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Old 3rd June 2004, 02:29 PM   #1
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Default voltage or current?

what affects the actual loudness of the music, the vrms, or current?
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Old 3rd June 2004, 02:35 PM   #2
sam9 is offline sam9  United States
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Yes.

Whichever you run out of first.


But assuming you have more than enough of each at your disposal, it is probably best understood as voltage. Except in the case of the two extremes of infinite impedance or zero impedance, there is no current with out voltage, and no voltage ("potential" is an other mater) without current.
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Old 3rd June 2004, 02:50 PM   #3
Duo is offline Duo  Canada
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The product of voltage and current is what affects the loudness of the reproduced sound.

This is coherent with the forumla where power is equal to voltage X current.

In a speaker, the impedance varies with frequency. This means that for a given voltage from the amplifier, the power used will not be the same for all frequencies since the current flowing through the speaker changes for impedance.

All amplifiers have a certain limit of voltage swing that they can output. This basically states the possible power output into a certain impedance of speaker as long as the power supply and transistors can handle enough current at that voltage to produce all the power.

I hope this clears the ideas a bit.
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Old 4th June 2004, 12:06 AM   #4
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SPL is proportional to the acceleration of the cone. The acceleration is equal to the force on the voice coil divided by Mms, or "a" proportional to "F", since mass doesn't change. Force applied on the voice coil is proportional to (equal to?) i*B*L. B and L are constant, and current depends on voltage (I = V/R) - note that impedance isn't constant, but varies with frequency.

So, it's voltage that gives you loudness.

EDIT: B is the magnetic field strength that the voice coil is subjected to by the driver motor, and L is the length of the voice coil (between the pole piece and the top plate, I think).
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Old 4th June 2004, 01:14 AM   #5
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Quote:
Originally posted by 454Casull
So, it's voltage that gives you loudness.
So how does a constant voltage (70V) amp work?

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Old 4th June 2004, 01:26 AM   #6
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by Cal Weldon


So how does a constant voltage (70V) amp work?

Cal
By using a transformer with taps to set the power taken from
the line in each loudspeaker - more power - more volume.

Also note 70V rms is just notional maximum voltage for the
power settings of each tap, the system can run at any lower
level, just the ratio of volumes of the loudspeakers is fixed.

And the total of all the power taps should not
be larger than the power output of the amplifier.

sreten.
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Old 4th June 2004, 01:59 AM   #7
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Thank you
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Old 5th June 2004, 01:16 PM   #8
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Default thx

youve all been extremly helpful!
thank u!
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