To "Free Air" or Not To "Free Air"?

[psycho72 10+ year member]

Did a search and I was not able to learn the things I wanted so here I am again. Lets get started. Free air, this would have me use my trunk as the box and to do this I need to seal off the trunk. How sealed does it really have to be? What are the drawbacks of free air?

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[squeak9798 5,000+ posts]

Well, you need to seal off the baffle that the speaker is mounted to so that the backwave can not interfere with the frontwave. How sealed? Sealed sealed. And really for infinite baffle (free-air), your trunk isn't the box.......there is no box. Just a subwoofer attached to a baffle so that the front wave and rear wave are isolated.

Drawbacks? Overall output will suffer (compared to sealed or ported). Can be difficult to impliment in some vehicles. Low mechanical power handling (if that matters to you).

 

[psycho72 10+ year member]

Overall output will suffer (compared to sealed or ported). Can be difficult to impliment in some vehicles. Low mechanical power handling (if that matters to you).

What exactly do you mean by "Overall output will suffer", it will not get as loud and deep as an enclosed woofer? What would make it difficult? So say a sub that is rated at 1000w RMS could only take 400w RMS now?

 

[squeak9798 5,000+ posts]

What exactly do you mean by "Overall output will suffer", it will not get as loud and deep as an enclosed woofer?

Deep; yes. Loud; no.

I'm a picture kinda guy //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif So here, look at this: http://www.imagedynamicsusa.com/website/tech/data_sheet_max12v3d4.html

Notice how the red line (the line that represents that sub in an IB alignment) is lower than the other two lines (sealed and ported). Those lines represent output across the frequency spectrum. The higher the line is, the higher the decibel level of the output. Between 20hz and 60hz, the IB setup simply has less output.

But, there are things to consider other than overall otuput. But moral of the story, if you are a basshead, IB probably isn't for you.

What would make it difficult?

It's not hard to build a box and toss it in your trunk. IB requires you to find a place to mount a baffle (or find a pre-existing space) large enough to mount the sub on, and then you need to seal that baffle area up so that the backwave and frontwave are isolated. It's simply a lot more work, and not something that will work well in every car (hatchbacks and SUV's for example).

So say a sub that is rated at 1000w RMS could only take 400w RMS now?

For example purposes yes, that would be right.

 

[Str8Up 10+ year member]

Deep; yes. Loud; no.
I'm a picture kinda guy //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif So here, look at this: http://www.imagedynamicsusa.com/website/tech/data_sheet_max12v3d4.html

Notice how the red line (the line that represents that sub in an IB alignment) is lower than the other two lines (sealed and ported). Those lines represent output across the frequency spectrum. The higher the line is, the higher the decibel level of the output. Between 20hz and 60hz, the IB setup simply has less output.

Ah, but if you look at the ID Max 10's, it shows that the free-air setup will be louder than the sealed setup..

Btw, I was REALLY REALLY considering free-air for my dual 10" ID Max. Was...

 

[squeak9798 5,000+ posts]

Ah, but if you look at the ID Max 10's, it shows that the free-air setup will be louder than the sealed setup..

But with sealed you can adjust box size to increase output. With IB, you're pretty much stuck with whatever Qtc it gives you

 

[Str8Up 10+ year member]

But with sealed you can adjust box size to increase output. With IB, you're pretty much stuck with whatever Qtc it gives you

True. And if the Total VAS of both of your subs is more than the volume in your trunk, the setup might sound bad.

Btw, I ditched the free-air idea. I'm getting my 10's put in the reardeck still, but a ported box will be built under it. Next Thursday, whooohooo, can't wait!

 

[psycho72 10+ year member]

....really for infinite baffle (free-air), your trunk isn't the box.......there is no box. Just a subwoofer attached to a baffle so that the front wave and rear wave are isolated.

Nice woof (LOL, sub pinup, LOL).

Now for the comment above, would it be feasable to use the trunk as a ported encloser to benifit from the monstrous space it probivdes. For example lets say I built a baffle covering the rear seats, turning 110 degrees, then 90 degrees up to the rear deck. Screwed it all into place, siliconed it up. Sprayed the trunk (including the lid) & the part of the box visable in the trunk with Rhino liner. Covered it in Brown Bread. Replaced the foam weather stuff with rubber and tightened down the trunk lid (hell I'll rig up one of those cadillac trunk thingys that wrench down the trunk after you close it) for more pressure on the rubber seal. If I did all that would that be sealed enough to add a port and basically make my trunk a 10 cubic foot (I am guessing on that one as I have no idea how big it is) box for say 2 or 3 fifteens tempests (or whatever combo would be happiest in the huge enclosure)? Am I living in dream land (I tend to go way overboard with projects, especially because I usually want it all).

***edit***okay I think I may be going way too far...someone smack me quick!!!

 

[Str8Up 10+ year member]

Nice woof (LOL, sub pinup, LOL).
Now for the comment above, would it be feasable to use the trunk as a ported encloser to benifit from the monstrous space it probivdes. For example lets say I built a baffle covering the rear seats, turning 110 degrees, then 90 degrees up to the rear deck. Screwed it all into place, siliconed it up. Sprayed the trunk (including the lid) & the part of the box visable in the trunk with Rhino liner. Covered it in Brown Bread. Replaced the foam weather stuff with rubber and tightened down the trunk lid (hell I'll rig up one of those cadillac trunk thingys that wrench down the trunk after you close it) for more pressure on the rubber seal. If I did all that would that be sealed enough to add a port and basically make my trunk a 10 cubic foot (I am guessing on that one as I have no idea how big it is) box for say 2 or 3 fifteens tempests (or whatever combo would be happiest in the huge enclosure)? Am I living in dream land (I tend to go way overboard with projects, especially because I usually want it all).

***edit***okay I think I may be going way too far...someone smack me quick!!!

Why don't you just buy another 10" w6 and have your local car audio shop build you a custom reardeck, and that should be plenty. Sealed, or ported like mine will be. All the output in the car with you hitting off your rear window...

 

[psycho72 10+ year member]

Why don't you just buy another 10" w6 and have your local car audio shop build you a custom reardeck, and that should be plenty. Sealed, or ported like mine will be. All the output in the car with you hitting off your rear window...

Because I want cleaner and louder. I was really listening to it and I like the sound at lower levels but when I turn it up it starts to sound like crap (not really that bad but I noticed the diff) but I like the bang at higher volumes so I need somehting that will bang clean!

 

[Str8Up 10+ year member]

Because I want cleaner and louder. I was really listening to it and I like the sound at lower levels but when I turn it up it starts to sound like crap (not really that bad but I noticed the diff) but I like the bang at higher volumes so I need somehting that will bang clean!

If the reardeck thing is still a possibility, get 2 decent 12's and get a custom ported reardeck tuned to like 32hz... That should be plenty, especially if they're high power 12's with the proper power to them. No worry of theives being able to steal them either, unless they take your car and have time to disassemble your reardeck, lol.