At first glance, it may appear counterintuitive to place the drivers 180deg apart. This observation may be true for higher frequencies (shorter wavelengths) where two drivers would only be 3dB louder than one. But for the case of subwoofers where the wavelength of sound being reproduced is considerably larger than the inter-driver spacing, the wavefronts from each driver sum totally, giving a 6dB increase in output. That’s double acoustically power.

To put that in perspective; to achieve a similar increase at higher frequencies, you would need to employ four drivers, or one four times the area. Even double the area – which is all we require in the world of sub-bass – would present it’s own set of issues in terms of engineering because we are already using a 13.8” cone.

There is a further benefit to using two drivers and that relates to thermal compression. With two drivers, you have two voice coils, with double the area. This greater area makes it easier to dissipate heat, the build-up of which, limits maximum power levels, compresses dynamic peaks, and generally distorts the signal – It causes distortion. In the bass arms race, bigger is not always better, but more, is.

NEWTON’S THIRD LAW

For every action, there is an equal and opposite reaction. When you push a speaker cone out in response to a signal, an equal force is applied to the structure of the basket and cabinet, to which is fixed, trying to move it in the opposite direction with exactly the same force. Use two drivers pointing in opposite directions, and these forces cancel, totally.

Of course, opposing drivers change nothing when it comes to the pressure inside the cabinet, resulting from the pressurization and rarefaction caused by the drivers pumping in and out. This significant force literally bends the cabinet walls, causing them to emit bass out-of-phase with the drivers, robbing us of output and introducing cabinet colorations. To cope with that, we resorted to good old-fashioned over-engineering, with inch-thick minimum HDF cabinet panels (2” on the driver baffles) and further internal bracing.

So, with our dual opposed drivers and massively engineered cabinets, vibrations within the cabinet structure become hardly noticeable to the touch, even when the subwoofer is playing at substantial SPL’s. Place your hand on an Arendal Sound subwoofer and you will feel very, very little indeed, even if all hell appears to be breaking loose within the room.

The end result is rock solid, undistorted bass that may not move the planets Newton was thinking of, but it will move you.