Double 21'' Subwoofer project

[Shrewm]

Firstly I want to tell you that i have practically no idea of how to do this.. I've only built one or two speakerboxes, and that was without any calculations...

I know it may sound stupid to make such a massive sub as my first try, but for the PA I'm setting up it's what I'll need... And I consider myself quite handy, so as long as I can find out all the hows, there shouldn't be a problem.

So, what I want to do is; I want to build a subwoofer with two 21'' subwoofer loudspeakers.. I'm gonna make it a passive subwoofer with no inbuilt filter, so what I need to know is basically just how to figure out the dimensions of the speakerbox, but of course I'm grateful for any other usefull information or tips you might have.

Thanx!

/Shrewm

[cowanaudio]

G'day Shrewm

You could do much worse than to build the B&C design:

http://www.bcspeakers.com/suggested.php?id=0000000011

It's only a single 21. A double box would probably be too big to move.

Cheers

William Cowan

[chris661]

Provided you know the speaker's parameters, you can use winISD. I recommend the beta version, as the alpha is just silly when you come to putting in a new driver.

When you have put in the driver's parameters, try using different types of box (sealed, ported etc), until you find something to suit you.

Basically, keep changing the box size and port tuning until you have something which suits you.

Most people would choose a response as flat as possible, but that would make the box huge, so you will have to compromise.

Have fun

Chris

[454Casull]

What's wrong with the alpha version?

[Twellmann]

The alpha version is Extremely sensitive when you put in the data for a new driver, if it's not spot it won't work.

[fb]

If you input the data in the order that winISD wants, it works

Check the help file

[Shrewm]

Hi, and thanks for your replies
I'm sure Winisd is a nice program, It's just i have no clue of how to use it.. I read some about the program on their forum, but I'm too much of a beginner to understand it, lol.

I found finished drawings on subwoofers which seem neat.. Though, i don't know how much the parameters differs from speaker to speaker (of the same size ofc) so maybe that's a bad idea ._.

As you can tell I don't have much experience, so if you have any tips of good books/magazines/websites or whatever for a beginner I'd really appreciate if you shared it

/Shrewm :>

[Twellmann]

Originally posted by fb
If you input the data in the order that winISD wants, it works

Check the help file

Help file?? hmm.... No that can't be right

[jogi59]

Originally posted by Twellmann
The alpha version is Extremely sensitive when you put in the data for a new driver, if it's not spot it won't work.

For a new driver in WinISD, put in only the following parameters and let WinISD calculate all other values
Qes
Qms
Fs
Vas
Re
Le
Sd
Xmax
Pe

[chris661]

Problem - the parameters I have are rounded, so they disagree slightly with others, meaning winISD is very unhappy.

You also need to know voice coil length and daft things like that...