Testing the speakers
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Important: Always test the speaker before plastering over it
Using a multimeter and without the APU protection device connected, check the nominal impedance
(DC resistance) of the speaker at the amplifier end of the speaker cable. Allow for approx. +/– 10% for
cable resistance. The impedance should coincide with the values on the respective datasheets.
Amina recommends a tone sweep be used at a moderate volume level (0.5 Vrms). Such a test will
quickly highlight any buzzes or rattles that could be caused by loose screws, cables touching the
speaker or loose elements/studs within the wall itself.
If the plasterboard is not securely fastened to the joists this could also create a buzz or a rattle. Apply
more screws if necessary - particularly around the speaker location.
Ensure that the speaker cable is not touching any part of the speaker (or backbox) as this can lead to
buzzes and rattles. To avoid this it is advised to lay the cable behind the mineral wool or other wadding.
If metal studs are used, ensure the crossover point of the studs are secured together. This can be
achieved by applying drywall screws through the wall surface and through the metal joists. If they are
not secure this may well lead to audible vibrations and rattles.
Check cable continuity back to the amplifier by using a multimeter to check the impedance. After
connection to the speaker, the impedance (at DC) should coincide with the values on the respective
datasheets. If it measures significantly different, check for breaks or shorts in the cable.
Play music to check for buzzes and rattles during transient peaks. Do not judge the speaker’s sound
quality at this stage. Once plastered over it will sound as intended.
Always connect the APU when testing, except when measuring impedance.
Perform these tests again after the plaster is dry.
If the correct 2mm thick plaster coat has been applied, the speaker face, when tapped with fingers, will
sound slightly more hollow than the surrounding areas of plasterboard. If there is little or no difference
between these two sounds it is almost certain the plaster coat is too thick. This will compromise the
speaker performance.
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Amina have a lot more information available from its technical help desk for those wishing to measure
frequency response curves at different stages of the installation.
Please c44 1480 354390 for assistance.
Continue on to Section D (page 23 - plastering & decorating)
CAUTION:
Without plaster on the surface of the speaker it is highly efficient and will generate very high sound pressure
levels with minimal power input. Take care to protect your ears when testing at this stage.
Testing
