By clicking on the icon 
, the menu for the output channels filter settings will appear as per image to the side.
1. Xover L/R Link:
when activated, the modifications applied to one of the channels (right or left) will automatically be applied also to the other one. To activate it click on the blue flashing light.
2. Invert Phase:
it provides the ability to invert the phase of the channel under examination by 180°. It can be activated by selecting the green flashing light. This function can be useful to solve alignment problems among the different filtered channels.
3. Filter Type:
it enables the selection of the different types of filters that can be assigned to the channels.
Full Range
Low Pass
High Pass
Band Pass
WARNING: in this case pay utmost attention to the filter adjustment. Speakers have mechanical limits which must not be exceeded and could lead to damage to the components.
4. Filter Model: it enables the selection of the applicable type of filter
Butterworth (IIR)
Linkwitz (IIR)
Bessel (IIR)
FIR (to be enabled during the Wizard see sec. 7.2.2)
When starting the software, the bit One HD Virtuoso offers the Butterworth as a standard filter model. By changing the model to Linkwitz or Bessel, the change will be made only to the channel (mono) or channels (stereo - Xover Link activated) concerned.
If a FIR type system configuration was set up, the PC software will not allow to manage other types of filters. If you wish to switch to the Butterworth / Linkwitz or Bessel, (IIR) filters, proceed by converting the configuration file as suggested in sec. 8.2.1.
Difference between IIR and FIR filters.
IIR digital filters faithfully simulate analog filters (active or passive), approximating phase and frequency behavior. Like their analog equivalents, they are affected by unavoidable phase rotations at the cut-off frequency, which are different based on the type of curve used (Butterworth, Linkwitz, Bessel), however still perceived when listening.
In practice, for instance, a fourth-order low-pass IIR filter (24 dB / Oct) at 200 Hz cut-off, plus a high-pass symmetric filter, results in a phase rotation ranging from 0 to -360 degrees along the whole audio spectrum. This phase alteration affects the perception of the sound image, which highlights inaccuracies in terms of coherence and stability.
Think of a 3-way system where the door-mounted 18 cm woofer is 400 Hz crossed with the middle-range, installed on the a-pillar next to a tweeter, itself crossed with the middle-range at 5.000 Hz, using crossovers with IIR filters. The system phase alteration reduces the focus of the instruments on the virtual stage. For this reason, a number of audio enthusiasts prefer to adopt 2-way systems with a woofer and tweeter crossing at 2.500 Hz with a slope of 6 dB / Oct, so as to limit phase rotations as much as possible. This solution, however, presents a number of significant disadvantages, mainly due to increased distortion and lower tweeter power. With a slope of only 6 dB / Oct., the music signal around the cut-off frequency is simultaneously generated by tweeters and woofers to a considerable extent. Since a tweeter and a woofer have very different electro-acoustic parameters, the sum of the two emissions does not produce clear output signals, which results in less clarity in the reproduction of musical transients.
Improved acoustic quality with the use of crossover filters and FIR equalizers.
The use of FIR filters guarantees an important result: the phase behaviour is linear, free from rotations or indecisions. This also makes the use of filters with a very high slope (up to 48 dB / Oct) possible, without altering the phase response. Such a high slope for the filter enables the midrange and tweeters mounted on the a-pillar to work at lower frequencies without any issues with power handling, thus raising the emission front.
Therefore thanks to the FIR filters the advantages of three or multiple-way systems are completely exploited taking in-car listening experience to a different level. When listening, a system that uses FIR filters provides great clarity in transients reproduction, such as the acoustic piano hammer strikes or the drums. The stereophonic image is deeper and definite. Instruments in the virtual stage are more focused and seem to have more space between them. Even the intervention of any equalizer over the frequency response, when available in FIR technology, does not modify the audio signal phase, allowing more precise and detailed corrections without conditioning the audio quality.
5. Cut-off frequencies:
- Hi-P Hz 10 ÷ 20000: filtro High-Pass
- Lo-P Hz 10 ÷ 44000: filtro Low-Pass
The cut-off frequency can be selected by:
- clicking on the corresponding drop-down menu, selecting the frequency range and the value;
- clicking on the corresponding drop-down menu, then moving from value to value with the arrows controls (up / down) on the PC keyboard;
- clicking on the corresponding drop-down menu and then moving from value to value with the use of a mouse featuring a rotating finger wheel.
- Click on the cut-off frequency (Lo-P, Hi-P) section and edit the required value through the keyboard.
crossover frequency example
WARNING: in this case, pay due attention to the filter adjustment. The speakers have mechanical limits that should not be exceeded and that could lead to their breakdown.
6. Filter slope
- Hi-P Slope
6/12/18/24/30/36/42/48 dB/Oct. (Butterworth)
12/24/36/48 dB/Oct. (Linkwitz)
6/12/18/24/30/36/ dB/Oct. (Bessel)
- Lo-P Slope
6/12/18/24/30/36/42/48 dB/Oct. (Butterworth)
12/24/36/48 dB/Oct. (Linkwitz)
6/12/18/24/30/36/ dB/Oct. (Bessel)
When starting up the software, the bit One HD Virtuoso offers Butterworth with 12 dB/oct slope as default slope. By changing the slope, the change will be applied only to the channel you are working on.
Eg.: if you are adjusting the Front Woofer, the change will affect only that channel (right and left, if linked). If you selected Band Pass as filter type, the slope will be applied to both hi-pass and low-pass. With the Band Pass filter type the filter slopes can be unbound.
Crossover frequency 80 - 2000 Hz @ 12 dB/Oct.
Crossover frequency 80 Hz @ 6 dB Oct. Hi-pass
2000 Hz @ 48dB Oct. Low-pass
Crossover frequency 80 - 2000 Hz @ 48dB/Oct.
Crossover frequency 80 - 2000 Hz @ 48 dB/Oct. Hi-pass
2000 Hz @ 6dB Oct. Low-pass
7. Channel Map Filter settings
This window shows the filters, cut-off frequencies and phase customization of each single component of the audio system. It is possible to change the parameters by first selecting the loudspeaker with the mouse, then setting the parameters as described in the points 1. 2. 3. 4. 5. 6.
8. Channel map
This window shows the channels that make up the system and if the L / R link is active. Through the Mute button, it is possible to exclude one or more speakers present in the system during the calibration.
Pass-through Mode Filter Setting.
In the case of Pass-Through mode with selection of the Master input, the cut-off frequencies of the channel bandwidth will not be editable, and by default will be set using the ones detected by the “Input Dashboard” analysis.