MGrant1957
Building a pair of new Boxes for a small hatchback and want to try 4th order with a single 8" internal driver with 8" passive radiators used in place of the ports as this will result in a smaller box, and I have a few questions....

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not to scale but the question is how do I determine what frequencies to tune the two passives to? Do I put the driver in the larger or smaller chamber? these PRs are mass adjustable so given the drivers Fs of 33.7 Hz, AJDesigner says should tune the overall box to 53.5Hz with the smaller chamber at .6 FT^3 and the larger chamber at 1 Ft^3, how do calculate the required tuning freq. for the front and rear chambers? and if required, how do I reduce the mass of the high-tuned passive?

Thanks for any info/advise.
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MGrant1957
well that didn't work, I'll try this:
two chamber box with a driver mounted in a divider mounted off center of the box. each chamber has a passive radiator mounted 90 degrees from the driver. each passive will be tuned to a different frequency. the passive mounted in the smaller chamber with the driver will be tuned to Fh of 86.9Hz while the second passive radiator will be tuned to Fl of 32.9Hz
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D-Bass
i like having more PR surface area than driver surface area.
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MGrant1957
did some more research and I think I'd be better of with a 4th order bandpass.
I'm using Dayton Audio SD215-88 drivers matched
with a pair of Dayton Audio SD215-PR passives,
both have a Vas of 1.4 cu. Ft.

Using AJDesigner, I got the following results:
Vf=1034.21 cu. in.
Vr=1714.82 cu. in.
Fb=53.49Hz
Fl=32.93Hz
Fh=86.89Hz

These figures go well with the 4 ch speakers that will be at the 4 corners in the car. my best estimates give me a box that has internal dimensions of 9.5x22.5x12.85 inches.

I will be using acoustistuff to dampen internally.
Do I need to include the vol. of the driver or passives in my calculations? and how accurate do I need to be in building the box? can I build something close and tune it with mass on the Passive radiators?

Any thoughts/comments/advice?

thanks.
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