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Building a Headphone Measurement Lab - Page 3

post #31 of 355
4/10/10 at 7:07pm
Need to test the impact of beer on headphones too, so pack a keg.
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post #32 of 355
4/10/10 at 7:31pm
Thread Starter 
Quote:
Originally Posted by grawk View Post
Need to test the impact of beer on headphones too, so pack a keg.



Can't believe this isn't already on the list.


Fxt!

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post #33 of 355
4/10/10 at 9:49pm
This is going to be a great tool for those of us who don't get to hear a headphone before getting them, and also to get to know our headphones better. Nice to see you in action Tyll.
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post #34 of 355
4/11/10 at 1:07am
Measurements of Stax, AKG K1000s, Sony QUALIA 010, JH Audio phones???

How long til you ready to post curves?

-

Who is this, if not Wolfgang, Hans, or Fritz? Maybe Jack?


.
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post #35 of 355
4/11/10 at 9:33am
Looking forward to the outcomes of this project, keep up the great work Tyll!

A thing that I would be interested in, that partially touches the burn-in measurement request, is measurements of several phones of the same type, to see how large the variations are. Differing views of the sound quality and charateristics can often be explained by different ears and needs, but sometimes I get the feeling that variations in phones might be the explanation. The unique graphs you can get for the HD800s at least tells a story in that direction.
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post #36 of 355
4/11/10 at 2:08pm
Tyll, just a thought: Have you contacted John Atkinson at Stereophile magazine for measurement advice? Stereophile has been supportive of the headphone hobby over the years and I bet John would be willing to help in some way! He's been measuring exotic stuff forever!
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post #37 of 355
4/11/10 at 8:42pm
Quote:
Originally Posted by 3DCadman View Post
Tyll, just a thought: Have you contacted John Atkinson at Stereophile magazine for measurement advice?
Or better still... go in the other direction and offer your services to them... with a view to making some money out of it!
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post #38 of 355
4/11/10 at 9:43pm
best wishes for satisfaction, scary thrills and a sense of wonder in the new venture, Tyll.

may your challenges be great and your headaches be small.....

chuck
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post #39 of 355
4/12/10 at 12:17am
Quote:
Originally Posted by Tyll Hertsens View Post
The method in general will evolve from what we've been doing at headroom. There is impulse response and phase data that we've been collecting for years but not showing because I'm not sure if it's meaningful. One of the great things about doing this work now as more of a community project, is that there are some very accomplished engineers/scientists among the members, some of whom have already expressed an interest in helping to analyze the data.
That almost sounds like you might be willing to make public your captures so anyone can download and check out the raw data, if that's the case, count me as one of the people doing back flips with excitement. Too often not only is the capturing platform and test methodology not made public, but the logs, and data captures that backup the 'results' are left a mystery.

Can't wait to see how things develop from here.
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post #40 of 355
4/12/10 at 2:39am
Would love to see some electrostats measured.
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post #41 of 355
4/12/10 at 10:44am
Thread Starter 
Quote:
Originally Posted by thisbenjamin View Post
That almost sounds like you might be willing to make public your captures so anyone can download and check out the raw data, if that's the case, count me as one of the people doing back flips with excitement.
Ahh, yes, well there will be some strings attached to the raw data. I'm not sure exactly what they will be yet, that will have to be worked out in detail with the Board of Directors. There are some non-compete clauses with HeadRoom that will have to be navigated. Also, I paid a good deal for the gear, and while I want it to strongly benefit the community, I will also have to have some income streams as a consultant which may require some protection of the data.

But! There will be access to the raw data by a team of hobbyists who will work to make it interpretable (you may want to participate with that effort), and there may be a limited set of headphones which have raw data published so that a wider number of folks will have a chance to play with the data for themselves.

There will certainly be an opportunity for members to get their own personal headphones measured as a pay service and, of course, then you will get a complete spreadsheet of data.

I know this may sound a bit disappointing, but I promise there are some killer graphing packages out there that will allow hobbyists to do some cool things with the measurements like subtract one graph from another so you can see the difference between headphones.

Check out this website as an example of some of the cool graphing tools that are becoming available.
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post #42 of 355
4/12/10 at 6:43pm
Interesting stuff, man
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post #43 of 355
4/12/10 at 8:21pm
Thread Starter 

First measurements in the box.

I think it was Dread who asked about the effect of the chamber walls on open headphone acoustics, where reflections might get back into the cans and they certainly do. Just not a lot.

Here's the FR of Senn HD800 in on the head in different positions in the box:




Here's the graph.



Here's a day later with the acoustic treatment in the box.



Looks like there's a bit less bumps and wiggles between 500Hz and 6kHz

Here's FR measurements of four headphones.



The rise in FR between 2kHz and 5-8kHz is due to the Head Related Transfer Function of the head. By the time flat sound in the outside world reaches you eardrums, there's a peakyness to it, just like the above.

We're gonna talk about this frequency response curve a LOT.

I also looked at pink noise generated in the box both with and without the acoustic treatment.



The foam creates some extra bumps and wiggle from selective absorption and mixing up the modes in the chamber a bit.

With the foam in, I moved the head around the box without any headphones on. Quite a bit of variation.




Then I measured with pink noise in the box and the head in one position with sealed headphones on; then with the headphones off; then with the headphones back on again to see if it was fairly repeatable with replacing the headphones.



You can see the light blue and red trace follow each other fairly well after replacing the headphones on the head.

Otay, let's see if we get low enough noise floor to see the blips in the harmonic distortion spectra. Here it is with HD800s and the door open and closed.



You can see it would have been hard to see the harmonics if there had not been a chamber.

Here's the HD800 against the HD201 --- which of course has much more distortion.



Think the rise between 2.2 and 3.7kHz is from exiting vibrations in the plastic housing.

Looks like the noise floor is low enough to see the needed details.
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post #44 of 355
4/12/10 at 9:16pm
This is starting to get really interesting!

So I believe the plan for next year is that you will be building acoustically perfect rooms to host CanJam in?
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post #45 of 355
4/12/10 at 10:50pm
Thread Starter 
Quote:
Originally Posted by Landis View Post
So I believe the plan for next year is that you will be building acoustically perfect rooms to host CanJam in?
No, I'll be drilling small holes in people's head and peering in to see what's goin on in there while you listen to headphones.














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