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Newbie Ohm Question

post #1 of 12
Thread Starter 

Greetings,

 

I'm looking at purchasing the DT-770 headphones and I'm using a MOTU Track 16. MOTU tech support has informed me that the headphone out on the device is 30 Ohms and 200 milliwatts.  Would I be better off getting the 80 ohm or 250 ohm version of the DT-770s?  From the basic information I've gathered online (and the 1:8 rule) it looks like I should go with the 250 ohm version.

 

Any clarification/advice would be greatly appreciated.  Thanks!

post #2 of 12
Quote:
Originally Posted by Sentient808 View Post
 

Greetings,

I'm looking at purchasing the DT-770 headphones and I'm using a MOTU Track 16. MOTU tech support has informed me that the headphone out on the device is 30 Ohms and 200 milliwatts.  Would I be better off getting the 80 ohm or 250 ohm version of the DT-770s?  From the basic information I've gathered online (and the 1:8 rule) it looks like I should go with the 250 ohm version.

Any clarification/advice would be greatly appreciated.  Thanks!

 

Plugging the 80-Ohm Beyers into a 30-Ohm source is not a big deal.

But i do prefer the 250-Ohm DT770 to the DT770 80-Ohm anyway.

post #3 of 12
Thread Starter 

Thanks. I think I'd prefer the 250 Ohm version from people's opinions and what I've read.  I guess my real question is, would the 30 Ohm output from my MOTU be enough to drive the 250 Ohm headphones efficiently?

post #4 of 12
Quote:
Originally Posted by Sentient808 View Post
 

Thanks. I think I'd prefer the 250 Ohm version from people's opinions and what I've read.  I guess my real question is, would the 30 Ohm output from my MOTU be enough to drive the 250 Ohm headphones efficiently?

 

The output impedance is not really a big factor for driving the headphones, voltage (and current) seem to be what counts for driving headphones.

I would guess (?) your MOTU can decently drive the 250-Ohm headphones.


Edited by PurpleAngel - 4/21/14 at 2:49pm
post #5 of 12
Quote:
Originally Posted by PurpleAngel View Post

The output impedance is not a factor for driving the headphones, voltage (and current) seem to be what counts for driving headphones.
I would guess (?) your MOTU can decently drive the 250-Ohm headphones.
Actually, output impedance is a factor in driving headphones, as the relationship between amplifier impedance and headphones impedance creates a voltage divider, limiting the efficiency of getting power into your headphones. If both are matched, then the voltage as measured at the headphone jack will be half of what the amp is trying to output.

Of course, power is what we're after, and power is a function of voltage and current, so very high headphone impedance can limit how much power the amp can supply. If you want a good image of this, check out the "specs" tab on the Valhalla (30 Ohms output impedance). The Max Power specs are:

100mW RMS/channel @ 50 Ohms
420mW RMS/channel @ 300 Ohms
210mW RMS/channel @ 600 Ohms

You can see that amp can deliver the most power somewhere in the middle because higher headphone impedance will limit the current, but lower headphone impedance will limit the voltage.

Anyway, not to get too off track...the biggest component to "will this amp work" is probably going to be your headphone efficiency. The higher the efficiency, the easier to drive. From there, if you have a high impedance (and 250 Ohms is kind of high) you can also check maximum power output of your amp @ that impedance.

I would look these things up and list them, but IE is acting up and I have to dash. I'll try to get back to this later.
post #6 of 12

Oops


Edited by PurpleAngel - 4/21/14 at 2:50pm
post #7 of 12
Thread Starter 
Quote:
 Actually, output impedance is a factor in driving headphones, as the relationship between amplifier impedance and headphones impedance creates a voltage divider, limiting the efficiency of getting power into your headphones. If both are matched, then the voltage as measured at the headphone jack will be half of what the amp is trying to output.

Of course, power is what we're after, and power is a function of voltage and current, so very high headphone impedance can limit how much power the amp can supply. If you want a good image of this, check out the "specs" tab on the Valhalla (30 Ohms output impedance). The Max Power specs are:

100mW RMS/channel @ 50 Ohms
420mW RMS/channel @ 300 Ohms
210mW RMS/channel @ 600 Ohms

You can see that amp can deliver the most power somewhere in the middle because higher headphone impedance will limit the current, but lower headphone impedance will limit the voltage.

Anyway, not to get too off track...the biggest component to "will this amp work" is probably going to be your headphone efficiency. The higher the efficiency, the easier to drive. From there, if you have a high impedance (and 250 Ohms is kind of high) you can also check maximum power output of your amp @ that impedance.

I would look these things up and list them, but IE is acting up and I have to dash. I'll try to get back to this later.

Great information, thanks.  The only info I have right now on my MOTU interface is that the output specs are 30 ohms and 200 miliwatts. 
 

For the DT-770 Pro headphones, the applicable specs I could find were:

 

Nominal impedance acc. to IEC 60268-7: 250 ohm
Nominal SPL acc. to IEC 60268-7: 96 dB
Nominal THD acc. to IEC 60268-7: < 0.2%
Power handling capacity acc. to IEC 60268-7: 100 mW

post #8 of 12
I think your MOTU will be okay. I don't know if it will be "great", but I doubt you'll be disappointed with the combination, and the 770's look like great headphones in general, so you'l probably be happy with them.

An amp with more power output will probably sound "better" with the 770's, but again, not necessary. More power just means that the amp can more easily drive your headphones and allow for a greater range of volume. You're still going to get the biggest sound improvement by getting better headphones.

For some extra recommendations:

Try the 770's before you buy. This isn't always possible, but if you can, do it. It will give you the best feel for the headphones.

Try the combination before you buy. This can be harder, but if you can find a store that will let you demo with your gear or what you will be using, you'll have the best confirmation. I know Guitar Center carries some headphones. Maybe your local store has both...

If you can't try at all, you can always check used. At least then you will have spent less than if you bought new-in-box, and you can always resell if you don't like them.

Anyway, good luck smily_headphones1.gif
post #9 of 12
Thread Starter 
Quote:
Originally Posted by superjawes View Post

I think your MOTU will be okay. I don't know if it will be "great", but I doubt you'll be disappointed with the combination, and the 770's look like great headphones in general, so you'l probably be happy with them.

An amp with more power output will probably sound "better" with the 770's, but again, not necessary. More power just means that the amp can more easily drive your headphones and allow for a greater range of volume. You're still going to get the biggest sound improvement by getting better headphones.

For some extra recommendations:

Try the 770's before you buy. This isn't always possible, but if you can, do it. It will give you the best feel for the headphones.

Try the combination before you buy. This can be harder, but if you can find a store that will let you demo with your gear or what you will be using, you'll have the best confirmation. I know Guitar Center carries some headphones. Maybe your local store has both...

If you can't try at all, you can always check used. At least then you will have spent less than if you bought new-in-box, and you can always resell if you don't like them.

Anyway, good luck smily_headphones1.gif

Great, thanks! I also emailed Beyer and they replied saying that both the 80 and 250 ohm versions should be fine on my device. I asked Guitar Center and the only way I could try the headphones is if I buy them, so I might just have to take the risk blindly.

I'm an audio engineer for a living so getting the best quality I can (either in the 80 or 250) with my setup is ideal, but it seems like I might not be able to A/B them without paying a price and selling one of the models on EBay afterwards.
post #10 of 12
Quote:
Originally Posted by Sentient808 View Post

Great, thanks! I also emailed Beyer and they replied saying that both the 80 and 250 ohm versions should be fine on my device. I asked Guitar Center and the only way I could try the headphones is if I buy them, so I might just have to take the risk blindly.
I'm an audio engineer for a living so getting the best quality I can (either in the 80 or 250) with my setup is ideal, but it seems like I might not be able to A/B them without paying a price and selling one of the models on EBay afterwards.

 

They are only very slightly different, if you pump enough juice thru them they sound 95% a like.

post #11 of 12
The 250 ohm DT-770 only needs around 63.143 mw to be driven well (http://www.head-fi.org/t/668238/headphones-sensitivity-impedance-required-v-i-p-amplifier-gain). 

My 250 ohm DT-990 was fairly easy to drive. A portable cmoy was more than enough. I'm not familiar with your MOTU, but I wouldn't worry about the 250 ohms being hard to drive. Also, the 80 ohm DT-770 is the more bassy version. 
post #12 of 12

Hello, what about sennheiser hd 600 for motu track16 ?

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