Wheelock MX-8 Mixer Specifications download pdf (Page 10)

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Wheelock Speaker System Calculator

Much of the information contained in this book has been condensed into a simple and easy to use sliderule calculator

availablefromyourlocalWheelocksalesrepresentative.Thispowerfultoolcalculatestherequirednumberofceiling

speakersorhorns,powerrequirements,wiresize,etc.,foragivensizearea,ceilingheightandbackgroundnoiselevel.

Thecalculatorisdesignedforbothselfamplied(24VDC)andcentralamplied(25/70/100volt)systems.

How much power?

Alwaysdesignthesystemformaximum“headroom”...whichmeansplentyofreservepowertoallowforfutureexpansion

orunusualvolumerequirements.Forexample,forofceenvironments,trytodesignforatleast1 watt of power for

eacheightinch(centralamplied)speakerand/orfull power for eachselfampliedspeaker.Whatthismeansinterms

ofhardwareiscorrectamplierpowersupplysizeandproperwiresize(moreaboutthislater).

What does this kind of reserve power actually mean? 70 volt speakers and horns typically incorporate a number of

differentpowersettingsorwattage“taps”.Thesetapsdeterminetheamountofpowerthatthespeakerwilldrawfrom

theamplier.AWheelockST-C8ceilingspeakerwithonewattappliedwilltypicallygenerateabout95dB@1meter,

whichisjustaboutthedistancetosomeone’searsiftheywerestandingunderthespeaker,and95dBisoverkilltosay

theleast,ina60dBofceenvironment!However,inorderforthespeaker,tappedat1watt,toactuallyreceive that 1

watt,theampliermustbeatfull power. That’s right: Pedal to the metal, volume control to the max. Although most

modernamplierscanoperateinthismanner,it’smoreidealtooperateanyamplierwiththevolumecontrolsatornear

theirmidwayposition.Thisgivestheusersomeexibilityandoverallsystemcontrol.

Considerthis:Withtheamplierat50%power(approx1/2volume)thespeaker,tappedat1watt,willactuallypull1/2

wattfromthespeakerline.With1/2wattofappliedpowerthespeakerwillstilldeliver92dB!Rememberpowerand

the 3 dB rule? Cutting the power from 1 watt to 1/2 watt results in a 3 dB drop in volume. A speaker tapped at only 1/8

wattwouldstilldeliverbetterthan80dB,assumingtheamplieristurneduptomaxpower.At1/2volumethissame

speaker,tappedat1/8watt,wouldstilldeliverbetterthan75dB.Thus,inaquietofceenvironmentasingle100watt

centralampliercouldpoweralargenumberofceilingspeakerstappedat1/2,1/4or1/8wattwithsufcientvolumefor

6 dB-over the ambient noise.

This calculator is also available and

dowloadableonCooperNotication’s

websiteatwww.coopernotication.com

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Wheelock MX-8 Mixer Specifications Page 10