sE Electronics Reflexion Filter
Description
What is the Reflexion Filter?
The Reflexion Filter is basically a portable device for recording live sound
sources with reduced room ambience. It is an advanced composite wall which is
positioned behind any microphone by means of a variable position stand clamp
assembly which ships with the product. The main function is to help obtain a
dry vocal or instrument recording. This is especially useful in studios
without proper acoustic treatment, but can also be used to help record takes in
control rooms, where the performer also has to operate the recording device, or
in rehearsal studios to reduce ambient noise.
The Technical Bit:
The Reflexion Filter has 6 main layers. Firstly, a strong layer of punched
Aluminium which allows sound waves to pass through it, diffused, to a layer of
absorptive wool. The sound waves then hit a layer of Aluminium foil which helps
dissipate energy and break up the lower frequency wave-forms, and from here
they hit an air space kept open by rods passing through the various layers. The
air gap acts as an acoustic barrier. The sound waves then pass to a further
layer of wool and then through an outer, punched, Aluminium wall which further
serve to absorb then diffuse the remaining acoustic energy.
The main absorber has 4 formed pieces of state-of-the-art specialist acoustic
absorptive material attached to its face via the extended separation rods,
which further serve to absorb and then diffuse the sound waves as they pass to
the main filter.
The stand
assembly comprises a mic stand clamp fitting, which attaches by means of a
vertical joint to the horizontal bar assembly onto which both the Reflexion
Filter, and any standard fitting shock mount can be fixed. The microphone (in
its shock mount) can then be moved both vertically and horizontally along the
bar, and the Reflexion Filter itself can be moved vertically to obtain the
optimum working position.
How does it work?
The various layers both absorb and diffuse the sound waves hitting them, so
progressively less of the original source acoustic energy passes through each
layer. This reduces the amount of energy hitting un-treated walls and other
surfaces so there is less of the original source reflected back as unwanted
room ambience to the mic. The Reflexion Filter also helps prevent any reflected
sound reaching the back and sides of the mic. Its shape and size have been
carefully tested to maximize absorption while keeping coloration down to only
around 1dB, and leaving the microphones polar pattern unaffected.
The Results
'Independent test results from the Tongji University Audio Lab in
Shanghai show audio image colouration with
and without the sE Reflexion Filter. The tests (carried out by
China's leading
Acoustic
Engineering
University completely independently) clearly
show extremely low levels of coloration when using a microphone with the
Reflexion Filter while recording (20Hz to 20KHz).
This was
one of the greatest challenges in designing the RF. Other companies have now
started to try and copy our designs (without breaking the patents which are
what make the Reflexion Filter actually work!), but fail to achieve such good
results because the designs are too simplistic.
The RF
comprises several layers of Aluminium and patented acoustic fibreboard separated
by acoustically isolating air gaps... and therefore manages to remove large
amounts of room ambience with a very compact design. The whole idea was to make
the unit as effective as possible, but in the smallest space... otherwise what
would be the point... you may as well treat a wall behind the mic.
The shape of the RF is also critical to the design as it randomises any
Reflections back from the surface of the filter. Products which are
semicircular (without the flat diffuser panels the RF has) will concentrate any
inconsistently reflected frequencies onto the mic... the worst possible
scenario.
Another very poor design though is a simple 'V' shape behind the mic. This
creates one of the worst coloration problems you can manage to achieve when
recording audio. Think about problems of Bass Accumulation in room corners...
the bass is accentuated worst in 90 degree corners, so any baffle placed behind
a mic which is this shape creates huge coloration problems in bass frequencies.
This also adversely affects higher harmonic frequencies because of the massive
energy in bass frequencies exciting these higher harmonics. A simple flat panel
on a wall positioned behind the mic is a much better solution, as it does not
create coloration, but still limits at least some of the early reflections in
the room.
More independent test data will be available soon (approx Mid March). For
independent reviews on the performace of the RF please check our reviews section.
In Summary:
All in all, its a very clever and desirable piece of kit. It allows you to
record vocals, guitars etc with a drier sound without having to have an
acoustically treated room. Its portable. It uses state of the art materials. It
works and its a fraction of the price of acoustically treating your studio
environment!