Rockford Fosgate 360.6 用户手册
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About the Dynamic Power Measurements
The Audio Graph PowerCube is a test instrument used to measure the
output of an amplifier in accordance with IHF-202 industry standards. The
IHF-202 standard is a dynamic power measurement and was developed
as a means of measuring power in a manner that best represents the Real
World operation of an amplifier. Many manufacturers, including Rockford
Fosgate, at times will measure amplifier power into a fixed resistor (4 ohm,
2 ohm). While this method is useful in some types of evaluation and
testing, it is not representative of an amplifier that is connected to a speaker
and playing music.
The Audio Graph PowerCube is a test instrument used to measure the
output of an amplifier in accordance with IHF-202 industry standards. The
IHF-202 standard is a dynamic power measurement and was developed
as a means of measuring power in a manner that best represents the Real
World operation of an amplifier. Many manufacturers, including Rockford
Fosgate, at times will measure amplifier power into a fixed resistor (4 ohm,
2 ohm). While this method is useful in some types of evaluation and
testing, it is not representative of an amplifier that is connected to a speaker
and playing music.
Music
Music is dynamic; the sound waves are complex and constantly changing.
In order to simulate this, the IHF-202 standard calls for the input signal to
the amplifier to be a 1kHz bursted tone. This signal is input (on for 20
milliseconds) and reduced 20dB for 480 milliseconds. The signal is
gradually increased in level until the amplifier's output exceeds 1% Total
Harmonic Distortion (THD). At 1% distortion becomes audible, therefore,
any power produced above that level is considered
Music is dynamic; the sound waves are complex and constantly changing.
In order to simulate this, the IHF-202 standard calls for the input signal to
the amplifier to be a 1kHz bursted tone. This signal is input (on for 20
milliseconds) and reduced 20dB for 480 milliseconds. The signal is
gradually increased in level until the amplifier's output exceeds 1% Total
Harmonic Distortion (THD). At 1% distortion becomes audible, therefore,
any power produced above that level is considered
unusable
. Many
manufacturers represent their amplifiers' output power in excess of 10%
distortion. They use many names for this measurement, such as Total
Maximum Power or Maximum Output Power. This is not indicative of the
distortion. They use many names for this measurement, such as Total
Maximum Power or Maximum Output Power. This is not indicative of the
actual usable output power
.
Listening to Loudspeakers - Not Resistors
A loudspeaker is not a resistor. A resistor's value (resistance measured in
ohms) is fixed. A loudspeaker's impedance is dynamic. It is constantly
changing in value, dependent upon the frequency of the input signal.
Therefore, measuring power with the amplifier loaded into a 4 ohm
resistor is not the same as measuring power with the amplifier connected
to a 4 ohm speaker. Most people do not listen to music through a resistor.
A loudspeaker is not a resistor. A resistor's value (resistance measured in
ohms) is fixed. A loudspeaker's impedance is dynamic. It is constantly
changing in value, dependent upon the frequency of the input signal.
Therefore, measuring power with the amplifier loaded into a 4 ohm
resistor is not the same as measuring power with the amplifier connected
to a 4 ohm speaker. Most people do not listen to music through a resistor.
A 4 ohm speaker may experience a drop in impedance 4-6 times lower than
its nominal (printed) impedance. A speaker will also create phase shifts in
the signal that is passed through it. These phase shifts happen because a
speaker is an inductor (voice coil) and a capacitor (compliance of the
surround/spider), as well as a resistor (voice coil wire).
its nominal (printed) impedance. A speaker will also create phase shifts in
the signal that is passed through it. These phase shifts happen because a
speaker is an inductor (voice coil) and a capacitor (compliance of the
surround/spider), as well as a resistor (voice coil wire).
To simulate a speaker the Audio Graph PowerCube measures output
power into 20 different loads. It tests at 8 ohms, 4 ohms, 2 ohms and 1
ohm. Each of these impedances is also tested at –60
power into 20 different loads. It tests at 8 ohms, 4 ohms, 2 ohms and 1
ohm. Each of these impedances is also tested at –60
°
, –30
°
, 0
°
, +30
°
and
+60
°
phase angles. These different impedances and phase angles repre-
sent the shifts in impedance and phase that can occur in a typical
loudspeaker.
loudspeaker.