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In Reply to: RE: The relevant point is that both of them rely upon switch boxes -nt posted by E-Stat on June 21, 2010 at 08:48:01
Sadly, it in not possible to conduct a comparative test without switching between the two things under comparison.
While It is possible to have a person at each end to switch the physical cables, this is not as fast and as others doing blind testing have found, the people doing the switching can intentionally or more often unintentionally affect the test consistence with what they belive.
For example(s) cold fusion the conclusions from the Princeton University paranormal research (pear) work.
To remove that operator effect, a mechanical switcher was used, which from an engineering view would have added an insignificant alteration in the “in vs out” signals or amplifier loading.
One cannot make such a switch that has no effect in the most skeptical view, all one can do in the engineering view is make that alteration a very very small effect relative to the differences (between cable properties in this case) one is looking for.
Thus, having a switch which represented a few inches of the best cable under consideration, when that cable is 10 to 30 feet long, represents an insignificant effect.
Insignificant especially when compared to what the test (and other similar tests) generally revealed about how terribly strong the automatic “filling in the blanks” part of our conscious experience of “hearing” is, compared to what one can honestly draw from the acoustic signal alone.
This was generally humbling to the attendees, maybe like realizing one’s own “response curve” more or less followed the equal loudness contours instead of being FLAT. But, hey, that’s the only thing we are aware of, what we experience and like many things we know no differently until someone actually measures it.
Best,
Tom
Follow Ups:
Sadly, it in not possible to conduct a comparative test without switching between the two things under comparison.Uh, yeah. Do we have anyone in the audience who doesn't understand this? :)
While It is possible to have a person at each end to switch the physical cables, this is not as fast and as others doing blind testing have found, the people doing the switching can intentionally or more often unintentionally affect the test consistence with what they belive.
And the assumptions keep rolling in... I've used my wife (a university pharmacy professor) to proctor changes. First of all, she doesn't even know which cable should be "better". Secondly, and more importantly, I've left the room through one door and she enters through another where there is no opportunity for visual cues. And no, she doesn't stamp her foot once with one choice and twice for another. :)
Thus, having a switch which represented a few inches of the best cable under consideration, when that cable is 10 to 30 feet long, represents an insignificant effect.
Your response is a perfect example of the pitfalls of substituting assumptions for empirical data. The obvious concern is not the effect of a "few inches" of cable. It is that the switch exhibits crosstalk such that you are not comparing A with B. You are comparing AB with AB. All that you had to do to answer my repeated questions about first establishing a control is reply "No, I did not use a control. I assume that the box exhibits perfect isolation between the cables and that it has no possible effect on the outcome.
I guess your test system is likewise an irrelevant part of the test. I'll stop here since you seem to have difficulty with simple, direct answers. Thanks anyway!
rw
Edits: 06/22/10
> Secondly, and more importantly, I've left the room through one door and she enters through another where there is no opportunity for visual cues. And no, she doesn't stamp her foot once with one choice and twice for another. :) <
LOL!
I've found a similar method to work wonderfully. Doesn't require a switchbox, allows for long term listening and is foolproof. That's all that matters to me.
To be honest, I don’t know what you’re asking for, bare with me here, I am in engineering. When I say insignificant, to me that means something in particular, it doesn’t mean it’s gone but very small.
You ask about measurements, this is how one concludes what insignificant is relative to what your trying to measure, for electrical components I use one of these;
http://www.testequipmentconnection.com/index.php?main_page=search&search=4274A&gclid=CK3Ar9-StKICFQQMDQodfmWg5g
For networks, I use one of these;
http://www.testequipmentdepot.com/usedequipment/hewlettpackard/spectrumanalyzers/3562a.htm?gclid=CKiLiqmStKICFVD75wod2iBA4g
Or a TEF-20 to measure driver impedance curves as with the tower. Also, a network simulator program which with some steering can derive the equivalent circuits for most drivers and deal with a drivers as the load for a filter network etc.
It is relatively easy to measure the signal at each end of a cable too, even using music as the test signal, without a switcher too. That way if one is in doubt about the signal being altered and if it is according to network theory, one can examine the difference and see how close that is to predicted based on measured parameters.
AS for the listening system used back in the cable tests, the amplifiers were several, a threshold stasis (mine) a mcintosh 240, a QSC pl-236, in the amp listening a chevin something and several crowns were added.
The speakers were an early version of a full range horn product used in commercial sound.
The goal (for the last 12 years) was hi fidelity for a large group of people, all the problems one faces get worse as the size of the room increases. My solution was to make a full range horn system where all of the drivers combined coherently into one source with no lobes, no crossover phase shift, constant directivity and high output, all things desirable for home hifi too..
The closest “hifi speaker I have measured “in time” was a manger which was admittedly somewhat better than the SH-50. The SH-50 does go about 30 dB louder, two octaves lower and has about 1/1000 the distortion at livingroom listening levels and does reproduce a square wave “out front” for more than a decade spanning both crossovers. While not aimed at hifi, they are about as close as commercial sound has at the moment and a few have found their way into livingrooms, search here SH-50.
A more typical large scale “hifi” use;
http://audioheritage.csdco.com/vbulletin/showthread.php?26261-IMAX-cinema-sound&p=265081
Best,
Tom Danley
rw
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