[rsaavedra]

Tyll, now that you are undertaking your own measurements project, I have a question for you.

Years ago I remember checking Headroom's freq. response graphs extensively, in particular right after the measurements for the HD650 were published. And I remember comparing them in detail with the HD600, from which response it did not really seem to depart that much, from what I can remember.

Now I plot the FR of both the HD600 and the HD650 on the Headroom pages, and I really don't recall at all the FR graphs of these two headphones having this specific kind of difference in the upper half of the spectrum.

IIRC, former graphs on headroom showed the HD650 had more upper treble than the HD600, now its the other way around; and the mids and upper mids of both were much more similar.

The HD600 also had a more pronounced depression around 6kHz (which was always associated to the so called legendary "veil"). I remember that trough going deeper in the HD600 than in the HD650 on Headroom's graphs. This current FR of the HD600 (or HD650) does not reflect that former state of affairs at all.

Do you know if there were any important changes in the way things were measured or smoothed out, that might have been the cause of this current (and to me rather different) FR graph of the HD600? And if there were new ways of measuring, were those applied equally to both the HD600 and HD650 to produce these current FR graph of them?

 

[rsaavedra]

Follow up on my previous post. Just occurred to me to simply google "frequency response HD600", and voilá: found the older Headroom graph for the frequency response of the HD600's:

 

[Tyll Hertsens]

Good questions, mate, I think the answer is I don't know.

One of the things I'm working on right now is the issue of how to take the most reliable measurement. The IEC spec requires placing the headphones on the head 5 times and then averaging the measurement. I've played around a bit with moving headphones around to see how things change, and the answer is considerably.

I was going to post some measurements I've taken this week, but here's the problem:

The weather outside is stellar, and going to get crappy over the weekend, so I'm taking the day off to go motorcycle riding.

I'll post some graphs over the next few days though. It's a very important issue and I'd love to get some feedback from you guys.

Toodle-ooo, off to ride!!!

This bike today:

 

[rsaavedra]

Quote:

Originally Posted by Tyll Hertsens /img/forum/go_quote.gif

Wow nice, enjoy!

 

[grawk]

tyll's got his priorities straight

 

[rhythmdevils]

Quote:

Originally Posted by rsaavedra /img/forum/go_quote.gif Tyll, now that you are undertaking your own measurements project, I have a question for you. Years ago I remember checking Headroom's freq. response graphs extensively, in particular right after the measurements for the HD650 were published. And I remember comparing them in detail with the HD600, from which response it did not really seem to depart that much, from what I can remember. Now I plot the FR of both the HD600 and the HD650 on the Headroom pages, and I really don't recall at all the FR graphs of these two headphones having this specific kind of difference in the upper half of the spectrum. IIRC, former graphs on headroom showed the HD650 had more upper treble than the HD600, now its the other way around; and the mids and upper mids of both were much more similar. The HD600 also had a more pronounced depression around 6kHz (which was always associated to the so called legendary "veil"). I remember that trough going deeper in the HD600 than in the HD650 on Headroom's graphs. This current FR of the HD600 (or HD650) does not reflect that former state of affairs at all. Do you know if there were any important changes in the way things were measured or smoothed out, that might have been the cause of this current (and to me rather different) FR graph of the HD600? And if there were new ways of measuring, were those applied equally to both the HD600 and HD650 to produce these current FR graph of them?

It could be the new versions of HD650 and HD600. I noticed a big difference in frequency response with whatever changes happened with the silver screen, and a lot of people have said the same thing, even when comparing old/new side by side. I haven't heard as much about the HD600, but it also has silver screens now, and I never liked the HD600 much until this pair.

 

[rhythmdevils]

Tyll, I had an idea about these graphs a while ago and might as well throw it out there now. It seems it would be nice to callibrate the dummy head for the way we hear, so that we don't have to try to see through the normal peaks to find the parts of the graph that represent the headphone's response.

I myself, feel that the gold standard for neutrality is the grado HP1000 and would love to see the graph zero'd out with its measurements. Then all other headphones would be in comparison to the HP1000, and all of the dips and peaks would represent the way a headphone sounds.

 

[Jamey Warren]

Quote:

Originally Posted by rhythmdevils /img/forum/go_quote.gif Tyll, I had an idea about these graphs a while ago and might as well throw it out there now. It seems it would be nice to callibrate the dummy head for the way we hear, so that we don't have to try to see through the normal peaks to find the parts of the graph that represent the headphone's response. I myself, feel that the gold standard for neutrality is the grado HP1000 and would love to see the graph zero'd out with its measurements. Then all other headphones would be in comparison to the HP1000, and all of the dips and peaks would represent the way a headphone sounds.

I really like this idea. In fact we have played around a little bit with it at HeadRoom using some different graphing tools. I found it really interesting to look at and am anxious to see the results after Tyll dials in his measurements a little more. Also looking forward to seeing what Tyll comes up with on his own.

 

[rsaavedra]

Quote:

Originally Posted by rhythmdevils /img/forum/go_quote.gif I myself, feel that the gold standard for neutrality is the grado HP1000 and would love to see the graph zero'd out with its measurements. Then all other headphones would be in comparison to the HP1000, and all of the dips and peaks would represent the way a headphone sounds.

Ditto. I've asked so many times for this, even as far back as in 2005.

I think it is really almost absurd that so many headphone enthusiasts in the world, a few people/companies making measurements, and still to this day there are no published FR measurements of the HP2, or the R10 for that matter.

 

[rsaavedra]

Quote:

Originally Posted by rhythmdevils /img/forum/go_quote.gif It could be the new versions of HD650 and HD600. I noticed a big difference in frequency response with whatever changes happened with the silver screen, and a lot of people have said the same thing, even when comparing old/new side by side.

I wouldn't think that's the case, because what seems different is mostly the FR response of the HD600, not the response of the HD650. I think the graph of the latter remains pretty much the same as the first one I ever saw.

If there are differences in the responses of the newer models, then probably the measurements of the HD600 reflect the new model but not so the measurements of the HD650 (unless this one really didn't change its response that much, which would be rather odd, if the same change caused such a difference in the HD600).

My best guess is that probably the response graph of the HD600 reflects the response of a newer model and/or a newer way of smoothing out the measurements. But the graph for the HD650 probably has never been updated with either the newer 650 model, or said newer smoothing methods.

 

[emmodad]

Tyll, current (print) issue of Pro Audio Review has an article about headphone comparison (some broadly diifferent units); some discussion of measurement, not incredibly thorough; does have some observations about variations on frequency response incl thoughts on pro vs audiophile perceived user needs.

fyi, and maybe contact for some resources to extend your networking in the "pro audio" world......

cp

 

[JohnFerrier]

Quote:

Originally Posted by emmodad /img/forum/go_quote.gif Tyll, current (print) issue of Pro Audio Review has an article about headphone comparison (some broadly diifferent units); some discussion of measurement, not incredibly thorough; does have some observations about variations on frequency response incl thoughts on pro vs audiophile perceived user needs. fyi, and maybe contact for some resources to extend your networking in the "pro audio" world...... cp

PAR Bench Test - Studio Headphones

ProAudio is not using compensation?

 

[Tyll Hertsens]

Quote:

Originally Posted by grawk /img/forum/go_quote.gif tyll's got his priorities straight

Ahhhhh ... I needed that!

Oh well, back to work ...

Quote:

Originally Posted by xnor /img/forum/go_quote.gif Do you have any ideas why the square waves look so different?

Yeah, I think it's both placement and the J$ pads. But, hang tight, I'm gonna show you some stuff about square waves soon.

Quote:

Originally Posted by xnor /img/forum/go_quote.gif And could you do the isolation response without headphones on the dummy head?

Yeah, it's the yellow line here.

Quote:

Originally Posted by barnaclebeau /img/forum/go_quote.gif Another metric that I don't think anyone considers...consistency? Does one brand new pair of HD650's measure the same as another brand new pair?

Over time, as more and more headphones get measured, this will start to be possible.

Quote:

Originally Posted by barnaclebeau /img/forum/go_quote.gif Once your test procedures are efficient enough to allow 'willy nilly' testing, I'd love to see what difference member's DIY mods make. You could be the definitive 'dyno tester,' to borrow from another DIY hobby.

I'd love to do that.

Quote:

Originally Posted by rhythmdevils /img/forum/go_quote.gif Tyll, I had an idea about these graphs a while ago and might as well throw it out there now. It seems it would be nice to callibrate the dummy head for the way we hear, so that we don't have to try to see through the normal peaks to find the parts of the graph that represent the headphone's response.

This IS the $64k question. Unfortunately it's FAR harder than you might imagine. I do think we can make some significant headway if we work the problem carefully. That starts with the literature --- and I've been doing some reading --- and continues with myraiad attepts to to elegantly simplify the data. That's a rock strew path ... I'll be addressing just one bit of it here in a minute.

Quote:

Originally Posted by rhythmdevils /img/forum/go_quote.gif ...would love to see the graph zero'd out with its measurements. Then all other headphones would be in comparison to the HP1000, and all of the dips and peaks would represent the way a headphone sounds.

Quote:

Originally Posted by Jamey Warren /img/forum/go_quote.gif I really like this idea. In fact we have played around a little bit with it at HeadRoom using some different graphing tools.

Jamey is being modest here and has been hammering on this for years. Really, all of this investigating only becomes possible when there's an independant concerted effort to do it. HeadRoom --- and rightfully so, IMHO --- has not been able to dedicate a lot of resources to measuring the headphones really well. It's not what they do.

Quote:

Originally Posted by rsaavedra /img/forum/go_quote.gif Ditto. I've asked so many times for this, even as far back as in 2005. I think it is really almost absurd that so many headphone enthusiasts in the world, a few people/companies making measurements, and still to this day there are no published FR measurements of the HP2, or the R10 for that matter.

And it's why I'm so damned exited about doing it now. However it's important to remember a few things: 1) Eventually, you'll have to pay a little for it ... just a little though. 2) It's important to do this work stepwise with significant rigor and develop a solid method for acquiring the needed data. Then, when we're really satisfied, start measuring for raw data like crazy. 3) Then, it will still take some significant programming to build the tool to see it on the web. (Need volunteers here! Feel free to PM me!!!)

Quote:

Originally Posted by emmodad /img/forum/go_quote.gif Tyll, current (print) issue of Pro Audio Review has an article about headphone comparison (some broadly diifferent units); some discussion of measurement, not incredibly thorough; does have some observations about variations on frequency response incl thoughts on pro vs audiophile perceived user needs.

Thanks for that linky. Umm ... maybe it's best for the moment to say that measuring headphones is not easy, and also say that even with my considerable experience with the gear, I consider myself a novice. We're going to learn a lot about this stuff together.

Speaking of which, I'm gonna close out this post and start a new one about the HD 800 data I took day before yesterday.

BRB

 

[Tyll Hertsens]

Let's see, there's two issues to have a bit of a chat about ... let's start with the miserable one and get past it: Headphone Measurement Equalization.

Say you had a perfect speaker and played pink noise. If you measured that with a perfect lab microphone, and the acoustics between the speaker and the mic didn't do anything, and looked at the signal from the mic in a spectrum analyzer you would get a flat line.

Now, pull the microphone away, and put your head in the sound field. What would the signal at your eardrum (the mic diaphragm) see?

The answer is not a flat line. A number of things happen the change the sound away from flat before it reaches your eardrums. You get some acoustic gain from the size and shape of your body; you get reflections and directional gain from the shape of your outer ear; and you get some increased highs due to the ear canal resonances.

Unfortunately, there remains a great deal of divergent opinion among researchers regarding what curve is correct to compensate for headphone listening.

Toole measured a whole bunch of headphones, plotted the ones that people said sounded good and superimposed the free-field transfer function (black blob) over the good sounding cans. It looked like this:

Mead Killion (founder of Etymotic) says headphones should follow the diffuse field response.

I don't have a graph to show, but David Greisinger (long time engineer at Lexicon) contends these curves should be calculated with ear canal information included.

The one I have historically used at HeadRoom is the Head Acoustics diffuse field calibration curve that comes with the head and is a measurement done under special acoustic circumstances on that particular head.

It looks like this:

So, the experiment I did the other day was to position the headphones as best I could, take a measurement, and then change the position slightly. Five measurements were taken: centered, up-forward, up-behind, low-forward, and low behind. The data looks like this:

You'll notice two things: it looks somewhat like the various compensation curves mentioned above, and once you get above 8kHz the data moves all over the place.

Here's the Head Acoustics compensating curve laid down over the HD800 FR data.

Here's a raw HD800 FR curve set (L and R) and the same curve with the Head Acoustics DF curve subtracted out.

Then I smoothed it very heavily to get the noise out of the highs.

My conclusions are:

• The IEC says headphones should be repositioned five times and averaged. I need to redo the experiment and average all the measurements together, but it certainly looks like all the crud above 7kHz is noise from ear reflections, and that averaging a bunch of measurements at slightly different positions will indeed produce a curve that more accurately represents the acoustic energy spectra more accurately.
• That the DF curve that comes with the head is likely not the best background subtraction to make because ... well because there's so much darn controversy about it. However, taking the data on a head is probably a good place to start since so much of what these curves look like are due to the very specific shape of an ear in the earpiece.
• It's time to go watch a movie with April.

 

[Feanor]

Man this is a very exciting project, congrats!

One thought: am I the first one to whom your measurement box looked a bit like some kind of freakish torture box? It should be fun explaining it away in customs...