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How to Conduct Speaker Directivity Checks

BS EN ISO 140-4:1998 requires speaker directivity to be checked as part of Annex A. This is a mandatory requirement of the SITMA Certification Scheme and must be completed and recorded onto the SITMA Portal annually.

Speaker Directivity can be checked either by the certified tester, or at a facility that offers this service.

The method for measuring and reporting is provided below:

SITMA Members can use our template to enter their data in and submit their Speaker Directivity Checks

Our current issue is: Issue 1.2 – 1st April 2024

Click Here to How to Conduct Your Speaker Stability Checks
1
Position the Speaker
Place the speaker on its tripod in a non-reflective environment, ideally an anechoic chamber at a height of around 1.5m ±0.5m.
2
Setup the Sound Level Meter
Setup the sound level meter on its tripod to the same height as the speaker.
Where the speaker cannot be placed in an anechoic chamber, a calculation is produced showing the microphone is only measuring direct noise, not reflected noise.
Where measurements are made at 1.5m, it can be assumed no indirect sound is measured where:
- No reflective surfaces exist within 7m
- Where reflective surfaces to exist, at least 100mm of dense absorbing material is present to reduce reflections
3
Calibrate the Sound Level Meter
Calibrate the sound level meter using its calibrator
4
Align the Speaker and Microphone
Align the speaker and microphone such that the speaker's front (on-axis position) is directly facing the microphone.
5
Turn on the Speaker
Using pink noise, turn on the speaker to its normal sound insulation testing volume (usually circa 100dB in frequencies 100Hz to 3150Hz).
6
Measure On-axis Response
Measure the on-axis response of the speaker at this position, directly in front of the speaker. Measurements shall be made for a minimum of 6 seconds, ideally 10 seconds. The microphone is static during the measurement.
7
Rotate and Repeat
Rotate the speaker 30 degrees and repeat the measurement. repeat this process every 30 degrees until all 360 degrees has been measured (12 measurements in total).
Note – if using a hemisphere polyhedron speaker (cabinet loudspeaker), the microphone itself may need to be moved 30 degrees rather than the speaker.
8
Hemisphere Polyhedron Speakers
This procedure must be completed in 2 planes for hemisphere polyhedron speakers, with at least 50cm change in heights.
9
Analyse Data (self-checking only):
Import the data into FOS017 to plot the recorded data to create a directivity graph.

Ensure the following specification is met: 𝐷𝑖𝑟𝑒𝑐𝑡𝑖𝑣𝑖𝑡𝑦 𝐼𝑛𝑑𝑒𝑥 = 𝐿360 − 𝐿30, 𝑖

Frequency Range Directivity Index
50Hz to 83Hz
No Requirement
100Hz to 630Hz
±2dB
800Hz
±4dB
1000Hz
±8dB
1250Hz to 5000Hz
±8dB
10
Upload the completed spreadsheet onto the SITMA Portal.

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