InnerFidelity Update November 2014

It's been scary in the laboratory the last couple of months!

For quite a few years my Audio Precision tester (2522) has had the occasional glitch...the output would turn off during one of the tests, or it would regulate a level that was wrong, just odd things from time to time, here and there. Well, this started to get a little worse over time, then one day about two months ago, it did it a bunch. Ugh. A $30k tester is not something you like to see go belly-up on you.

So, I shut 'er down, un-cabled everything, and brought the tester and the computer that runs it out to the garage for a good vacuuming and re-seating of cards and connectors. It was pretty dusty, but looked in good shape; I crossed my fingers and brought it back upstairs and commenced to run it. It glitched on the the first two times through self-test....and then it started working just fine. I grabbed Yolanda, my jet black cat, and waved her over the box a couple of times, and then went back to testing cans. All was good for about two weeks---still had an occasional glitch, but I'd turn a blind eye for the moment. And then about two weeks latter, it totally went bonkers.

All sorts of thoughts went through my head. Maybe I had a bad cable? Maybe the measurement head had an intermittent? Or maybe the mike pre-amp between the head and the tester? Oy. Where's my paddle?

I called the Audio Precision support folks. (Which, I have to say, are unbelievably good. They've helped me numerous times in the past with programming questions.) I explained what I was seeing, and after a long series of "uh huh"s from the tech guy as I talked, I finished and he asked me to hang on so he could talk to someone else. That someone else was the hardware guy, who, after chatting with the tech support guy, picked up the phone to tell me the news.

"Yup. It's a known problem. The Fairchild chips that communicate between the tester and computer go bad and you get all sorts of symptoms. You'll need to send it in for repairs."

Well, long story short, my boss and financial management were terrific, as was Audio Precision's service folks, and I now have my tester back and it's working like a champ. Did quite a few measurements this last week after getting it back---I re-measured a number of known headphones and compared measurements (which were great), and then started re-doing the tests that had glitches in them I had done as the tester was failing, and then I tested some new cans. Not a single glitch (well, some operator error), and some tests ran faster than ever. There's one particular point where the tester regulates the signal level in the headphones to set a specific SPL level that often takes quite a while to settle in; those steps are quicker now. Anyway big thanks to my management and AP for getting my tester back so quickly and in such good nick.

Headphone Measurements new with this Update!
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:

Sennheiser Urbanite and Urbanite XL - I reviewed the Urbanite and found it very good---nicely balanced with a solid bass and good bass-to-mids balance, but I felt it a tad rolled-off up top. Not sure yet if I'll review the Urbanite XL, it isn't quite as strong in its category as the Urbanite. It lacks low bass and sounds somewhat too mids-forward, but I haven't started comparing it to other cans in it's class yet. We'll see.

Blue MOFI - I measured this headphone passive, turned On, and with On+. The sound was okay, but not without troubling aspects to me. Seemed solidly built and ergonomic, but it weighed too much for it to be comfortable for me.

Philips Fidelio X2 - Read about it here, Wall of Fame material. Close to the Harman curve, but interpreted though Philips engineer's both subjective and objective analysis. If it weren't for a little bit of graininess they would have knocked the HD600 of the Wall of Fame.

Bose Quiet Comfort 25 - Well, they've done it again. These things slay as travelling and loud environment headphones. Yes, they do have some weirdnesses to their sound, but the problems are fairly minor as noise cancelers go, and the noise canceling itself is excellent.

Thinksound On1 - One of the more glaring examples of a headphone sounding much better than the measurements might indicate. Sound's a bit rough, but otherwise very musical---something about the wood cups one might suppose. Definitely leaning toward a review on these.

Sony MDR-Z7 - I was hoping these would blow the doors off the expensive, sealed, over-ear headphone category, but it's not to be. I like them, quite a bit, they're competitive, but the bass is a tad loose and something's a little amiss elsewhere but haven't put my finger on it yet. On the other hand, they're drop-dead gorgeous, supremely comfortable, the Kimber-designed cables are lovely, and the companion PHA-3 amp/DAC is equally sexy. Have to do a lot more listening to know where all this stuff will end up, but SOny's new gear is definitely getting a review.

Meelectronics Air-Fi Matrix2 AF62 - Holy crap! For $99 these are awesome! Yeah, they're a little cheap looking, but man, if you need a pair of wireless headsets and don't want to spend much, these are a must. Wall of Fame bound; review quite soon.

Three Koss Cans - My first headphone was the venerable Koss Pro4AA circa 1974. There's no way that first headphone sounded as bad as the current Pro4AA. Yuck. The other two Koss' are the new cans I heard at RMAF. The SP330 on-ear is my favorite of the two, measurements show a slight channel imbalance but the overall FR is sweet for a relatively low cost can, both on paper and on-ear. The SP540 is a bit thick sounding and bass response is a bit loose. I'd have to listen more to provide a better description...they're decent sounding but, just like the Urbanite XL, they fall a little short of being a cool as their little brother.

Sony XBA-Z7 - Only had them in my ears for about 10 minutes and thought they were good but a little zingy. Likely they'll just go straight off to ljokerl for review consideration.

Speaking of ljokerl - As usual he sent me a little batch of IEMs to test. The V-Sonic VSD35 and GR07 Classics looked pretty darn good to me. The UBSound Fighter no so much, and the Havi B3 Pro1 was an abomination.

That's it for this time around. Have a fun Halloween. The kids don't know what to think when I answer the door. (See pic above.)

Inks's picture

ON1, sad case of having a very nice FR but poor distortion. No wonder it sounds rough, though with such a nice FR it still sounds solid I bet.

Z7, bass has high distortion so no wonder it sounds loose there despite the somewhat linear FR there.

Wow the AF62 sure is impressive, specially for wireless.

Crazy how the GR07CE measures quite different from the GR07 MKI. Were the same tips used? Also, seems like the channel balance is quite off, despite the manufacturer claiming a 1.5db difference at most in their units. Perhaps the insertion depth on the two sides of the CE are different, I noticed this in your other measurements, like the UE600 and IE800.

That Havi B3 is clearly defective I'll say. Those get such praise and I can't imagine people liking them with such performance. That distortion is terrible as is the matching, I'll say, try another pair, definitely not a good idea for joker to review based on this unit.

wink's picture

The face looks OK, but ohhhhhhh man, that shirt.
It will be all trick and no treat around your neighborhood.

Gelocks's picture

Hello Tyll.

I see that you have measurements for M&D MH40s and House of Marley Liberate XL. I already have the MH40s and I like them a lot. I was wondering if the House of Marley cans sound as good as they seem to measure (they look similar to the MH40s...)


Gelocks's picture

seems out of whack :)

namaiki's picture

I'd guess that the QC25 impedance is very high because of the inbuilt noise cancelling amp/circuitry. I gotta say that the FR almost reminds me of the old Denons.

I really wonder why the Sony Z7 bass distortion is so high even with those huge drivers. Maybe they needed to chuck a stronger magnet in there, but really I have no idea.

SkylarGray's picture

Low-frequency distortion in headphones is not typically a function of diaphragm size or magnet size/strength.

Here are a few of the top mechanisms (in no particular order) that can cause low-frequency harmonic and intermodulation distortion in dynamic headphones:

A) Motor Design When a motor structure is not optimized, specifically at voice-coil excursion limits, we typically see higher LF harmonic distortion. Ideally, motors should be modeled and simulated with FEA software to efficiently guide & redirect the magnet field where needed, minimize stray fields, arrive at flux symmetry through the gap above & below the voice-coil's resting point (which is hopefully in the dead center), minimize non-linear voice-coil influence on the field, and carefully sculpt the so-called "BL" profile (strength of magnetic field x length of coil immersed within it at any given point in the coil's travel). High amounts of LF distortion are usually a symptom of a motor design that is not optimal in one or more of these areas.

B) Driver Airflow Management & Symmetry Turbulent airflow within a driver's interior structure (around the magnetic gap, through basket vents, around other "nooks & crannies") is a major source of non-linear behavior in small drivers, such as in headphones. Klippel has more info on this phenomenon, which seems to mostly affect higher frequencies. More important for LF distortion is driver airflow symmetry—particularly radial symmetry. Any radial asymmetries result in a build-up of pressure and potential turbulence in those semi-isolated areas of asymmetry. The voice-coil and connected diaphragm structure will then tilt and rock at mostly bass frequencies, resulting in resonances and...distortion. Take a look at the MDR-Z7's basket. Like nearly every dynamic headphone driver on the market, it does not have radially symmetric venting due mainly to the positioning of its terminal PCB on the back side.

C) Back Volume to Front Volume Venting By creating a damped vent in the baffle of a headphone, one can control the blending of an out-of-phase rear-side "wavefront" with the front-facing acoustic output of the headphone. Most manufacturers use this technique for a few reasons, chief of which is to fine-tune low-frequency voicing. The "backwave," which is out-of-phase at LFs, combines with the "frontwave," cancelling at those low frequencies. Side-effects are increased low-frequency distortion as well as comb-filtering and coloration throughout the rest of the spectrum. [by the way, I'm putting terms like "frontwave" in quotes since at mid and low frequencies, a headphone with a decent earpad seal is actually operating via the pressure chamber effect, and there is no actual wavefront.] You can see this type of venting around the edge of the MDR-Z7's baffle. It is surprising how common this technique is, given its detrimental nature to headphone distortion and resonant performance.

ALL THAT SAID, I had more fun listening to the MDR-Z7 than any other headphone at CanJam this year, so I'm planning to pick one of these up.

steble's picture

It would be fun to read about the successor to Sony MDR-1A namely Sony MDR-1A


mikeaj's picture

By the way, that's VSD3S, not VSD35, in case people have trouble searching for it later.

mikemercer's picture

because of your amazing picture
But I did!!


DaveK1977's picture

The frequency response there looks about right compared to what I heard, but I sure didn't expect the sloppy waves and balance issues. The new ones don't have any of the foam in the cups that vintage ones have, and the appearance of the parts and assembly doesn't bear up to close scrutiny. They look the same, but they don't sound the same.

tdockweiler's picture

Looking forward to the Koss SP540 when I can actually afford new headphones. Since i'm the DJ100 fanboy, does it have any similarities to the DJ100 or Tony Bennett? I hope so, but i'm worried it's much darker. I bet it's thicker sounding and bassier due to the memory foam pads.

I also wonder if the BT540i has the same measurements as the 540. The design is a lot different, but the 540i has bluetooth built in.

What was Koss thinking with the new Pro4AA? Certainly they wouldn't release a product without measuring it first.

Their UR55 is one of the few $30 headphones worth measuring and is some good competition for the Porta Pro. Probably uses the same driver too. It's not for big heads though!

GNagus's picture

The measurements provided are of the Matrix in wired mode. Are there any measurements of the headphones in wireless mode? Or maybe i misunderstood something.

The Bose QC25 can be used with no power/battery. Are there any measurements of the phones in this mode?

Audioaddict's picture

Intersting to see the MDR-z7. You really need to hear the MDR-z7520 It's been getting decently popular for good reason, i think these destroy the NAD Viso's and I haven't heard the new Shure cans but I really think the MDR-z7520 is the best over ear sealed sub 500$ headphone you can buy. I'd be willing to send mine in for a measurement and hopefully a review

Oktyabr's picture

Hiya! Just to settle a bit of a debate... in your review you said it was the impedance of the X2 that kept it from knocking the HD600 from the Wall of Fame and in this November update you say it was "a little bit of graininess". Which is it? Both? Thanks!

clippit's picture

Only MDR-Z7 and XBA-Z5

liemonka's picture

Any plans to follow up with MDR-Z7 review?