# Free air subs, boxed in ?



## quentin508 (Apr 12, 2005)

I thought it would look cool to put free air subs in my car...they go in the space between back seat and trunk. I want to see how it sounds with a box and was wondering, could I make an enclosure to fit around the back of the subs and amp? I have pics of the set up at http://www.cardomain.com/memberpage/775251 

I appreciate the response


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## TheMadCheshire (Dec 30, 2004)

I dont think building a box for them would be too hard. Mine sits with the sub facing the trunk lid and flushes up against the rear deck supports. All you can see is the wood, but its flush. You really needa figure out the angle to build the box accordingly. In my experience, a sealed has always hit harded than an IB setup, but i donno about sound(more like i just dont remember). Unless the subs are supposed to be for IB setup, like specifically for that application, i think a sealed box would make them sound better cause they prolly are designed to be in a box.


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## lnfamous (Sep 14, 2005)

Freeair subs are garbage, Even the JL ones... subs firing into a car sounds awful also. Loudest point is 15 feet away from a sub. Unless you're thinking of doing this for a cosmetic reason it's not a very good idea.


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## sr20dem0n (Mar 19, 2003)

Some of the most successful sound quality competitors in the world use infinite baffle sub setups, with them firing into the car.

The loudest point is 15 feet away from the sub? What? In a car the loudest point is the spot where you get the most constructive interference between the various reflections, which could be anywhere from the windshield/dash joint, the kickpanel area, the rear window, inside the trunk, or (and this is the most likely answer) right at the sub's cone (or the port entrance if it's a ported setup).


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## Biscuit (Mar 5, 2005)

Dude...just get a 3 cubic foot sealed box and you will be much happier.


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## wes (Apr 30, 2002)

Biscuit said:


> Dude...just get a 3 cubic foot sealed box and you will be much happier.


Please stop posting unless you have real world experience with these things. The suspension on a free-air sub is DESIGNED to be in a free air (infinite baffle) setup. If you want too build a box get subs MEANT to be placed in an enclosure.


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## wickedsr20 (Aug 8, 2002)

lnfamous said:


> ... subs firing into a car sounds awful also. Loudest point is 15 feet away from a sub.


You can't be serious.


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## Biscuit (Mar 5, 2005)

Well why would you want a sub to be free air anyway? I would understand if it was an 8 but 10s or 12s? hmmm....


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## sr20dem0n (Mar 19, 2003)

Because an infinite baffle install will give the highest sound quality out of any alignment available (provided the sub is built for IB)


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## Slayer2003 (Jun 4, 2003)

I thought about this when I first got my sentra.

Can't be done unless you rework the hinges for the trunk.


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## wickedsr20 (Aug 8, 2002)

sr20dem0n said:


> Because an infinite baffle install will give the highest sound quality out of any alignment available (provided the sub is built for IB)


The only reason I don't see a lot of IB set-up is that it seems no one wants to properly seal up the trunk to get the sub to perform the way it should. 

Not to mention I like the idea of building the ideal enclosure for whatever type of speaker I use to get the most out of what I have. I will always recommend a sealed or ported box over an IB set-up. The box won't come apart, but trunk seals tend to leak under pressure.


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## sr20dem0n (Mar 19, 2003)

yeah, IB would be a major pita to pull off properly


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## Matt93SE (Sep 17, 2003)

meh... I've been running a pair of 12" Focal 33F (13" IB subs) for several years now and they sound great. MUCH greater clarity and impact than my JL 10w6s, on much less power.

they don't have the same max SPL rating and they have issues with frequency doubling below about 30hz and dash rattling volumes, but at that point it doesn't matter what they sound like anyway.

at more normal listening levels, I can get these things to play down to 10hz without issue and they sound awesome. clarity and impact like I've never heard on a 12" in the past.. the cones are very stiff and light, which provides a great kickdrum. they don't have a ton of excursion though, so ultimate SPL isn't the goal with them.

for those of you that like to crack the pavement, IB subs aren't the way to go. For people who like accurate sound and don't want to kill your trunk space, then IB subs are great.


the install wasn't that hard either.. Since I'm running no rear speakers at all, I took some 1/4" plywood and sealed off all of the holes in the rear deck. once that was down, I laid several layers of dynamat across the whole rear deck to keep rattles and buzzes down, and it effectively sealed off all the tiny holes in the deck.
Then I took some spray foam and sealed off the vents near the rear glass and all of the gaps around the rear seat belts (wrap the belts themselves loosely in plastic wrap so the foam won't stick to them. almost completely seals off around the belts, yet they still function when needed).
also pulled the little vent flaps out of the bottom corners of the trunk and sealed them off with aluminum sheet metal.

once all that was done, I saw easily a 5dB increase in max SPL, and the lower frequency limit dropped dramatically. before, all I would hear is chugging/rattling back there below about 20hz.. now that I've sealed off the deck, it's smooth down to well below 20hz and you can just feel the air moving (and your eardrums flapping) inside the car..


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## captain_shrapnel (Sep 10, 2004)

Yeah, IB doesn't necessarily need a sealed trunk (or other enclosure), it just needs to be sealed off from the front of the cone. As long as the positive pressure from the front isn't cancelled by the negative pressure from the rear of the cone, then the baffle is essentially "infinite".


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