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Old 07-14-2002, 07:21 PM   #1
Lee

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Which enclosure type is right for me?

Quote:
4.4 Which enclosure type is right for me? [IDB, DK]
This answer is not designed to tell you exactly what kind of enclosure to build, but rather to give an idea of the advantages and disadvantages to the simple configurations (Infinite baffle [1st order], Sealed [2nd order], Ported [4th order] and basic bandpass). Building and designing more complicated systems (order > 4) is not for the light at heart.

4.4.1 Infinite Baffle ("free-air")
Advantages...
No box necessary!
This means it's usually cheaper to design and implement in your system
Disadvantages...
Requires that a good seal be obtained between front and rear of driver. In a car, this can be quite difficult and may require the installer to remove trim panels to plug any holes that would let energy "bleed through".
The responsibility for damping cone motion rests solely on the driver's suspension. As fatigue sets in, this becomes a critical issue in infinite baffle set-ups.
Less efficient in the sub-bass region than above mentioned enclosures.
Potentially more expensive drivers than good boxable woofer - The suspension must be extremely hearty and long-lasting to withstand high power applications.

4.4.2 Sealed Box
Advantages...
Small enclosure volumes
Shallow (12 dB/Octave) roll off on low end
Excellent power handling at extremely low frequencies
Excellent transient response/ group delay characteristics
Easy to build and design
Forgiving of design and construction errors
Disadvantages...
Not particularly efficient
Marginal power handling in upper bass frequencies
Increased distortion in upper bass over ported design
When using high power and small box, magnet structure is not in an ideal cooling environment

4.4.3 Ported Box
Advantages...
3-4 dB more efficient overall than sealed design
Handles upper bass frequencies better with less distortion
Magnet is in good cooling environment
When properly designed, a ported box will slaughter a sealed in terms of low frequency extension
Disadvantages...
Size (not so critical outside the mobile environment)
Woofer unloads below Fb
More difficult to design/ can result in boomy, nasty sounding bass if misaligned

4.4.4 Bandpass Box
Advantages...
When properly designed and implemented, can provide superior LF extension and efficiency.
Cone motion is controlled more and therefore mechanical power handling is increased.
Cones are physically protected from contents of trunk flying around.
Output is easily channeled directly into the interior of sedans.
Disadvantages...
Difficult to build (not recommended for newbies), and very sensitive to misalignment due to calculation or construction errors.
Their characteristic filtering often masks any distortion that occurs as a result of amplifier clipping or overexcursion and thus will give the user no warning that the driver is over-stressed and about to fail.
Need substantial mid-bass reinforcement to make up for narrow bandwidths in efficient alignments.
Transient response is largely dependent upon the alignment chosen....wider bandwidths will result in sloppier performance, narrower bandwidths (and thus higher effiencies) result in better transient performance.
They can oft times be quite large.
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