Box Technology

[Rex]

AP Mats

USD AP Mats An AP subwoofer system is one which employs 2 enclosure volumes coupled with a purely resistive element, the AP Mat. When such a system is properly designed, it is possible to control the woofer cone movement by the energy transfer though the precision acoustic resistance of the AP Mat. The completed system will be considered A-periodic, or over-damped with a Q well below 0.7 Qts. In contrast, most car audio systems are grossly under damped, with Q's greater than 0.8 and higher. These high-Q systems have poor transient response, nasty peaks in their frequency response and high rates of roll-off. The result of controlling cone motion with a resistive AP Mat is a very low system Qt. A-periodic systems feature excellent transient and phase response, smooth frequency response and extended very-low frequency reproduction with quicker attack, less bass hangover and lower cone distortion.

* Constructed of high-quality MDF and special high-density FMSTM damping material * Regains trunk space by using a very small box size (less than 0.33 cubic feet) * No expensive meters needed to "tune" the enclosure * Very predicatable flat frequency response * Power handling of small sealed box w/ bass of a large box. * Provides detailed bass response, and lower distortion. * Improved transient response versus other boxes designs. * AP Mat enclosures extend lower than conventional enclosures. * Comes with easy to follow installation instructions. * Available for 10", 12" and 15" subwoofers

Subwoofer Compatibility 10" Subwoofer Qts of 0.39 or less 12" Subwoofer Qts of 0.45 or less 15" Subwoofer Qts of 0.45 or less

Isobaric - SealedWhen enclosure space must be at a minimum, sealed isobaric designs work very well. These usually require half the space of a basic sealed enclosure, but require twice as many drivers and will acheive the same acoustical output as the single driver show above in the larger enclosure.

Isobaric - Sealed (Compound Loading)Another isobaric enclosure with the drivers facing the same direction. Obviously this will require a larger enclosure than the one shown above, but again, output will be the same.

Isobaric - Sealed (Back to Back)Another variation of an isobaric enclosure. It doesn't matter which way the two drivers face, but if you have the space to use this enclosure, you should be able to use a simple sealed enclosure instead (only one driver reguired!).

Isobaric - Sealed (Planar Loading)Odd spaces will require unique box shapes. This isobaric enclosure can be a great solution for such a space. Remember, the volume of air space between the two drivers is not crucial to the design of the enclosure, (however, you do not want to make it too small) only the volume of the main section of the enclosure (that of the rear enclosed driver).

Isobaric - Bass ReflexIf space is at a premium or just a smaller enclosure is desired, an isobaric design may be used. The volume of the enclosure wil be approximately half the space of the above enclosure with the same results. The downside is you will need two woofers vs. one and the output will be the same.

Isobaric - Bass Reflex (Compound Loading)This is a variation of the above enclosure. As long as the woofers are mechanically in phase, it doesn't matter which way they face each other, however this will require a larger enclosure to accomodate the magnet and frame assembly of the outer woofer and is more complex to build.

Isobaric Bass Reflex - Passive Radiator EnclosuresPassive radiator systems are very similar to ported systems. Instead of a tuned port, a "drone cone" is used to extend the low frequency response. Most look like a flat diaphram, some may look like a woofer, but will have no magnet structure. The response is similar to a ported system, but the cut-off frequency is slightly higher, and the cut-off slope is slightly steeper. Many of you may have seen the very small enclosures made by Stillwater Designs® that used 4'' drivers with a passive radiator (not sure if they still make these). These worked extremely well (for what they were) in vehicles that literally had next to no room at all to mount a conventional enclosure inside of the vehicle (i.e.: Jaguars XJS, mounted under the seats).

Isobaric Single Reflex - Band Pass EnclosuresThe single-reflex band pass enclosure is basically a combination of a sealed and vented enclosure. These can be fairly small enclosures, though larger than a sealed enclosure. They offer great power handling, good low frequency response, but are not as efficient as vented enclosures (top of this page), and are more complex to build. However, when built correctly, these make excellent enclosures and are often used by competitors. This is often referred to as a fifth order enclosure, but it's not. The addition of a crossover makes it a fifth order system.

[PoorManQ45]

Good post rex. Now I'll just link to this thread when asked about AP and ISobarik enclosures

[nab911]

So where exactly do you mount hte mat?

[PoorManQ45]

YOu make 5walls. The front, top, left, right, and bottom. You leave off one wall, usually the back, and mount the AP Mat in its place.

[audtatious]

Good stuff Rex.