then
1) In TIME Domain press A and then B, then type in 20 and ENTER, then press C
(It means Acquisition, Bandwidth, 20kHz, Chebyshev)
2) Press A and then L, and type in {65535} and ENTER
(Means Acquisition, Length, 65535 points)
The measurement time is long at 1081ms, file storage will be big.
(Normally 3637 points, because 50ms for 20Hz lowest resolution +10ms = 3meter distance variation, file storage very small, measurement speed fast, efficient)
then
3) Press A and then A again and then T (means Acquisition, Autorange, Tight)
4) Press F and then S, and key in {65535}
(Means FFT, Size, 65535 points)
The Frequency Resolution will be 0.92Hz, file storage big, computation calculation time long, not efficient.
(Normally use 3030, because value too high is beyond the naked eyes capability, Frequency Resolution drop to 20Hz, file storage small, computation calculation time fast, very efficient.)
round down because easy to type.
Since we only want results from 20Hz to 20kHz, the step 1), 2), 3) and 4) make sure when the impulse response is converted to frequency response using the FFT Execute, the display will automatically be in the range of 20Hz to 20kHz.
It is because lowest resolution is 20Hz, it will not show anything less and because maximum bandwidth is 20kHz, it will not show anything more, very convenient J. It is accurate as long as you do not need anything below 1kHz. Again to be discussed later.
5) Press F, M, S, and type in 8 then hit ENTER, and type in 1 then hit ENTER.
(Means FFT, Mode, Sensitivity, 8 ohms, 1 meter)
6) In Frequency Domain, press V, M, M, D and type in {0.05} and hit ENTER.
(Means View, Magnitude, sMoothed, Decibel) Means apply a 0.05 = 1/20 octave smoothing to the entire curve.
7) Press S for Setup and S again for saving and key in new setup name. Done. Do not forget to turn the stimulus volume up to –10dB.
The MLSSA frequency response transfer function offset file contains an output/input voltage ratio. The amplifier’s volume have to be turned up to match MLSSA output to achieve a 1:1 ratio, hence the set-up file default 1volt/volt is left unchanged.
This is why MLSSA recommend not to change amplifier volume but to use internal MLSSA stimulus to control the output volume.
65535 points acquisition is not by default, see official manual for instruction. This feature can also be enabled permanently in MLSSA.INI. The disadvantage of using 65535 points is no OVERLAY feature available because “Insufficient Memory to Display Graph”.
Reference off-set curve also need to be removed in order to have overlay features. To do so, press R and then F (means Reference, Free).
A bad trade-off, only useful for saved FRQ files when they have been EQUALISED, hence you do not need reference file on memory.
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