A Pair of Westra XW-165-1394..

Hi all,

I'm very newbie about subwoofer enclosure design.

I have a pair of Westra XW-165-1394 and they said (some of my friends) me they're very good bass drivers... So I plan to make a iso-barik vented box for them. That's the parameters:

Technische Daten
Belastbarkeit RMS 60 Watt
Kennschalldruck 1 Watt/ 1m 86 dB
Impedanz Z 4 W
Resonanzfrequenz fo 44 Hz
Gleichstromwiderstand Re 3,7 W
Mechanische Güte Qms 2,51
Elektrische Güte Qes 0,87
Gesamt Güte Qts 0,62
Äquivalentvolumen VAS 30 Liter
Eff. Membranfläche A 143 cm2

When I calculate a vented box with WinISD, I had very good results: that 24.5Hz (-3dB) with 60 liter box, one port and iso-barik installation!

One: Is 24.5Hz enough?
Two: Does Fo means Fs?

And the final: How can I install that drivers as iso-barik?

Thanks in advance for your helps and sory for my bad English..
to install the drivers in a "clamshell" iso-baric design, all you need to do, is drill one su8b mounting hole in your box, drop one of the subs in to the hole, and put the other sub on thop of it SO THAT THE TWO CONES ARE FACING EACH OTHER. Line up the screw holes on the two woofs, and screw into the box. TADA! isobaric!

and this is ABSOLOUTLY crucial, you must wire the OUTER driver OUT OF PHASE from the INSIDE driver, meaning if the red is on the positive and black on the negative for the inside driver, the outer driver must have the wires REVERSED. this is absoloutly important, and failure to do this COULD cause woofer damage.

If you already have the drivers, and winisd says that is your f3, well, you might as well try it out! and f3 of 25hz is well enough for a music sub, and better than alot of those "subwoofers" you get in home theater in a box kits.

Happy building

PS: I dont know any foreign languages, but Resonanzfrequenz is probably Resonant frequency in english, which is the fs, so id say that f0 and fs being the same is a safe assumption.

I guess I understant that. If I'm wrong please warn me:

To install two drivers in compund (iso-barik) style;

My drivers are 6,5" so I'll drill a 6,5" hole to my 60 liters box (bottom side). I'll install my first driver to inside of my box normally, and install the second driver to bottom of first and they will stand as face to face.. like that |< >| is it?

For wiring; the outsider must be reverse pol (for + pin I'll connect amplifiers - pole) and the insider connects normal (+ to +, - to -). And when the insider moves left for example the outsider moves right same time...

Does all true?

Thanks a lot for your assistance.
Yes you're ok.

You should design a spacer to make some space for your 6.5" surrounds. They should not touch each other when they are face to face. The spacer must be completely air tight, no air can leak. If there's air leaks, both drivers will not be able to work as one.

This website might help you a bit :


Good luck!
I see different mounting positions there! Are those all possible? For example if I install my drivers as "Piggy Back Tunnel" it changes what?

As I can see "Clamshell" is the worst position to applicate. Should I use same volume of box for the other positions? Or any program can you recommend to calculate to various isobarik positions?

And the final question: in this forum; another topic is about dipole installation. Does dipole installation = "Piggy Back Tunnel" ?

Thanks a lot...
You did not read correctly. Clamshell is the best isobaric configuration.

Yes, all configurations are possible, but not as good as Clamshell.

The volume of the box stays the same for every position, but Clamshell will be closer to the simulated curve.

Dipole installation is a single woofer on a baffle, no box, both sides are exposed to the air.