14
B
IQUAD SAMPLE RATE
Biquad coefficients must be calculated by a filter design program. Any
program that calculates biquad coefficients must do so at a specific sample
rate. The IL-DSP operates internally at two different sample rates:
•
44.1 kHz if the input sample rate is 44.1, 88.2 or 176.4 kHz
•
48 kHz if the input sample rate is 48, 96 or 192 kHz
Therefore, unless you are sure that you only will be playing back at one of the
above sets of sample rates,
2
you will need to calculate and load two sets of
biquad coefficients, one at 44.1 kHz and one at 48 kHz.
To load biquads at a specific sample rate, simply select the appropriate radio
button and then use the
Process
or
Import
button as described on the
previous page.
B
IQUAD CALCULATION SPREADSHEET
The community-developed biquad calculation spreadsheet allows biquad
coefficients for many filter types to be calculated, including notch filters,
Linkwitz transforms, and filters with arbitrary Q-factor. Access this
spreadsheet here (requires Microsoft Excel):
•
All_digital_coefs_v1-20101026.zip
R
OOM
EQ
W
IZARD
(REW)
Room EQ Wizard (REW) is a free acoustic measurement and analysis tool,
available for Windows, Mac and Linux. It can generate a bank of parametric
EQ biquads based on a measurement. Room EQ Wizard can be downloaded
here:
•
http://www.roomeqwizard.com/#downloads
For guidance on using this feature, please refer to this app note:
•
2
Android devices only output at one sample rate and convert all other sample rates.
Typically, Android devices output at 48 kHz although we have also seen 96 kHz. In any
case, loading biquad coefficients at 48 kHz only should suffice for an Android device.
