[So Far]

Hey guys, I'm back in the headphone game after a very long time, mainly because of all the hype around the new planar drivers that is being implemented in cans like the Aiva and M570 (which I got my eyes on). Issue is my current amp; I'm using an SMSL M6 that has a output impedance of 10 ohms while the M570's have 32. I read briefly about the 1/8 rule but would love more input since there isn't much out there in terms of personal experience, especially with planars.

 

[ProtegeManiac]

Hey guys, I'm back in the headphone game after a very long time, mainly because of all the hype around the new planar drivers that is being implements in cans like the Aiva and M570 (which I got my eyes on). Issue is my current amp; I'm using an SMSL M6 that has a output impedance of 10 ohms while the M570's have 32. I read briefly about the 1/8 rule but would love more input since there isn't much out there in terms of personal experience, especially with planars.

Planars don't tend to have much of a penalty on the damping factor so you don't need as much as 1:8. Unless you have something with absurdly high impedance I'd worry more about power, and chances are, only OTL amps and speaker integrated amps/receivers/preamps tend to have both problems.

 

[PurpleAngel]

Hey guys, I'm back in the headphone game after a very long time, mainly because of all the hype around the new planar drivers that is being implements in cans like the Aiva and M570 (which I got my eyes on). Issue is my current amp; I'm using an SMSL M6 that has a output impedance of 10 ohms while the M570's have 32. I read briefly about the 1/8 rule but would love more input since there isn't much out there in terms of personal experience, especially with planars.

While 1/3 (10-Ohm source with 32-Ohm headphones) is not the most desirable, at most it might give you a slightly bloated bass.
I've plugged 32-Ohm headphones into a 10-Ohm source and I did not have any real issue with it.

 

[serman005]

As noted above, the fact is, sometimes these suboptimal ratios actually work out fine.

 

[tomb]

Planars don't tend to have much of a penalty on the damping factor so you don't need as much as 1:8. Unless you have something with absurdly high impedance I'd worry more about power, and chances are, only OTL amps and speaker integrated amps/receivers/preamps tend to have both problems.

^ This, along with the following two posts as well.

 

[Scgorg]

Electrical damping is how the power from the output is distributed. If your amp puts out 1V and the output impedance of the amp and the input impedance of the headphones are the same only .5V will actually go to the headphone. The issue is that most headphones do not have a flat impedance curve, that is to say, their impedance changes depending on frequency. Typically planars have a flat impedance with a slight rise in the top octave due to induction while dynamics will have a big bump at or around their resonance frequency (and the same rise due to induction). What this means is that you actually don't boost the bass with a high output impedance like some people like to allude to, rather you decrease the surrounding frequencies since they are receiving less voltage comparatively. On IEMs damping factor is much worse to figure out due to the wild impedance curves many IEMs have due to the fact that they use crossovers/multiple drivers, luckily we avoid this in full size, single driver headphones.

"So then it doesn't matter for planars where the impedance is flat?" someone might ask. The answer is both yes and no. Electrical damping also has to do with how well the amplifier can control the driver itself, having too low damping factor results in measureable differences in the transient response of drivers, how audible this is I will leave up to other members of this forum, but the output signal WILL be further from the input signal compared to using a low OI amp (less fidelity, which I suppose is opposite of what audiophiles chase after). The biggest audible issues with using a flat impedance planar on an amplifier with high output impedance would be the fact that you need more power to overcome the suboptimal distribution of power from the output which not every amp might have, just food for thought.

As for anecdotes. I've used both the MrSpeakers Ether and Ether Flow on a Woo WA7 in Hi-Z mode and noted no adverse effects.

Edit: Also worth mentioning that a few headphones are designed so that they will be electrically overdamped by using a low OI amp, this is exceedingly rare and the only example I can think of from the top of my head is the MySphere 3.1