[koonhua90]

This might sound silly, but which one is easier to drive, a low impedance IEM or a high impedance IEM?

If I am not mistaken, impedance is the resistance to AC current, so it follows from logic that the high impedance IEM or headphones are usually harder to drive, right?

But I read somewhere in this forum that sometimes low impedance IEM can be hard to drive too. Why is that? Can anyone with some knowledge on this matter shed some light on this?

 

[KramitDfrog]

You're right - it also has to do with the sensitivity, usually measured in db per mW.

So the watts going through your headphone is determined by the voltage of your source and the impedance of your headphone, and the amount of sound is determined by the amount of db your headphone produces for that number of watts.

So, if that db per mW is high (say 120db/1mW) and your impedance is low (say 16ohm), you'll have a very easy to drive headphone.

Most IEMs are very easy to drive.

 

[ClieOS]

For my understanding, it is basically because Power (P) = Current (I) ^2 x Resistance (R). If you want to maintain the same power output to the IEM when you lower the resistance, you need to increase the current. The problem is most portable source have very limited current output capability. The same formula P = I^2 x R is also P = V^2 / R (V is voltage). For the same power, If you increase R, you will also need to increase the voltage. One of the main reason higher impedance IEM is hard to drive is because most portable source don't have high enough voltage.

 

[Arjisme]

So what exactly do we mean when we say a headphone is hard to drive? It requires greater voltage? Greater current?

 

[semisight]

Quote:

Originally Posted by Arjisme /img/forum/go_quote.gif So what exactly do we mean when we say a headphone is hard to drive? It requires greater voltage? Greater current?

Actually, IIRC it's the output resistance of the source that stays constant. So voltage and current are proportional.

 

[Arjisme]

Quote:

Originally Posted by semisight /img/forum/go_quote.gif Actually, IIRC it's the output resistance of the source that stays constant. So voltage and current are proportional.

Yes, Ohm's Law. So what do we mean when we say a headphone is hard to drive?

 

[Anonanimal]

Quote:

Originally Posted by Arjisme /img/forum/go_quote.gif Yes, Ohm's Law. So what do we mean when we say a headphone is hard to drive?

I think it very much so depends, and you should definitely take it w/ a grain of salt when you hear it.

A high-impedance headphone, e.g. Beyerdynamic T1 @ 600 Ohms, will be considered by many to be "hard" to drive because it will require significantly more voltage swing for reference volumes than, say, a Denon AH-D1001 @ 32 Ohms. Conversely, the Denon (even though it is probably slightly more efficient) is going to require more peak-to-peak current than the T1 for the same volume levels.

When you hear someone saying that a particular headphone seems hard to drive, I'd say you need to take it in the context of the equipment he/she is using to drive said headphones. I know it doesn't really answer your question fully but I think given the range of what you'll hear from various impressions, it's possibly the best you may be able to expect.

 

[Prog Rock Man]

A hard to drive headphone should have a high impedance and low Sound Pressure Level (SPL) which is also sometimes referred to as sensitivity.

Grados are considered easy to drive with their low impedance at 32ohms, but they have a lower SPL at 98 db/V. AKG K701/2 are considered hard to drive with 62 ohms and SPL 105. But the really hard to drive headphones are the likes of the Goldring NS1000 which with noise reduction off are 100ohms and an SPL of 93.

 

[Mintz]

So would a pair like the Sennheiser HD 25-1 II be considered an easy or hard to drive headphone since it is 70 ohm and 120 SPL?

 

[Spyro]

It should be easy. I always default to the SPL/Sensitivity and try to look for it to be at least above 115dB.

The Grado GR8 is 120 Ohms but 118dB sensitivity so it gets pretty loud despite being high ohms. UM3X is 56 ohms but 124dB sensitivity so it will still get to dangerously high volumes.

 

[koonhua90]

Thanks for the reply everyone, but then what about the current provided to the low impedance phones, as said by ClieOS. I believe in what he said, as in that to provide the same power when resistance is lower, the current has to increase.

But the thing is, impedance is not exactly resistance, it's the imaginary part of resistance. I think that the signal should have a varying voltage and current, as opposed to having constant voltage or current, right? Please correct me if I am wrong.

The reason I posted this thread is because I find that both my Samsung Yp-Z5 and Ipod nano need a very high volume (60-70% of max volume) to even drive Monster Miles Davis and IE8 (both dynamic) properly. But when I used balanced armature phones, I can achieve same volume at a lower volume on the players.

 

[kameenadesi]

hi koonhua!  I've been dying to get your advice...

I currently have the CK10 and IE8 and i use them solely for trance music..

You're the only headfier i know of who has the SM3, FX700, and JH16

I prefer a sound like the IE8...it has the immersion, dynamic bass, soundstage, EMOTION, and fun factor that my CK10 does not have... and i need an IEM that can provide all those characteristics of the IE8, for trance

The IE8 has lost its sparkle and is now kinda boring..

I am guessing that the SM3 is more analytical than fun, as it probably wont have the dynamic bass and emotion that the FX700 can provide...

So do you think its worth spending the big bucks on the JH16, or should the FX700 be better or just as good? for trance that is... 

Thanks in advance koonhua, much appreciated...sorry my private message was acting up, this is the only way i could contact you..

 

[goodvibes]

ClieOS got it. It's complicated but higher impedence is not necessarily more difficult to drive. In fact it should be better regardless of requirement if within the voltage swing of a device as damping factor will be better. Adding a resistor doesn't count as it will actually decrease damping factor at the phone but that's not always a bad thing either. Of course, if difficult is in regards to battery drain then it's still complicated.

 

[T.F.O.A]

Sorry for bringing this up again, but since found this thread might as well use this one instead of making another one.
So, how do you really tell high or low impedance iem then?(i've read the posts above like 5 times and i still don't get it, can somebody use a simpler term?)
 
If it's by numbers, what are the numbers? and what do you have to check from your DAP or whatever source you're using, to know whether it can drive your iem or not?
 
Sorry for bringing this up again, just curious.
 
Thanks

 

[goodvibes]

Lower impedance is closer to a short and will pull more current from a device. It will also generally be less easy to control. High impedence will require more voltage so you need to turn the volume up higher but it may not be pulling more energy from the player. Best would be high impedance and high effeciency. There's no universal recomendations here as some players have higher output impedances than others but once you get over 30 ohms or so for a phone, it should be fine.