Saturday, 15 May 2021

MEASUREMENTS: AKG Q701 "Quincy Jones Signature" (2012) & AKG K260 (vintage 1987-1988). And recent interviews with audiophile cable/power people [Shunyata / AudioQuest].


For today's post, let's have a listen and look at the two AKG headphone models above separated by about 25 years in age. On the left we have the AKG Q701 "Quincy Jones" Signature Reference-Class Premium Headphone which was released in 2011. I bought this one (I preferred the black rather than some of the funky colors like neon green) in late 2012.

On the right, we have a rather uncommon AKG K260 - first edition released in 1987-1988, borrowed from my friend linnrd locally. A later versions of this headphone was relabeled with the "Professional" name attached. There's also a Philips version from back in the day using AKG as OEM. This particular one here is used but still in good condition which I cleaned up a bit before more critical listening and measurements.

Notice the "AKG look" with the leather or faux-leather headbands and the thin plastic/metal semicircular arches up top.

The AKG Q701:

First let's start with my Q701's. These "Quincy Jones" edition headphones were released in 2011. The design is very similar to the AKG K701 and K702. They all use what AKG calls the OFC "flat-wire voice coil" and "varimotion 2-layer diaphragm". As far as I am aware, they're all "Made in Austria" as well.

Unlike the Sennheiser HD800(S) where the earpiece mount incorporates a tilt so the drivers radiate at an angle towards your ears, the Q701 has angled earpads which we can see from above. I quite like the warm and soft feel of these puffy large velour pads which surround the ears. The headset is light, 230gm without cable.

Notice the tilt towards the front with the ear pads.

The cable is removable and have a nice locking XLR-type connector on the left earpiece.


The package is quite complete, including both 10' and 20' cables along with adaptor for 3.5mm to 1/4" connectors.

Let's take a look at the measurements:


As you can see, the frequency response compared to a "flat" Harman 2018 target curve shows roll-off below 100Hz similar to the Sennheiser HD800. There's an interesting +3dB bump in the midrange from 1-2kHz and then it dips in the upper-mid by up to -6dB into 3.6kHz. The upper treble region shows a peak up to +7dB into 8kHz and settles back to the 1kHz baseline before 10kHz. If we compare this to the HD800, we see it's not as bright overall.

Like the Sennheiser HD800, certain "bright" music could be a little annoying if there's too much energy around 8kHz.

That waterfall decay is the best I have seen among my headphones tested! These open-back headphones (including the Sennheisers) show a very nice, steep decay presumably due to little cup resonance. They sound "airy" and precise. The price to pay however is less powerful bass extension.

Impedance sits generally in the low-60Ω and AKG specs this as a "62Ω" headphone which is pretty well exactly what I'm seeing at 1kHz. A small resonance peak at 108Hz is seen.

Harmonic distortion is well-controlled, looks to be mainly non-objectionable, even potentially "pleasant" second harmonic, remains <1% for much of the audible spectrum, and as usual, increases into the bass/sub-bass.

Voltage sensitivity is 93dB at 0.25V, or 105dB/V - exactly what AKG lists as the spec. Notice that this is lower than my Sennheiser HD800 which measured at 109dB/V. This lower voltage sensitivity plus the lower impedance makes the Q701 a harder headphone to drive. Yeah, you can still drive this with a mobile headphone jack (the other day I was driving these with the inexpensive Soditer dongle off my phone) but better amplifier obviously recommended.

As an open headphone, noise isolation is poor:

Essentially no attenuation of noise until 1kHz, and about -10dB at 5kHz.

Likewise, this headphone leaks noise:


Average of 80.5dB SPL at 1" or 59dB SPL @ 1'. Not as bad as the Sennheiser HD650/HD800 but still quite audible to those around. Notice that the leakage is particularly bad around 2kHz.

The bandlimited 100Hz square wave looks pretty good. Quite clean - similar I think to the cleanliness of the Sennheiser HD650.


Not bad looking "square" waves given the low frequency limitations. The leading edge isn't as clean as the Sennheiser HD650, but the leading edge rise time is nice and steep as an indicator of "speed", I suppose.

How does it sound?

No need to say too much here I think. Lots of folks already have commented about the K/Q70X series of headphones by now. Basically, this is a good sounding "reference" AKG headphone. The open-back nature and the large earpads feel comfortable and the sound is spacious. While these headphones are lightweight, sometimes I find the lumps on the headband which are supposed to distribute the pressure can be a little uncomfortable but easy to overcome with reseating on the head.

A friend has the K702 headphones and although I did not have my Q701 to listen side-by-side, I think it sounds the same.

Yeah, I think the angled earpads do add a little "space" to the sound quality. A bit more "air" like the Sennheiser HD800 but not quite to the same extent - I'd like to say about "60-70%" if I have to guess. It pushes the center image like vocals forward from deep inside the head. I was quickly flipping back and forth between this and the K260 (discussed below) on Peter Cetera's "Even A Fool Can See" on World Falling Down and the effect was quite obvious when A/B listening like this. Note again that the effect does not sound anything like real speakers! While it's a nice effect, I would not say it's essential in any way (in fact, with the Dekoni Blue, I prefer the non-angled Elite Velour ear pads over the angled Elite Hybrid as previously discussed).


The AKG K260:



Above you see linnrd's AKG K260 headphones. This is one of the earliest models which came out back in 1987-1988. I don't see a serial number on the headphones to report. Here's a video about the slightly later generation K260 Professional on YouTube where the reviewer really likes them. He mentioned that these were designed with "lumped parameter model" and even talked about comparing these to Stax Lambda!? The old Philips SBC 3178 is said to be the same headphone.

Notice that these are a "semi-open" design; there are a few vertical vents on the back and there are some side slits as well where that black backpiece sinks into the silver outer cup.

Initially, when I put these on my head, I was really quite unimpressed - "midrange mud" came to mind... And I mentioned this on an April 11 comment here. I was wrong ;-).

I spent a bit more time on these. Took off the ear pads. Took the black foam pad off the driver itself and found that over the years, the foam had gotten "stuck" to the grey paper material in front of the driver, this was distorting the sound. Here's what the cleaned driver itself looks like liberated from the ear pad and foam in front of it:


Once I put the foam piece and ear pads together, the sound cleared up markedly and it "made sense" why some folks like these old headphones!

Before we get to the sound, I just want to say that the build quality of these are certainly not the best I've ever played with! These are a bit creaky, low-density plastic, and the shiny painted (a couple places color flaking off) chrome silver reminds me of plastic toys from the '80s. They are literally featherweight headphones. Unfortunately the cable is a non-detachable ~10' cable with 1/4" end so I could not get a weight with the headset only. They feel even lighter than the Q701 (approximately 200gm).

Although I gather not too many of these headphones were made (unsuccessful AKG seller, compared to the much more popular AKG K240), you see these mentioned once awhile on forums and I see that Moby used these for mixing much of his body of work - in fact, here's Moby's K260 listed for sale:


So how does this headphone measure?


Not bad at all. That slight bass mismatch between the two sides is a real finding which persisted regardless of the positioning I used to improve the seal against the measurement rig. We see a typical dip into around 3.5kHz (down to -6-10dB) which could be beneficial to reduce subjective harshness.  

The upper treble was a little less "hot" compared to the Q701 above and certainly less than the Sennheiser HD800. Notice that at the same time, it did not feature that "dark" scooped frequencies from 5-10kHz seen in the Sennheiser HD650.

The waterfall plot looks pretty good as well. Not as smooth as the open headphones but we see -40dB decay within 10ms for all frequencies down to 100Hz. Electrical impedance is indeed high; these are spec'ed as 600Ω and I'm seeing more like 700-850Ω, with a driver resonant frequency at 130Hz. Voltage sensitivity of 89dB SPL/0.25V implies around 101dB/Vrms. Indeed, this headphone is not as sensitive as the Q701 with a significant difference being the "high" impedance load compared to the Q701's "medium" impedance of 60Ω (with ramifications as discussed before).

For an old headphone from 1987, harmonic distortion looks pretty good although notice that the bass distortion is higher than more modern headphones I've tested. Below 125Hz, THD is above 1%, the Q701 is better than this and a modern closed headphone like the AKG K371 likewise has lower distortion (as previously measured).

As a semi-open headphone, the noise isolation and sound leakage sits as expected between the open and closed designs. Here are the results for this headphone:


Interesting. No isolation from outside noise until above 3kHz with these original late-'80s ear pads. By 5kHz we do get a pretty good -18dB reduction though.

Since it's semi-open, the maximum sound leakage was from the rear of the ear piece near the openings. On average from 100Hz to 10kHz, leakage is 71dB SPL measured at 1", or 49dB SPL @ 1' - about 10dB better than the open Q701 above. Most of the leakage tends to be from 1kHz to 5.5kHz.

Let's look at some 100Hz square waves:

Left Channel

Very interesting "square" waves. I have not seen this kind of pattern with other headphones up to this point. Looks like a pattern of low frequency attenuation with a dip below zero before the next square edge transition. I've read comment about this as perhaps correlating with poorly controlled bass (not that there's much bass with these anyways). To me this might correlate with harshness as I'll discuss below.

How does it sound?

Well, once I cleaned out the headphone and old pads, these sound very good! What a neat experience to listen to an old headphone that is used but well cared for, made before I graduated from high school to get a sense of how "vintage" (almost 35 years old) transducers compare to modern devices.

While the build does leave much to be desired and the original earpads can be upgraded to modern replacements, the comfort is still good and I would have no problem listening with these for hours. Clamping force is relatively weak on these (less than the Q701), so can feel like they might fall off with vigorous head movements.

While the treble is nice and neutral, I found that it sounded a little grainy at times. Modern compressed pop like Taylor Swift's recent evermore (DR6 average) tended to show more of this in the highs (eg. guitar plucks on "Willow") and even her voice seems to be a little rougher, more "etched" than usual compared to headphones like the Q701. This sounded also very evident in The Greatest Showman soundtrack like the song "This Is Me". It almost seems like it's accentuating the peak-limiting in some of these productions. I wondered if the square wave performance above could be a reflection of this "graininess" on these "loud" dynamically compressed tracks. This could be beneficial in the studio to pick out anomalies like frank clipping.

The other issue is that bass is rather weak. Songs with a fair amount of sub-bass content like Malia/Boris Blank's "Celestial Echo" (Convergence) sounded weak compared to even the Q701 which itself is no great bass machine. The high end on this track sounds good, but again, a hint of excess graininess on the vocals and the synth percussion. I would say that these headphones are good for acoustic music without much deep bass, small classical quartets sounded great. If you listen to Go: The Very Best of Moby (speaking of Moby using these for production work) with these headphones, you'll miss some of the bass on many of those tracks!

"Soundstage" is mostly the usual right-left-inside-the-head affair. Sounds good with binaural like this or your favourite ASMR. ;-)

The sound basically is much better than the build quality would suggest. The treble graininess was a bit more than I would be happy with when listening for fun, and the bass roll-off made the sound less than "full bodied". I could not help but to think that if the treble quality here were to be transported onto the Sennheiser HD650 (sans graininess), that would have sounded awesome! 

Thanks again linnrd for the opportunity to try out a vintage and relatively rare headphone!

--------------------

To end, it's been awhile since I have read/listened to audiophile cables and power systems discussions. Overall, I've just been happy with my inexpensive 10AWG power cord with Hubbell plugs. ;-)

I see that there have been a couple of interviews with cable/power accessory people in the last number of months. Here's Caelin Gabriel of Shunyata and the San Francisco Audiophile Society (September 2020). And here's Garth Powell of AudioQuest and Audio Excellence Canada (May 2021).

I do not recommend watching the videos completely unless you're truly fascinated in this kind of stuff. As an observer of humanity, it is interesting watching people answer questions. The nonverbals like mannerisms and words selected give us an idea about character. Fascinating watching someone like Caelin Gabriel present his case and answer the unchallenging questions being presented by folks who seem to have consumed the Kool-Aid. There's an attitude that comes through and the way he has prepared (or not) for this interview also speaks to this. As expected, he keeps talking about noise and clock issues (eg. 56:30 - 60:00 for a few minutes taste) to push his products. At no point is he showing us any evidence that this is a problem or that his products are able to ameliorate issues. Sure, buy the US$8000 fancy power strip with hospital outlets, Stereophile says it's good. ;-)

As for Garth Powell, it's fascinating that he talks about using subtraction techniques (like this DiffMaker test, or more recent DeltaWave Audio Null Comparator) to detect differences with his power products. The problem is that he has zero data to show despite this clearly being presented as some kind of discussion about his measurement protocol for cables! It's all talk, and he throws out numbers like "20dB" differences with various AudioQuest Niagara products (is that down at something like -120dB noise floor? :-) It's quite amazing that he talks like this and throws out jargon (18:40) which could be true but there's simply no demonstration at all to put these hand-waving and hypothetical claims into a concrete example so anybody even understands whether his statements are referring to differences that could have audible relevance for humans. Is this good enough for audiophiles in the 21st Century? I think not.

I don't understand. Can they not see how poorly these interviews come across with claims of "profound effect" these days in the face of actual tests like the Audioholics test/critique of the AudioQuest cable? Guys, show a little more transparency, less talk (hot air), more demonstration of effect to actually show the supposed "research" being done! Last week, we talked about Michael Fremer and the Wilson XVX in his room. I guess that back in early March there was a need to highlight power products in the magazine and he wrote this article about his power issues after installing a natural gas generator and switch. Well, I seriously hope if the audible changes are real, rather than the usual hysterics, that Fremer would simply measure the problem and how something like an AudioQuest or PS Audio device can fix it; not gonna hold my breath on this though from him or Stereophile.

As for the interviewers, I appreciate that at least Audio Excellence Canada pushed Powell a little while remaining nice to the man. But wow, the San Francisco Audiophile interviewer and crew were totally "softball" or even delusional when it came to questions for Gabriel. Hilarious at 1:57:10 when the guy claims that Shunyata products used with a TV resulted in visual changes in brightness and "blacks darker" or something like that. Even Gabriel agrees and suggests using his cables for digital photographers to hook up to their computers to see a difference! Hmmm, maybe Shunyata should measure that and present the data. That would also open up the home theater and computer markets! Imagine how happy the sales guy might be to push a high-margin Shunyata power cable with that 8K 85" Samsung QLED TV purchase or the latest Apple Mac Pro. I don't know whether to laugh or cry thinking that the "head honcho" of the company can say these things with a straight face, or that the audience do not seem to be rolling their eyes.

I wonder if we look back at these interviews in 5 years just how well they will age. Will these individuals be seen as audio luminaries, or examples of guys pushing snake oil? I'm willing to bet it's very much the latter, and probably very obvious for many audiophiles already.

Alright, enough for a week! Originally I wasn't going to publish this article since Google/Blogger seemed to have pulled a few of my older articles and I would have needed to spend time restoring them this weekend. I know a few bloggers were complaining so I suspect something strange must have happened yesterday - some kind of bug/hack? Looks like this got fixed... Yay.

Hope you're all doing well and enjoying some wonderful music... Sunny, warm weather here in "Beautiful British Columbia"; time to get out!

18 comments:

  1. I almost thought your blog was attacked by MQA hackers at one point... ;-)

    Funny, it took your photo to make me realize the angling of my K702 earpieces...I never noticed it! This of course moves the image more to the front of the skull rather than straight between the ears and improves the soundscape, but cannot give the full loudspeaker image that depends on secondary reflexions from the walls.

    As mentioned in very small characters on the box, my pair is "designed and engineered in Austria" but made in China. I don't think the quality is impaired except for the transparent plastic guide under the side pieces that broke very early on. Somebody else mentioned this also. I wonder if the Q701 "made in Austria" has better plastic, or maybe metal?

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    1. Hey Gilles,
      I'll have to pay more attention when I visit my friend and have a look at his K702 to check out the plastic and see if it's also made in China. On initial inspection, I thought it felt the same as what I have here.

      LOL regarding hacking ;-). I doubt any self-respecting hacker would be working for MQA at this point!

      Delete
  2. Great work as usual. I also really like audiosciencereview on youtube as he does some great "science" video on audio. https://www.youtube.com/channel/UCWp1NY1KXGwcOh1RxKp_-FA

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    Replies
    1. Yeah, nice to see Amir's work on YouTube as well (I like that one can playback at 1.5x to speed things up with videos sometimes ;-).

      Overall, good that the more objective folks are bringing out material so audiophiles can see that there is a lot of material out there to read, watch, and know about.

      It takes away from the single viewpoint promoted by the usual mainstream audiophile press and presents a much more realistic diversity of opinions out there... And I think more "true" in terms of whether things work or whether it's hype.

      Delete
  3. > Very interesting "square" waves. I have not seen this kind of pattern with other headphones up to this point. Looks like a pattern of low frequency attenuation with a dip below zero before the next square edge transition

    This is just the normal high-pass behavior. SPL intgral is zero so curve must go below zero (depending on the order and Q-factor of the bass roll-off it will bounce around zero many times until it disappears in the noise floor -- in theory the ringing is infinite).

    Just look at any step response (SR). And a square wave is an overlay of time-shifted step responses. In this case the corner frequency of the roll-off is so high that the zero crossing of the SR happens to be before the next edge, that's why it is visible here.

    With other headphones you'd see the same thing if you used a lower frequency, like 30Hz. The lower you go the more it will look like a step response plot as the tails have settled and their contribution to the next section of the square becomes minimal.

    Regards, Klaus (known as @KSTR online)

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    1. Thanks Klaus,
      Appreciate the input on this. Yeah, that was my suspicion... Just had not seen the amount with other headphones as I did with the K260. Will be interesting to compare this with others over time.

      Delete
  4. > As for Garth Powell, it's fascinating that he talks about using subtraction techniques (like this DiffMaker test, or more recent DeltaWave Audio Null Comparator) to detect differences with his power products. The problem is that he has zero data to show despite this clearly being presented as some kind of discussion about his measurement protocol for cables! It's all talk, [...]

    Yeah, just talking as usual, meh.

    If they really were any serious, they probably should hire me ;-)

    Inspired by Paul Kane's fascinating DeltaWave software which certainly is the pinnacle of readily available tools for that, I just recently found a way (demo here) to improve the quality of the residual so I could make tiniest distortions audible (and therefore also better suitable for later analysis), things already buried way down in the noise floor (of an ADI-2 Pro FS or FSR, mind you).

    If there were cable distortion or whatever "cable characteristic" other than simple (and usually fully negligible) frequency response changes, provided this is any systematic, correlated to the signal... well, I think I would have found it by now, but I haven't (for signal cables, speaker cables are on the todo list).

    KSTR

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    Replies
    1. I'm beginning to see more snake oil in our hobby than I ever thought I would.

      Delete
    2. Wow Klaus, that's amazingly precise work with your null testing man! Down to the level of those <0.0001dB differences with the RME reference level switching.

      Granted, I'm sure we can still go out there and find a Golden Ear who has the putative ability to "hear" these differences; especially the cable differences of course! ;-)

      Delete
    3. Hey Jim... Oh oh... You're overdosing on the "Red Pill", my friend.

      Congrats! And make sure to share those reality pills with other audiophiles!

      On a serious note, indeed we're digging very deep into the "nature of things" here and while framing results in the context of whether something (like audio cables) actually make a difference, the real "star" of the show is actually human psychology - our own perceptual limitations and cognitive leaps we make.

      [Discussed awhile back: http://archimago.blogspot.com/2015/10/musings-meditations-on-limitations-of.html]

      I generally don't blame audiophiles for reporting the things they do. After decades of the audiophile press claiming this and that, audiophiles are literally "primed" to hear things which the "tribe" declared to be true.

      I do blame the "professionals" like Powell, Gabriel, and the audiophile magazines for their own lack of insight and perpetuation of untruths. Typically unwilling to explore contentious issues (when was the last time Stereophile measured cables?). Many of these writers subsequently unable to turn from their previous opinions.

      So John Atkinson, are you still witnessing the "birth of a new world" with MQA these days? ;-)

      Delete
    4. So I am starting to "trust the science" afterall.

      Delete
    5. :-) Thought you always did Jim!

      Delete
  5. "Even Gabriel agrees and suggests using his cables for digital photographers to hook up to their computers to see a difference! "

    ^^^ This kind of stuff is just so telling. It's clearly a Big Tent type of marketing, just expanding the number of products that will "benefit" from their cables...more cables to sell!

    It's a claim that's so easy to check, objectively.

    There are all sorts of patterns and instruments you can use to discern any change in the image on a display: resolution patterns, black level/contrast/gamma patterns, color depth etc. There are tons of professional calibrators, like the guys who calibrated my plasma and home theater projector, who use tools like spectroradiometers which can measure contrast and color with far more sensitivity than the human eye. With every calibration I'm presented with measurement graphs and charts showing the changes in all the visual parameters pre and post calibration.

    If adding a different cable produced and actual alteration to the image, let alone one obviously visible to our eye, it would immediately show up on the measurements. But despite the fact some high end cable companies and reviewers have claimed for years that expensive HDMI cables can produce sharper, more dynamic, more colorful, more dimensional images, I've never heard of anyone showing measured evidence. Nor has, to my knowledge, any professional calibrator run in to any such evidence. (And having spent decades on the AV forums in threads devoted to image quality and calibration, I'd think such evidence would have shown up at some point).

    So this fellow's claims about images improving using a new cable would be very easy to demonstrate if true. So...where is the evidence?

    There is an almost Trump-like aspect to telling these type of....claims.
    It's so easy to check if true, but it's not really aimed at the critical thinking skeptic but rather at the target audiences who have already partly or wholly bought in these types of claims already.



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    1. Exactly Vaal,
      We don't need to mince words since comments like these about cables and computer video are simply lies. Gabriel as a representative of his company is simply lying to consumers as he promotes this kind of thinking.

      It's simply dishonorable in character to speak like that. The same goes for contentious stuff like Bob Stuart and his mistruths and twisting of words when it comes to MQA.

      Delete
  6. it is more like Biden-like aspect to telling these types of...claims.

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