Newbie question about 4th order subwoofers

[red]

Hello
I have a problem.I want to build a 4th order subwoofer using this tutorial:
http://www.diysubwoofers.org/bnd/4thorder.htm
My question is if I could use some chineese driver with Xmax ~9mm (since are the only drives available here that "look" good enough).It says on it 220 watts and it is diameter 8".I was thinking that it may have too small xmax.There are no TS parameters and no probing on how the driver sounds like.I konw I can determin the TS parameters but should I buy such a stiff driver?Pls help me out because I am doing it for the first time...and I have no ideea what to do.

[BAM]

If you can't measure the T/S parameters then I suggest selecting a different driver.

[red]

maybe I asked the wrong question...
Can I use a any driver for the subwoofer?
I will measure the TS parameters after buying the driver if there isn't other way to find them out.

[paulspencer]

First if you want to design a subwoofer, you want to be sure that the driver that you have is suitable. You MUST have the parameters, or hear the driver you have in mind in a sub that is similar to what you would like to build.

My suggestion: if you can't get the TS parameters, don't get the driver. Otherwise you won't know if it will be suited to a design that you like. This can cause problems like:

* you want vented but you can't fit a vent in the box that is big enough without port noise - so you end up needing passive radiators
* you might find that it won't have as much SPL as you thought
* it might need a box bigger than you can accept

The list goes on ...

Also, consider looking beyond what you can get locally - check with overseas suppliers if they ship to your location, and ask for quotes for shipping cost (and how long it will take) ... don't forget to add customs.

Also, I suggest you have a look at the LDSG website, one of the best online DIY audio resources - it will give you an intro to the most commonly used DIY drivers based on the recommendations of people who have used them, and it also has links to suppliers:

http://ldsg.snippets.org/idx.php3#S2

for guidelines on what to look for in a sub driver:
http://ldsg.snippets.org/sect-1.php3#SUBS

Hope this helps,
Paul