Hi,
I'm a New member from New Orleans. I have a 98 F-150 supercab with 2 12" sony extreme subs facing downfire in a sealed box with a 1000w sony amp pushing them. The box is 55"L - 10"H - Bot Depth is 12" and Top Depth is 15" with the seat anchored to the box. I think I have way to much air space. The speakers call for 1 cub of air space.
Could someone tell me the proper size box I sould have for these subs? Weather down fire or upfire would be beter? Any box designs or ideas would also be appreciated.
You can fire those subs down and it will be fine. and yes according to sony they want 1 cubic foot. That box is approx imently 4 cubic feet so you need to get rid of half the space. You can do this two different ways. Either cut a whole wack of 2x4s up and put them inside to take up enough airspace. Or the better option, is to take the top of the box off and put in two walls. One to seperate one sub from the middle and one to seperate the other sub from the center. That way you will have two sepeate enclosures and a then a large empty space i the center. I guess the third option is to just throw away that box and build a completly new one. I think the one you have can just be modified though to serve your purpose.
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double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer
Subwoofer Qualification Formula For Downfiring Configurations
I am often asked if a particular driver is suitable for using in a down-firing configuration. Below is a formula that takes into consideration the effects gravity will have on the "sag" of the cone structure of any woofer. You will need the Fs, Vas, Sd (surface area of the cone), and the Xmax to determine the relative long term usefulness of up or down-firing any woofer.
You can calculate the sag of a driver from:
Percentage of Sag = 24,849 / ( Xmax * Fs²)
where
- 24,849 is a constant value based on the relationship of acceleration due to gravity and Pi.
- Xmax is the maximum linear excursion of a loudspeaker voice coil while remaining within the magnetic flux field (mm).
- Fs is the free-air resonant frequency of the woofer (Hz).
The following is the same formula, including the relationship of acceleration and Pi in this case:
Percentage of Sag = 981,000 / (Xmax * (2 * Pi * Fs)²)
where
- 981,000 is acceleration due to gravity (mm/S²) * 100 (for the percentage).
- Xmax is the maximum linear excursion of a loudspeaker voice coil while remaining within the magnetic flux field (mm). - Fs is the free-air resonant frequency of the woofer (Hz)
- Pi is the ratio of a circle's circumference and diameter, usually rounded to 3.14.
As a general rule of thumb, any time the sag exceeds 5% of the driver's Xmax, it's not recommended for a down-firing subwoofer application.
-- from Parts Express resource index
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hmmm, I dint know about that. I just know I tried it before and it worked well. In fact it was the best I have ever heard a sony sub sound. Well I guess you learn something new every day
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double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer
DYohn Thanks.... that's a bookmark
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