Gramophone Dreams #7 Measurements

Sidebar: Measurements

The primary specification for headphones is impedance: too low and the 'phones will not sound at its best with some sources that have high output impedances; too high, and while the headphones will be easy to drive, they might not go sufficiently loud. The upper solid trace in fig.1 shows how the NightHawk's impedance varies with frequency, measured with the headphones on my head; the lower solid trace is a 10 ohm resistor. The NightHawk resembles a 24 ohm resistor at all audio frequencies, the impedance hardly varying and the phase angle (upper dotted trace) remaining close to 0°. Only at ultrasonic frequencies does the impedance start to rise, presumably due to the voice-coil inductance. So while the NightHawk has a fairly low impedance, its frequency response will not change when driven by a source with a high output impedance.—John Atkinson

Fig.1, AudioQuest NightHawk, electrical impedance (solid, top) and phase (dashed); and of 10 ohm resistor (solid, bottom) (5 ohms/vertical div.).

handler's picture

Dear Herb and Stereophile:

I share Herb's initial impression with the AQ NightHawk. When I carefully auditioned the NightHawk shortly after it arrived at my local dealer, it sounded overly-warm, congested, lacking highs, and kind of hollow sounding. Definitely not a 'phone I'd want to own or recommend to anyone. However, I obviously did not get to audition the Hawk again after hundreds of hours of playing time. If there's such a drastic different after break-in, however, it would most definitely show up in a measured frequency response. Therefore, Stereophile, I beg thee: PLEASE PLEASE measure a broken-in pair of NightHawks and a freshly-out-of-the-box pair, and publish the response plots. I'd like to see what's actually happening after "break-in." I'm sure many readers would be interested also.


dalethorn's picture

I have the NightHawk, and that won't make a significant difference. It didn't for me. But the NightHawk is a most unusual headphone nonetheless - it responds to changes in gear like a chameleon, and is capable of producing the most amazing sound. Hard to explain. I haven't had another headphone (of 150 or so) that's like the NightHawk.

tonykaz's picture

That's more'n my wife's got shoes.

Is finding a keeper all that hard?

Phew, that's a new headphone every month for 12 years or so.

Betcha Tyll, up in the frozen North ain't got that many.
or maybe even Jude here in Michigan.

You must have a special Room to Store all of em.

Tony in Michigan

ps. I've owned a few more than a Dozen and thought I was an impulsive buyer.

dalethorn's picture

Headphones are fairly cheap, like digital cameras, music players, etc. You can buy 150 headphones for less than the price of a decent car - even a few "flagship" headphones. The point for me is I don't have anything to sell, so I can offer a common-man's perspective on audiophile sound via headphones. But I should say up front - the selections today are amazing in value, and with hundreds of DAP's, DAC's, amps, and the plethora of DSP's/apps floating around, you can get awesome sound for very little money.

tonykaz's picture

Oh how right you are about the Car Prices!!, I've spent most of my life in the Auto Industry and don't own one. I bought my wife an entry level Kia Soul for an out-the-door cost of $21,000. ( I stay on the Bicycle my Cardiologist insists on or a Taxi if I need to get to the Airport ).

I have most of my Headphones packed away somewhere with only my favorite two out and playing, one wireless and one wired.

Does "nothing to sell" carry the meaning that you don't sell-off any headphones or that your opinions aren't biased like so may reviewers seem to be ( or have to be )?

I've always seemed to trust your posts, you seem to offer honest opinions.

I'm just beginning to trust my opinions but I doubt that they're all that useful.

I'm looking at the Garage1217 stuff, leaning to the Sunrise based on AtomicBob's recommendations. He's having an Affair with the Schiit Multibit stuff. Hmm. I'm slow-to-rise to bait. My impulsive days are over.

Thanks for writing back, aaaallllllllways nice hearing from y'all.

I only commented cause I saw it was you!

Tony in Michigan

ps. you're out there in the Left Coast somewhere, aren't you?, probably never gonna meet ya. too bad

dalethorn's picture

I've been known to sell some of my used headphones, on forums where I know the people. I don't do eBay or anything like that. As far as biases go, I have biases, prejudices - all that stuff, but since I don't work in the audio industry or have any relationships there**, I operate independently. Some people call it a hobby, but hobbies to me are pastimes, and I don't have that kind of spare time to waste. So I call it something else - a personal ongoing project with a goal: To determine how to get the best sound for the least money possible. I'm not against spending big for my personal satisfaction, but I keep in the forefront of my mind why I'm doing this - to help others who are on a very limited budget, where I was for quite some time.

**I have gotten an occasional free sample - probably about 10 percent of my total headphones, but the most expensive of those samples has been in the mid-$200 range. One thing you have to understand about reviews is that if you have a site that monetizes those reviews, you can justify the time invested by the returns in publishing, since you're not selling and reviewing too. In my case, time is the vast majority of my investment, since headphones are relatively cheap, up to $1000 or so anyway.

Edit: East coast this month.

nklewis's picture

Hi Herbie,

This year, I sold off my tri-amped speaker system based around a 5.5-foot-long 1930s horn used wideband 110-6000hz with Western Electric 720a drivers from the 1940s. These were driven with some nifty 2A3 amps with a 6SN7 driver, which was good but not as good as the 10Y-45 IT coupled amplifier powered by a 250V stack of lead-acid batteries that I built in 2007, specifically to drive these horns. But, it was fussy.

Now, I'm listening to (oh so boring) Sennheiser HD600 cans, driven by a Metrum Octave DAC through some of Dave Slagle's 600 ohm autoformers. The Metrum is an R2R dac with no output stage. The output comes right off the resistor ladder, goes through the autoformer, and into the headphones.

This sounds really good. It is better than my SLA battery-powered 01A-71A all-DHT headphone amp, with the same DAC. I tried the 4x more expensive HD800 cans on this rig, and preferred the HD600. Gain seems to be adequate with headphones of at least 97db/mW efficiency. I also tried a number of other amplifiers, which all sounded broken compared to my 71A amp, or, for that matter, my battery-powered 2SK170 jfet amp.

I'd give the DAC-direct strategy a try. If you find something better, great. But, don't be surprised if you don't.

Preddy's picture

have you tried Beyerdynamic DT990Pro or T90?

I got myself T90 and extremely pleased with the result!