RAM Audio LMS244 Digital Controller
17
General considerations in realising measurements
It is extremely important to accurately realise the measurements of the transducers for the subsequent
results to be reliable and valid. The following list can be considered as a useful guide in obtaining
good measurement files.
1 -
Ensure that measurements of each way are obtained at the same distance from the source
(several meters) and with the microphone situated at a height you consider to be the central listening
point. This way, the magnitude and phase information is the same for all the measurements.
2 -
The measuring equipment should to be equally calibrated for every measurement, i.e. no change
should be made to signal gains, sensitivity, sampling frequency, etc. from one measurement to
another.
3 -
It is recommended to use smoothing in the measurements (between 1/3 and 1/6 Octave) in order
to obtain readings with few peaks. Furthermore, keep in mind that the human hearing function is
similar to the function of a spectrum analyser smoothing about 1/3 to 1/5 Octave.
4 -
Measurements should be made introducing the measurement signal directly to the power amplifier
to be used and under normal operating conditions so as to include in the measurement the gain of
each amplifier.
5 -
In the case of measuring with MLS (Maximum Length Sequence) and windowing the temporal
response in order to avoid reflections in the readings, use the same temporal window in all
measurements / outputs and with a starting time common to all of them. This way the same phase
information will be obtained and the final electro-acoustical addition will be correct.
6 -
In the high and mid frequency ranges, measurements will invariably be correct especially when
measuring with MLS avoiding reflections in the measurement by windowing time. For low and mid-low
frequencies, unavoidable problems e.g. reflections and stationary waves will falsify the readings in as
far as phase and magnitude are concerned. In such cases, measurements should be interpreted.
Reliable measurements in these frequency regions are only obtainable using an anechoic chamber or
by measuring in a free-field situation.
7 -
Store all files exported to ASCII in the same directory with significant names for you to remember
which measurement it is.
8 -
Should the LMS244 be used as a bandwidth equalizer, it is possible to achieve the measurements
of a complete system and equalize it in the INPUT EQ section to correct the general response.
3.11. Dynamic Configuration & Noise Gate
Following the Output EQ section are the sections for Output Delay and Output Gain. The operation of
these parameters has been described previously. This brings us to the last section of the signal
processing path which is the section for Dynamic control (compressor/limiter) and independent noise
gate per output.
This section enables the final dynamic control and provides the ability to limit the power provided to
each output. Access is once again via clicking on the relevant icon.
The Dynamic Configuration/Noise Gate window