User Manual

– 9 – AtlasSound.com
Specifications are subject to change without notice.
Owner’s Manual
MA40G / MA60G
Mixer Amplifier
1601 Jack McKay Blvd. • Ennis, Texas 75119 U.S.A.
Telephone: [phone] • Fax: [phone]
Measuring a Speaker System's Impedance
Note:ItisimportanttoonlyuseanAudioImpedanceMeterandnotaconventionalVolt/Ohmmeter.
A true audio frequency impedance meter is essential for reliable installation of background music and paging systems in residences,
office buildings and public areas. Avoid costly service calls and amplifier damage by verifying actual speaker system impedance prior
tooperation.Unlikeconventionalvolt/ohmmeters,whichmeasureDCresistance,anAudioImpedanceMeterunitutilizesaninternal
frequencyoscillatortomeasuretrueimpedance.Itmayalsobeutilizedwith70.7Vand100Vspeakerlinetransformers,L-padsand
matching Impedance volume controls. There are several Audio Impedance meters on the market, if you need to buy one we suggest
going to MCM Electronics, Parts Express or search the internet for “Audio Impedance Meter”.
Measuring 70.7V or 100V Distributed Speaker Systems
Largedistributedsystemstypicallyutilize70.7V(NorthAmerica)or100V(Europe)typesystemtogreatlyeasetheconnectionof
multiple speakers and facilitate long cable runs. Shown below are speakers connected in parallel with wattage ratings to calculate
the overall load of the system. Connecting an Audio Impedance Meter to a speaker arrangement such as this will provide the overall
impedance of the system.
Usingthefollowingformulayoucancalculatetheloadimpedancefromthespeakerselectedwattage.Theaccumulativewattageof
the speaker system must not exceed the maximum wattage output rating of the amplifier or damage may occur. In this example the
measurementfora70.7Vdesignwiththreespeakersof15Weach,thesystemimpedancewouldmeasurecloseto111Ω. Formula
70.7Vx70.7V=4998,4998/45W=111Ω. The amplifier power requirements would be at least 60W for the system to operate
properly.Note:Itisalwaysrecommendedtousealargerampthanneededwithpowerheadroomofatleast25%.Calculatetheload
impedanceandcompareittothemeter'saudioimpedancereading.Note:Theywillneverbethesameduetotheadditionalwire
impedance,butiftheyarewithin10%ofthemaximumimpedanceratingoriftheimpedanceishigherthanthemaximumrating,
proceed connecting the load to the amplifier. If they are not recheck your speaker taps or check for shorts.