Some obversations on
Sealed vs. Vented
enclosure designs...
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So, to recap: The vented design as modeled above has:

> Greater max SPL than the sealed design

> Has more bass extension with equal or less cone excursion

> It emulates the sealed box Qtc, or response roll off, for the relevant portion of the passband

> The increase in group delay results in little additional phase rotation

> It utilizes the same enclosure volume as the sealed example

> Its transient response is much better than a traditional vented QB3 alignment, and only somewhat
than the sealed design

Other possible alignments:

Increasing the enclosure size while holding the tuning frequency constant will result in emulating a lower
Qtc response roll off, and lower f3/f10 frequencies. For example: The RS225 in a sealed enclosure with
a Qtc of .6 required a 64 liter enclosure. To obtain the same transfer function in the vented design only
required a 50 liter enclosure tuned to 20 Hz, and it was able to provide 2 dB more SPL than the sealed
without exceeding Xmax. Additional group delay was only 36 degrees at 22 Hz.

In Conclusion:

In this article, I have suggested that vented designs with small enclosures and low tuning can be an
attractive alternative to the traditional sealed box, offering  advantages that may compensate for their
marginally worse transient response in many instances. The ability to plug the vent and return to a
sealed box design makes it a risk free venture.

Curt Campbell
Copyright 2006