JAMO R 909, Technical Description

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A ‘low pass’ bass fi lter is applied to match the higher bass output to that of the
mid and treble levels, so that they integrate smoothly. However, at the lowest
frequencies the bass is not fi ltered at all, a tactic which allows the woofers to reach
down to an amazing 25Hz with unmatched precision and attack.
It may be hard to believe it’s possible but a quick demonstration is all it takes to be
convinced - sit down, take a listen to the R 909 and you’ll hear the proof!!
T H E D R I V E R S
WOOFERS
In order to obtain a full frequency response the woofer basically needs to fulfi l
two criteria: it has to be of high effi ciency and have suffi ciently low resonance
frequency.
As most woofers are developed to work in a cabinet
(which necessitates heavy cones in order to reach
the desired resonance frequency – typically around
45Hz) we had to develop a special woofer for this
open-baffl e application. A woofer constructed for a
dipole application is utterly different to a traditional
boxed driver.
The cones used, for instance, are lightweight air dried paper cones with rubber
suspension which allows both fast acceleration and deceleration. To optimize
air fl ow the sturdy magnesium basket is of a very open construction. In order to
minimize mechanical losses (created by over/under pressure behind the cone and
the huge 2in/50mm voice coil), the magnet also features a vented polepiece as well
as a ventilated basket behind the spider.
We actually managed to reach a resonance frequency of 27Hz!
The overall result is a driver capable of delivering an extremely fast and fi rm bass.
MIDRANGE
Designing a loudspeaker cone involves striking an optimum balance between
stiffness and low weight. Magnesium meets both criteria, resulting in highly
effective and dynamic sounding reproduction.
The end product is a cone that can reach up to 9k Hz before any signifi cant cone
break-ups occur. This makes for extremely low distortion throughout the range
plus a very open and detailed midrange for optimum voice reproduction.