replacement driver data calculator

for ported enclosures

Please address all comments and complaints to the caretaker.

An example

Let's suppose that you measure your box and find that:

Its *inside* volume is 3370 in^{3}, or 55,224 cm^{3}. That's about 55.2 liters.

The port is circular with diameter 3". That's an area of about 7.1 in^{2} or 45.6 cm^{2}.

The length/depth of the port is 4". That's about 10.2 cm.

Then:

Compute the volume of the port. Here that's about 465 cm^{3}, or 0.465 liters. Round it up to 0.5 account for wall thickness. Now subtract that from the box volume. So we're down to 54.7 liters.

Estimate the volume occupied by the driver itself. Let's assume an 8" (nominal) driver. Using an (adapted) empirical formula^{*} from Leach's book, the occupied volume is roughly 1.7×10^{-4}×8^{4} ≈ 0.7 liters. That gives a net box volume of about 54 liters.

* The formula for a nominal/advertised diameter *D* in inches is 1.7×10^{-4}×*D*^{4} liters. For *D* in centimeters, it's 0.67×10^{-4}×*D*^{4}.

And then:

Put those numbers into the calculator. Unless you know what *Q _{L}* is about, just leave it set to 10. Anything else is just a guess anyway.

Use the vertical slider to look at the response curves for the different alignments. Find a range of parameters that makes you happy.

Note the corresponding driver parameters. Then go look for a woofer/subwoofer with similar specs.

Of course, *of course!* There are *other considerations:* driver diameter, cutout diameter, overall frequency response (this calculator is only about the low end), efficiency, power handling, impedance, etc. But I hope this calculator helps with the most mysterious parts. Good luck, bonne chance, viel Glück, buena suerte, boa sorte, حظا سعيدا, 好运, 행운, 幸運, זאָל זייַנ מיט מאַזל, удачи, सौभाग्य, pob lwc.

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