Dipolar means the sound is distributed from both the front and rear of the speaker – in opposite phase.

The reason for using dipolar surround speakers is not that you should be able to pinpoint their physical location; on the contrary, they should add a ‘3D’ ambience to the surround effects, making you feel part of the action.

A dipolar front speaker’s sound radiation will emerge from the back and bounce from the rear and side wall before reaching your ears, creating a slight delay in the sound from the front and back. The 2nd order reflections adds ambience and gives you the impression of a much larger room.

A dipolar front speaker is to be angled in slightly from the rear wall. Due to the angling the rear sound will be bouncing off two boundaries before reaching your ears. The reflections add ambience and gives you the impression of a much larger room.

The 1.7in/43mm thick front baffle is made from no less than seven layers of MDF board, glued together and shaped under high pressure. The rounded shape provides optimum working conditions for the drivers as it prevents diffraction and improves rigidity even further.

The baffle itself is attached to a 57lb/26kg cast-iron base housing the cross-over network and the bi-wiring XL binding posts, they connect directly to the crossover network placed inside the base, so securing the best possible signal path. A solid double 5x60mm stainless steel brace with a special damper ensures a rock solid connection between the baffle and the base.
 

In order to fulfill the R 909 brief we also had to use state-of-the-art technology for the midrange driver. Employing a patented Neodymium magnet arrangement, the Seas unit uses a magnesium cone for its stiffness and low weight, both vital qualities for dynamic response. Thanks to the HCC (Hard Conical Cone) technology the driver is able to reach all the way to 9kHz before any significant cone break-ups occur. This makes for extremely low distortion throughout the range plus a very open and detailed midrange for optimum voice reproduction. Turned from solid brass the centre-plug has a cooling effect on the voice-coil, providing greater power-handling capability and most importantly, extra sonic stability when playing at high volume levels.
 

There was only one choice when it came to choosing a tweeter to reproduce the delicate treble frequencies… the legendary Revelator from Scan Speak. However, since this model features a relatively large face-plate, it would have needed to have been placed further away from the midrange than would be ideal. So, in order to obtain a seamless transition with the midrange driver, we chose to fit a smaller cast-alloy face plate.

The tweeter features a 1in textile dome which is coated several times to obtain a unique combination of dynamic linearity and resonance damping, the result being an incredibly smooth, linear, dynamic and incredibly transparent sound.

The driver´s Symmetric Drive Technology - a copper ring on the pole that extends past the voice coil, curving into the dome chamber - practically eliminates electrical phase shift. And, just as it does with the midrange, it also lowers distortion significantly.

To eliminate turbulence the double-damped, optimized chamber behind the magnet system is also equipped with an anti-resonator-plug. And the specially designed chamber under the cloth surround minimizes air noise and compression. Actually this tweeter is so carefully manufactured that damping unwanted resonances using ferro-fluid - the usual way - is rendered unnecessary!
 

Most woofers are developed to work in a cabinet, and as a woofer constructed for a dipole application is very different from a traditional boxed one we had to develop a special woofer for this open-baffle application.

These huge bass drivers employ high quality magnesium baskets plus lightweight, air-dried paper cones with a rubber suspension. The time-consuming process of letting the cones air-dry – instead of just pressing out the water in the former - has resulted in a thicker, and thus more rigid, material for the same low weight. Although paper cones might be out of fashion in some circles they have the ability to start/stop moving incredibly quickly, can reach very, very deep and they endow the drive unit with great sonic precision and musicality.
 

As should be apparent from the drive unit descriptions, we wanted to start out with drivers of immense fundamental quality, precisely so that we would only need minimal assistance from the cross-over!

Consequently, the cross-over in the Jamo R 909 is of a relatively simple – in the most positive sense of the word – low-order configuration. The advantages of using the 2nd order filters that are in the R 909 is that both electrical and phase angles are kept at very small values, something that´s of great importance both in terms of sound quality and the eventual load on the amplifier. The use of quality Solen foil-capacitors and air-coils in the crossover further ensures sound quality.