How to handle loudspeakers and directivities in Odeon

Q: How do should I use a CLF file?

A: It is recommended to download and install the CLF viewer, supplied here http://www.clfgroup.org/viewer.htm, so that you can see all the details described by the directivity file. One of the important parameters in the CLF file is the sensitivity of the loudspeaker, i.e. the SPL 1m away, for a given (electrical) input. The input can be measured either in Volts or in Watts. Double-click on the sensitivity button in the CLF viewer to see all the references about sensitivity.

ODEON uses the sensitivity file to extract the sound power that appears in the point source editor. Generally, the sensitivity is given to 1 Volt or 1 Watt reference. This means that the overall gain in ODEON should be set to 0 dB.

For making simulations with the maximum output by the loudspeaker, the value for the gain displayed in the directivity file should be used in the overall gain field in ODEON. This value corresponds to the maximum voltage or power supplied and is calculated either by 10log(Vrms,max/2.83) or by 10log(Wmax).

Q: What is a directivity file?

A: A directivity file describes how power is distributed around a source for different frequency bands. Loudspeakers typically are highly directive at high frequencies, so that most of the sound power is emitted in front of it. The standard format for making directivity files is called Common Loudspeaker Format (CLF) and was developed by the CLF-group (www.clfgroup.org). Such files have an extension of .CF1 or .CF2, for CLF version 1 and 2, respectively. The .CF2 format is the newest one including phase information.

Q: Unavailable directivity data?

A: If the directivity data of interest is not available in the CLF format, then assist the CLF-group by encouraging the manufacturer to make such data available. Free tools for this purpose can be obtained at www.clfgroup.org.

Q: how do I manage directivity files?

A: In version 9 and later it is possible to use subdirectories for directivity files. This makes it possible to organize directivity patterns in folders e.g. to keep directivities from a specific manufacturer in a folder of its own making it simpler to make use of large libraries of loudspeakers. Simply make subdirectories for each loudspeaker manufacturer in the above mentioned directivity files directory and store the relevant directivity files there.