dual woofer and the effect on box size

[holger honda]

Hello pardon a silly question.
I have been researching DIY speakers for a while and bought some books on the topic.
What I havent yet seen is a good model to calculate box and vent size for a speaker with two identical drivers.All boxprograms and formulas seems to be for single woofer projects!
But the market is packed with speakers with dual drivers and a tweeter.Any ideas or links out there?

[kelticwizard]

WinISD is a freeware program that models one, two or more drivers in a single enclosure and models one, two or more ports as well. Easy to use.
www.linearteam.dk

Of course, you can use most any program to model the response curve of two woofers if you just multiply cone area, (Sd), and Vas by two. Impedance issues are something else-that depends on the hookup.

[sreten]

Simply not true.

Nearly all software allows you to enter the number of drivers.

But you are correct in that multiple drivers is mathematically
fairly trivial, and most tomes consequently ignore the details.

For two drivers you need double the box size.

sreten.

[kelticwizard]

Sretan:

Subwoofer Simulator by our own F4ier is one program that does not model more than one woofer. It is found on his home page and on the FRD Consortium page. BoxModel by Bullock and White is another. So not all programs allow you to model more than one woofer without changing things around.

As far as doubling the box size, that is good for closed boxes, but that will lead to mistuning in a ported box. So if, for some reason, Holger finds himself using a program without the capability of multiple drivers, he is better off doubling the Sd and doubling the Vas of a single driver.

Of course, there are many programs that indeed do allow the modelling of multiple drivers.

[sreten]

Hi KC,

of course a double box size will require a different port,
but I suggest if you don't know this then you are going
to struggle to compare single and dual drivers anyway.

As you know, you don't need to model multiple drivers,
if you know how to transform single driver results to
multiple drivers.

sreten.

[ingvar ahlberg]

The JBL speakershop program allows any number of identical drivers, realy ok program too, i´ve only used it for vented and closed designs, simulated response matches real life result quite close