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Speaker enclosure types for all applications, what type is best for your project?





Speaker enclosure types

woofer box types


Below are examples of automotive sub woofer enclosure boxes) for many different applications.


Designing a car audio woofer system:

With any high-end audio sound installation, you should stick to a very logical and straightforward procedure. The most important factors are size, performance, cost, and ease of construction.

First decide how much room you would like to dedicate to your woofer system; usually, the bigger the box, the better. This will inevitably affect the other parameters of the design process. High-performance systems usually require large woofers or enclosures. This will typically raise the price of the system and increases the amount of time required for installation.

Once you have decided on how much space your woofer box will occupy, you should then determine what type of enclosure is right for your particular application. The simplest type of woofer system is the "infinite baffle." The infinite baffle is simply a barrier that separates the front of the speaker from the back of the speaker; this barrier is called a baffle board. A typical infinite-baffle installation in an car stereo sound system consists of mounting the woofer's on the rear deck of the vehicle or on the back of the rear seat. As with any infinite-baffle design, it is very important that sound waves do not reach from the rear of the speaker to its front. If this occurs, cancellation will occur and bass response will suffer.

An infinite-baffle system is usually the simplest way to install woofers in your vehicle. You should expect good performance from this type of installation, and since there are no enclosures to build or design, installation time and cost are kept to a minimum. Unfortunately, there are several disadvantages to the infinite baffle. When a speaker is mounted in an enclosure, the air inside the box acts like a spring against the speaker cone, and the buildup in pressure provides mechanical damping and prevents excessive  speaker cone movement. But an infinite-baffle installation does not use an enclosure, so the damping is poor, resulting in "hang-over" and lack of definition. The power handling of the speaker will also be reduced since the infinite baffle provides very little control over the speaker cone excursion.


What type of enclosure is best for your project?




Sealed Box

This is a sealed enclosure that uses a calculated volume of air as a spring" to help dampen and control woofer cone movement. Sealed enclosures can have a relatively smooth roll-off and flat response.

Pro's: Small boxes, higher power handling, excellent dampening and transient response, easy to design and build, can be forgiving of design and construction errors.

Cons: Efficiency vs. output



Ported Enclosure

Ported enclosures use a tuned port or vent to increase output at lower frequencies. Air inside the vent acts like a piston or motor that moves in the phase with the woofer reinforcing frequencies.

Pros:  Increased efficiency, increased low frequency output, relatively low distortion.

Cons: Larger enclosures less tolerant of design/construction errors, no woofer control below tuning frequency.




Aperiodic enclosures utilize an external membrane to dampen the woofer and flatten out the impedance curve of the enclosure.

Pro’s: Extremely small enclosures, very flat response, excellent low extension.

Cons: Low efficiency, usually needs larger subwoofers to perform, EXTREMELY difficult to design and tune properly.


Isobaric (most commonly “push-pull”)

An enclosure that uses two woofers mounted face to face, one wired reverse polarity.  This alignment effectively cuts the vas in half.  The general rule of thumb for an isobaric enclosure is twice the woofers, twice the power, and half the box size3.

Pros: Very small enclosures, increased power handling, driver non-linearities canceled out (lower distortion).

Cons: Very low efficiency, due to the small size of the recommended enclosures for our woofers an isobaric alignment is not practical.


Sealed Inverted

Sealed Box (Inverted woofer)

Often mistaken for an Isobaric set up, this is simply a woofer mounted in a sealed box with the magnet facing out.  This is done for cosmetic or depth reasons only. There is no sonic benefit.


Acoustic Coupled

Acoustic Coupled

Two woofers sharing a given volume.

Pro’s: Can be easier to build than a divided enclosure.

Cons: Output can be affected each driver relieving slightly different information, enclosure is more likely t flex without the additional bracing of the divider (usually need additional bracing).


Infinite Baffle

Infinite Baffle: a.k.a. Free-air

A woofer mounted to a surface that isolates the front wave from the back. (A woofer in an enclosure which has a larger vas than the woofers vas).

Pros: Very low system resonance, minimal space used in the vehicle.

Cons:  Limited efficiency/output, no control of the woofer below its fs, usually very difficult to seal front wave from back.


Single Reflex Band pass

Single reflex band pass

Sealed enclosures that play into a tune enclosure that acts an s a low pass filter... This increases efficiency within the “pass band” or usable frequency range of the enclosure.

Pros: Can be made very efficient within the pass-band”, can be designed for increased gain in a band of frequencies, increased power handling within the band.

Cons:  Distortion hard to hear so, it’s very easy to destroy woofers, increased gain designs sacrifice low end response, relatively large enclosures very difficult to design and build, very sensitive to design/construction errors.


Dual Reflex Band pass

Dual Reflex band pass:

A ported enclosure in which the woofer plays into a tune-ported enclosure that acts a low pass filter.  This creates a highly efficient system with two resonance frequencies.

Pros: Can be even more efficient than a single reflex band pass; excellent dampening at resonance, increased power handling at resonance 

Cons:  EXTREMELY difficult to design/construct, not forgiving of designs/construction errors like a ported enclosure it looses woofer control below f3, steep low frequency roll-off (24db) very large enclosures.


Ported SPL

Ported (SPL)

Extremely large enclosures with very large port area.  These enclosures have high ripple and are used to pinpoint and boost a specific frequency.

 Pro’s:  Very high SPL

Con’s:  Very high f3 (woofer control is lost below f3), trying to reproduce musical frequencies will result in woofer failure.


Transmission Line


 A form of Transmission Line, this enclosure uses a port that is a fraction of a wave length to couple with the woofer.

Pros: Can be built to maximize out put at a particular frequency (SPL purposes)

 Cons:  Difficult to build, giant enclosures, easy to blow woofers, not practical unless used for SPL competition, experimental.





Here you will find more detail about each speaker box and which one is right for your application.


Woofer box Laboratories



Box Design




Speaker enclosure types


Speaker boxes design


Sealed box


Ported woofer box


Infinite baffle


Sealed Inverted




Speaker polarity and impedance


Speaker wiring:Parallel, Series, Series-Parallel





Woofer box calculators index


Calculating speaker enclosure volume


Rectangle sealed enclosure volume calculator


Circle port to slotted port calculator


Triangle Box volume calculator


Parallel- Parallel Load Calculator


Port length calculator


Series - Parallel load calculator




Bass cancellation







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