Help... Don't Understand Headphones Specs?

G

Guest

Guest
Archived from groups: rec.audio.tech (More info?)

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).
 
G

Guest

Guest
Archived from groups: rec.audio.tech (More info?)

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.


--
HEADPHONE SENSITIVITY

http://www.headwize.com/tech/dbohn1_tech.htm

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.

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.

Power output? About 12 mW.

--

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.

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.

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.

--

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.

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.

http://www.youreq.com/musiceq/headphones/sennheiser/hd-515.asp

--

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.




Jerry G.
=====

"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).
 
G

Guest

Guest
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...
>
>
>
>
>
> 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.
>
>
> --
> HEADPHONE SENSITIVITY
>
> http://www.headwize.com/tech/dbohn1_tech.htm
>
> 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.
>
> 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.
>
> Power output? About 12 mW.
>
> --
>
> 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.
>
> 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.
>
> 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.
>
> --
>
> 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.
>
> 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.
>
> http://www.youreq.com/musiceq/headphones/sennheiser/hd-515.asp
>
> --
>
> 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.
>
>
>
>
> Jerry G.
> =====
>
> "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).
>
>
>
 
G

Guest

Guest
Archived from groups: rec.audio.tech (More info?)

>
>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?

Frequency response specs on headphones are total BS. They mean nothing and are
putthere by the marketing department.

Sensitivity is how loud the 'phones will play with a given input.

Impedance is the AC resistance the 'phones present to the amplifier. Generally
not a problem but you may find systems with lower impedance have higher output.


Noise reduction is how much the 'phones shield you from outside noises.

Bottom line, you have to listen to the different sets to determine which set is
best for you.






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).
>

The ohms rating on a speaker (impedance) is the AC resistance that the speaker
presents to an amplifier.

This can be very important. The amplifier carries a recommended impedance
rating.
i.e. 120watts@4 Ohms. & 80 Watts@8 Ohms.

Do not use speakers or sets of speakers that have lower impedance than the
amplifier is rated for. In the above system you could safely use a 4 Ohm
speaker or 2-8 Ohm speakers wired in parallel on the amplifier because it can
handle 4 Ohms.

If you used two 4 Ohm speakers wired parallel on the system, you would present
a 2 ohm load to the amplifier which would cause the amp to overheat and
possibly self destruct.




Richard H. Kuschel
"I canna change the law of physics."-----Scotty
 
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