[Me x3]

  (...) In the case of the Senn vs. the Beyer, the Senn is efficient enough that enough power can be developed at lower voltages to do OK (but it still wants the higher voltage).  Perhaps the Beyers cannot.

 
Consider a fixed voltage (let's say 1.5 Vrms) the Sennheiser HD600 sounds louder than the Beyerdynamic DT880 250 Ohm, and it also drains less current since it's has a higher impedance.
 
You need less voltage swing and less current to drive HD600 to the same level (vs DT880).
 
I think that's enough to say that HD600 is easier to drive than DT880 250 Ohm version.

 

[tomb]

 

  (...) In the case of the Senn vs. the Beyer, the Senn is efficient enough that enough power can be developed at lower voltages to do OK (but it still wants the higher voltage).  Perhaps the Beyers cannot.

 
Consider a fixed voltage (let's say 1.5 Vrms) the Sennheiser HD600 sounds louder than the Beyerdynamic DT880 250 Ohm, and it also drains less current since it's has a higher impedance.
 
You need less voltage swing and less current to drive HD600 to the same level (vs DT880).
 
I think that's enough to say that HD600 is easier to drive than DT880 250 Ohm version.

That's just re-stating, but fine.

 

[billybob_jcv]

You're right, of course, what I was trying to reference is the typical specs you see on amps, such as what is shown for the audio-gd NFB-15:

Audio-gd NFB-15 Output Power:
3500mW/25 ohm
1800mW/50 ohm
900mW/100 ohm
300mW/300 ohm
150mW/600 ohm

And then to link this to the Innerfidelity measurements of the headphones:

Beterdynamic DT880-250:
Volts RMS required to reach 90dB SPL: 0.299 Vrms
Impedance @ 1kHz: 236 Ohms
Power Needed for 90d BSPL 0.38 mW
Broadband Isolation in dB (100Hz to 10kHz): -3 dBr

Together, those two specs tell me the NFB-15 has plenty of excess "output power" available when the DT880-250 is generating 90 db SPL, correct? As the impedance that the amp sees increases, which goes down, the voltage, the current or both? Since P(W) = V(V) * I(A), something must be going down, or the amp's measured output in milliwatts would stay the same, right?

lol - I may not know how current flows, but I do know how airplanes & rockets fly. If you ever want to put an amp into a geostationary orbit, I'm your guy...

 

[Keithpgdrb]

I have to appologize.  I've gone brain dead.  I have the 880's 600 ohm, not the 250.

 

[tomb]

You're right, of course, what I was trying to reference is the typical specs you see on amps, such as what is shown for the audio-gd NFB-15:

Audio-gd NFB-15 Output Power:
3500mW/25 ohm
1800mW/50 ohm
900mW/100 ohm
300mW/300 ohm
150mW/600 ohm

And then to link this to the Innerfidelity measurements of the headphones:

Beterdynamic DT880-250:
Volts RMS required to reach 90dB SPL: 0.299 Vrms
Impedance @ 1kHz: 236 Ohms
Power Needed for 90d BSPL 0.38 mW
Broadband Isolation in dB (100Hz to 10kHz): -3 dBr

Together, those two specs tell me the NFB-15 has plenty of excess "output power" available when the DT880-250 is generating 90 db SPL, correct? As the impedance that the amp sees increases, which goes down, the voltage, the current or both? Since P(W) = V(V) * I(A), something must be going down, or the amp's measured output in milliwatts would stay the same, right?

lol - I may not know how current flows, but I do know how airplanes & rockets fly. If you ever want to put an amp into a geostationary orbit, I'm your guy...

IMHO, what this shows you about the NFB-15 is that it's a typical solid-state amplifier.  As impedance increases, its voltage is limited while at the same time, current becomes less important in the power contribution.  Thus, power capability drops as impedance increases.
 
It's important to understand, however, that not every amp is like that.  A rudimentary OTL tube amp might have a power-impedance relationship that is opposite that.  A transformer-coupled amp (whether solid-state or tube) might have very consistent power capability over a wide range of impedances.
 
It all depends ...
 
How airplanes & rockets fly?  Funny ... I spent 15 years with Lockheed.

 

[Me x3]

Audio-gd NFB-15 Output Power:
3500mW/25 ohm
1800mW/50 ohm
900mW/100 ohm
300mW/300 ohm
150mW/600 ohm

 
If those specs are true, that's a voltage limited amp. The amp is able to reach around 9.5 Vrms at max.
 
P = V * I = (V*V) / R
 
9.5 Vrms into 50 Ohm
P = (9.5 * 9.5) / 50 = 1805 mW
 
9.5 Vrms into 300 Ohm
P = (9.5 * 9.5) / 300 = 300 mW
 
9.5 Vrms into 600 Ohm
P = (9.5 * 9.5) / 600 = 150 mW
 
For the sake of comparison:
 
The little Fiio E10 is able to reach around 2.5 Vrms at max with loads over 80 Ohm (Voltage limited for loads over 80 Ohm)
 
2.5 Vrms into 80 Ohm
P = (2.5 * 2.5) / 80 = 78 mW
 
2.5 Vrms into 300 Ohm
P = (2.5 * 2.5) / 300 = 21 mW
 
2.5 Vrms into 600 Ohm
P = (2.5 * 2.5) / 600 = 10.5 mW
 
With loads under 80 Ohm the Fiio E10 run out of current before reaching 2.5 Vrms (and distortion raises)
 
2.5 Vrms into a 32 Ohm load drains 78mA since:
 
V = I * R -----------------> I = V / R
 
2.5 / 32 = 78 mA
 
Fiio E10 can't supply 78mA
 
Actually, it's capable of no more than 2 Vrms into 32 Ohm load
 
2 Vrms into 32 Ohm
P = (2 * 2) / 32 =  125 mW
 
I = V / R
I = 2 / 32 = 62mA

 

[billybob_jcv]

I pulled those specs directly from the audio-gd NFB-15 web site:
http://www.audio-gd.com/Pro/Headphoneamp/NFB1532/NFB15.32EN_Specs.htm

I worked for Lockheed for 3 years in the mid 1980s as my first job out of college, then a whole bunch of other aerospace companies before jumping to IT right before the dot-com bubble burst in 2000.

 

[banquier]

Tried O2 combo with DT880 250ohm, Not perfect on all instrument but overall good!

 

[PurpleAngel]

  Tried O2 combo with DT880 250ohm, Not perfect on all instrument but overall good!

 
Wow, this thread you commented on has only been dead for 6 months.

 

[rigodeni]

I own the whole DT series and the HD 600. I recently did a complete comparison in my DT 880 Pro 250 Ohm review. I don't think the HD6xx series are a worthwhile upgrade. In fact it's a downgrade in some areas. I would start looking at your DAC and more importantly your amp. Cheaper solid state amps tend to be overly bright or V-shaped. I'm loving the DT 880 with my TEAC UD-H01 DAC and Schiit Valhala amp.