HD Omni, headphone impedance

[Exodius]

hi everybody :)

i've got a dirty (for me) easy (for you) question.

i can't know if the HD Omni headphone output can handle Beyer Dyn DT770 250Ω and i would like to know if some of you use a DT770 and/or which one is better with the HD omni : the 80Ω or the 250Ω (or a higher impedance headphone) ?

thanks,
Exodius

[Drew Mazurek]

Originally Posted by Exodius

hi everybody :)

i've got a dirty (for me) easy (for you) question.

i can't know if the HD Omni headphone output can handle Beyer Dyn DT770 250Ω and i would like to know if some of you use a DT770 and/or which one is better with the HD omni : the 80Ω or the 250Ω (or a higher impedance headphone) ?

thanks,
Exodius

Page 10 of this document says the Omni's headphone outs are 600ohms.

http://akmedia.digidesign.com/suppor..._v90_69707.pdf

[Exodius]

Hi Drew

thanks for your message, so i have to take the 250Ω !?

[Drew Mazurek]

Originally Posted by Exodius

Hi Drew

thanks for your message, so i have to take the 250Ω !?

Sorry, I'm not an electronics expert, but it's my understanding that the impedance of the headphones primarily influences how the amp will be able to "drive" them. So higher impedance headphones will be less loud than lower ones. In other words, both of them will work, but their level may be different as well as any sonic differences.

Please, someone with more knowledge than me correct/clarify this.

[propower]

What the OMNI manual says...

The HD OMNI Headphone output is set to
power 600 Ohm headphones at +3 dBV.

What it does not say:
- what signal was driving the HP?
- Is this a maximum output number?

What I think this says...
3dBV = 1.41 Vrms
(1.41 Vrms)^2 / 600 Ohms = 3.3mW

If this were the maximum output power that would be at least a factor of 10 worse than any HP amp I can think of. At least 30mW and hopefully 100mW would be more what I would expect.

If on the other hand the 1.41 Vrms were the voltage limit - that would drive 80 Ohm phones with 24.8mW. The DT770 series are specified for 96dB at 1mW (all models I believe). If we assume that the ratio of "dB output" to "power in" is something like 2X the power for 6dB increase then...
2mW = 102dB
4mW = 108dB
8mW = 114dB
16mW = 120dB
32mW = 126dB
If this were true then 25mW would be a little more than 120dB. Tons more than I would ever want or need

So - what does this spec mean?? I really can't say .

I can say that I have owned the OMNI a couple of times and my favorite phones are 80 Ohm DT770 Pros. I have tracked guitars, vocals, and mixed using these many times with no issues at all. Tons of volume headroom without ever pushing the HP amp. Note though that I rarely listen to anything over 90dB.

[Exodius]

i don't get everything but i understand that you own a HD omni and a DT770 80Ω, and the 250Ω would be tricky ^^"

thanks propower :)

P.S :i think the "600 Ohm headphones at +3 dBV" is an average

[TVPostSound]

I have 2 types at 64 and 55 ohm, and sound great

2 others are 600 ohm, and are very weak.

That seems to confirm Drews theory


Does that help?

[Exodius]

not really help 'cause it's a 250Ω but a little bit indeed :

You've tried with the omni ?

thx TVPostSound

[TVPostSound]

It means as the impedance rises, the headphones are getting weaker with the Omni.

[Exodius]

i know it but the 250Ω is between your 50Ω ("sound great") and your 600Ω ("it's very weak")

so... yea, 80Ω is maybe the best choice :)