I am pushing 1100 watts to it and havn't had a problem with it in over a year. The L7's are bulletproof subs and will take a beating if setup properly. Since you have 2 subs you might want to put them in a sealed box to save some space. 

I have heard of 2000 watts being pushed through them in burps and the sub will take it.




scrappy said:


> So with the subsonic filter on would I need to build a new box.
> 
> I already have a 1 farad cap and a yellow top battery.


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## sr20dem0n (Mar 19, 2003)

new94 said:


> I have 2-12" Alpine Sub's that are in sealed boxe'sat the moment, one box is mounted to the driver's side fender and the other is anchored down against the back seat facing the rear of course. I made both boxes approx. 1.5cf according to what i was told from a few guy's, is this acceptable for 12's in a selaed enclosure? It sound's good but i don't want to overheat them and/or blow them due insufficient air space, can a dual bandpass fit in a B13 Sentra and if so would it be worth losing the room?


1.5 per sub is pretty good, how much power do you have going to them?

And bandpass is crap, they're normally "one note wonders". Unless they're specifically designed to your exact subs and built perfectly, they'll play a select few notes very loud, and the rest is left in the dust. Very poor sound quality, very loud, that's about it....don't waste your time


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## sr20dem0n (Mar 19, 2003)

scrappy said:


> So with the subsonic filter on would I need to build a new box.
> 
> I already have a 1 farad cap and a yellow top battery.


Why would you need to build a new box if you turn the subsonic filter on? All it is is a highpass filter with a very low cutoff frequency.

Now you should build a new box regardless, one that's more suited to your sub and tastes, and you should get/turn on a subsonic filter to protect the sub, but you don't need to build a new box because you have a subsonic filter on.


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## scrappy (Jun 30, 2002)

My amp already has a subsonic filter Ill go turn it on. Is it hard to get the seams right to make the box airtight? What do you think about putting the amp rack on the box?, my amp rack I have now is in front of the box and I like the amps showing through the seats. As far as sealed or vented Ill have to see how much room I have with the amp rack and everthing I never use the trunk so Im not to concerned with saving space just making it fit


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## sr20dem0n (Mar 19, 2003)

If you take your time and watch your measurements/cuts it's easy to build a box with good sealed joints.

You can put the amp rack on the box if you want, nothing's wrong with it, just keep in mind it makes things much easier to steal if someone breaks into your car.


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## scrappy (Jun 30, 2002)

Good point about easier to steal if its all together. You mean to tall me my one way viper alarm wont stop them  the subsonic filter was on the crossover was turned way high towards 200 so I turned it down, what do you think I should put it at never played with the sub amp since getting it just the mids amp


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## new94 (Jan 9, 2004)

I have the Alpine V12 amp f-400 wired parallel and the sub's are 8ohm's/each so they're only running the amp at 4 ohm's and it pound's pretty hard, so i assume the boxes are ok for now!


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## sr20dem0n (Mar 19, 2003)

scrappy said:


> Good point about easier to steal if its all together. You mean to tall me my one way viper alarm wont stop them  the subsonic filter was on the crossover was turned way high towards 200 so I turned it down, what do you think I should put it at never played with the sub amp since getting it just the mids amp



Are you sure the subsonic filter goes up to 200? That sounds more like the lowpass filter....the subsonic should go from maybe 20-50hz


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## scrappy (Jun 30, 2002)

It was the low pass filter I was talking about. The subsonic filter is 12db/octave set at 25hz it is only on and off so why do you think they blew if the subsonic filter was on


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## Russia (Jul 24, 2003)

Check out www.subzoneusa.com for some measurements of custom L7 boxes.


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## sr20dem0n (Mar 19, 2003)

scrappy said:


> It was the low pass filter I was talking about. The subsonic filter is 12db/octave set at 25hz it is only on and off so why do you think they blew if the subsonic filter was on



12dB @ 25hz?

That's a pretty weak slope for a SSF, and that's also a very low cutoff frequency. If your box was tuned at 40-45hz like most prefabs are, the subsonic wouldn't have done much of anything since it's set so low. You normally want the subsonic set ~5hz below the tuning frequency to be on the safe side.

A ported box can control the speaker's excursion down to a half an octave below the tuning frequency, below that the speaker behaves like it's not in a box at all and the power handling drops like a rock. For a 40hz box, this means the sub's excursion would be controlled by the port down to ~30hz, and since the subsonic filter has a cutoff frequency of 25hz, at any frequency in the high 20's all hell would break loose and the subsonic wouldn't do anything to stop it. Not many songs have frequencies that hit that low, but all it takes is one with the volume a little too high.


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## scrappy (Jun 30, 2002)

[email protected] hz thats what the manual says.
So if I build a new box the subsonic filter isnt going to matter with it being set that low and not adjustable If i tune the new box to 35hz like you suggested will that be good or do I need ot to be 30 hz? Also what do you think about those subzone boxes


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## sr20dem0n (Mar 19, 2003)

With a 25hz SSF I would tune a little lower than 35, somewhere around 32-33 should be just fine.

And I've never heard of subzone boxes


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## scrappy (Jun 30, 2002)

Well I guess the subzone box isnt going to work tuned to 37 hz. It looks alot like the one I have except there it is divided in the center of the port. Guess Ill build a box


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## Chicago Tony (Apr 15, 2003)

http://www.kicker.com/ShowPage.cfm?filename=04L7SOLOSUB.HTML&menu=SUBWOOFERS

If your looking for an enclosure to build here is Kicker's website. Go to the technical manual. They have some ideas you can use to build one. Hope this helps.








scrappy said:


> Well I guess the subzone box isnt going to work tuned to 37 hz. It looks alot like the one I have except there it is divided in the center of the port. Guess Ill build a box


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## scrappy (Jun 30, 2002)

How much doyou think Ill lose if I go with a sealed box? Not really sure if I can fit the box and my amps in the trunk at the proper tuning I need


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## Chicago Tony (Apr 15, 2003)

Are you going to run 1 or 2 subs? You can put them each in as little as .88^3 to as large as 2^3 sealed but the larger the better it will sound. You can't tune a sealed box.
I have my L7 in a 2.5^3 ported enclosure tuned to 38 hz. With the box and my amps I have no trunk space at all. 




scrappy said:


> How much doyou think Ill lose if I go with a sealed box? Not really sure if I can fit the box and my amps in the trunk at the proper tuning I need


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## sr20dem0n (Mar 19, 2003)

scrappy said:


> How much doyou think Ill lose if I go with a sealed box? Not really sure if I can fit the box and my amps in the trunk at the proper tuning I need



You lose ~3dB (same as cutting the power going to the sub in half) by going sealed over ported. This is at most frequencies, as you get closer to the tuning frequency the difference grows to 6-10dB or more depending on what the tuning frequency really is.


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## scrappy (Jun 30, 2002)

Sounds like Im going to have to find a way to make it fit with the amp rack and everything. The port will be tuned around 32hz


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## scrappy (Jun 30, 2002)

What do you think of two sealed boxes one on each side of the trunk? Is that better than one sealed box?, still looking for away to fit a ported box. I might take out my spare tire and put my amps in the tire hole if the fit need to go out and pull the box out and amp rack down to take some measurements


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## sr20dem0n (Mar 19, 2003)

There's a chance that you'll get more cancellation and less output that way, but there's no way to be certain.


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## scrappy (Jun 30, 2002)

I was wondering about the cancelation. Guess Ill have to find another way then. sr20 demon whats your box ported at?


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## sr20dem0n (Mar 19, 2003)

26hz
the low end is retarded, but that's partially because the sub is retarded


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