SLAPS is a patented system that dramatically increases subwoofer efficiency and capability for ultra low frequency reproduction. SLAPS stands for Symmetrically Loaded Audio Passive System. As the name indicates, SLAPS is built symmetrically which distinguishes it from traditional passive devices. SLAPS integrates identical components in its suspension and design ensuring the unit is moving identically in both directions. The revolutionary efficiency and performance are the result of the pneumatic coupling between SLAPS and the active driver. SLAPS overcomes the limitations known from conventional closed and ported designs that prevent radical excursion and deep response. The unique design allows the active driver compression-free movement resulting in deep, dynamic and hard-hitting bass response. The only thing a SLAPS has in common with a traditional passive device is that it is passive, besides that few similarities exists. Conventional computer modeling software will not work correctly with SLAPS and will in most cases greatly overestimate the internal volume of the optimal cabinet.

Why use SLAPS radiator instead of a sealed or ported cabinet?

• SLAPS increases a subwoofer efficiency and capability for ultra low frequency reproduction (very deep Sub-bass) without the drawbacks of traditional designs.
• SLAPS opens up new subwoofer designs where even very small enclosures can be tuned to quite low frequencies. SLAPS can be custom tuned for optimum performance in a wide range of housing sizes and device configurations.

How does SLAPS work?

• A subwoofer design with SLAPS consists of an active sub woofer driver and a cabinet (sealed cabinet) and a SLAPS passive radiator.
• The SLAPS device is controlled by the active device through the alternating pressure and counter- pressure (vacuum) which occurs in a sealed cabinet when the active device plays bass. It gives you much better performance due to the increased surface area and the fact that the particles of air inside the enclosure and outside the cabinet moves with the same speed and in a near phase relationship.

A traditional bass reflex port design- the system is limited in performance due to the air in the reflex port not being in phase or at the same speed of movement as the air in front of the active driver.

(Phase means that the active device and SLAP work almost concurrently and simultaneously creates respectively pressure and counter-pressure at the same time)

How do I get started with my own design?

• You have to decide on what size bass speaker to use.

You've probably already given some thoughts to what size subwoofer you want to use and you probably also have a rough idea of how large your cabinet should be. Here are a few guidelines that you should follow:

• In principle you can choose what size bass speaker you want to use but it is recommended to use from 10 inch and up to 18 inches. There is in principle no limit to how many woofers or SLAPS devices you can use in the same cabinet. However it is important not to use a SLAPS smaller than the active woofer since it is not an efficient design. Using a larger SLAPS than active woofer is no problem. There can be several smaller SLAPS units, as long as the sum of which at minimum equals the surface area of the active device.
• It is important that the chosen woofer is a "LONG STROKE" or "LONG THROW" ie a woofer designed for Sub-bass.
• Active woofer unit should preferably have a resonance frequency (FS) of 30Hz or less and not more than 35 HZ. This data can be found in the woofers datasheet. The technical term is called- FS / Fs or F0 but it can also be listed as the resonance frequency or free air resonance or just resonance.
• If the selected woofer unit is of poor quality this will influence performance. Look for a woofer with a large magnet and heavy duty voice coil. It is important that the voice coil has a high winding height and is of large diameter. (Does not apply to neodymium2 magnets which are typically physically smaller)

Use number of SLAPS units.

• Whichever size woofer you choose will determine the size of the cabinet. It is important that the cabinet is solidly constructed so it does not vibrate or rattle. Typically 16 mm MDF or thicker. Particleboard or plywood are also excellent materials. You can also make the cabinet in acrylic or plexiglass. The most important thing is that the cabinet is completely sealed and does not vibrate.When using SLAPS, it is very important that the chassis is 100% sealed all joints and terminals / devices and SLAPS so no air can get either in or out.
• The following shows the cabinet size should be used with the different sizes of woofers. This covers all long stroke woofers of all brands. It is important that you do not exceed the maximum specified enclosure volume. The air inside the cabinet acts like a spring and the larger the enclosure the lower the linear output. This also introduces distortion.

• 10 inch: 20 - 45 liters internal volume sealed cabinet
• 12 inch: 30-60 liters internal volume sealed cabinet
• 15 inch: 35-100 liters internal volume sealed cabinet
• 18 inch: 50-140 liters internal volume sealed cabinet

The bigger the cabinet, the lower the system resonance will be. If the minimum size cabinet is desired the system resonance can be lowered by adding weight to the SLAPS see section 4 of this manual.

• Internal damping material should not be used as that lowers the precision of the pneumatic coupling between the active and passive driver.
• Make sure to design your cabinet so that there is room for both the woofer and SLAPS device and the excursion of the SLAPS. If the subwoofer is to have a build in amplifier, then also account for the cabinet space it needs.

Hz Hz

Deep bass tuning of your SLAPS subwoofer with the addition of weight to the moving mass.

• Your SLAPS membrane has a given net weight from the factory. This specific weight can be increased and adjusted to the cabinet resulting in a deeper bass. A higher moving mass on the SLAPS lowers overall system resonance and increased membrane inertia is pushing it towards lower frequencies.
• All you need is a drill, a drill bit, a bolt, a few nuts and some washers and a weight ( letter scale or similar)

IMPORTANT. Note that 25 Hz as the resonance is a very deep bass and 20 Hz, the lowest frequency that can be perceived by the human ear. With SLAPS and a good woofer it will be possible to tune your system down to below 15 Hz which is the subsonic region that can only be felt as pressure waves. You will of course try to tune your own design as far down as possible, but never try to add more extra weight than 350-400 gr as it may harm your speaker design.

• You can place your SLAPS on either side of the cabinet or the back of the cabinet. If you have room on the front you can also place your SLAPS next to the active woofer. By placing SLAPS right next to the active woofer so you run the risk that at the acoustic resonance frequency there may be a negative interference which and the can lower the overall sound pressure level of the deepest bass tones. The lower the resonance is set, the less likely it is that there will be an issue.
• Best results are obtained by placing it on the back or side of the cabinet.
• The SLAPS device can also be mounted on the bottom of the cabinet. Note that when doing so you can not add extra weight to the SLAPS.
• Now you have both a cabinet with a woofer and a SLAPS mounted and all that remains is to connect the wires to the active woofer.