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In Reply to: Re: wha? posted by Matts_ on February 28, 2007 at 21:13:42:
...is its output measured 1M away, driven by a solidstate amp driven with a 1KHz sinewave. The amp is connected first to a load resistor of 8 Ohms; the input is adjusted to create an output of 2.83VAC. That does happen to be 1 Watt into the 8-Ohm load, but read on. The resistor is disconnected and the speaker is connected to the amp, and the acoustical output is measured. Note that this standard measurement of sensitivity ignores the speaker's impedance.The older standard of efficiency is measured the same way EXCEPT...the speaker is indeed driven with 1 Watt, defined as that Voltage needed to drive 1 Watt into a load resistor equal in value to the speaker's impedance.
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Tin-eared audiofool and obsessed landscape fotografer.
http://community.webshots.com/user/jeffreybehr
Follow Ups:
as "standard" when it comes to measuring this! every speaker company does it differently, and NO speaker is going to be equivalent to an 8-ohm resistor in terms of a load for obvious reasons (it has impedance, not resistance and is interactive). Also, this use of "sensitivity" for this supposed msmt is at odds with it's other uses in electronics- I have always thought purposefully so to mislead people that it means something, and there are the gullible they are successful with...
...simply doesn't understand the industry standards.BTW the possessive form of "it" is "its", not "it's".
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Tin-eared audiofool and obsessed landscape fotografer.
http://community.webshots.com/user/jeffreybehr
just hucksters who try to make the gullible believe there are! Russ57 has one of the games id'd below, there are many others. Almost every co. does it differently. Only a couple companies that make drivers actually give out how they test, actually use anechoic chambers, etc. If you know the diff btwn an resistance and impedance why did you write that whole thing about setting power with an 8-ohm resistance and then replacing it with the speaker? No one who understands would write that up as if it were legit, cause it's not.
It was common to rate speakers according to how many dB they produced at 1 meter when powered with one watt.Now if the speaker is called an 8 ohm speaker and we feed it 2.83 volts that is the same because [2.83(2.83)]/8 ohms is one watt. But some dishonest speaker guys decided to pull a fast one and use 2.83 volts instead of one watt to power the speaker. As pointed out that is the same for an 8 ohm speaker. But if will send 2.83 volts to a 4 ohm speaker we are feeding it 2 watts and it makes the speaker appear to be more efficient than it is.
So for that reason when the spec is given in dB/meter with one watt it is called efficiency but it is called sensitivity when we use 2.83 volts as the input instead of one watt.
IMHO one watt should always be used. But given that a good quality solid state amp will double its wattage into half the load it is accepted. Just think how efficient 2 ohms speakers would look!
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