Analysis Settings

The analysis Settings alter the way REW carries out some of its calculations.

View Settings

Impulse Response Windows

The Left Side and Right Side window selectors offer a choice of window types to be applied to the impulse response data before and after the peak. These are the defaults applied to new measurements, window types for existing measurement can be altered via the IR Windows toolbar button.

The Spectral Decay Left and Spectral Decay Right window selections are applied to the impulse response data when generating the Spectral Decay and Waterfall plots.

Impulse Response Calculation

The Decimate IR selection controls whether REW reduces the sample rate of the impulse response to correspond to the range of frequencies in the measurement. Selecting this option greatly reduces the impulse response size for low frequency measurements and speeds up processing of the data.

The Calculate Ref Response selection controls whether REW calculates the impulse and frequency responses of the soundcard left channel reference input when it is being used as a calibration reference for the right channel signal (see Soundcard Settings). If this option is selected REW carries out additional calculations to allow the frequency response of the reference input to be displayed, this increases the calculation time for each measurement - this option only needs to be selected if you need to see the response of the reference input in addition to the measurement response, using the right channel as a reference works with or without this option being selected. The response of the reference input is shown as the Soundcard Cal trace on the Filter Adjust graph page.

Filter Calculation

When matching filter characteristics to resonances the optimiser does not limit filter attenuation, this allows it to correctly determine the required Q for each filter. Once a good match has been achieved, the attenuations are limited to the maximum that the EQ filters allow then the attenuation (but not Q) of each filter is re-optimised accordingly. If the Allow Doubled Filters option is selected the optimiser will allocate an additional filter for peaks that remain above the target level when optimisation has completed. The second filter is chosen according to the following criteria:

As an example, consider a peak at 100Hz that requires a filter with 21dB attenuation to bring the response down to the target, but our filters have a maximum attenuation of 15dB. A further 6dB of attenuation is required. If there is an unused filter then it will be assigned to provide this extra 6dB of attenuation at 100Hz. If not, but there is a filter being used to correct another peak (let's say at 45Hz) that has less than the required 6dB of attenuation, it will be re-assigned to make up the shortfall on the large peak so if the 45Hz filter only required 3dB (for example) attenuation to correct the 45Hz peak, it would be reassigned to apply 6dB attenuation to the 100Hz peak instead.

This process is repeated for each peak that remains above the target level until all available filters have been used or all peaks have been corrected.

If Drop Filters if <2dB is selected any Automatic filters which have less than 2dB attenuation at the end of the optimisation process will be freed up (their Type will be set to "None")

The list of filters for a speaker can be sorted using a button on the filter optimisation panel. The selection boxes specify the sorting direction (ascending, descending, or no sorting) and the key used for sorting (frequency, gain or Q).

Target Defaults

The default values to use for Speaker Type, Cutoff and Crossover slope are specified here, these will be used for each new measurement.

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