Testing audiophile claims and myths

[eucariote]

Quote:

Originally Posted by BlackbeardBen /img/forum/go_quote.gif
 
You're confusing the scientific method of null testing and electrical null (difference) testing; the second of which is what Ethan is talking about.  Null difference testing reveals all differences in two electrical signals.

Ah thanks, I'd just been skimming the thread.  Must remember to not shoot from the hip.

 

[Heidegger]

Quote:

I spent a good 5 minutes trying to come up wit a witty retort but this single paragraph is full of more idiocy than the rest of your posts in this thread of combined, cubed, and then possibly factorial-ed.  You really should try to understand this stuff before you trot it out as evidence to prove your point and fail spectacularly.  A few choice points...
 
Why is a test designed to look for stuff that gives off light a failure when it doesn't detect something that does not give off light?
 
Along those lines, what kind of magical energy do you propose is being transmitted with, yet is separate from, the electrical signals of an audio system which can be played via the transducers and perceived by humans but is unaffected by and undetectable to all the sophisticated measurement devices in the signal chain?  That's the fantasy you're proposing.  In reality, an audio null test will detect all differences between two signals.  It does not fail as a test because it does not take into account your state of mind.  That isn't part of the signal.
 
And here's the big one...
 
If dark energy "will never show up on any test or analysis" then how do we already know its there?  Quite the paradox...
 
At this point I'm really beginning to question things.  That paragraph is either the one of the most brilliant Poes I've ever seen or...well...something that's not very nice...  On the one hand I could be incredibly angry and on the other I could be incredibly depressed.  I don't need any more depression.  I think I need to adopt the Hitchens approach and browse Sound Science with a bottle of whiskey or something.  I need more practice on the one liners too.  I don't yet have the skills to win a debate while half drunk...

Maverick, I didn't say that the astronomical null tests were a failure. They find exactly what they are supposed to locate. As to whether the audio null tests pick up everything (everything relevant to how we experience sound), I necessarily leave that open since I don't have a firm enough grasp of these tests to be able to say one way or the other. Ethan's appeals to science and his experrience with these tests add a lot of weight to his argument, but a survey of the history of science finds scientists again and again claiming that something is "impossible" only to be proven wrong. Moreover, people who have just as much experience (or more) with audio matters than Ethan contradict some of his statements. What I know is that much of what is claimed on this thread seems to go against the experiences I have had with my audio equipment. (The placebo effect is a powerful thing though.)
 
I still have more questions for Ethan about null tests, questions that were not addressed in his video. For instance, it isn't clear to me how certain phenomena are registered to begin with so that they can, in turn, be nulled by the test. Is "sparkling sound" just a measure of how high the frequency goes? What does depth of soundstage look like when you measure it? How about the air around the strings, how natural their tone is, or whether a recording conveys the "wind" or "fanning" effect that you get when you attend a live classical music concert? How do these things show up as measurements?
 
As for the dark energy paradox: scientists see the effects of dark energy, but what dark energy (anti-gravity) itself is they have no idea at the moment, although there are several theories, some of them having to do with quantum fluctuations and virtual particles. The principal effect of dark energy is that the expansion of space, according to careful scientific measurements, is accelerating, which it shouldn't be unless you take "dark energy" into account.
 

 

[maverickronin]

Quote:

Originally Posted by Heidegger /img/forum/go_quote.gif
 
As for the dark energy paradox: scientists see the effects of dark energy, but what dark energy (anti-gravity) itself is they have no idea at the moment, although there are several theories, some of them having to do with quantum fluctuations and virtual particles. The principal effect of dark energy is that the expansion of space, according to careful scientific measurements, is accelerating, which it shouldn't be unless you take "dark energy" into account.
 

So we see its effects but is doesn't, "show up on any test or analysis."  Makes perfect sense to me!

 

[MacedonianHero]

Quote: I never did say measurements be damned

 
Actually, you did:
 

Ultimately it is how the particular gear sounds...measurements be damned so to speak.

 
Quote:

Using measurements for how music sounds exclusively is like taking FTIR & GC & UV/VIS Spectroscopy to determine what ingredients are in a particular dish to ascertain how it will taste. Can you do this, absolutely, but in the end, you really should also take a bite.

 
I understand your point and disagree only slightly: If audio gear is shown by measuring to be transparent, then you already know how it sounds because it has no sound. Which is as it should be IMO.
 
--Ethan

Actually I didn't my post was quite clear (at least to me ), talking my comments completely out of context...basically what I said was if it measures phenomenally, but sounds like crap...then "measurements be damned". Not that we should dispose of measurements, but they should be used hand in hand with our ears so to speak.

Please explain what you mean in the bold section, I'm don't get what you're trying to say here.

 

[BlackbeardBen]

Quote:

Thank you, Ethan!
 
I'm curious about how output impedance and its effects on how headphones perform. Afaik, the ideal output impedance would be 0, and as soon as that number rises, changes occur in the signal. Very few manufacturers specify output impedance, even fewer produce frequency response measurements. I'm looking for an amp, preferably portable, that can produce the amount of power required to drive an orthodynamic to satisfactory levels, like the HE-6, that doesn't manipulate its frequency response (intentional or otherwise) and doesn't add too much distortion. Where do I find something like that?
 

I forget where, but recently I read a post here on Head-Fi running through the numbers, showing the actual impact of typical high output impedance amplifiers on different impedance headphones.  Basically, you don't need to worry about it so much at typical values (with coil driven headphones as mentioned), as in all but the most absurd examples (120 ohm output impedance, 32 ohm headphone impedance, etc.).
 
Additionally, you could be said to be manipulating the frequency response of the Beyerdynamic DT-XX0 and T1 headphones whenever you use them with a low impedance amplifier...  They're designed for the "other", actually the "official", output impedance standard of 120 ohms.  Running them from low output impedance amplifiers is thus manipulating them...
 
The reason for the 120 ohm output impedance standard is the difficulty in achieving a low output impedance with specific amplifier designs that were at one point the most common.  You may know that many receivers and amplifiers have a headphone jack which is coupled to the amplifier's output via a resistor - that was the most common type of headphone amplifier until recently (with DAPs and computers taking the throne).  The same goes for typical tube amp designs - it's difficult or impossible to have low output impedance for some of the designs, especially those with output transformers.  The Meier claim of 200-600 ohm resistors is news to me though, I have to say.  It's also a hugely exaggerated worst-case scenario compared to normal amplifiers.
 
You don't get the maximum voltage transfer (i.e. best efficiency) with headphones/amps designed for that 120 ohm output impedance - but that's not often a problem for home use.  So I don't really see it as too much of a problem (at least if there was a clear demarcation on all headphones, stating the intended output impedance).
 


Quote:

If you're only going to be using orthodynamics with the amp then output impedance won't really matter.  Orthos aren't electrically damped so damping factor doesn't matter and they have flat impedance curves so a high output impedance won't change the FR.  Maybe Blackbeard can chime in about his balanced iBasso portable which seems to be a good way to get lots of power from a small footprint.

Interesting, I can't believe I didn't realize that before...   A flat impedance curve (as the resistive load of planar magnetics are) means no change in frequency response at different output impedances, as the ratio doesn't change.
 
The voltage transfer is still affected, however.
 
 
As far as the iBasso PB1 goes, I'm impressed with my HD 600.  Very much so, actually.  You can read all the reviews about it of course.  It sounds as flat in response to me as my Asgard does; actually I'm not even sure if I could tell them apart without turning the volume knob...
 
The voltage swing is real - that certainly makes a big difference over less powerful amplifiers.  Take the uDAC that I have for example.  From what I can tell, it implements deliberate clipping to allow higher SPLs on headphones that it can't swing enough volts for.  That allows it to drive the HD 600 better than its limited voltage swing would suggest, but you lose a lot of the subtleties of the music as a result.  Higher powered amplifiers don't have that problem.
 
I can't really say anything about its current capabilities...  Although, there is something interesting - it will drive the HD 600 balanced and my Alessandro MS-1i single-ended at the same time, and having half the gain for the Alessandro works out just about perfect in terms of volume.  They both play at about the same level, which makes them perfect companions for when you want to share your music.
 
Other than that little benefit, I do find balanced operation to be annoying.  It really limits what cans I can use with the full voltage swing, without the extra expense of custom cables.  I'm extremely skeptical of the benefits of balanced operation - the advantages electrically are absolutely minimal; most likely inaudible in the vast majority of cases.  I do wonder about the efficiency however - if balanced operation is the only way to implement such high power in such a small amp.

 

[b0ck3n]

The T1 has a flat impedance of 600 Ohm - is it safe to assume that the PB2 with its 10 Ohm output impedance won't mess it up? The HD 800 isn't flat (HeadRoom's down atm so I can't link a graph), wouldn't that be recipe for disaster with most amps (unless they're really low output impedance)?
 
I haven't exactly decided on what full-size I wanna get just yet, but an amp that's able to handle most, and on the go, would be ideal.

 

[maverickronin]

Quote:

The T1 has a flat impedance of 600 Ohm - is it safe to assume that the PB2 with its 10 Ohm output impedance won't mess it up? The HD 800 isn't flat (HeadRoom's down atm so I can't link a graph), wouldn't that be recipe for disaster with most amps (unless they're really low output impedance)?
 
I haven't exactly decided on what full-size I wanna get just yet, but an amp that's able to handle most, and on the go, would be ideal.

No way.  In absolute terms HD800's impedance curve is a bunny slope compared to the black diamonds of the T1.  The T1 is way off the scale at Headroom but Tyll's new site has impedance graphs with a proper scale on the Y axis.
 
In practice it won't matter anyway.  Only 10 ohms output impedance won't hardly change the FR of such high Z phones.  The important thing is the ratio of the 'phones impedance to its impedance plus the amp's impedance.  At its peak near 100hz the T1 measures 1400 ohms and at it minimum of 600 ohms is around 3khz.  1400/1410 and 600/610 are pretty close.   All that slope means is that the amp will need a good voltage swing which the PB2 should provide if the specs are accurate.  That extra output impedance will quite audibly effect things like BA IEMs though. A peak of 40 ohms @ 1.5khz (40/50) and trough of 10 ohms at 6khz (10/20) translates into a few dBs worth of difference but I'm tired as it is and don't feel like doing the math...

 

[b0ck3n]

Quote:

Quote:

No way.  In absolute terms HD800's impedance curve is a bunny slope compared to the black diamonds of the T1.  The T1 is way off the scale at Headroom but Tyll's new site has impedance graphs with a proper scale on the Y axis.
 
In practice it won't matter anyway.  Only 10 ohms output impedance won't hardly change the FR of such high Z phones.  The important thing is the ratio of the 'phones impedance to its impedance plus the amp's impedance.  At its peak near 100hz the T1 measures 1400 ohms and at it minimum of 600 ohms is around 3khz.  1400/1410 and 600/610 are pretty close.   All that slope means is that the amp will need a good voltage swing which the PB2 should provide if the specs are accurate.  That extra output impedance will quite audibly effect things like BA IEMs though. A peak of 40 ohms @ 1.5khz (40/50) and trough of 10 ohms at 6khz (10/20) translates into a few dBs worth of difference but I'm tired as it is and don't feel like doing the math...

I really appreciate the explanations you guys are providing, and realize that it isn't far off from trying to teach a monkey how to shred arpeggios.
 
One more question if I may, since you mentioned BA IEMs. Is there any benefit to amplifying a BA IEM other than achieving higher volumes? As they're usually low impedance and high sensitivity, volume isn't much of an issue straight out of a DAP - I'm just curious whether the extra power has its benefits.

 

[Prog Rock Man]

Quote:

.........This thread is discussing how subjective impressions relate to objective measurements.  My main points are 1) Just because the system of measurements we have today isn't completely perfect doesn't mean we can or should ignore them in areas which have been shown to work.  2)  Measurements may not exactly be able to tell you what you'll like but the they can as surely as death and taxes tell you what's more accurate.
 
........

I liked that so much it is worth highlighting.
 
If measurements find either no difference or a difference so small as to be inaudible, then any audibility is not in the kit, it is in the listeners mind and has been created by being able to see what we are listening to. We also know that becuase ABX tests find that without sight, many audible differences disappear.
 

 

[EthanWiner]

Quote:

I'm curious about how output impedance and its effects on how headphones perform. Afaik, the ideal output impedance would be 0, and as soon as that number rises, changes occur in the signal. Very few manufacturers specify output impedance, even fewer produce frequency response measurements.

I'm not much of a headphones expert. I know that with loudspeakers a low output impedance is desirable, for both frequency response and damping. I'd think the same applies to 'phones, but I honestly don't know. Ronin mentioned an exception, so maybe he can elaborate on "why" a low output impedance doesn't always matter. I can tell you that any amp that doesn't have at least minimum published specs is probably not worth considering. Frequency response and output impedance are both very simple to measure.
 
--Ethan

 

[EthanWiner]

Quote:

people who have just as much experience (or more) with audio matters than Ethan contradict some of his statements.

You can use Argument From Authority all day long, but it doesn't make your case. The difference between you and others who disagree with me, and me, is that I can explain the facts clearly and succinctly. I can explain what and also why every single time. They never can, so the result is often anger and then insults.
 
Quote:

I still have more questions for Ethan about null tests, questions that were not addressed in his video. For instance, it isn't clear to me how certain phenomena are registered to begin with so that they can, in turn, be nulled by the test. Is "sparkling sound" just a measure of how high the frequency goes? What does depth of soundstage look like when you measure it? How about the air around the strings, how natural their tone is, or whether a recording conveys the "wind" or "fanning" effect that you get when you attend a live classical music concert? How do these things show up as measurements?

 
Not understanding "how certain phenomena are registered" is a big part of the problem. You fail to understand some of the most basic things that define what audio is. In this case, audio is changes in air pressure for acoustic sound, and changes in signal voltages for audio passing through wires and gear. So all sound is "registered" as these changes. Once you understand that, then you understand why a null test shows all (electrical) differences.
 
--Ethan

 

[EthanWiner]

Quote:

what I said was if it measures phenomenally, but sounds like crap...then "measurements be damned". Not that we should dispose of measurements, but they should be used hand in hand with our ears so to speak.

The better explanation for "measures phenomenally, but sounds like crap" is to learn how to measure the right things.
 
Quote:

Quote:

If audio gear is shown by measuring to be transparent, then you already know how it sounds because it has no sound. Which is as it should be IMO.

Please explain what you mean in the bold section, I'm don't get what you're trying to say here.

This is very simple. IMO all audio "playback" equipment (versus creative recording / mixing effects) should aim to pass audio without changing it or adding anything new. This is definitely possible, and lots of gear is clean enough to not change the sound audibly. Sure, everything adds some amount of distortion, and skews the frequency response some amount. But if those changes are small enough they won't be heard. For example, a response within 0.1 dB is close enough to flat to not hear, and distortion and noise 80+ dB below the music will not be heard while the music plays. So if the standard tests for audio gear show that the gear is audibly transparent, then it will have no sound. And in turn you can know it will sound like any other transparent device.
 
--Ethan

 

[maverickronin]

Quote:

I really appreciate the explanations you guys are providing, and realize that it isn't far off from trying to teach a monkey how to shred arpeggios.
 
One more question if I may, since you mentioned BA IEMs. Is there any benefit to amplifying a BA IEM other than achieving higher volumes? As they're usually low impedance and high sensitivity, volume isn't much of an issue straight out of a DAP - I'm just curious whether the extra power has its benefits.

IME BA IEMs seem to be very sensitive to the quality of the amping.  I think its because they are bout low Z and very efficient.  They let you hear more of the source if it isn't completly transparent.  Also they do have rather crazy looking impedance curves as I showed in the link above.  I haven't done any blinded testing to back this up, but in sighted AB comparisons I notice differences between some amps that I don't notice with higher Z and/or less efficient 'phones.  Maybe its output impedance, maybe its something else electrical, maybe its placebo.  I don't have the equipment to measure it.
 
Some DAPs, like the Clip+, shouldn't have trouble driving most BA IEMs from the numbers I've seen which indicate low output impedance and another important factor for such small and cheap amps, no bass roll off with low Z loads.  My otherwise excellent Cowon D2+ does this.  Since the DAP market is such a disaster you've got to make a sacrifice somewhere and picked a flaw that can be remedied with another piece of equipment.  The High Z input impedance of any half decent amp will bring the bass back up.  I also tend to get fatigued rather easily without some sort of crossfeed and picked an amp (the XM6) that has that feature.  That's way overkill for just IEMs on the go but it also serves a my DAC at work and can power my full size 'phones at home as well.

Depending on your player, even a cheap amp may help with IEMs.  Fiio is coming out with a slim and sleek 3 channel active ground portable amp for around $60 which looks to be a decent choice if your need to choose a player with a so-so amp for other reasons like interface, formats, or storage.  I'd be all over it if it has crossfeed too.
 
Quote:

I liked that so much it is worth highlighting.
 
If measurements find either no difference or a difference so small as to be inaudible, then any audibility is not in the kit, it is in the listeners mind and has been created by being able to see what we are listening to. We also know that becuase ABX tests find that without sight, many audible differences disappear.
 

 
Quote:

I'm not much of a headphones expert. I know that with loudspeakers a low output impedance is desirable, for both frequency response and damping. I'd think the same applies to 'phones, but I honestly don't know. Ronin mentioned an exception, so maybe he can elaborate on "why" a low output impedance doesn't always matter. I can tell you that any amp that doesn't have at least minimum published specs is probably not worth considering. Frequency response and output impedance are both very simple to measure.
 
--Ethan

That does apply to conventional ("dynamic" as they are called in these parts) transducers with a diaphragm and a voice coil surrounding a magnet which are just miniature versions of traditional loudspeakers.  Some speakers and and increasing number of very popular headphones around here are alternatingly called orthodynamic, isodynamic, and planar magnetic and work a bit differently.  They are almost completely mechanically damped (often with precisely tuned layers of felt or other fabric) because they don't put out much (any?) back EMF in the first place and so they have no need of low output impedances to electrically damp them.  Second, they are almost purely resistive loads so the impedance of the driver is almost completely flat over the whole audible spectrum and won't cause the FR to vary due to the output impedance of the amp.
 
That's why AFAIK, amplifier output impedance doesn't matter for those types of drivers.

 

[b0ck3n]

Quote:

IME BA IEMs seem to be very sensitive to the quality of the amping.  I think its because they are bout low Z and very efficient.  They let you hear more of the source if it isn't completly transparent.  Also they do have rather crazy looking impedance curves as I showed in the link above.  I haven't done any blinded testing to back this up, but in sighted AB comparisons I notice differences between some amps that I don't notice with higher Z and/or less efficient 'phones.  Maybe its output impedance, maybe its something else electrical, maybe its placebo.  I don't have the equipment to measure it.
 
Some DAPs, like the Clip+, shouldn't have trouble driving most BA IEMs from the numbers I've seen which indicate low output impedance and another important factor for such small and cheap amps, no bass roll off with low Z loads.  My otherwise excellent Cowon D2+ does this.  Since the DAP market is such a disaster you've got to make a sacrifice somewhere and picked a flaw that can be remedied with another piece of equipment.  The High Z input impedance of any half decent amp will bring the bass back up.  I also tend to get fatigued rather easily without some sort of crossfeed and picked an amp (the XM6) that has that feature.  That's way overkill for just IEMs on the go but it also serves a my DAC at work and can power my full size 'phones at home as well.

Depending on your player, even a cheap amp may help with IEMs.  Fiio is coming out with a slim and sleek 3 channel active ground portable amp for around $60 which looks to be a decent choice if your need to choose a player with a so-so amp for other reasons like interface, formats, or storage.  I'd be all over it if it has crossfeed too.
 

So it's basically only beneficial when forced to use a crap DAP. I haven't seen any measurements of the iPhone 4, but I haven't noticed any audible flaws either. Perhaps I should just relax and enjoy the music then
 

 

[BlackbeardBen]

Quote:

That does apply to conventional ("dynamic" as they are called in these parts) transducers with a diaphragm and a voice coil surrounding a magnet which are just miniature versions of traditional loudspeakers.  Some speakers and and increasing number of very popular headphones around here are alternatingly called orthodynamic, isodynamic, and planar magnetic and work a bit differently.  They are almost completely mechanically damped (often with precisely tuned layers of felt or other fabric) because they don't put out much (any?) back EMF in the first place and so they have no need of low output impedances to electrically damp them.  Second As a result, they are almost purely resistive loads so the impedance of the driver is almost completely flat over the whole audible spectrum and won't cause the FR to vary due to the output impedance of the amp.
 
That's why AFAIK, amplifier output impedance doesn't matter for those types of drivers beyond voltage transfer efficiency.

Just clarified a few things there.
 
 
 
 
Also, I must say that personally I don't really like the "orthodynamic" and "isodynamic" terms...  They're more or less marketing terms used by Yamaha and Peerless (orthodynamic); Wharfdale (isodynamic); Sansui and Aiwa called them "omni-dynamic"; Fostex called them "RP type" for "regular phase"; and so on...
 
While none of those terms are necessarily wrong (or really less accurate in describing the driver than "dynamic" is, respectively), they're not the best terms IMHO.  "Orthodynamic" is a combination of "orthogonal" and "dynamic", more or less meaning "pertaining to, characteristic of, or acted upon by forces at right angles"; and "isodynamic" means, similarly (and I take this from dictionary.com):
 

•  Having equal force or strength.
•  Connecting points of equal magnetic intensity.

 
While both are true, they could be applied to one degree or another to both electrostatic and conventional coil ("dynamic") drivers.  Planar magnetic, however, avoids that entirely, although it doesn't preclude true ribbon drivers (although nor do ortho/iso-dynamic).
 
Anyway, I suppose it doesn't really matter so much, as long as everyone understands what's being talked about.  I'm just picking nits, having come from the speaker world where "planar magnetic" is perhaps the most well-understood term.  "Ribbon" (as refers to true ribbon drivers), however, is often misused for planar magnetic drivers like Infinity's EMIT and Magnepans...  That's actually the first term I knew for such drivers, until I learned about the difference in operating principle.
 
 
 
 
Anyway, let's get back to designing plasma headphones...