DVD Authoring Software Talk
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Mike S.
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 Posted: Thu May 03, 2007 11:54 am Post subject: Output power of earphone |
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I've been looking at a couple mp3 players and I noticed the
instruction manuals will say something like the Output power of
earphone is L 4mW, R 4mW. What does that mean? Does it mean the
earphones are 4mW or does it mean the mp3 player is 4mW? And what does
4mW mean? I assume it's low and that 10mW would be better. |
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Peter
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| Posted: Thu May 03, 2007 12:00 pm Post subject: Re: Output power of earphone |
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Mike S. wrote:
| Quote: |
I've been looking at a couple mp3 players and I noticed the
instruction manuals will say something like the Output power of
earphone is L 4mW, R 4mW. What does that mean? Does it mean the
earphones are 4mW or does it mean the mp3 player is 4mW? And what does
4mW mean? I assume it's low and that 10mW would be better.
Depends what you want to do. If you want to drive passive loudspeakers |
then 4 milliwatts will be barely audible, If you use inserted earbuds
then continual listening at 4 mW will damage your ears, 10 will blow
your head off. |
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Joseph Ashwood
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| Posted: Fri May 04, 2007 3:48 am Post subject: Re: Output power of earphone |
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"Mike S." <littleboyblu87@yahoo.com> wrote in message
news:1178178854.844069.274940@c35g2000hsg.googlegroups.com...
| Quote: |
I've been looking at a couple mp3 players and I noticed the
instruction manuals will say something like the Output power of
earphone is L 4mW, R 4mW. What does that mean? Does it mean the
earphones are 4mW or does it mean the mp3 player is 4mW?
|
It would probably help to think of the MP3 players as an entire
component-based home stereo system in a little box. The 4mW refers to the
power output of the amplifier, and the mentioned one will output 4mW
(milliWatt) into the left and an additional 4mW into the right. The entire
consumption of the MP3 player will typically be higher than this. You can
actually compute approximately the power consumption of the entire device if
you like by determining the capacity of the battery(ies) and the lifetime of
the battery(ies) in use, simply divide. So for example a fairly typical
player uses 1 AA battery (about ~1200mAh@1.5V = ~1.8Whour), and the device
lasts 40 hours, the device therefore consumes approximately 1.8Wh/40h = 45mW
during use. Obviously change the numbers as necessary.
| Quote: |
And what does
4mW mean? I assume it's low and that 10mW would be better.
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In general it is a fairly meaningless number, different manufacturers
develop their own measurement methods, and it is performed in specific
(again manufacturer designated) loads, so they values are only comparable
within a single manufacturer, and sometimes not even then. It is somewhat
useful if you have an impedence value for the wattage, and a frequency of
measurement, so for example 4mW into a 300 Ohm load @ 1KHz would likely blow
your ear drums out when you attach it to the more common 16 Ohm load. Also
of great importance is the sensitivity of the ear/headphones you are using.
I actually just bought a new pair today that deliver 100dB/mW and offer 16
Ohms @ 1KHz, this means that if the headphones are supplied a 1mW (again
this can vary widely depending on how the manufacturer measures) per ear
with a 1KHz rail-to-rail sine wave they will pump 100dB into each of my
ears, this is widely considered at least sufficiently loud, perhaps too
loud. In reality the actual numbers will vary widely, but the manufacturers
always print the numbers that make them look best. That 100dB/mw@1KHz is
probably close to accurate because the manufacturer for these delivers
dependable numbers for that. The 19mW of the mp3 player I plug them into is
wwwaaayyy off for these earphones, instead it probably delivers closer to
2.3 to 2.5 if I dared turn it up all the way.
The really important number is the number many manufacturers don't like to
publish, the dB SNR (signal to noise ratio), ideally you want an infinite
but 90 or higher is more than sufficient for 99+% of people.
Also important is how close to rail-to-rail the music you're listening to
is. If you are listening to modern pop/hip-hop/rock/etc it will be very
close to rail-to-rail and so will be louder than say some traditionally
recorded classical with a huge dynamic range, the result is that with the
pop/etc a lower number of milliwatts is necessary, the cost is that the
classical carries more of the original sound.
Joe |
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