Huron & SNAP Documentation
Huron & SNAP Documentation Huron & SNAP Documentation
HURON TECHNICAL REFERENCE files that are scaled down too low will produce output from the FIR filter that is well below full scale, resulting in poor signalto-noise performance in the D/A converter. The diagram below illustrates the way filter coefficient scaling effects the Convolver’s output level: Figure 98 — Scaling of filter output due to filter coefficients The amplitude of the filter coefficients (h(k)) determine the overall gain of the filter. More specifically, the filter scale (S) is defined as: N−1 1 S = ∑ h( k ) 2097152 k= 0 As a reference for comparison, the Huron Convolution Tools are supplied with an example file called c:\Huron32\sim\unity.sim. This file specifies an all-pass, unity gain filter. It contains one impulse in the first sample of the vector, and all zeros following this. The magnitude of the impulse is 2097152, which results in a gain of S=1. For most real filter responses, the overall gain S of the filter is mostly useful in defining the average gain of the filter, for white noise audio input. In reality, typical audio signals have most energy in a narrower band (from about 200Hz to 8000Hz). For this reason, it can be more meaningful to compute the gain S based on a band-limited portion of h(k). In order to achieve optimum data scaling in the Huron system, it is advised that all SIM files be scaled up to achieve a gain of S=1. This can be done by the following procedure : • Determine the gain (S) of a SIM file (or a collection of SIM files that are to be used together). Determine the gain for a band-limited portion of the SIM file. • Use the MultVec utility to scale the data up or down by a factor of 1/S. This means that the newly scaled SIM file should now have an average gain of S=1. • If a collection of SIM files are to be used together, then the relative amplitude difference between their gains must be preserved, so the files should all be scaled up by the same amount. The Lake Technology SimScale tool described below uses the formula 1/max(Sn) to achieve this result. HURON TECHNICAL MANUAL PAGE 292 2
↓ SimScale Avoiding Large Frequency Peaks HURON TECHNICAL REFERENCE The revision 1.0 Huron Convolver Filter is not capable of boosting any one frequency by more than 12dB This may make it impossible to scale up the overall filter to unity gain. If the frequency response of the filter (i.e. the FFT of h(k)) contains large, narrow peaks that are more than 12dB above the average frequency response level, then it will not be possible to scale the filter up to unity gain (S=1). SimScale is a windows program supplied with the Huron Engineering tools. It is used to scale a filter or a group of filters to unity gain. The program will either scale the filters so that the largest filter has unity gain, or the largest peak is no more than 12dB above unity. The function and operation of SimScale is described in the SimTools section of this manual. HURON TECHNICAL MANUAL PAGE 293
- Page 242 and 243: Note: In this version of SimScale i
- Page 245: Usage Simtowav Simtowav is a comman
- Page 248 and 249: Hamming Window Blackman Window Harr
- Page 251: Introduction to the Programming Too
- Page 254 and 255: Operation Starting Lake EQ ↓ To a
- Page 256 and 257: Slider Widget Toolbar Creating an E
- Page 258 and 259: High Shelf Tip: All the sliders can
- Page 260 and 261: Calculating the Equalisation Curve
- Page 262 and 263: ↓ To lock a Slider ↓ To unlock
- Page 264 and 265: Limits ↓ To alter the graph limit
- Page 267 and 268: Introduction 96kHz EQ Hardware Requ
- Page 269: Loading EQ 96kHz THE EQUALISATION T
- Page 273 and 274: Features Operation The VMixer The V
- Page 275 and 276: Note: When increasing the size of V
- Page 277 and 278: Muting ↓ To mute all output chann
- Page 279 and 280: Operation Starting ↓ To access th
- Page 281 and 282: Operation Starting ↓ To access th
- Page 283: Summary OTHER TOOLS • The BFormat
- Page 286 and 287: I/O Test Patching Selecting the For
- Page 288 and 289: Summary • To utilise I/O Test an
- Page 291: Fixed Point Digital Audio Data Repr
- Page 296 and 297: Figure 99 — SNR of the 16 bit A/D
- Page 298 and 299: Mechanical Specifications 1 3 Figur
- Page 301 and 302: Audio Input Levels Managing Audio S
- Page 303 and 304: HURON TECHNICAL REFERENCE • In ge
- Page 305 and 306: Angle Channels Glossary Angle chann
- Page 307 and 308: Order of Reflections HURON TECHNICA
- Page 309: SNR (Signal to Noise Ratio) HURON T
- Page 312: ↓ To specify an auto-logon domain
↓ SimScale<br />
Avoiding Large Frequency Peaks<br />
HURON TECHNICAL REFERENCE<br />
The revision 1.0 <strong>Huron</strong> Convolver Filter is not capable of<br />
boosting any one frequency by more than 12dB This may make<br />
it impossible to scale up the overall filter to unity gain. If the<br />
frequency response of the filter (i.e. the FFT of h(k)) contains<br />
large, narrow peaks that are more than 12dB above the average<br />
frequency response level, then it will not be possible to scale the<br />
filter up to unity gain (S=1).<br />
SimScale is a windows program supplied with the <strong>Huron</strong><br />
Engineering tools. It is used to scale a filter or a group of filters<br />
to unity gain. The program will either scale the filters so that<br />
the largest filter has unity gain, or the largest peak is no more<br />
than 12dB above unity.<br />
The function and operation of SimScale is described in the<br />
SimTools section of this manual.<br />
HURON TECHNICAL MANUAL PAGE 293
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