ok heres the deal.... and thanks Dirk for getting teh board back up i would donate but i am poor( if i come across extra cash ill give you a hook up) . i am doing a school project on teh car customization culture( how it started, what its progressed into, etc) and i have to do a physical project to go with it. i decided to build a box for my subs.

ive been wondering what all the theile-small parameters mean and how to use them to design a box( i could use this info in my paper, too) what ever formulas and stuff like that would be helpful. this info would also help for when decide to upgrade my subs, you know comparison shopping and the such.

 

Here's a website that should help you. It defines the most important t/s params, and also gives you the necessary information for desigining a bunch of different enclosures:

http://www.diysubwoofers.org/define.htm

 

Thanks jim... i book marked that site... also i d/led that winISD program that you use... what is a good curve to look for in a sealed box.... flat with slow drop off, faster slope, high db gain? i read thru the tutorial but it didnt explain some things

 

The curve really depends on what you're looking for. The reason that sealed boxes work so well in cars is that there is an enormous amount of cabin gain inside of a car, which means that the bass receives a big natural boost, and that boost level increases as frequency decreases.

Fool around with that program and you'll find that if you make the box too small, bass response drops off sharply and at a higher frequency. Make it too small, and you also get a big bump in output at a frequency slightly above the point where it starts to drop off. This is known as a "high Q" or "overdamped" alignment and will result in a boomy midbass and not much low frequency output.

On the other end of the spectrum is the "low Q" or "underdamped" alignment that you get when you make an oversized box. Going a hair too big might lower your -3dB point, but it'll weaken output slightly above that point. However, the rolloff comes at a slower rate, which means the really deep bass will have less rolloff than with a higher Q design. It's a trade off, and the "best" alignment is whatever suits your tastes and best blends with the cabin gain of your vehicle, which is probably around 12-18dB/octave starting around 150-200hz.

In most cases, a critically damped (mid q - a Q of .707) is what's considered "optimum" and what WinISD usually defaults to.

Your milage may vary.

 

okay thanks.. lol my box currently is like .8 per sub and you know how they are... they have crazy gain around 85hz i think but drop off to -3db cutoff at 50hz