HeadRoom V2 Measurement System: Bug List - Head-Fi: Covering Headphones, Earphones and Portable Audio

Tyll Hertsens · #1 (**permalink**) 02-04-2009, 11:02 PM

As many of you may have noticed, our new measurements are up. You may have also noticed that while they're better in some ways, they aren't as good in others.

Well, we're working on it, but it'll be a bit slow going. In an effort to make it a little faster going, I've started this thread so youz guyz can make comments about things that look erroneous. We've got a really cool guy, Derren, who's a Montana State U. student who's doing his postgrad work in psychoacoustics. He's been doing the measurements. I'm gonna turn hiim on to this thread and he'll monitor it for things that need looking into.

I can only ask that you bear with us, and lend a hand by notating any problems you find.

Measurements page is here.

I'll start: the triggering on square waves is not set properly and the squarewaves don't line up. (Fix is in the works for this, but it will take a while as all headphones need to be remeasured to fix it. We are currently doing that.)

Thanks folks!

wnmnkh · #2 (**permalink**) 02-04-2009, 11:40 PM

Tyll, are un-balanced HD650's and balanced HD650's same? I can't find un-balanced HD650 on the option.

Duggeh · #3 (**permalink**) 02-04-2009, 11:43 PM

Isolation specs are different for the same headphone in balanced and unbalanced configurations. Probably caused by not having the headphones mounted in identical position to the other test.

pompon · #4 (**permalink**) 02-05-2009, 01:30 AM

Balanced 650 ... no idea what cable they took!

I want to see HD650 with stock cable and HD650 with Equinox cable to see what happening with the graph!

janderclander14 · #5 (**permalink**) 02-09-2009, 08:58 PM

The Dt990 (2005) measurements which were available in the old version seem to have disappeared in the new one. Is it possible to at them?

Thanks!

CompressionalFlagellation · #6 (**permalink**) 02-10-2009, 02:47 AM

Testing different cables on the same headphone might help settle this argument. I'm not trying to destroy anyone's cable business here, I just want some objective truth. Thanks.

TheSloth · #7 (**permalink**) 02-10-2009, 08:30 AM

Quote:

Originally Posted by CompressionalFlagellation

Testing different cables on the same headphone might help settle this argument. I'm not trying to destroy anyone's cable business here, I just want some objective truth. Thanks.

Come on, the measurements available through the headroom measurements system aren't nearly comprehensive enough to give any 'objective truth' to this matter. Even if they were, they still wouldn't be complete and would not 'settle' anything.

And that's coming from someone who loves looking at measurements! Let's not turn working for better and more meaningful measurements into an argument about finding the 'truth'.

CompressionalFlagellation · #8 (**permalink**) 02-10-2009, 09:38 AM

Quote:

Originally Posted by TheSloth

Come on, the measurements available through the headroom measurements system aren't nearly comprehensive enough to give any 'objective truth' to this matter. Even if they were, they still wouldn't be complete and would not 'settle' anything.

And that's coming from someone who loves looking at measurements! Let's not turn working for better and more meaningful measurements into an argument about finding the 'truth'.

Ah, I won't argue with you at all on this one . I'm just curious if there's anyway to get close to the facts surrounding what various cables do to an audio signal; I mean, I'd imagine even a test that is far from perfectly accurate could help diminish some of the wild claims that people make about how certain grossly priced cables are making a huge difference in SQ.

It's so hard for me to accept things like, "everyone's different, only experience and listening can uncover a cable's 'sound signature'" yada yada. I want to shine the light on reality. If a person can hear a difference between cables, then I am convinced it can be measured.

But again, I acknowledge and respect whatever experience you may have with audio, it's probably far greater than my own. Thanks.

mulveling · #9 (**permalink**) 02-10-2009, 10:50 AM

Hah, the W5000 frequency response looks terrible. I bet your dummy head had the same fit problems with these cans that I did! I had to firmly press the cups against my head, squishing the pads in the process, to hear a sound signature approaching my "normal" favored HD650/L3000 type warmth.

Affixing/half-fitting the too-small W2002/L3000 pads in place of the larger W5000 pads was awkward, but resulted in an in-between sound that was an big improvement over stock, with no active pressing action required. Unassisted & stock, it sounded like that graph indicated - bright, lacking bass, completely un-enjoyable.

Tyll Hertsens · #10 (**permalink**) 02-13-2009, 12:03 AM

Quote:

Originally Posted by wnmnkh

Tyll, are un-balanced HD650's and balanced HD650's same? I can't find un-balanced HD650 on the option.

I think this got fixed, here's the graph.

Quote:

Originally Posted by Duggeh

Isolation specs are different for the same headphone in balanced and unbalanced configurations. Probably caused by not having the headphones mounted in identical position to the other test.

Yup...sort of. One of the problems with our isolation measurement is that there is a single speaker that is the sound source in an anechoic chamber. This causes some discrete audio paths to the ear that may resonate. It would be better if we did the isolation measurement in a "live" concrete room with 8 speakers in the corners exciting and reverberating throught the entire space creating a diffuse field of noise.

They're pretty close though.

Quote:

Originally Posted by pompon

Balanced 650 ... no idea what cable they took!

I want to see HD650 with stock cable and HD650 with Equinox cable to see what happening with the graph!

Quote:

Originally Posted by CompressionalFlagellation

Testing different cables on the same headphone might help settle this argument. I'm not trying to destroy anyone's cable business here, I just want some objective truth. Thanks.

I tell you what, after we get the straight up measurements working, I'll work on doing some experiments that I post here. I'll do different cables, but I'll also do stuff like measuring headphones on different positions on the head, and the Grados with all the different pads. But for the moment I need to get the basic stuff up. Good idea though!

Quote:

Originally Posted by janderclander14

The Dt990 (2005) measurements which were available in the old version seem to have disappeared in the new one. Is it possible to at them?

The old data doesn't work with the new data set (different number of samples), and we have to measure the headphones we carry first.

Quote:

Originally Posted by TheSloth

Let's not turn working for better and more meaningful measurements into an argument about finding the 'truth'.

Yupper, there are two truths here: the objective measureable truths; and what you hear. The two are related---measurements will tell you when there's more bass, or when there frequency response is wiggly and therefore has problems---but measurements won't tell you if you hear somethings as "deeper" or more "airy." I can tell you though that the better the headphones measure, the better they generally sound. That's for sure.

Quote:

Originally Posted by CompressionalFlagellation

I'm just curious if there's anyway to get close to the facts surrounding what various cables do to an audio signal.

There is test gear specifically designed for testing cables (they test for reflections and group delays and such), but those effects are far to small to be seen buried in the noise and much grosser features of the kinds of test we do on headphones.

I'll still give them a go, but I really doubt you'll see anything definitive.

Quote:

Originally Posted by mulveling

Hah, the W5000 frequency response looks terrible. I bet your dummy head had the same fit problems with these cans that I did!

Could be, but Darren works pretty hard to get a good seal. He knows what to look for. He's going to be cruising this thread for info, I'll ask him about remeasureing the W5000.

They've got other problems though.

BTW the D5000 and D7000 were remeasured and the measurements are up.

So that just shows to go you, there's hardly any measurable difference (at least with this type of measurement) between balanced and unbalanced, yet we all know that it makes a fairly easily audible change to hear.

wnmnkh · #11 (**permalink**) 02-13-2009, 04:02 AM

Hmmm, really? I see some viable difference between balanced D7000 and unbalanced one....

TheSloth · #12 (**permalink**) 02-13-2009, 09:38 AM

The balanced setup seems to show increased overshoot on the square wave measurement, which if I understand correctly is actually slightly worse performance...?

Bullseye · #13 (**permalink**) 02-13-2009, 06:36 PM

I believe there is a difference between just changing cables and changing cables plus balancing the headphones, ain't it?

So you can also balance headphones without any cable change, can't you?

TheSloth · #14 (**permalink**) 02-13-2009, 08:08 PM

Quote:

Originally Posted by TheSloth

The balanced setup seems to show increased overshoot on the square wave measurement, which if I understand correctly is actually slightly worse performance...?

And, by the way, as we are talking about bugs, what exactly is a '500hz swuare wave'?!

Tyll Hertsens · #15 (**permalink**) 02-14-2009, 12:20 AM

Quote:

Originally Posted by TheSloth

And, by the way, as we are talking about bugs, what exactly is a '500hz swuare wave'?!

Funny! Nice catch, mate.

The tricky thing is that the additional overshoot could just be from a different position on the dummy. Generally it means that the high frequencies are getting to the ear a little stronger. It really could be a lot of things besides the calbe or balanced configuration.

These are things we're going to have to figure out over time.