white lotus said:

  I've heard it said that not supplying sufficient power to a planar can cause roll-off in frequencies on each end of the spectrum.
 
Any truth to this?
 
If a planar is loud enough, does that mean it's receiving sufficient power? 

Click to expand...

as JCX said, in principal, lowering the volume is "not supplying sufficient power" ^_^ so because of equal loudness contour at different loudness levels, maybe some people got that idea when unable to go loud?
if the limit is current, I'm guessing the distortions would rise like crazy and bass or treble roll off may not be what we would care about.
 
I can't think of a reason why planars would do what you talk about, but then again I'm not much of an expert outside of pringles and manga(and even there, I'm self proclaimed expert).

Best way to know how underdrive distortion sounds like is to hear it for yourself.

https://www.dropbox.com/s/3p8ic8qqtvnc902/foobar2000-underdrive.zip?dl=0

This custom foobar2000 portable install is customized with a compressor plugin configured to produce 8dB of digital underdrive distortion on full-scale music. There's also an alternative DSP preset for analog distortion.

The reacomp plugin can be manually configured to change the distortion characteristics: the lower the "Threshold" slider on the left the greater the amount of total distortion, while changing the knee size changes the "analogueness" of the distortion (0dB = fully digital).



(note however that this experiment may not be used to determine the relative merits of digital and analog distortion, as changing the knee size also changes the total amount of distortion...)

Along the same lines, I've seen people argue against the use of planars with OTL amps. They say that the high input impedance on something like a Bottlehead Crack doesn't play well with the low impedance of a planar.
 
But as far as I know, the typical planar impedance curve is flat, unlike dynamic drivers. Why would the input impedance on an OTL make a planar sound bad?

I have no idea if such a concern has legitimacy or not, but talking about general theory, the damping factor can matter for a bunch of reasons:
-change in frequency response from non flat impedance on the headphone(usually not a concern for planar).
-damping factor as a mean to control the movement of the driver. it's a mixed salad of mechanical damping and electrical damping, and could potentially affect mainly low frequencies the most. it's fairly obvious on speakers, usually not so much on headphones.
-damping factor as a mean to ease up the work of the amp and get nominal efficiency(in an impedance bridging system, the amp should ideally be close to 0ohm). if the ratio is good then the amp usually only has one main job, being a good voltage amp and get enough voltage. if the ratio isn't good, the amp might have a harder time doing its job. so maybe the problem came from a given amp having troubles, and not really for how the headphone itself behaved? I can only guess at this point.