Analog Audio Processor AC-AAS for the phase-correct implementation of a Sub-Woofer System, realized with our High-End Power Amplifiers AC-PAZ75 und/oder AC-PAR75
The module is available as OEM product for developers and manufacturers of High-End speaker systems and optimized to work with our power amplifiers AC-PAZ75 and/or AC-PAR75.
Our unique selling proposition for your superior products:
The Analog Audio Processor AC-AAS is a novelty at the world market.
The AC-AAS eliminates as well as the AC-AAZ for the first time ever the Doppler effect, which is caused by every moving speaker membrane.
The Doppler effect is very well known. The resulting variations in the pitch can be heard, when a police vehicle with active siren is approaches and leaving the listener position. The same happens, when the speaker membrane is moving. For the reproduction of sound, this is especially disturbing, when, as in music, low and high tones are radiated from the same speaker membrane. Caused by the phase modulation due to the membrane movement, mix (alias) frequencies are generated. These Doppler-lines are non-harmonic and produce a rough sound impression.
The AC-AAS generates the audio signals for the side speakers as well as for a sub woofer with absolute correct phase and amplitude. Differently to standard 2.1 speaker systems, the side speakers get the full frequency range, however with 3.5 dB reduced amplitude at frequencies below 90 Hz. Such the full speaker membrane areas are used to produce the low notes, but too high membrane amplitudes for the side speakers are avoided. Using this approach the sub woofer can not be localized and can be positioned at nearly anywhere. We recommend, however, a maximum depth offset of ±1 m between the side speakers and the sub woofer in order to guarantee the correct addition of the SPL vectors. The AC-AAS allows several different arrangements with our high-end power amplifiers: One could use one or several AC-PAZ75 power amplifiers for the sub woofer. Optionally an on-board non-linear pre-distortion can be activated to reduce considerably the non-linarites of the speakers at low notes / large membrane amplitudes.It is, however, recommended to use one or more AC-PAR75 power amplifiers with on-board MFB control loop to completely eliminate any audible distortions.
The analog audio processor AC-AAS receives the audio signal differentially and applies a band pass filtering to suppress spurious signal far out of the audio band. It separates the the the high frequency band for the side speakers from the low frequency band for the sub woofer using a very special filter of 3rd order with 60 dB/frequency decade steepness and the physically shortest possible transit time. That avoids any perceivable depth displacement of the basic tone and the corresponding harmonic tones from musical instruments. The separation occurs at 90 Hz corresponding to an acoustical wavelength of close to 4m.
The low frequency band is added back to the high frequency band at a level of -3.5 dB and is available as differential signals for the side speakers. This requires, of course, side speakers which are able to reproduce low notes, which is, however, not a problem using the AudioChiemgau components.
The low band signals of the left and right channel are added and feed a variable gain amplifier. In case components from other manufacturers are used the AC-AAS offers a phase switch (±180 degrees) and additionally a variable phase stage (0 … -180 degrees at 90 Hz) to allow a perfect phase match to the side speakers. In case AudioChiemgau components are used, the phase switch and the variable phase stage are not needed and set to zero.
In the SUB frequency band frequencies below the audio band are filtered out. This avoids potential problems with infra-sound components coming from uneven vinyl records or digital recordings.
An on-board analog processer generates a signal representing continuously the speaker membrane position. This signal controls a phase modulator which exactly equalizes the phase modulation caused by the variable membrane position. Such the AC-AAS keeps the acoustic phase center at a fixed position and eliminates the Doppler effect.
The AC-AAZ has its own power supply fed by two windings of a transformer.
The AC-AAZ offers a build-in sequencer which supplies Standby and Mute signals to the connected power amplifiers in order to ensure an controlled and un-audible switching process when power is applied or removed.
