Archived from groups: rec.audio.tech (
More info?)
Thank you... this information is very helpful!
"Jerry G." <jerryg50@hotmail.com> wrote in message
news:35dm96F4lbjo3U5@uni-berlin.de...
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> This is too wide and complicated a subject to give a coarse over an email.
> Below is an extraction from a web page, as given above the first section.
> The second section is from some personal notes.
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> HEADPHONE SENSITIVITY
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http/www.headwize.com/tech/dbohn1_tech.htm
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> Headphone manufacturers specify a sensitivity rating for their products
> that
> is very similar to loudspeaker sensitivity ratings. For loudspeakers, the
> standard is to apply 1 watt and then measure the sound pressure level
> (SPL)
> at a distance of 1 meter. For headphones, the standard is to apply 1
> milliwatt (1 mW = 1/1000 of a watt) and then measure the sound pressure
> level at the earpiece (using a dummy head with built-in microphones).
> Sensitivity is then stated as the number of dB of actual sound level (SPL)
> produced by the headphones with 1 mW of input; headphone specifications
> commonly refer to this by the misleading term dB/mW. What they really mean
> is dB SPL for 1 mW input.
> Think about these sensitivity definitions a moment: headphone sensitivity
> is
> rated using 1/1000 of a watt; loudspeaker sensitivity is rated using 1
> watt.
> So a quick rule-of-thumb is that you are going to need about 1/1000 as
> much
> power to drive your headphones as to drive your loudspeakers since both of
> their sensitivity ratings are similar (around 90-110 dB-SPL). For example,
> if your hi-fi amp is rated at 65 watts, then you would need only 65 mW to
> drive comparable headphones. (Actually you need less than 65 mW since most
> people don't listen to their loudspeakers at 1 meter.) And this is exactly
> what you find in hi-fi receivers. Their headphone jacks typically provide
> only 10-20 mW of output Power.
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> Take another moment and think about all those portable tape players. Ever
> hear one? They sound great, and loud. Why you can even hear the headphones
> ten feet away as the teenage skateboarder that ran over your foot escapes.
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> Power output? About 12 mW.
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> --
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> The frequency response from a headphone is very much like a speaker. The
> wider and flatter the response, the better the specification for
> listening.
> The theoretical response for human hearing is from 20 Hertz, to 20,000
> Hertz. Normally we here sound as a tone from about 35 Hertz, and up to our
> limit. Below 35 Hertz we feel it more than hear it. As we age, our hearing
> sensitivity decreases, and so does our frequency response.
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> People in their teen years can usually hear up to about 18,000 Hertz, to
> about 20,000 Hertz. At about 40 years of age, the average person can hear
> up
> to only about 16,000 Hertz, they have not be exposed to excessively loud
> sounds over the years. At about the age of 70 the average person may not
> hear higher than about 10,000 Hertz. This is an average. There are people
> who can hear a wider or narrower bandwidth than what is in this example.
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> There are also factors such as the dynamic range, and the distortion
> factors. Speakers and headphones can have a variety of types of
> distortions.
> The lower the distortion figures the better. Most of the time, with higher
> end headphones, the Total Harmonic Distortion is published. To have
> headphones that can give the full 20 Hz, to 20,000 bandwidth within a few
> Db's with less than 0.5% THD, you will have to pay out a fair amount of
> dollars. AKG, and Sennheiser would be a suggestion of manufactures to look
> in to if you want good quality headphones, at a reasonable cost.
>
> --
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> The impedance is shown in ohms. The impedance should match to the
> specifications to the type of unit that you are planning to plug the
> headphones in to. They are very standard when matched to the required
> application. If you are buying earphones for an iPod, don't expect it to
> drive a set of 8 or 16 ohm headphones. These small devices usually need
> headphones that are up in the 30 to about the 100 ohm area. The small
> audio
> devices usually do not have enough power to properly drive low impedance
> headphones.
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> Below is a link for a very good set of headphones that I personally like.
> I
> consider these reasonably priced for the specs. They should be able to
> work
> on your iPod. They have a very wide bandwidth, thus being able to handle
> the
> harmonics.
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>
http/www.youreq.com/musiceq/headphones/sennheiser/hd-515.asp
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> --
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> If you really want to get in to understanding all of this type of thing,
> there is a lot of studying involved. The base is built up on complex
> physics, mathematics, and electronics.
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>
> Jerry G.
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> "CurtK" <CurtK@att.net> wrote in message
> news:32cId.10381$8u5.2668@bgtnsc04-news.ops.worldnet.att.net...
> I am really new to audio and am just trying to obtain a very high-level
> understanding of what audio specs mean. I have been trying the web and
> using Google Web and Group search. At this point I just feel overwhelmed.
>
> I am trying educate myself to buy two things. The first is headphones for
> my iPod. Could someone explain the various specs (sensitivity, impedance,
> response accuracy, noise reduction, etc.) at a very high- level? The
> other
> thing I need to do is replace my home audio system. The speakers are
> still
> good, but I need a new receiver. Could someone explain ohms rating on the
> speaker and what you need to be aware of when buying a receiver (this is a
> home theater system).
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