Crest Audio NEXSYS - VERSION 3.0, Руководство пользователя программного обеспечения

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NexSys v. 3.0 Crest Audio Inc.
band, number of sample points, number of cycles per sample point, and test signal attenua-
tion. Once this data is entered a test sweep may be conducted by clicking on the sweep but-
ton located below the graph. When the reference curve is completed you may elect to save
the reference which means that that exact curve will be used as the baseline for all subse-
quent tests.
Entering Test Parameters
Remember that the test signal is generated at the amplifier, so any limiters, crossovers, etc.,
at the head end will be out of the signal chain. First, enter the pass band of the test- if you
are testing compression drivers with a response range of 800Hz - 10kHz then this same
range should be entered. Next, enter the number of sample points. The maximum number
of points is 200 and this will produce the most detailed results- but it also takes the longest
time to perform and the detail it provides may not be required. Try using 50 sample points
first. If the detail of the curve is acceptable then leave that as a default value. If the 50 point
curve takes longer than desired then try a smaller number bearing in mind that the resolu-
tion of the curve will decrease.
Next set the samples per point parameter. This defines how may samples per discrete fre-
quency will be acquired, averaged and then reported to the host computer. Typically a value
of 3 yields consistent results without taking excessive time that additional samples would
require. Using larger numbers to acquire more samples will definitely slow the process.
Always enter an attenuation value that is high (30 dB for example) until you determine how
the system will respond. The reason is very simple- the test inserts pure tone into the ampli-
fier which may result in some very high SPL as compared to dynamic program material.
Always start with a large number for this selection. After running your first curve you must
determine if the amount of attenuation is correct for the test. Excessive attenuation may not
exercise the drivers (especially LF drivers in reinforcement systems) sufficiently to have the
test yield results that would indicate a failure. If the initial attenuation levels are high try
additional tests entering a lower attenuation value so that the drivers are fully exercised but
are at levels that are not painful to humans and other living things.
Distributed high impedance systems typically do not require the detail of testing or the
sound pressure levels that reinforcement systems do. With careful attention and some exper-
imentation on how to best set these parameters, impedance sweeps can take place largely
unnoticed. This testing procedure will however, be more effective if conducted at realistic
sound levels and duration.
Care must be taken when initiating an impedance sweep. Excessive duration or
sound levels could cause speaker damage or personal injury.
If any of the sweep parameters require changing you may either abort the sweep (click on
the abort button) or finished the test and select a new reference. You may need to run the
reference sweep several times in order to determine the optimum setup parameters. Once
you have determined the proper test settings save the reference. This will automatically use
the same parameters on all subsequent sweeps.
Be sure the reference sweep is done on the system when all speakers and speaker wiring is
working properly. This will ensure a proper reference sweep.
Page 15.2 Software Manual