CHANGSTAR: Audiophile Headphone Reviews and Early 90s Style BBS

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Author Topic: Musings on Future Measurements  (Read 2201 times)

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Solderdude

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Musings on Future Measurements
« on: July 30, 2015, 07:47:56 AM »

Even though FFT has a purpose I think it doesn't say that much except for constant signals.
Why not 40Hz + 60 Hz to test for bass distortion ?

Agree with D North on most of his 'questions' .

I would suggest to use OTHER types of test signals.
Like real music under real loads, or tests that can show 'dynamics' or 'linearity' in an easy way or think of other artificial signals.

If you test for dynamics for instance then.... how much dynamics do you want tested ?
For instance if you measure with about 100dB peak SPL (and regard that as 0dB) why would you need to measure below -70dB and call it relevant as it is inaudible?
Even at 120dB ... why would one call -90dB from 120dB relevant ?
The dynamic range of hearing may well be 100dB but NOT at the same moment for SURE.

Can someone explain the correlation between 'known' measurements and sonic qualities/attributes and defend those ?
Can you take 'brain issues' (See Anax's PRaT remark for instance) and correlate that to measurements ?
Can you take mood, tiredness and time of day into consideration when evaluating static signals ?
Can you take cognitive (brain) aspects of different people in consideration when evaluating technical signals ?
Does one NEED to do that ?
Can you correlate with the standard set of measurements ?
Do squarewaves or Dirac pulses say ANYTHING at all about sonic attributes (in amps and DACs) as they don't exist in music at all.
Can we agree on audibility thresholds and get them to hold up in a court of audiophiles ?

What's the point of using -3dB / -6dB other than for obvious power/voltage/current levels that are obvious ?
What's the point to -10dB or -20dB for FR in a headphone or not mentioning it at all ?

What's a representative load ?
A resistor would be fine for mimicking orthos and very few dynamics.
What capacitance and inductance do you guys use (I test everything with 1 and 10nF in parallel to the load for instance as well as resistive only)
A headphone is always connected to a cord, how is your dummy load connected ?
Should we use inductors or even complex (LCR) loads to mimic an 'average ?' headphone and standardise this of sorts ?

You know what I don't like about standards ?
You can design something to work well during known tests but slum it on other specs and get out on top measurement wise ?

The question for me is WHAT aspects do we want to measure and what type of signals do you need.
Not a question of what 'current' methods should we use and what uniform settings .... though that may very well be a contributing part of a measurement set.

« Last Edit: July 30, 2015, 11:27:04 AM by Solderdude »
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Marvey

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Re: Standard Distortion Spectrum Measurements For Amps (Changstar)
« Reply #1 on: July 30, 2015, 03:29:19 PM »

<<<stream of consciousness>>>

We have to start somewhere. Simple is a good place to start.
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Solderdude

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Re: Standard Distortion Spectrum Measurements For Amps (Changstar)
« Reply #2 on: July 30, 2015, 04:29:24 PM »

Ah too bad ...
I was hoping for more though  facepalm.
As the measurement suite is now, the only thing that can be 'proven' is that the O2 is better than Magni, Vali and Studio in all 'electrical' departments that have been measured in the other thread.
One can also prove the Studio performs better in the bass area than a lot of other all tube transformer coupled amps.
Speculation doesn't cut it in the world of measurements...  8)

Where is the adventure in sticking to the 'old' ?  :)p2

How to show in measurements that what cannot be shown in current measurements.
Sonic superiority like Studio > Vali > Magni > O2 as has been established subjectively ?

Surely there MUST be some proof somewhere ?  :-Z
I mean after all.... stereo is just 2 voltages varying in amplitude over time or is there more to it ?  :)p7

just teasing a bit ....
Following this with  popcorn
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Anaxilus

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Re: Musings on Future Measurements
« Reply #3 on: July 30, 2015, 05:46:51 PM »

No one has ever complained about the O2 having bad bass. People complain about it's Helen Keller level of resolution, lack of micro dynamics and tonally compressed and slightly foggy signature. Hell, you can hear that compared to an Ember. You helped to design that thing, you tell us.
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OJneg

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Re: Musings on Future Measurements
« Reply #4 on: July 30, 2015, 06:09:50 PM »

I myself am fine with the fact that the Studio or any vacuum tube amp will never measure as well as a modern opamp design or any solid-state amp that uses plenty of negative feedback. Perhaps because I understand the mechanism behind the non-linearity in those amps and how the others "get rid" of it. As others have mentioned, the moderately higher THD won't keep me up at night when I consider the whole system and chain from a macro perspective.

It still doesn't explain the difference in sonics but fortunately we have this other great tool called the auris aurea to determine that for us.

The standard measurement suite as it is gives us a good idea of what's going on from a circuit design view and is still worth running through for any and all amps that can be measured in such a way. But if we want to a get a better gauge of "sonic superiority", best to look at amps with topology and component selection in mind. IMO and IME that is the best indicator of perceived sound quality we have at the moment.
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Marvey

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Re: Musings on Future Measurements
« Reply #5 on: July 30, 2015, 06:17:57 PM »

But if we want to a get a better gauge of "sonic superiority", best to look at amps with topology and component selection in mind. IMO and IME that is the best indicator of perceived sound quality we have at the moment.

Heh

wire with tube and a mess of wires and a tube and another mess of wires

-or-

wire with tubes and cap and a tube and a mess of wires

-or-

wire with transistor and transistor and transistor and a loop going back to the first transistor.

-or-

wire with transistor and transistor and transistor (and a loop going back to the first transistor) and a cap and then a transistor and transistor and transistor with a loop going back to the first transistor.


The last one is Objective 2. Also, no such thing as wire with gain.
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Solderdude

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Re: Musings on Future Measurements
« Reply #6 on: July 30, 2015, 07:11:37 PM »

Oh I also understand the mechanisms behind negative, no, and even positive/forward feedback quite well, including the drawbacks and merits.
I also understand topologies and their up and downsides.
This does NOT explain the heard differences at all even though beautiful 'theories' go around by many designers and some even have valid points.

Indeed the standard measurement suite gives us (also me) a very good idea of what's going on.
Measurements as done by Atomic Bob for instance are outstanding examples of a nice set of measurements.
They are certainly worth running and say a LOT about amps and DACs for that matter.

I also understand that subjective detemined SQ and measurements do NOT correlate to measurements in a direct way and certainly not 100% which would have been nice.

Still, as you say, you can look at which components and topology are used and simply state that is the best indicator.
Nothing wrong with that and is what is usually done and subjective properties are coupled to components.
Unfortunately..... that does not reflect in any electrical measurements which would have been nice. 
Why ?

That's what fascinates me till this day.

This is why I kind hoped there was an interest in alternative test methods or test signals that can ADD to the current measurement suite and could potentially reveal what current methods do not.
I would like more realistic 'test dummy loads' and sort of create a new standard and measurements that could be used to give more insight to perceived sound vs measured values.

For instance most amps measure well with just a resistive load but may reveal 'potential problems' when loading them with a capacitance and or inductance.
The same capacitance with different resistive loads yields different results.
THAT's what I was sortof hoping for, not the usual 'I feel attacked... you tell me' comments that are NEVER constructive.

I hoped the measurement suite attempt was an honest attempt to compile a measurement suite with the usual + 'other, not yet appllied' test signals as well that could perhaps shed some light in other ways than the already known ones.
I was already glad Marv measured in other ways than just 1kHz and the usual 'tests' that are simply made that way so others can get test in a standardised way.

Alas.... I misread it and all seems to have to remain the same perhaps using some different frequencies for FFT only that deviate from the 'standard' measurements.

It's what I liked about Donald remarks and hoped the gurus here would see 'beyond' standard measurements and come up with inovative test ideas.

Well maybe some day..
Count me in WHEN it gets constructive.
I have NO interest in playing the usual word games and childish remarks that are meant to be funny.
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Anaxilus

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Re: Musings on Future Measurements
« Reply #7 on: July 30, 2015, 07:23:51 PM »

Well parts of your post seemed a bit more than cheeky. Your use of emoticons came off as a bit pretentious and condescending (a la Macedonian Hero) in the usual objective manner. So consider it lexical ambiguity. I'd like to think I know you better than that by now, but when one employs the usual flame bait posting tactics they usually get the same flame bait responses. That said, let's get back to it. As for lexical ambiguity, let's change the following absolutist remark to something more constructive:

"I also understand that subjective detemined SQ and measurements do NOT correlate to the usual current measurements in a direct way and certainly not 100% which would have been nice."
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Marvey

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Re: Musings on Future Measurements
« Reply #8 on: July 30, 2015, 07:33:16 PM »

For instance most amps measure well with just a resistive load but may reveal 'potential problems' when loading them with a capacitance and or inductance. The same capacitance with different resistive loads yields different results.

Easy. Use a real load like a real HD600 or LCD2 like what Craig does. You can throw a cap and coil into the circuit to simulate the impedance, but that doesn't exactly simulate the non-linear behavior of drivers (if you've seen Klippel results, you would know). It's a good next step. Maybe you can put together a schematic to simulate HD800 (very popular headphone) impedance curve. As far as orthos, they are more similar to each other than not in terms of impedance. 32 ohms. Easy. Representative of Audeze, HFM, and even T50RP (close enough to 50).

This is why I kind hoped there was an interest in alternative test methods or test signals that can ADD to the current measurement suite and could potentially reveal what current methods do not.

No shit Sherlock. Unfortunately, I don't have all the fucking answers right now. Do you? Did you even bother what reading what I first wrote: "We have to start somewhere. Simple is a good place to start." Rome wasn't built in a day. Changstar headphone measurements have evolved over time. Let's take this step by step, unless you already have all the answers. I don't want ideas, I want methods and results.

And yes, I do have some ideas on more evolved measurement methodologies that I am keeping to myself. However the first step is to get everyone who is doing these organized and in-line to begin with. It's important to have a strong foundation, consistent results, no?

Count me in WHEN it gets constructive.

Post when you have something constructive. I've had enough of idiots at company meetings who propose pie-in-the-sky ideas with no idea how to get there.
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OJneg

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Re: Musings on Future Measurements
« Reply #9 on: July 30, 2015, 07:57:19 PM »

This does NOT explain the heard differences at all even though beautiful 'theories' go around by many designers and some even have valid points.

I don't suppose you have any better theories. Let me guess, it starts with "expectation" and ends with "bias"

Still, as you say, you can look at which components and topology are used and simply state that is the best indicator.
Nothing wrong with that and is what is usually done and subjective properties are coupled to components.
Unfortunately..... that does not reflect in any electrical measurements which would have been nice. 

No, I'd say that different components and topologies tend to result in very different electrical measurements. Whether these differences are positive, "below the threshold of audibility", or negative is a different story, but they certainly are quantifiably different.

I hoped the measurement suite attempt was an honest attempt to compile a measurement suite with the usual + 'other, not yet appllied' test signals as well that could perhaps shed some light in other ways than the already known ones.
I was already glad Marv measured in other ways than just 1kHz and the usual 'tests' that are simply made that way so others can get test in a standardised way.

I am very open to a new sort of test signal that could provide insight into the dynamic or "sonic" abilities of any given black box. If you have any sort of specific tone-burst or square wave or another sort of stress signal in mind that you think might be a valid stress test for amplifier performance, let us know and I for one would be happy to explore the idea. In terms of using some sort of musical signal...well that's certainly an interesting idea but I wouldn't know where to start

Count me in WHEN it gets constructive.

The fundamental problem with your original post is that it's not particularly constructive. It's really just obfuscating and running circles around itself. Perhaps it's a language barrier thing or maybe just an internet communication misunderstanding, but you do speak like that a lot. I think we've all got accustomed to how we communicate with each other.... so I have no idea why you're surprised to see The Belligerent One or Chairman Marv having fun at the expense of your ideas. Best to take everything in stride rather than whining and abandoning ship.
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