Rigid Diaphragm Technology (RDT
®
) mid-range and
bass drivers
Bass and mid-range driver cones use RDT, a unique
technology developed specifically by Monitor Audio’s
engineers for the Platinum series of loudspeakers*.
Designed to reduce mass and increase cone stiffness,
RDT applies ultra-thin skins of C-CAM to a core of
honeycomb Nomex
®
** material, creating a structure
which is extremely light but incredibly rigid. At only
40μm thick, the C-CAM skins are half the thickness
of a human hair, yet when bonded to the hexagonal
honeycomb core they form an RDT cone, which is 150
times more rigid than a single layer of 200μm C-CAM
alloy, but has a fraction of the overall mass. These
properties allow the cone to operate as a lightning-
fast piston for a clearer more natural sound. The
cone’s new concave geometry has been refined by FEA
analysis to provide a smooth frequency response and
eradicate break-up.
To optimise the performance of the RDT cone,
Monitor Audio has developed motor systems in
which a focused magnetic gap and copper eddy
rings work together to produce a higher level of
linearity and lower distortion than was previously
possible. Magnet plates and poles are CNC machined
to very precise standards, ensuring consistency.
The Platinum mid-range driver utilises an ‘under hung’
voice coil design to further optimise linearity and
reduce distortion. High energy NeFeB rare earth
magnets are used for high efficiency, and a large
2” (50mm) voice coil is specified to handle powerful
dynamic impulses. Its RDT cone is driven directly
by the voice coil to provide an extremely articulate
mid-range response and seamless integration
with the other drivers.
Platinum’s bass drivers use long-throw voice coil
windings for long excursions at high power levels,
giving deeper, more controlled and potent bass.
The larger 8” (200mm) drivers employ dual spider
arrangements for extra stability. Their direct-drive
RDT cones have no dust cap or joints to interfere
with the driver response over the working band.
* PLW-15’s driver is C-CAM only
** Nomex
®
is a registered trademark of E.I DuPont de
Nemours and Company
