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Billy Jack

How many cubic feet

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9 hours ago, ///M5 said:

Easy to understand if you ignore the single specification of Sd and instead focus on what is important for the box design.  Of course your math is off too.  480 cm2 * 2 << 1210 cm2

It is easy enough to design a woofer for a small box, but you aren't getting around Hoffman's law if you do.  Just because there are drivers on the market that do this doesn't make them good.  Pick your own compromises, stop using brands to do it for you.

My math isn't off, I said "almost" as in close, but not quite, 480+480=960 for the 12's, and 1210 for the 18 which is only 250cm2 difference so that's still real close to say 21/2 12's which would still only need 3.75-6.25 cubic foot, to the 18's 6-8 cubic foot. Does the FI  BTL V3's not use the same motors, like so many other brands, for all sizes of the woofers?  Guess that is where the difference in cone area, woofer size, to air space ratio comes from. Geez what would it take to run a 21" inch driver a u-haul truck with a car size box in the back. 

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On December 21, 2016 at 10:41 PM, frogcase2002 said:

Are you planing on having the enclosure built into the trunk or be able to go in and out?

Didn't see this response. I plan on having the box built and sliding it in  then putting one battery on each side of the box in the back of the trunk where it widens up behind the wheel wells. I'm thinking I can mount my amp on the back dask since it's huge and has no speakers in it. Back windows are already tinted so heat shouldn't be a big problem plus it will be close to the middle A/C vents blowing back through the seats to. With the interior of the car being so small and the trunk being pretty good size I'm thinking the little car should get pretty nasty loud off 1 15" or 1 18" on around 3k. I wanted a hatch back but there few are far between where I live. I detail cars for 2 different lots and neither one had anything close to a hatchback I would buy. I actually got paid to detail this car and never took it back. It's a 2012 1.4 turbo ltz, silver with black wheels and black ralley stripes. My cousin owns the lot so he gave it to me at his cost $5k. 

Edited by Billy Jack

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I would forsure do a single 15 over the 18 . .  Iv only seen a couple cars ever than can properly fit an 18 in a trunk . .

Way better to have the right space than have a bigger sub in to small of an enclosure . . .  Forsure can get crazy loud with a single 15

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Two motors lets you use a smaller box than one motor.

 

Go with the fifteen in an optimal enclosure and call it a day. You're not sounding like you're willing to go the extra mile to trunk an eighteen. 

 

You literally have the dimensions at hand to calculate box size, why did you post here instead of just multiplying the dimensions and dividing by 1,728

 

The SSA Tech team is a band of the most helpful posters, it's not a job title. They are the boards most knowledgeable and trustworthy posters. Wouldn't it be easier for you to learn this basic calculation so you know how to double check your builders work to make sure you really got what you paid for. 

Even if your builder does all the work for you, still no reason to ask that question here. You couldve done (32x32x18)/1728 and had your answer in much less time than it took to post that. 

 

When trunking a large woofer, you need to take into account giving the woofer enough space to breathe in the trunk so, space between the cone and trunk lid. For an 18, something like 6-9"

Decide your goals first, don't just buy something to say you have it.

Edited by SpeakerBoy

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On December 23, 2016 at 11:37 PM, SpeakerBoy said:

Two motors lets you use a smaller box than one motor.

 

Go with the fifteen in an optimal enclosure and call it a day. You're not sounding like you're willing to go the extra mile to trunk an eighteen. 

 

You literally have the dimensions at hand to calculate box size, why did you post here instead of just multiplying the dimensions and dividing by 1,728

 

The SSA Tech team is a band of the most helpful posters, it's not a job title. They are the boards most knowledgeable and trustworthy posters. Wouldn't it be easier for you to learn this basic calculation so you know how to double check your builders work to make sure you really got what you paid for. 

Even if your builder does all the work for you, still no reason to ask that question here. You couldve done (32x32x18)/1728 and had your answer in much less time than it took to post that. 

 

When trunking a large woofer, you need to take into account giving the woofer enough space to breathe in the trunk so, space between the cone and trunk lid. For an 18, something like 6-9"

Decide your goals first, don't just buy something to say you have it.

Thank you for the advice. Like I said before, I never build any of these boxes, so I have never learned how to calculate all this stuff.  What is the 1728 you spoke of, I'm not sure what your talking about there, and yes I will most likely go with a 15" just to be on the safe side. And if I had knew how to calculate the box I would have, but I'm pretty sure my calculations where off. I used a online box calculator and plugged the numbers, and best I could come up with was 7.1 cubic foot, tuned to 31htz, but that still didn't tell me if it would fit, just what was optimal for that peticular woofer.  I  think I'm gonna have SSA draw up the blue prints for a 15" box, and give it to my friend to build, so I know I'm getting the right box tuned correctly, and all that good stuff. I'm pretty sure a 15" inch BTL will still be pretty nasty in a compact car on 3k watts. My only real concern is using the factory source unit, it's the first time I haven't used a aftermarket unit, but we will see how the Audio control eq sounds I guess. 

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Divide by 1728 to get cubic feet from cubic inches

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11 hours ago, SpeakerBoy said:

Divide by 1728 to get cubic feet from cubic inches

Damn that's over 10 cubic foot but that's before port, bracing, and wood thickness of course. Still would have to fire a 18 upwards so I think I will stick with 1 15" BTL. That should leave enough room to run it inverted so the 6 NEO magnets are facing the back seat. That's gonna look badass I can't wait. :hsughexile:

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Forgot to subtract the width of the wood .  Got to subtract 1.5 from each measurement and thats if its all just a single layer of 3/4 inch wood .  . .  You would have like 8.8 cubes befor any displacement

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What you want to tune at? Just because you have the volume, you may be dicked on getting the vent long enought.  May be hard to get it long enough in that box. 

 

Id do 2 12's.  just me...

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1 hour ago, Kylar96 said:

What you want to tune at? Just because you have the volume, you may be dicked on getting the vent long enought.  May be hard to get it long enough in that box. 

 

Id do 2 12's.  just me...

Problem with 2 12's is the price. Your talking $1200 just for the subs and it would take a considerably larger amp to run 5k watts instead of just 2500. More batt, more amperage from a alternator, more wire, and so on. Considering a single 18" or 15" has almost as much cone area or more then 2 12's it should be almost as loud on similar power. I got just over $2k to do my sub stage, so if I went that route I would have to buy almost everything, and probably take a few months to save up for electrical upgrades, wire, and what ever else the $2-$2300 wouldn't cover. Don't get me wrong, I'm sure 2 12" BTL's Neo's on 5k watts would be brutal in a small car like the Cruze, but your talking a extra $1000 bucks to make it happen, unless I went cheap on my amp, and electrical, and I don't wanna do that. Now if I had just unlimited funds or went with cheaper subs that would be fine but a kind of had my sites set on a BTL NEO. I just think those 6 neo magnets running the sub inverted facing the cabin with the back seat laying down is gonna look bad ass and be decent loud if I can get it set up right. I had planned a Sundown 15ZV5 until I saw the new BTL's. But who knows the way things been going I may have the money to do 2 12's and 5k watts, could always get one 12, and a 2k watt amp, and buy a second sub, and amp later, like I did with my other 2 systems. We will see, I'm gonna order everything I can the first of the year,  if I can post picks I will when I get it going, probably take a month or two. 

Edited by Billy Jack

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