Quality Control
Thiele-Small parameter measurement
New file formats (import and export)
Improved impedance measurements
1/3 octave band smoothing
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Returning Features |
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Log chirp joins chirp, MLS, tone, impulse and user-defined stimuli
RT60 measurements
3-D waterfall displays
Reverse energy time curve
Continuous, octave or 1/3-octave
Editing of time waveform
Stereo 32,000 point FFTs for good low frequency resolution
Macros for automated operation
Extensive on-line help
MATLAB format supported
HP inkjets supported (color/mono)
1/3 through 1/12 octave display
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Quality Control |
A Quality Control module has been developed for SYSid. A system (speaker, electronics, etc.) is measured and the magnitude of the frequency response is compared against a pre-defined reference standard (e.g., +/- 3 dB from a mean value). SYSid will indicate a 'Pass' or 'Fail' result. The reference is defined by testing one or more products known to be good. The average of these good products' responses becomes the reference. Next, the user selects tolerance bands, in dB, above and below this reference. And finally, the user may permit a specified number (from zero on up) of data points to lie outside of the tolerance band. Data files are automatically numbered as they are acquired. After collecting a set of measurements, the mean and the standard deviation may be calculated with the statistics command. They can be used to determine the degree of 'statistical control' of the process.
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Spectral Contamination |
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SYSid's spectral contamination measurement is a unique way to measure and quantify transducer clarity and definition in a subjectively meaningful way. For design engineers, spectral contamination tests using time domain averaging will reveal the true distortion contribution of each component (cone, spider, surround, magnetic system, etc) of a speaker system.
Spectral contamination is a graphic analysis of cross-modulation products ('self-noise') produced by a system excited by a multi-frequency signal. Multi-tone tests are far more representative of the rigors of music or speech reproduction than traditional stimuli. The resulting non-linear distortion products (the noise between the tones, which are distortion products generated at frequencies where no excitation energy is present) correlates with subjective perceptions of quality, such as 'clarity' and 'coloration'. (See Spectral Contamination Measurement, by Deane Jensen and Gary Sokolich, AES preprint 2725, 85th AES Convention, 1988).
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By its nature, multi-tone testing elicits a lot of distortion products. Air pressure buildup behind the dustcap causing it to buckle and balloon, air whistling over leadout wires that are not firmly down on the collar, bobbin vent holes being submerged below the pole piece, flex leadout wires buzzing against the cones, surround resonances and many other anomalies can now be seen and quantified. The effectiveness of remedial measures may now be examined.
Extracting valid data requires separation of the distortion signal, which looks
like noise, form the ambient noise. This is particularly difficult when testing
a transducer at low sound pressure levels. SYSid separates the response of the
transducer under test from the ambient noise using time domain averaging. Sample
spectral contamination plots of a typical stimulus, a mediocre speaker and a
good speaker are on the last page. |
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