Benefits of High Impedance Headphones?? - Page 3

Yes. That gain is surprisingly low. The gain on most of my headamps (SP and MAD models) is around 10-18 ohms. The SBH I have ordered is 15 ohms. All of these amps have lower Vrms output too. My older 120 ohm HD-595s play louder on both amps than my K-701, but this has a lot to do with the relative efficiency of the two models. To get the listening volume up on the SP (OTL) to the same level as on the MAD (Transfomer coupled) holding the volume control fixed, I need to use relatively high gain inputs (mu higher than 40) and either 5687s or 6BL7GTAs as outputs (not 6SN7Gts), and even then the SP isn't quite as loud.

Moral of the story: If you love low impedance, relatively inefficient headphones make sure you have an amp that can drive them well.

In that test I had the gain set to low, but I changed the settings to see objective results at different settings. My point is that I wanted to make sure I was not "just listening too loud" in my Opera observations. The tests proved me accurate that I was listening at the recommended levels and that my amp is 75% to 100% of it's effort to present much of my content. If higher headphone impedance levels become more of the norm, we all need to make sure our amp output can keep up.

You lost me with this analysis of the specs. I understand the Opera gain numbers but from there on.... Would you mind explaining it to the novice level?

Care to clarify? Lemme guess, FOTM?

You are less likely to blow the phones with the high resistance. That is good enough for some.

Indeed - between myself and a friend we went through 3 sets of HD595s in a month. We guess that the higher impedance of 600s and 650s have kept them safe for years

I don't know that I can

Ok with 8 dB Voltage gain = 2.5 x linear amplification factor?

input V x 2.5 = output V

iPod max output ~ 1 Vrms

1 Vrms x 2.5 = 2.5 Vrms output from the Opera's output when the analog input is connected to an iPod

2.5 V << 13 V where 13 V is what Jan specs the Opera at being able to put out - and might be desirable with some 600 Ohm headphones

so with a popular source component the Opera with analog input doesn't have enough gain to use its capability

I assume the DAC portion can drive the Opera to the full 13V spec'd output V

Hello, i am Rohan an audio engineer and i have just joined head fi so a HI! to all,

 

Regarding Impedance

 

What is impedance?

Simply the AC resistance of the "voice coil" + magnetic field coupling of the magnet inside the headphone.

 

What is its impact?

From simple electronics,

 

we know        Voltage = Current X Resistance

and                Power=  Voltage X Current  (or P=VI)

 

now lets take an example,

 

For a headphone to deliver 2 watts of power (a headphone never outputs such high power just an EXAMPLE)

it can be

at 1 Volt with 2 Amps of current            i.e P=2X1=2watts

also at 1 Volts with 2 Amp's of current the headphone has an impedance* of Resistance = Voltage/Current  thus, R=1/2 Ohm (just an example not actual values) 

 

Also,

 

the same output with 2 Volts and 1 Amp. and R=2/1=2Ohms

 

*life is int that easy impedance is actually quite complex and different driver designs have different impedance's at different frequencies and amplitude (voltage, instantaneous or loudness)

 

Now,

   

Why are high impedance headphones manufactured?

1.) The displacement (amount of movement) of the diaphragm (the thing that actually vibrates and produces sound) is better controlled via a more accurate flux (magnetic field to pull and push the diaphragm). This gives better accuracy and more performance at lower frequencies.

 

2.) The impedance is increased by using a different wire for the voice coil and most importantly more turns. More turns or loops creates a larger field (area of magnetic influence), in lay mans terms bigger magnetic area for the coil to move more efficiently.

 

3.) It also allows SS amps to work more efficiently with lesser distortion have a look at data sheets and a graph of distortion vs output impedance for most audio op-amps and you'll get the idea.

 

Problems with high impedance

1.) Difficult to drive for low powered devices which are configured with lower gains.

2.) Most need an amp with a different gain (most headphone amps are more geared towards current rather than voltage i.e low impedance than hi impedance)

 

Do high impedance headphones sound better than low impedance ones?

Actually, in headphones "sound stage" or "airiness" or simply the experience depends upon the following,

       1.) Frequency response, the curvy graph shows that volume decreases or increases with change in frequency this is actually the complex magnetic field pulling and pushing with different amount of force at different frequencies, impedance affects this in complex ways but to make life easy, it makes it more somewhat "straight" or linear.

        2.) Distortion, represents the amount of "change" from the actual signal to the real signal (input signal to output signal) the reason why this is measured by a square wave is because square waives are difficult to drive as they have a "part" DC in them which in theory does not generate flux. Impedance does not a large effect on this.

        3.) Build and design, (to long i cant type so much :P )

 

So to conclude,

High Impedance is only a ddifferent approach in energy delivery in basic terms its relative to rather faster flowing electrons (hi impedance) or MORE but slower electrons (low impedance) how they effect sound is dependent on the magnetic filed generated and diaphragm construction (physical response of diaphragm).

 

Hope this clears the air.

 

Rohan

Edited by rohan575 - 2/10/11 at 4:00pm

that was a nice explanation.. thanks Rohan575

 

 

High impedance headphones are for classic tube circuitry that had high voltage but low current delivery.

 

The transmission line standards in studio settings calls for 600 ohms, and 600 ohm headphones had the maximum power delivery since max power occurs when supply and load impedances are matched. High damping rates were not an issue back then.

 

Low impedance headphones are for low voltage sources with higher current delivery. In other words, modern portable battery operated units.

 

Just match the right type of headphone with the right source. The DT880 can be had in 32, 250 and 600 ohm versions. Some of the old Sennheiser headphones were 2000 ohm.

 

There are also other things to consider, such as sensitivity and the impedance curve. Headphopnes with a resistive impedance curve do NOT need a low output impedance amp, but those with a highly reactive impedance curve should be driven by an amp of much lower output impedance. Otherwise, the impedance fluctuations form a highly variable voltage divider network.

please note:

 

I stated it in terms of speed of electrons, it is not! speed of electrons in a conductor is constant, rather the potential that they are accelerated under changes

Hi,  I agree with most what you are saying expect the part about 600 ohm transmission lines.

600 ohm transmission lines have no application to driving headphones. Neither does maximum power delivery. You do not want to match supply and load impedances.

If you drive a 600 ohm headphone with a 600 ohm output impedance headphone amp you will have very poor efficiency in the amp/headphone interface and a damping factor of 1.
 

 

If high impedance makes for better sound why are all speakers (at least those I am aware) spec'd between 4-8 Z and not, say, 600-1200 Z? 

 

Also, impedance is the voltage–current ratio at a particular frequency.  The impedance varies across the frequency spectrum.

 

For further consideration is this interesting post by tomb:

 

There is a hypothesis that hasn't been proven with extended testing, but can be one explanation for why Grados sound better with tubes. It has to do with the over-emphasis toward zero output impedance that exists with many solid-state amps. Contrary to conventional wisdom around here, Grados at 32 ohms do not necessarily prefer amps with low output impedance. Dsavitsk has postulated that the higher damping factors resulting from low output impedance may actually contribute to Grados sounding harsh. He's designed/built enough amps to test this out on a real basis. From my limited experience, I would agree. Grados will sing with certain types of tube amps, but border on unlistenable harshness with ultra-low output impedance solid state amps.

Great summary Rohan, Thanks

Hi,

Please refer to this:

Go to "Head Fi" Home page

scroll to bottom of page

you will see a list of articles

click on "all articles"

then go to page 3 of "all articles"

on page three you will find a link to an article called "Headphone Impedance"

this may go some way to answer your question

 

I agree with your comment about the low Z headphones and high Z headphones, there are lots of good low Z designs and lots of good high Z designs.

As for Grados, the textbook answer is "use a very low output Z headphone amp"...............OTOH if you like the sound of a hi output Z tube amp, then go for it!

I have a pair of Q701 which I enjoy using with my relatively high output Z OTL tube amp. It goes against the rules but I still like it!

 

 

 

You can currently buy 16 ohm speakers off the shelf from a variety of sources (speakers for guitar amps, hi-fi, and automotive) and historically speakers were made in a VERY VERY wide variety of impedances, with some going as high as several hundred ohms. 

 

Regarding SS amps: none of that mattered when everything was transformer coupled. You just got the transformer wound for the speaker you had. When speakers were almost only sold in big integrated boxes (you know the old style tube radios) this was not difficult or even prohibitive. 

 

Regarding why we dont have other impedances TODAY I'l ask you a question, and tell you the answer. 

Are 4 and 8ohms better, or is that just what non-technical users are familiar and comfortable with? Its the later. The best item for the job depends on the job. Period. Anyone who gives you a default answer on BEST is a fool. People default to 4&8ohms because that is what they are familiar with.