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Helike 1.0 UA-E3010 | User manual
Released in November 2020, updated in June 2022
USound GmbH | www.usound.com | [email protected]
master EQ and DRC processing is applied to the input signal. The crossover EQ is applied to each of the
outputs and is therefore ideal for filtering specific speaker signals, e.g., low-pass for the woofer outputs.
Figure 9: Helike 1.0 .json configuration file structure
To customize the acoustic response, download the sample.json file and open it in a text editor.
8.2.
FILTER CONFIGURATION
The digital filters implemented in Helike 1.0 UA-E3010 are biquadratic filter functions. The filters use a
direct form I implementation and follow the difference equation:
y[n] = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
where the first three coefficients (b0, b1, and b2) represent the numerator coefficients (feedforward
coefficients), and the last two (a1 and a2) represent the denominator coefficients (feedback coefficients).
Some tools and literature designate coefficients a0, a1 and a2 as feedforward coefficients and b1 and b2 as
feedback coefficients. Make sure to cross-check the naming convention applied by your tool or literature.
Note also that some tools/literature use a negative sign in the difference equation for the feedback
coefficients. In this case, the feedback coefficients must be negated when copying them to the .json file.
Figure 10 shows the EqCoefficients section of the Helike 1.0 UA-E3010 configuration file. Eight filter
stages are available for configuration in each EQ block. To change the filter behavior, the coefficients for the
desired filter response need to be added in the .json file manually. Use a tool of your choice (e.g.,
https://www.earlevel.com/main/2013/10/13/biquad-calculator-v2/)
to generate a set of biquad filter
coefficients and transfer them into the editor.
