REL Acoustics Britannia Range User Manual
25
TECHNICAL
The Britannia range utilizes an unique (Patent applied for) loading system called Acoustic
Resistive Matrix (ARM) loading. This unique to REL system offers significant advantages
over conventional reflex loading. Firstly, it significantly lowers the system resonant
frequency, this on its own is a very worthwhile advantage over simple reflex loading, but it
also offers the very important benefit of much reduced port noise (chuffing). Its action is a
cross between ordinary reflex loading and a transmission line. Because it has similarities
to a transmission line, it means it also has less stored energy compared to a reflex, this
translates into a faster sound. Rhythmic timing is improved, yet it also offers far higher
output sound pressure levels for its driver size compared to a closed box. By designing the
port to fire down onto the floor, it means the Britannia series have all the benefits of a
downward firing sub, but also all the benefits of forward firing for impact and excellent
dynamics for home movies. Remember the very lowest frequencies that are felt, rather
than heard, emanate from the port, it is somewhat similar to having two drive units, each
optimised for it’s particular purpose.
The particular adaptation of ARM loading used in the new Britannia series is a third
generation on from our previous methods. A lot of thought and experimenting has gone
into these models to ensure they represent the highest possible performance for their size.
Each cabinet is manufactured from 30 mm thick MDF (Medium Density Fibreboard). This
is the material of choice where the very highest quality is demanded. There can be no
substitute for weight and density as far as low frequencies are concerned.
Each model in the Britannia range uses incrementally more powerful drive units, amplifiers
and larger cabinets compared to the base model. The drive unit fitted to B3 is a bespoke
driver with an exceptionally heavy and powerful motor assembly. This is very important to
maximise dynamics and control. The driver fitted to the B2 mode is an upgraded B3 driver
with a heavier cast chassis, this driver handles greater power both through greater linear
extension and the ability to dissipate more heat, and this translates into greater bass depth
and volume. To help control this power and to further minimise port noise, both the B2 and
the B1 models incorporate Balanced ARM loading. This is a refinement of the ARM
loading that is used in the B3, it offers even greater bass depth and increased power
handling without excessive port noise. The B1 model represents state of the art design.
Because it has a 12 inch drive unit and an even more powerful amplifier together with
Balanced ARM loading (as in B2) it can approach sound pressure levels that can be too
high for comfort. The port noise of all models is very low and is totally innocuous in
practice.
All REL amplifiers are fully DC coupled to avoid phase shifts and compromises in their low
end performance. The line level and filter stages are fully regulated to ensure total
isolation from the power amp stages. The filter stages are unique designs using the highest
quality components. The capacitors are high quality nitrogen filled polystyrene types of 1%
very close tolerance and an indefinite life. The use of very close tolerance components
also ensures consistency of performance throughout the production life of each model.
The filter board is identical for all three models and is designed so that each fine
adjustment equates to a semitone, offering musically correct increments of the filter.
There is further filtering of the higher frequencies to ensure optimum performance at all
settings of the ABC. The built-in power amplifier is built onto a separate circuit board and
uses ultra rugged audio grade MOSFET output devices. The power supply is the engine
house of the amplifier, the smoothing capacitors are long life with very low equivalent
series resistance (ESR), and the bridge rectifier is very conservatively rated at 35Amps.
Most of our competitors boast about using 6 Amp or perhaps 10 Amp rectifiers. We feel
this is short-changing the customer. It must mean a higher impedance path between the
source of power (the AC mains) and the amplifier supply rails. The transformers are ultra
quiet audio quality toroid types with very low losses, these are especially manufactured to
our strict specifications. Great care has been taken to deliberately over engineer all REL
products to ensure ruggedness in service. This ensures an exceptionally robust, long
lasting device. For all practical purposes it will probably outlast its owner!
