isobaric design. calculations anyone?

[keyser]

hi,
i have two visaton W 300 S woofers lying around. I have already calculated a good reflex-box. however, 150 liter times 2 is still 300 liters!
That's a bit too much for me. Now i am thinking about using the two to get an isobaric subwoofer. I know what it is. The box volume will be half of 150 (75 liters). I don't know how i am supposed to calulate the bass-reflex or Fb.
anyone?
thank you

 

[Svante]

Half Vas, keep fs and Qts.

 

[keyser]

ok,
what would this do to my tuning frequensie and port-length with a 104 mm pipe?
i've already got the new boxvolume, its 150/2= 75 liters.
The reflex pipe for the 150 literbox should be 10.5*20 cm to be tuned at 25 hertz.
what happens to the pipe when in 75 liter isobaric?

 

[BassAwdyO]

The box tuning is not effected by the speakers in the box. The response is! In my experience always mount Isobaric subs vertically (with the magnets in a vertical line). This gives more excursion as the cones sag.

 

[Ron E]

ok,
what would this do to my tuning frequensie and port-length with a 104 mm pipe?
i've already got the new boxvolume, its 150/2= 75 liters.
The reflex pipe for the 150 literbox should be 10.5*20 cm to be tuned at 25 hertz.
what happens to the pipe when in 75 liter isobaric?

The tuning frequency stays the same. The port length will about double for the same diameter pipe. A smaller box needs a longer port to maintain the same tuning...

Do a search for the formula, or enter the parameters for teh driver with Vas cut by one half and figure it out with a program.