InnerFidelity Update November 2016

Many of you will be aware that I've had some trouble with distortion measurements lately. Well, fortunately it had gotten so bad and consistent that I was able to identify a repeatable problem and trouble shoot the system. Turned out to be a combination of a noisy power supply in the headphone amp I use, and a corroded power connecter to the mic pre-amp. I switched out the headphone amp and bought a small motorcycle battery to power up the mic pre-amp and BOOM! the problem is gone! Phew. So I went back and did some re-measuring of what headphones I still had here, and measured a few that were laying in wait. Good times.

As usual I've updated the AllGraphs.pdf of course, and added the cans to the measurement datasheets page. I've also linked to the measurement sheets to the headphone name in paragraphs below. New additions include:

HiFiMAN Edition X V2 - Yet another example of why you can't completely trust measurements, the Edition X V2, like the preceding Edition X, has some very unusual unevenness in response between 300Hz and 2kHz...only worse this time around. I don't have the first Edition X here to compare (review here) but from memory it sounds at least as good. A very gentle, soft, inviting sound, though a little distant. Looking at the measurement I would have expected something really bad sounding. Just not so. Weird.

Status Audio CB-1 - And then on the other hand we have the $79 Status Audio CB-1 full-size closed headphone. Here the measurements look pretty good, but the sound is somewhat courser and more uneven that it appears in the measurements. Still, not a bad headphone at the price.

Radius IEMs - And then there's the times when you can't trust your ears. I heard these Radius IEMs at the end of RMAF and thought they sounded pretty good. Got them home and spent some quality time listening only to find my first impressions were pretty unreliable. The HP-NHA11 and HP-NHR11 have way too much bass. The dual-driver (piezoelectric/dynamic) HP-TWF31 and HP-TWF41 were substantially more neutral, but were a little too laid back in the presence region and too hot in the top octave. Of the two, I preferred the HP-TWF31 as it seemed a little smoother through the treble. Not bad at all really, but not what I was hoping for after my first impressions.

Etymotic - Got the new ER4 series IEMs in for measurement. Boy, these guys know how to work with a single balanced armature receiver! This is a really nice refresh of the ER4. Personally, I significantly prefer the ER4XR with its slightly emphasized bass response over the ER4SR's essentially flat response. I'll send these off to ljokerl to see if he wants to review them.

Mr. Speakers - Dan Clark has sent me current samples of both the Ether Flow and Ether Flow C for measurement. These two headphones definitely had distortion measurements that were way off. Remeasured them both with much better results...though distortion was still a tad higher than I'd like to see but now under 1%. Ether Flow review here, and Ether Flow C review coming soon.

Foster 443742 Variants - Did a big survey of the Foster 443742 variants and have now added them to the list. They include: Denon AH-D5000; Massdrop Fostex TH-X00; Fostex TH610, TH900mk2, and TH900Mk2 with TH610 pads; E-Mu Teak, and with Rosewood and Mahogany cups.

Focal - The new high-end Focals are great, I've reviewed both the Utopia and Elear, and have now added them to the list. Turns out swapping pads on the Utopia may be a good thing. Here's the measurements for the Utopia, Utopia with Elear pads, the Elear, and the Elear with the Utopia pads.

Noontec Zoro II Wireless - Man, I really like this little headphone. Keep this one in mind for gift giving this holiday season. Whether in wired passive mode or wirelessly with Bluetooth, this little headphone delivers.

Beats Solo3 Wireless - The recently reviewed Beats Solo3 Wireless is the first headphone with Apples new W1 chip and it appears they've done a pretty good job preserving the good sonic qualities of the Solo2. In wired passive mode the sound quality is near identical to the previous version, and going to Bluetooth wireless mode only causes a slight reduction in low bass response.

Sennheiser PXC 550 - My review brought out what a great attempt at a contemporary travelers headphone it is...but I also found it had a somewhat annoying spike in response at 5kHz that became fatiguing for me. It was apparent in listening and in measurements in wired, wired with ANC, and wirelessly with ANC modes. So close, and yet so far away.

That's it for this batch. Have a great turkey day, hug the family, drive safe!

FLTWS's picture

Will you be re-doing the Senn HD800S measurements?

castleofargh's picture

it's something I've wondering about for a long time, and I assumed that the compensated left/right were different(relatively to raw) to correct some variations between left and right couplers(also when multiple measurements were done obviously the averaging would explain stuff), but now that I see the ER4sr and xr measured, there is no doubt left, what's up with the 9khz values on the compensated curves? both the er4sr and xr are certified within 1db up to 10khz. and I doubt etymotic failed to do it twice on your pairs(my pair is well within margin when I measure it).

tony's picture

This makes a greater story, maybe the best I've heard since reading Stoddard relating the problems involved with his latest designs and the delays involved.

I spent a couple of decades troubleshooting General Motor's Manufacturing systems, multiple problems are typical ( usually it's 3 or more problems that sum to shut-down an operation ).

I admire your turning to simple & clean DC, seems an elegant & affordable solution. I know an Ocean Yachter that uses a 175 watt Solar Panel to keep his battery charged ( instead of the little Diesel Generator ), he's running all his instrumentation off DC with minimal issues, hmm.

You might pursue a Career in repairing Technical Things, the travel alone could drive you to becoming a recluse in the Frozen North and possibly take up a hobby/business in some niche field like woodworking, headphones or motorcycle travel reviewing ( stories for the Iron-butt types ).

Thank you for the report, nice to read you again !

Tony in Michigan

RudeWolf's picture

But I'll fire it anyway.

How come your 90dB THD readings are always higher than 100dB readings? If we measure THD as a percentage of "extra" energy received from the transducer, then in a perfect world it shouldn't change with increase of fundamental tone energy. In the real world most systems show a distortion increase as they are pushed closer to their limits.

In the last 2 years my team has measured over 1000 headphones with REW and our distortion measurements on 83dB and 93dB show a THD increase during higher energy levels.


Dreyka's picture
briskly's picture

The simplest explanation: THD+Noise.

Temme's explanation about drivers loosening is interesting, and I don't believe that nonlinear:linear relation is always monotonic.
This explanation doesn't carry over well to Tyll's results in that the distortion reduction is often broadband, whereas suspension nonlinearity is generally concentrated below Fs and a couple octaves above it.

RudeWolf's picture

On lower levels THD spikes don't poke out of the floor? That would make sense.

Is Tyll's measurement box that noisy?

castleofargh's picture

it's a dummy head in a box in a room. it's already a serious effort compared to most people who don't own an anechoic chamber, but there is not much that can be done about low freqs noises from cars, bears protesting about the genocide on bees, and Tyll singing Don Giovanni. those are the kind of stuff that always happen when you measure the most sensitive devices.
and I imagine the box itself adds reflections that might be registered when everything else is super quiet and clean.

RudeWolf's picture

We usually do our measurements with a pretty high noise floor, the aim is to just find out any trouble spots like resonances and less about absolute distortion measurements.

Usually we do measurements at 83dB/93dB and calibrated/uncalibrated. And so far we've never seen distortion figures drop on higher SPL's. Maybe the treshold of linearisation is above 93dB.

briskly's picture

If you are only looking for specific harmonics, you can focus the analyzer onto a small interval around the expected frequency and avoid including most of the noise spectrum.

The method used here to determine THD+N is simple, sweep a sine with a concurrent notch filter at measurement. This necessarily summs the input noise over the entire frequency range into the measurement. The low level fuzz you might see would support the noise idea.

As for how noisy this jig is, I don't know particulars. Tyll also did just mention having an electrical noise problem. The box can only provide so much attenuation of external sound.

donunus's picture

Do you plan on reviewing the new Sennheiser headphones? Seems like no one cares about these around the web. Are they that bad? Talking about the HD 4.2 or the 2.3 for example.