or Connect
Head-Fi.org › Forums › Equipment Forums › Sound Science › Amp Voltages, Impedance, and other confusing numbers
New Posts  All Forums:Forum Nav:

Amp Voltages, Impedance, and other confusing numbers

post #1 of 16
Thread Starter 

Hello 

 

I started my Headphone journey 2 years ago. I decided to buy me some good sounding IEMs and aftter some time of research I decided to buy the Shure SE425.

They were supposed to sound neutral, good for mobile use etc.

Today I'm about to upgrade, over-ears HPs.

I backed the Kickstarter Projekt "Geek Out", a mobile USB DAC/AMP..

They had 3 Versions, 470, 720 and 1000 mW.

I didn't think a lot about it and backed for the 720mW Version, thinking it should drive most Headphones.

 

Today I remembered the early scene from the movie back in the future, where someone powers some crazy speaker setup and gets pushed against the wall because there was too much power.

 

So I started thinking: will I damage my sensitive Shure SE425 with 720mW? I started asking in the dedicated Forum for the backers and got redirected to http://www.headphone-amplifier.com/calculator.htm in order to calculate what kind of amp I need for different HPs, to achieve 110-120dB (I got told) -

 

 

Well, here an example:

 

Sennheiser HD 589:

Impedance (Ohms) : 50

Effectivity (dB/mW) : 112

 

Signal Level (mV) : 720

 

RESULT:

 

SPL(dB): 122.16

Power(mW): 10.37

Current(mA): 14.4

meaning that the 720mW Geek DAC/AMP will drive them good

 

So I put the Shure SE425 specs into the calc and this is the outcome:

 

 

Shure SE425:

Impedance (Ohms) : 22

Effectivity (dB/mW) : 109

 

Signal Level (mV) : 720

 

RESULT:

 

SPL(dB): 122.72

Power(mW): 23.56

Current(mA): 32.73

 

 

Well, I arrived at the same dB Result

I have double the Power and more then double the current.

Is this killing the IEM? Can't I just lower the volume, or put some kind of resistor?

 

Sorry for noob question, I'm new to amping.

post #2 of 16
Impedance and wattage needed to drive a particular set of phones to a certain level drives us all crazy.

The complicating factor is that impedance of a headphone/earphone isn't a constant (though less varied in an IEM for all but the frequency extremes).

The only risk with excess wattage is if you turn the amp on with Nile's latest album playing at full volume. smily_headphones1.gif If you make sure to keep the volume at 0 before plugging on and turning on, always a good idea, and don't listen at brain-frying volumes, you should be fine.


Sent from my iPad using Tapatalk
post #3 of 16

Headphones don't need much power at all:

HD598 requires about 0.8 V or 9 mW for 110 dB SPL.

SE425 requires about 0.2 V or 2 mW for 110 dB SPL.

 

Make sure you always have the volume set much lower than this, else you risk permanent hearing damage.

post #4 of 16
Thread Starter 

Does that mean, that if I use an AMP with 1000mW, because one day maybe I'll buy a very demanding pair of Headphones, I still can use them with low impedance IEMs? just be careful?

post #5 of 16

Not necessarily.

 

At some point the usable volume control range will be so small that you will wish for a gain switch or lower power amp.

post #6 of 16
Quote:
Originally Posted by BaTou069 View Post
 

Hello 

 

I started my Headphone journey 2 years ago. I decided to buy me some good sounding IEMs and aftter some time of research I decided to buy the Shure SE425.

They were supposed to sound neutral, good for mobile use etc.

Today I'm about to upgrade, over-ears HPs.

I backed the Kickstarter Projekt "Geek Out", a mobile USB DAC/AMP..

They had 3 Versions, 470, 720 and 1000 mW.

I didn't think a lot about it and backed for the 720mW Version, thinking it should drive most Headphones.

 

Today I remembered the early scene from the movie back in the future, where someone powers some crazy speaker setup and gets pushed against the wall because there was too much power.

 

So I started thinking: will I damage my sensitive Shure SE425 with 720mW? I started asking in the dedicated Forum for the backers and got redirected to http://www.headphone-amplifier.com/calculator.htm in order to calculate what kind of amp I need for different HPs, to achieve 110-120dB (I got told) -

 

 

Well, here an example:

 

Sennheiser HD 589:

Impedance (Ohms) : 50

Effectivity (dB/mW) : 112

 

Signal Level (mV) : 720

 

RESULT:

 

SPL(dB): 122.16

Power(mW): 10.37

Current(mA): 14.4

meaning that the 720mW Geek DAC/AMP will drive them good

 

So I put the Shure SE425 specs into the calc and this is the outcome:

 

 

Shure SE425:

Impedance (Ohms) : 22

Effectivity (dB/mW) : 109

 

Signal Level (mV) : 720

 

RESULT:

 

SPL(dB): 122.72

Power(mW): 23.56

Current(mA): 32.73

 

 

Well, I arrived at the same dB Result

I have double the Power and more then double the current.

Is this killing the IEM? Can't I just lower the volume, or put some kind of resistor?

 

Sorry for noob question, I'm new to amping.

 

Are you sure your calculations are correct?

 

In the first paragraph you say 720mW and then you use 720mV. They're not the same.

post #7 of 16
Thread Starter 
Quote:
Originally Posted by proton007 View Post
 

 

Are you sure your calculations are correct?

 

In the first paragraph you say 720mW and then you use 720mV. They're not the same.

 

Well, no, I'm not sure. Thought that Work = Power*Time, assuming that Time=1 ;)

How would the right calculation be?

for Example:

 

Shure SE425:

Impedance (Ohms) : 22

Effectivity (dB/mW) : 109

 

Signal Level (mV) :???

post #8 of 16
Quote:
Originally Posted by xnor View Post

HD598 requires about 0.8 V or 9 mW for 110 dB SPL
SE425 requires about 0.2 V or 2 mW for 110 dB SPL.

Peak, or RMS? I come up with 12.59 mW and 1.26 mW for 110 dB peak SPL.

10^((110 - 99) / 10) = 12.589
10^((110 - 109) / 10) = 1.259

Edit: the sensitivity of the HD598s is 112 dB per Volt, not per mW (which converts to 99 dB/mW with an impedance of 50Ω).
Edited by skamp - 11/20/13 at 3:14am
post #9 of 16
Thread Starter 

I want to get my question straight, but first:

 

I'm well aware that this is:

 

1) no "help me find a good Headphone" Thread

2) a list of very different sounding Headphones (Since I'm not asking for help to choose the right one)

3) a list of Headphones with very different specs

 

All I want to know is if I need the 720mW, should I update to a 1000mW, or downgrade to a 450 mW Geek.

 

These are the specs I could find, I guess some specs arent relevant or not enough to determine what I need... but some of you have experience and the Geek will be my first DAC/AMP...

 

So there are some headphones I already use, others I'm considering to buy (didn't choose yet which one)..

 

The Question is: If I use the 1000mW, could I damage my Shures for example, but drive the more demanding headphones? If I choose a less stronger model, could I drive my shures but not the more demanding one?

I'm really confused right now...

 

Having some of and thinking of buying one or more of the following Headphones, and having the Geek Out USB DAC/AMP at 720mV with the option to upgrade to 1000mV, should I upgrade, or even downgrade the Geek?? 

 

Have:

 

 

Shure SE425:

 

  • Sensitivity109 dB
  • Impedance22 Ohm
  •  

 

Monoprice 108323 Premium:

 

Impedance 40 ohms
Sensitivity 100 +/- 3 dB / 1mW (S.P. L at 1 k Hz)
 

 

 

Made a list of HP I'm considering to buy (one or two of these):

 

Sennheiser HD 589:

 

Impedance 50 Ohm
Sound pressure level (SPL) 112 dB (1kHz / 1Vrms)

 

Sennheiser HD 600: or (650)

 

Impedance 300 Ohm

SPL 112 dB at 1kHz

 

Philips Fidelio X1:

 

Impedance 30 Ohm

max Power input: 500 mW

 

Sony MDR-1R:

 

Sensitivity (dB/mW) 105 dB/mW

impedance: 1Ohm at 1kHz

 

NAD Viso HP50:

 

Maximum power: 30mW

Impedance: 32ohms

 

Mr Speakers Mad Dog:

max input power: 3000 mW

Sensitivity: 98dB

Impedance: 50 Ohm

 

HiFiman He-400:

Sensitivity: 92.5 DB
Impedance: 35 Ohm

 

I think the most reasonable is to upgrade to the 1000mW one, and to drive a demanding Headphone, and if I cant use the low impedance IEMs with them, so be it.

Am I wrong with my point of view?

post #10 of 16
Your least sensitive headphones are the HE-400 (92.5 dB/mW), and those require only 56.23 mW to reach a peak SPL of 110 dB, 177.83 mW to reach 115 dB (but that's really pushing it, you'll go deaf at that rate). So that's pretty much your highest power requirement. Surely you can see that 700 mW is already completely overkill, let alone 1000 mW. So much overkill, that the amp might very well completely inappropriate for your headphones and IEMs, forcing you to set volume very low, with little to no room to play with, and possibly channel imbalance.

Edit: also, it's not Sennheiser HD 589, it's HD 598.
Edited by skamp - 11/20/13 at 4:29am
post #11 of 16
Thread Starter 
Quote:
Originally Posted by skamp View Post

Your least sensitive headphones are the HE-400 (92.5 dB/mW), and those require only 56.23 mW to reach a peak SPL of 110 dB, 177.83 mW to reach 115 dB (but that's really pushing it, you'll go deaf at that rate). So that's pretty much your highest power requirement. Surely you can see that 700 mW is already completely overkill, let alone 1000 mW. So much overkill, that the amp might very well completely inappropriate for your headphones and IEMs, forcing you to set volume very low, with little to no room to play with, and possibly channel imbalance.

Edit: also, it's not Sennheiser HD 589, it's HD 598.

Hifiman writes on their page that the HE-400 are specially build to be driven from a portable player.

 

Are you saying that with all the listed Headphones here, I dont need more then the 450mW Geek.

The 720/1000 mW Versions are made for Headphones in another leage, like LCD-2/3/X for example, or HD 800?

 

Whats with the Sennheiser HD 598, or 600s?

post #12 of 16
Quote:
Originally Posted by BaTou069 View Post

Hifiman writes on their page that the HE-400 are specially build to be driven from a portable player.

That's a lie. An iPod wouldn't drive those to comfortable levels.
Quote:
Originally Posted by BaTou069 View Post

Are you saying that with all the listed Headphones here, I dont need more then the 450mW Geek.

I think I've been quite clear.
Quote:
Originally Posted by BaTou069 View Post

The 720/1000 mW Versions are made for Headphones in another leage, like LCD-2/3/X for example, or HD 800?

Not "in another league", that doesn't mean anything. For headphones with very low sensitivity, like the HE-6 (83.5 dB/mW). The LCD-2s, LCD-3s and HD 800s are not less efficient than the HE-400s.
Quote:
Originally Posted by BaTou069 View Post

Whats with the Sennheiser HD 598, or 600s?

I've already covered the HD 598s. The HD 600s are similarly efficient, at 97 dB/mW.
post #13 of 16
Thread Starter 

Thank You a lot.

So I will downgrade the Geek to a 450mW model, and like this I can choose any of the listed headphones above, and concentrate on choosing the right one :gs1000smile:

post #14 of 16
Quote:
Originally Posted by BaTou069 View Post
 

Hifiman writes on their page that the HE-400 are specially build to be driven from a portable player.

 

Are you saying that with all the listed Headphones here, I dont need more then the 450mW Geek.

The 720/1000 mW Versions are made for Headphones in another leage, like LCD-2/3/X for example, or HD 800?

 

Whats with the Sennheiser HD 598, or 600s?


I took a look at the Geek out project you mentioned.

 

I'm not sure what design they're using, but it doesn't look exactly right. For instance, the max they have is 4Vrms with 1000mW, that comes out to 250mA.

 

The way I see it, an amp should be a voltage source first, this one's limited when it comes to voltage and has plenty of current. Seems to me because of the USB supply they're using.

So, for low impedance headphones (<64Ohms), turning up the volume just a teeny bit will be ear blasting and risks damaging the headphone and your ears, for higher impedance (300 Ohms+), it just won't have enough Vrms to hit 115dB peaks.

This is considering both the low/high impedance headphones have fairly similar sensitivity.


Edited by proton007 - 11/20/13 at 5:06am
post #15 of 16
Thread Starter 
Quote:
Originally Posted by proton007 View Post
 


I took a look at the Geek out project you mentioned.

 

I'm not sure what design they're using, but it doesn't look exactly right. For instance, the max they have is 4Vrms with 1000mW, that comes out to 250mA.

 

The way I see it, an amp should be a voltage source first, this one's limited when it comes to voltage and has plenty of current. Seems to me because of the USB supply they're using.

So, for low impedance headphones (<64Ohms), turning up the volume just a teeny bit will be ear blasting and risks damaging the headphone and your ears, for higher impedance (300 Ohms+), it just won't have enough Vrms to hit 115dB peaks.

This is considering both the low/high impedance headphones have fairly similar sensitivity.

Are you talking about the 1000mV model?

Regarding the list of Headphones I'm considering to buy, where the range of impedance is between 30 and 300 Ohm, which Geek model would you recommend me to get?

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Sound Science
Head-Fi.org › Forums › Equipment Forums › Sound Science › Amp Voltages, Impedance, and other confusing numbers