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hi,i have been into home cinema for years,i have just ordered parts from the USA to build my own sub,i have realised through researching the subject how little i knew,and i am still struggling,on this forum trying to learn a little more,i was reading the threads on setting up the speakers and sub and i am lost again concerning decibels,if 0db is just audiable and 120db is very loud how can people listen to films at -10db can someone explain in simple terms how this works,like is reference level a set figure and -db is below this,help
 

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Your confusing two different things. The -10db is the volume level on the receiver. My Kenwood goes from -92 (no sound) up to -4 max volume. I think they do this just to confuse people. The other db is accual sound levels that you'd see on a sound level meter.
 

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They are both the same thing, but are measuring from different points. The reason the numbers are negative on most HT receivers, is that you can calibrate "0" as reference level. Thus below that is negative with respect to reference level. dB is only a unit of comparison, so what you are comparing is why they don't seem to match up. In this instance though they represent the samet hing.
 

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thanks for the info i am getting there bit by bit, so if lets say you turn the volume on my amp to 00 and on a spl for arguments sake it reads 100db if if someone says they are listening to a film at -10db it is actually 90db,have i understood it correctly.
 

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Try this link for a little help on dB.
http://www.sss-mag.com/db.html

In general, the level listed on your amp and the spl you read from an spl meter will not correlate with someone else's speaker and amp combination. Speakers have different efficiencies and the distance the meter is from the speaker all affect the readings. The SPL behaves with an inverse square law with respect to distance from the source.


..Doyle
 

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a decibel rating is always comparing one signal to another reference, DbW is decibels referenced to 1 watt while Dbm is referenced to one milliwatt. 0Dbw would be 1 watt while 3Dbw would be 2watts and 6Dbw would equal 4 watts. + 3 dbs equals twice the power -3dbs equals half the power 6dbs=4 times 10dbs= 10 times and 20dbs = 100 times the power.
 
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