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To briefly highlight the calibration process, the configuration begins with measuring the room’s impulse room at the listening location and for each loudspeaker. Then computational software is used to write FIR and IIR filters (the latter is dedicated to low-range amplitude incidents, the FIR filters work full range) which reverse the room  effects and loudspeaker nonlinearities. The Amethyst then applies these filter in real time.

Because most room correction filters are a-causal, there is some delay. Most DRC systems allow the operator to control this delay with configurable parameters. The Trinnov room optimizer is today’s state of the art in that field and allows a very precise setup of the frequency response, phase and delay but also generates 5 automatic presets (compensation filters) which provide interesting results already. For further fine-tuning of their results, you need to work on target curves and other optimization parameters.The Amethyst will store internally (this number can be increased if saved to external disk) up to 29 user-defined presets which in my opinion are more than sufficient to support a few pairs of speakers.

Digital room correction or DRC systems are not normally used to create a perfect inversion of the room's response. A perfect correction would only be valid at the precise location where it was measured. A few millimetres outside that window the arrival times of various reflections will differ to render a narrow inversion imperfect. And imperfectly corrected signal may end up sounding worse than uncorrected signal if the a-causal filters cause pre-echo. Room correction filter calculation systems thus favour a more robust approach and employ sophisticated processing to produce an inverse filter which will work over a larger usably area and avoid bad-sounding artifacts outside that area, albeit at the expense of peak accuracy in the measurement location.

The Trinnov maintains the advantage of very precise sweet-spot setup whilst adding the option to widen it with multi-point calibration weighting and advanced filter features. The Optimizer analyses the measurements in the time-frequency domain to identify early reflections. Depending on their amplitude, frequency, direction and arrival time, the Optimizer will compensate for them to a certain extent - or not try to compensate. After this process each loudspeaker’s response is theoretically ‘cleaned’ from the early reflections which digital technology can correct. Later reflections are not touched.

The Trinnov also identifies resonance modes where they can be clearly differentiated, i.e. roughly up to 300Hz. It applies individual filters to compensate for each resonance mode. It analyses the room’s frequency response related to the coloration of the room’s reverberation index across the mid and high frequencies.

Another filter compensate for that coloration. That’s the concentrated know-how hiding inside the Trinnov box which is so impressive. The Trinnov Optimizer to my knowledge is the most subtle correction processor to intelligently balance between truly helpful corrections and those liable to create more problems.

Another substantial improvement is the graphic analysis of a room’s main acoustic features. For each speaker and each measurement point, the Amethyst displays amplitude versus frequency plot, phase rotation versus frequency, group delay and impulse response. A further amplitude response curve of direct sound vs. early reflections is also available and useful to better reveal crossover, room modes and reflective issues.