REL Acoustics ‘ST III’ User Manual
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TECHNICAL
Strata III
Strata is designed as a closed box system. For its cabinet volume and drive unit, this offers
the best compromise between extension and power handling. With smaller cabinets, such as
Strata, the addition of a port to make it a reflex design can result in excessive port noise
heard as chuffing sounds on very low frequencies, such as organ pedal notes. The 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.
Storm III and Stadium III
Storm III and Stadium III use incrementally more powerful drive units, amplifiers and larger
cabinets compared to Strata. The drive unit fitted to Storm is a bespoke British made Volt
driver, the driver fitted to Stadium III is an upgraded Storm III driver which handles greater
power and gives more depth. Because of these improvements, advantage can be taken of
reflex loading. The port noise of Storm III and Stadium III is very low and is totally innocuous
in practice. The ARM (Acoustic Resistive Matrix) loading in Stadium III further aids the
reduction of port noise and adds more control to the air flow. The usual advantages of lower
distortion, greater power output are further benefits of using a reflex design.
Stentor lll and Studio III
Stentor and Studio use a very powerful and more sophisticated amplifier to drive the single
driver of Stentor and the dual drivers of Studio. Stentor III and Studio III have Super Arm
Loading, this is a series of chambers and baffles which effectively, in conjunction with the port
tube, produce the overall length of the port required. This method also eliminates port noise.
The drivers are again British made units, specially developed for REL by Volt Loudspeakers.
They have extra large magnets and very stiff suspension.
All Models
For maximum performance we believe the electronics, cabinet and the drive unit should all be
designed to work together.
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.
Great care is taken over the star earthing to maximise sound quality.
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), the bridge rectifier is very conservatively rated at 35 Amps. The
transformers are ultra quiet audio quality toroids 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!
