I'm in the process of building an SPL box for my 12" Orion HCCA. I estimeate it will be around 10 cu. ft. after the sub, port and bracing. Using WinISD I find that the higher the tuning frequency the higher peak I get. Does this mean it will go louder the higher I tune the box to? I heard you should tune it to the resonant frequency of your car but I don't know what that is. Would it be worth trying to find that out? And also is there a limit on how high the frequencies you use when you compete is Dbdrag or IASCA?

First of all 10 cubes is WAAAAYY too big.
You don't want to do over 3.5 cubes with that(less with more power), at the most.

What kind of power you running?

As far as tuning higher, yes you will find that from a daily tune, as you tune higher, you generally peak louder. However, you can only do this so much. I would say in a street install, you're tuning probably wouldn't exceed 45hz.

The best thing to try is to tune to say 34hz, and keep chopping the port inch by inch to peak it out. Then go from there and build a box more ideal for that tuning etc... It's all about testing.

yes I agree...10 cubes with that sub will give you damn near no output because the woofer will be swimming in a box that big so will have no control whatsoever leading to a really crappy sounding and not loud install.
I would tune it to 42hz...that seems to be a happy medium between all out SPL and still sounding decent. Also 3.3cubes is probobly a good size box for that 12 for SPL

__________________


Current Canadian Record holder Street A 154.1dB
2008 dBDrag North American Finals 3rd Place 155.0dB

2 10" TF Ones + 1 American Bass 1000.1 + Odyssey 1750

All the Dbdrag world record holders have massive boxes that take up the whole back of their car, i'm sure they are more than 10 cu. ft. I heard bigger is better. Keep in mind this is a pure SPL box, no music will be played when its in this box, I'll build another box for that.

[ August 23, 2003, 10:08 AM: Message edited by: Mustang 5.0 ]

An relatively easy way to find your resonate frequency would to build a plain, testing box for your car. Put the car on a meter and run a sign sweep or run different tracks on a SPL Disk (DB jams for example) you will be able to see on the screen what you are hitting when you change your freqency. there will be a note that is louder than most. Now build your actuall box to peak at or near the frequency. This method is about as simple as it gets. And like the others say, this box will sound like garbage for regular listening.

__________________
If there's anything worth doing, it's worth doing right!

^^^^^^^^^^^^^^^^^^^

That method will not work to determine the cars resonant frequency. You need to do all that AND also measure the box and sub outside of the car from the same distance. Then subtract the free air measurment from the in car. The largest peak after subtracting the free air is where you want to tune to.

10 cubic feet is a little large, many top SPL competitors are actually using smaller boxes than a few years ago. I would say between 4-6 cubic feet will be better for that driver.

For a single 12 i agree that 10 cubic feet is a little big.. i'd try 4-6 myself..

Well, I decided to tune it to 55 hz. I tried to go higher but the port length was like 1-2 inches and that didn't sound right. I can always put something in the box to take up space if it sounds bad.

__________________
1990 Mustang 5.0 <br />Soon to be system:<br />Pioneer DEH-P7200<br />Soundstream Reference 405<br />MB Quart components<br />Orion HCCA 250r<br />Orion HCCA 12d<br /><a href="http://members.sounddomain.com/terminator" target="_blank">My install</a>

well i seen you at future shop and man that box is big. too bad it doesn't post big numbers.... do the math without the winISD you are better off