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Topic: Several issues related to blind testing. (Read 36042 times) previous topic - next topic
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Several issues related to blind testing.

Reply #75
While I believe the shoe analogy to speaker break-in is quite apt, the internal-combustion engine one is not.


It's the old, I'll pick and choose my metaphors..

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Shoe leather, like (I assume) speaker surrounds, ship with a material stiffness which changes due to use and never stops changing.


I already debunked that. Speaker surrounds change rather quickly to an in-use state that persists for a while, when they are used after a long period of idleness. Let them be idle for a long time, and they tend to return to their former state.

Unlike shoes, loudspeaker surrounds last for very long times except when they chemically degrade due to environmental considerations. That's a key point - the loudspeaker surrounds that degrade and crack are generally all made from polyurethane foam, and its environmental facts that makes them break down, not actual use.

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The cause is a gradual stretching and eventual loss of elasticity.


Doesn't generally happen.

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(plus degradation of material properties due to oxidation and other environmental exposures).


A completely different issue.

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Piston rings, on the other hand, are exposed to friction (purposeful friction in the case of an unseated ring) which eventually declines as material is worn and deformed to the point of, if not equilibrium, at least a point where the rate of change decreases dramatically as the moving parts are well "mated".


This no longer happens because the cylinder bores and the rings are now well-matched as built.

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It is my understanding that there should be no frictional wear in any speaker design, and thus all "break-in" would be of the type more akin to shoes than engines.


Again, this has already been debunked. Shoes are relatively short-lived compared to loudspeaker surrounds. Shoes often quite visibly  and permanently change shape. Speaker surrounds don't, except for environmental degradation which is indepdent of use.

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The scary thing about that is, IMHO, that if one accepts the proposal that some "good" speakers require break-in,


Only people who believe in audio myths take speaker break-in on faith.

The source of much of my information is people who have done extensive technical tests of the T/S parameters of loudspeakers, such as David Clark who invented the Dumax machine for the purpose. Clark has been a personal friend for about 35 years.

http://www.audioxpress.com/reviews/media/3...razella2154.pdf

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one is accepting that the materials used in their construction are ones which have significant changes in their elasticity over a relatively short amount of time.


Doesn't generally happen.

Several issues related to blind testing.

Reply #76
Especially audiophile class gear is usually able to provide even laboratory grade voltage from even dirtiest input sources. Huge caps and toroidal transformers often physically show off these capabilities. These circuits flatten ripple of many volts without the bat of an eyelid. How is the tiny mV lowpass effect of an artistically plaited mains cable supposed to make even the slightest difference here?


What you're describing is called "brute force" power supply filtering, and it is *never* used when the goal is the cleanest possible DC power. The alternative is to use a combination of moderate brute force filtering and solid state voltage regulation which is cheap and effective. Solid state regulation is *really* effective and requires only power with moderate brute force filtering.

Toroid power transformers have the technical advantage of vastly reduced hum fields. They are neither new nor are they the exclusive domain of high end audio. For example the old Bose 1800 power amp (circa 1980) used a toroid power transformer. Currently, toroids are widely used in relatively inexpensive audio gear such as many pieced by Behringer.

Several issues related to blind testing.

Reply #77
I did not want to express that toroidal transformers are an exclusive feature of high end gear. As you write, they are not. Neither did I intend to promote what you call "brute force" voltage regulation, you probably mean classic shunt based designs. Solid state solutions have become very capable in this regard. But if an AC is very flaky even the best IC can't continue to provide stable power out of nothing, so larger caps can make sense, where a lot of current is needed out of a potentially flaky AC source. And since high-end is usually over-engineered anyway, protection against input AC introduced distortion is standard.

My post just noted, that there is usually nothing to worry about AC wise especially in high end amplifiers. That doesn't exclude that moderately priced gear can't be just as fine in this (and many other) regards.

Several issues related to blind testing.

Reply #78
But if an AC is very flaky


IME, the most common form of flaky AC would be AC whose voltage is marginal, which big caps can't and won't help.

If you have noisy AC , big caps won't help, either.

If you have internmittant AC , there's only a fairly narrow window of duty cycle for the internmitant factor where bigger power supply caps could help.

Probably the best insurance against distortion caused by flaky AC is a power supply that drops a large voltage across the series regulator or uses a voltage regulator with a low drop-out voltage.

Many of the power supplies I see in high end equipment such as this:Rediculous Power Supply looks to me like its just for show.



Several issues related to blind testing.

Reply #79
Many of the power supplies I see in high end equipment such as this:Ridiculous Power Supply looks to me like its just for show.

The link doesn't go to where it's labeled, maybe this is better:

http://www.computeraudiophile.com/ps-audio-dliii-dac-review
Kevin Graf :: aka Speedskater

Several issues related to blind testing.

Reply #80
Placing the heat sinks right next to the electrolytic capacitors in the DLIII looks like bad engineering to me. But they are probably so ridiculously oversized, that they didn't care.

Probably still somewhat over-engineered, but much less hocus pocus while measuring exceptionally well:
and realized how off-topic this is getting. Feel free to split or remove, if you deem it necessary.

Several issues related to blind testing.

Reply #81
Why not carefully record the signal coming from the output terminals of your amp and provide samples for us to evaluate?


Let's say I did, you listened, and found the samples sound different. In that case, we're back to square one - what would you do with these results?

The recorded waveforms would be compared using software to identify where differences existed.  This could help in developing explanations for the differences in the perceived sound.

It is hard to imagine what could be adversely affecting your setup such that an ordinary power lead is not adequate for your amplifier to perform correctly.  Perhaps you reside near a powerful radio transmitter that creates abnormally high radio frequency voltages at your power outlet, that certain power leads are able to attenuate.

I note that ordinarily the filtering included in a modern hi-fi amplifier should be adequate to reject stray radio frequency signals present in the mains power supply.  [Or other noise for that matter.]

Jessenov1, there really is no need for you to bother your wife with a more rigorous ABX procedure.  You can simply record a few seconds of the audio source with power lead A in place, then the same few seconds with power lead B in place; and upload.  Then anyone interested could download the two versions and do their own comparisons.

Several issues related to blind testing.

Reply #82
How is shielding the last 1-2 meters from the outlet to the amplifier supposed to make a difference? The mains cable installation under your walls is unshielded and a much larger antenna. LessLoss cables aren't shielded either. They have just three separate wires with a large diameter with a conductive coating with higher resistance than the core.

Several issues related to blind testing.

Reply #83
Rpp3po, if the cables are of the design you have described then it is indeed hard to imagine how they could possibly have any benefit, under any circumstances, apart from spurious benefits such as robustness, and a funky look.  But jessenov1 may (conceivably) possess a power lead that does actually shunt radio frequencies, and an amplifier power supply unit that doesn't.

There is still the bottom line that any of these sorts of claims should be able to be backed up with high quality A B recordings of the audio output of the amplifiers that are claimed to have benefitted from the "super duper" power lead.  The websites for these special leads are strong on rhetoric, but silent when it comes to audio recordings.

Several issues related to blind testing.

Reply #84
The often cited skin-effect is a real phenomenon. It can make iron melt at just 50 Hz with an AC current, that could be 10 times higher as DC without the metal even getting warm. The higher the frequency the greater the current density at the outer surface of a conductor.

The funny thing is - and that's why I really don't know why in heaven cable manufacturers chose especially this phenomenon as a marketing vehicle - HF attenuation decreases with wire diameter. That means the best HF filter wires are the thinnest ones and precisely not the finger thick sausages you can buy at audiophile stores. Increased diameter means larger surface for the outer HF carrying layers and lower impedance for HF content.

LessLoss tries to sell, that a resistive but conducting outer layer would cancel out high frequencies, because they would gather in the resistive layer and get eliminated. But current gathers were it finds least resistance and will just move further towards the inside of the conductor, so you could just use a smaller diameter cable for the same "effect"! I would call the claimed filtering ability an outright lie. Any standard copper cable with an only slightly smaller diameter than LessLoss' would already be a better filter than their "solution". But many other "high end" cable manufacturers are sitting in the same boat here.

The only thing you can really do in a cable is active low pass filtering using capacitors or ICs. But that's the power converter of your amp/DAC usually doing anyway, it's far from black magic and very effective circuits are available since before I was even born.

If an overpriced piece of gear as jessenov1's sounds different with an actually filtering cable (unlike the LessLoss), something is really wrong with that gear and its makers don't understand even simplest electronics. Instead of dropping even more bucks for expensive cables, the malfunctioning unit should be exchanged for something properly working.

Several issues related to blind testing.

Reply #85
The often cited skin-effect is a real phenomenon. It can make iron melt at just 50 Hz with an AC current, that could be 10 times higher as DC without the metal even getting warm. The higher the frequency the greater the current density at the outer surface of a conductor.


Well, letsee. The skin depth calculator at http://www.microwaves101.com/encyclopedia/calsdepth.cfm says that the skin depth at 60 Hz is about 1/3 of an inch. So basically, for skin effect to be relevant at 60 Hz, the wire has to be pretty large.

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The funny thing is - and that's why I really don't know why in heaven cable manufacturers chose especially this phenomenon as a marketing vehicle - HF attenuation decreases with wire diameter.


Well, usually the cable manufacturers are claiming reduced HF attenuatioin. Hence the desire for a large cable diameter. Our buddy who is trying to sell power cables based on maximizing HF attenation, and your comment applies to this. Basically, he's got one heck of a long row to hoe.

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That means the best HF filter wires are the thinnest ones and precisely not the finger thick sausages you can buy at audiophile stores. Increased diameter means larger surface for the outer HF carrying layers and lower impedance for HF content.


HF attenuation is what the speaker cable guys want to claim that they are minimizing, so that works for them.

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LessLoss tries to sell, that a resistive but conducting outer layer would cancel out high frequencies, because they would gather in the resistive layer and get eliminated. But current gathers were it finds least resistance and will just move further towards the inside of the conductor, so you could just use a smaller diameter cable for the same "effect"!


But if you do that, you move the whole wire into the region of maximum conductivity within the skin deptn, and that counteracts the HF attenuation that he is trying to maximize.

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I would call the claimed filtering ability an outright lie. Any standard copper cable with an only slightly smaller diameter than LessLoss' would already be a better filter than their "solution". But many other "high end" cable manufacturers are sitting in the same boat here.


Totally agreed.


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he only thing you can really do in a cable is active low pass filtering using capacitors or ICs. But that's the power converter of your amp/DAC usually doing anyway, it's far from black magic and very effective circuits are available since before I was even born.


One of them is called a power transformer. Unless you try to build one with good HF response, they will be lossy at high frequencies - sort of like a filter... ;-)

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If an overpriced piece of gear as jessenov1's sounds different with an actually filtering cable (unlike the LessLoss), something is really wrong with that gear and its makers don't understand even simplest electronics. Instead of dropping even more bucks for expensive cables, the malfunctioning unit should be exchanged for something properly working.


Again totally agreed.

Several issues related to blind testing.

Reply #86
Well, letsee. The skin depth calculator at http://www.microwaves101.com/encyclopedia/calsdepth.cfm says that the skin depth at 60 Hz is about 1/3 of an inch. So basically, for skin effect to be relevant at 60 Hz, the wire has to be pretty large.

Well, yeah. But it can be a problem.


















In gigawatt-level power generation facilities...
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That means the best HF filter wires are the thinnest ones and precisely not the finger thick sausages you can buy at audiophile stores. Increased diameter means larger surface for the outer HF carrying layers and lower impedance for HF content.


HF attenuation is what the speaker cable guys want to claim that they are minimizing, so that works for them.


Yeah, but what they don't tell you is that with a teensy cable the excess attenuation is very, very small, and that it could go up to .01dB (GASP!) with that firehose-sized cable.

Arny, if you're going to be at AES, drop by the first bit of Ethan's workshop. The cognative stuff we were talking about over dinner is what I'm going to present, you could consider my part of the presentation as 'why do we think the same thing sounds different'.
-----
J. D. (jj) Johnston

Several issues related to blind testing.

Reply #87

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That means the best HF filter wires are the thinnest ones and precisely not the finger thick sausages you can buy at audiophile stores. Increased diameter means larger surface for the outer HF carrying layers and lower impedance for HF content.


HF attenuation is what the speaker cable guys want to claim that they are minimizing, so that works for them.


Yeah, but what they don't tell you is that with a teensy cable the excess attenuation is very, very small, and that it could go up to .01dB (GASP!) with that firehose-sized cable.

Arny, if you're going to be at AES, drop by the first bit of Ethan's workshop. The cognative stuff we were talking about over dinner is what I'm going to present, you could consider my part of the presentation as 'why do we think the same thing sounds different'.


Me at an AES? Surely you jest! I don't work for a megabucks company, just me, myself, and I!

Thanks again for the dinner and company in Detroit.

Several issues related to blind testing.

Reply #88
The real reason for my post is a test I conducted over the weekend, different aspects of which raised the qiestions in the OP.

First, I was comparing 2 power cords sighted, and thought the difference is there, but pretty insignificant, so these two weren't good candidates for blind test (which I would've most likely failed). My next thought was to compare one of the two (the one I prefer) to the stock cord, but finally, since I own several cords, I decided to pick for blind testing the one I thought sounded significantly different (worse) in sighted auditions.

Here's how test was organized:

1. Power cords were utilized on amplifier, going straight to the wall.

2. NO LEVEL MATCHING was performed - since both cords are of sufficient (and rather heavy) gauge, I don't see any need for that, and would dismiss without further discussion any notion that only loudness was affected by replacing the cords.

3. I enlisted my wife, who doesn't care for sound quality, but acknowledges visual appeal of certain components (including speakers), as helper.

4. I hanged old shower curtain, sufficiently opaque, from the ceiling using several pins so that it hid all components (but not speakers) from the sight at listening armchair. Wife was located behind the audio rack so she wasn't visible, either, and was instructed not to manifest herself in any way.

5. All of the above was performed in my listening room, which is 17'x11'x7.5' finished part of the basement, and is separated by a door from unfinished part. Some acoustic treatments present (first reflection points and couple of bass traps).

6. The procedure was as follows:

- I listened to short fragment (~15 sec.) of the same track sighted, with wife replacing cords A and B. Twice to each was enough for me to establish the differences. I determined that A is "better" and B is "worse".
- I left the room, closing the door. Wife was instructed to replace the cords in arbitrary order, making note of which one is currently plugged under sequential #. On wife's command, I returned to the room, and listened to exactly the same ~15 sec. fragment used during sighted audition. I made a note of which one, in my opinion - A or B - was used, under sequential #.
- Previous step was repeated 10 times, after which we compared notes. Intention was to continue, if results are unsatisfactory - but that turned out not to be the case, so test was stopped. It wasn't my intention to post it here, or anywhere else for that matter, otherwise it would continue.

In short, all 10 tries were successful, with me reliable identifying correct cord.

7. Relevant details of the system:

- Simaudio Supernova CD player
- Reference Line Preeminence 1B passive "preamp"
- Plinius SB-300 amplifier
- KEF Reference 3.2 speakers

8. Track used:

- Saturnus - beginning of the track "Embraced by Darkness", from "Veronica Decides to Die" album.


Now, back to my questions:

- what useful information can anyone but myself take away from that experiment?
- would anyone be willing to spend money on the same exact power cords, considering they are moderately expensive ($200-500 range used), to repeat the experiment?
- without using the same exact system - how would we know that another person's system is of equal resolution to mine, or at least of enough resolution to detect these differences?
- how would we know that another person's hearing is in good enough order?
- how would we account for possible bias NOT to hear any differences (seems pretty actual here)?


I'm all ears.


Can you prove that these power cords deliver a different electrical signal. Feed the 2 cords the exact same sine wave, and see if they make any changes to it that can be measured. then feed these cords a more realistic depiction of an AC signal (not a pure sine wave but cloe) and see if they affect the signal at all (apart from minor attenuation).
Finally, even if very slight changes in the electric supply at the end of these cords were measured, do you really believe your amplifier is so poorly manufactured it would alter its performance based on very slight fluctuations in voltage?

In other words, I don't believe for a moment there is any difference in the "sound" because of your 2 power cords. It's all in your head.
Either you have an overly active imagination, or it IS possible that one had a faulty contact with the plug point or the IEC receptacle that led to undesirable noise.

Just Joe


 

Several issues related to blind testing.

Reply #89
Can you prove that these power cords deliver a different electrical signal. Feed the 2 cords the exact same sine wave, and see if they make any changes to it that can be measured. then feed these cords a more realistic depiction of an AC signal (not a pure sine wave but cloe) and see if they affect the signal at all (apart from minor attenuation).
Finally, even if very slight changes in the electric supply at the end of these cords were measured, do you really believe your amplifier is so poorly manufactured it would alter its performance based on very slight fluctuations in voltage?

In other words, I don't believe for a moment there is any difference in the "sound" because of your 2 power cords. It's all in your head.
Either you have an overly active imagination, or it IS possible that one had a faulty contact with the plug point or the IEC receptacle that led to undesirable noise.


Current signal measurement technology is so sensitive that it is pretty much a given that any change will cause a measurable change in performance. Just loop a power cable differently, and it will be measurably different. Therefore, you have to ask a different question, which is whether or not the change makes a significant or audible difference. Hence the importance of reliable listening tests.

 
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