[Redoo]

Hi to all,
 
I have tried to search a previous answer to a question in the forum but since now I can't find it...
 
I have read in the specs that the AKG K601 (120ohm) and K702 (62ohm) both have a max input power of 200mW, I am searching a small desktop power amp (for a starting point I have checked the E09k that someone seems to have used with these...) that can correctly drive these headphones however there is something unclear to me:
I see the the E09k stated a specs of >900mW at 32ohm and >150mW at 300ohm Vs for example the E17 that has >250mW at 16ohm and >30mW at 300ohm
What I don't clearly understand is why I have read that many times the E09k (or E09) is used for a headphones like K702,K701,K601 (same max input power of 200mW)? Isn't it too much power from E09 to the drive them considering their ohm and max input power? I suppose that at 120ohm and 62ohm the E09k send a lot more than 200mW of power to them.There isn't risk of damage the driver?
I think I have missed something technical about this...
Can you please help me understand a bit more about this?
Many thankks for your help

 

[PurpleAngel]

Quote:

Hi to all,
 
I have tried to search a previous answer to a question in the forum but since now I can't find it...
 
I have read in the specs that the AKG K601 (120ohm) and K702 (62ohm) both have a max input power of 200mW, I am searching a small desktop power amp (for a starting point I have checked the E09k that someone seems to have used with these...) that can correctly drive these headphones however there is something unclear to me:
I see the the E09k stated a specs of >900mW at 32ohm and >150mW at 300ohm Vs for example the E17 that has >250mW at 16ohm and >30mW at 300ohm
What I don't clearly understand is why I have read that many times the E09k (or E09) is used for a headphones like K702,K701,K601 (same max input power of 200mW)? Isn't it too much power from E09 to the drive them considering their ohm and max input power? I suppose that at 120ohm and 62ohm the E09k send a lot more than 200mW of power to them.There isn't risk of damage the driver?
I think I have missed something technical about this...
Can you please help me understand a bit more about this?

For years, the over driving of headphones was a problem that many very smart people spent countless years and decades trying to solve this problem.
Then the solution was finally discovered, they called it "The volume knob".

 

[PleasantSounds]

The stated max input power relates to continuous load that the headphones can handle, but the nature of sound is that it consists mostly of impulses. Usually headphones can handle much more power than their stated value, but for short periods of time. Sustained load causes that too much heat is generated in the coils and eventually their insulation will get damaged by the heat.
Amps that can deliver excessive power could cause this type of damage, but at the same time they produce less distortions at normal listening levels and will handle high power impulses much better. Many of them have adjustable gain, so that you don't damage your sensitive headphones with too much power.
It's a bit like with sports cars: you don't need 500kW engine to achieve the legal speed limit, but it sure helps
I drive my Q701s from a 3W amplifier at pretty high volume levels and they handle it fine. If I provide too much power, they complain by distorting the sound and I know that I need to dial the volume down a bit. 

 

[mikeaj]

There is a big difference between (1) maximum power that an amp is capable of and (2) power actually delivered by the amp.  For a given headphones, the power delivered by the amp depends on the input level, gain setting, and volume setting (unless you are exceeding the maximum output of the amp, in which case even if you increase the input level or gain or volume, you may not get any more volume).
 
If you start to approach 200 mW power delivered to those headphones, they will be distorting badly.  Moreover, they will be extremely loud, loud enough that you don't want them on your head.  Granted, out of all midrange and higher headphones, these have a relatively low sensitivity and max power rating, so at the max rating, it may be more like extremely uncomfortable and harmful, rather than excruciatingly painful, like it would be for some other headphones.
 
At a typical listening volume, the average level will be no more than 1 mW.  If you're actually using about 1 mW on average typically, that is reaching levels that are considered harmful for long-term exposure (many hours in a day, would be considered an occupational hazard).

 

[Redoo]

many thanks to the ones who "really" wanted to help me understand more. my doubts started when I saw on the FiiO website specs that (for example the E09k) the mW delivered to the headphone are = or > of 150 at 300ohm so I started to think that when I connect a 300ohm headphone and the volume was at the lowest position it sends minimum 150mW which was quite absurd for me...but they indicate equal or more in math symbols in the specs... So the 150mW are the the maximum that the amp can send at 300ohm and not the minimum, now the volume pot have sense again. Do you know if the mW/ohm relationship is somewhat "linear" or it totally depends on the amplifier components ? I'm a bit worried that at 62ohm with the K702 I have "little room" for control volume considering the maximum of 900mW at 32ohm that this amplifier deliver.I don't want to have only a margin from off to 9 o'clock for adjust the volume or worse... I would like to drive "decently", as a starting point, my K601 and the K702 using for both the same E09k if possible. Sorry if my english is not perfect.

 

[PurpleAngel]

Quote:

many thanks to the ones who "really" wanted to help me understand more. my doubts started when I saw on the FiiO website specs that (for example the E09k) the mW delivered to the headphone are = or > of 150 at 300ohm so I started to think that when I connect a 300ohm headphone and the volume was at the lowest position it sends minimum 150mW which was quite absurd for me...but they indicate equal or more in math symbols in the specs... So the 150mW are the the maximum that the amp can send at 300ohm and not the minimum, now the volume pot have sense again. Do you know if the mW/ohm relationship is somewhat "linear" or it totally depends on the amplifier components ? I'm a bit worried that at 62ohm with the K702 I have "little room" for control volume considering the maximum of 900mW at 32ohm that this amplifier deliver.I don't want to have only a margin from off to 9 o'clock for adjust the volume or worse... I would like to drive "decently", as a starting point, my K601 and the K702 using for both the same E09k if possible. Sorry if my English is not perfect.

I though I was really helping, It comes down to the volume knob and what your ears tell you.
Each model type of each manufacturers headphone's may or may not match another model's volume at a given rotation of the volume knob.
Also another factor beside Ohms (resistance, impedance) is sensitivity which is different from different models.
Is always going to come back to what your ears tell you.

 

[PleasantSounds]

Quote:

many thanks to the ones who "really" wanted to help me understand more. my doubts started when I saw on the FiiO website specs that (for example the E09k) the mW delivered to the headphone are = or > of 150 at 300ohm so I started to think that when I connect a 300ohm headphone and the volume was at the lowest position it sends minimum 150mW which was quite absurd for me...but they indicate equal or more in math symbols in the specs... So the 150mW are the the maximum that the amp can send at 300ohm and not the minimum, now the volume pot have sense again. Do you know if the mW/ohm relationship is somewhat "linear" or it totally depends on the amplifier components ? I'm a bit worried that at 62ohm with the K702 I have "little room" for control volume considering the maximum of 900mW at 32ohm that this amplifier deliver.I don't want to have only a margin from off to 9 o'clock for adjust the volume or worse... I would like to drive "decently", as a starting point, my K601 and the K702 using for both the same E09k if possible. Sorry if my english is not perfect.

 
Yes, the specs saying  power output >150mW @ 300 ohm means that the maximum power delivered to 300 ohm headphones is going to be at least 150mW.
 
Regarding the relationship between headphone impedance and the amp's power output - it is not linear. Another factor that affects it is the output impedance of the amplifier, but there may be other factors as well. If it can be calculated, I have never seen the actual formula.
 
For the K702 I wouldn't worry that any of the FiiO amps is going to be too much for it. If you are concerned then make sure that the one you're getting has a gain switch and set it to the low level.