enthusiasts often seek flawless frequency responses from their
amplifiers and speakers. When a high-end equipment is installed
in to the listening environment, such as typical living room,
these curves are degraded. The distortion is caused by walls,
floor and roofs of the listening room. The early reflections will
inflict both constructive and destructive interferences, thus
introducing up to +/- 6dB peaking or attenuation per single reflection.
The worst of all are the modal resonances also known as the "standing
waves", which will impair the bass response with even as high
as 30 dB peaking and narrow resonances which decay slowly. Every
room has commonly at least a couple of high-Q resonances.
technology concentrates in modelling the mechanism behind these
standing wave resonances with room geometry. Simple models can
be derived from room dimensions, the larger the room, the
lower the frequences. In reality there exists multiple resonance
frequencies that can be modelle as standing waves, the room modes.
As these resonances have very low frequencies, they are difficult
to be tamed with absorbing materials which in general offer poor
efficiency for the lowest ranges.
technology is designated to eliminate the devastating room resonances,
but it in fact also compensates for the response of the whole
basis of the technology relies in measuring the transfer function
from the sound source to the listener with microphone. As the
counter-model of the room is achieved by sophisticated algorithm,
both amplitude and phase characteristics of the system will be
improved. The algorithm is capable of making crucial decisions
of which phenomena can and should be compensated for. For example
the steep gaps in the magnitude response are always extremely
local by nature and hence should never be corrected by narrow
peaking filters or such. As a result of the robust counter model
designing algorithm of Anti-Mode 8033, the result is achieved
with fully automatic process where the user is spared from the
calibration program self-generates sweep-like measurement signals
and picks up the data with included microphone. The process will
autonomically define parameters of the room modes, such
as center frequency, Q-value, gain, frequency antisymmetry etc.
The DSP will further convert this data to complex zero-pole presentations
into the Z-domain in order to derive optimal counter-model for
the system. This will eventually lead to the designs of custom-fitted
Anti-Modal Filters, AMFs. Up to 24 distinct AMFs can be designed,
although far less are usually ever needed for one position. The
extra AMFs give the algorithm more freedom when extending the
effective area of the compensation for more globally improved
the DSP computes digital IIR coefficients for the AMFs to be used
in real-time operation after the calibration. In computations,
accurate 32/40 -bit integer arithmetic is addressed, which will
virtually set unlimited space of parameters for the system.
the operational mode the pass-trough delay of the signal is approximately
3.8ms. This is mainly due by converters and small enough to be
inaudible. It can, however be taken care of with basically every
A/V receiver on the market by adding distance of the subwoofer
by 1 meter (3 feet).
products in the market utilize fixed band graphical equalizers
when trying to struggle against room distortion. This kind of
solution is very inaccurate and is potentially incapable against
narrow resonances that can occur at arbitrary frequencies. They
usually also involve the user for measurements and fine tuning.
Some equipment also only tries to compensate for the amplitude
response ignoring phase completely. In such cases the compensation
will not lead to improved transition response. Another problem
in he existing parametric equualizers is the limitations in their
spectral resolution. Missing a center frequency by even as small
a deviation as 1 Hz, the modal characteristic can be made even
worse than the original. In 8033, the spectral resolution is improved
and the computation power of 24 AMFs is enough to make even the
worst room compatible with subwoofers.