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Discussion Starter #1
Im building a downfire box for a porsche carrera and it will be a downfire box. the only question I have is how much of a gap will I need. Its going behind the back seat on top of the factory sub location. the factory contour is slightly round, so on the sides I have about 2" and in the middle I have about 1" but with the speaker in it will only be about 3/4" in the middle and 1 3/4" on the sides. will this be enough. Im thinking about scratching the box and doing a fiberglass one, seems a little bit easier right now and will look better imo. any help will be greatly appreciated.
 

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If you can stay between 1"-2" you should be fine. Most (if not all) of the JL stealthboxes that downfire have around this.
 

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should have 1/4 diameter of the sub to avoid causing a bandpass effect.
 

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This ^
 

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Discussion Starter #5
so a 10" sub should have around 3"s of a gap between the floor and the sub.
thanks for the input. Im not happy with how this is turning out. not saying its a bad install but im just not stoked. I could ditch the downfire and flip the box over, but that defeats the stealth look.
 

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Some info here:
http://www.diymobileaudio.com/forum...-do-downfiring-need-some-advice-pointers.html

Also, make sure your sub is capable of being inverted. I didn't even know there was a formula for this until chad pointed it out.
Parts Express - Subwoofer Qualification Formulae For Downfiring Configurations

As for the gap, I know 25-50% of the diameter is optimal, but rarely have I seen this much. Usually space dictates much less. I added a couple examples from the JL site. I'm not saying it's right just because they did it, but it's tough to argue with sucess.
 

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