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KikeG
 
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Default Why DBTs in audio do not deliver (was: Finally ... The Furutech CD-do-something)

(ludovic mirabel) wrote in message ...

We're talking about Greenhill old test not because it is perfect but
because no better COMPONENT COMPARISON tests are available. In fact
none have been published according to MTry's and Ramplemann's
bibliographies since 1990.


I gave a link to one at my previous message, related to soundcards and
a DAT (
http://www.hydrogenaudio.org/index.p...hl=pitch&st=0&
). It revealed some audible differences. Soundcards and DATs are audio
components, aren't they?

There's another one concerning just a soundcard he
http://www.hydrogenaudio.org/index.p...d6a76f1f8d0738
It finally revealed no audible differences.

About Greenhill's test and level differences:

PINK NOISE signal: 10 out of 11 participants got the maximum possible
correct answers: 15 out of 15 ie. 100%. ONE was 1 guess short. He got
only 14 out of 15.
When MUSIC was used as a signal 1 (ONE) listener got 15 corrects,
1 got 14 and one 12. The others had results ranging from 7 and 8
through 10 to (1) 11.
My question is: was there are ANY significant difference between
those two sets of results? Is there a *possibility* that music
disagrees with ABX or ABX with music?
I would aoppreciate it if would try and make it simple leaving
"confidence levels" and such out of it. You're talking to ordinary
audiophiles wanting to hear if your test will help them decide what
COMPONENTS to buy.


Citing Greenhill's article, refering to 24-gauge cable: "Its 1.8-ohm
resistance resulted in a 1.76-dB insertion loss with an 8-ohm
resistive load".

I don't know if this has been addressed before, but this 1.76 dB loss
corresponds to a pure resistive load. Speakers are quite different
from pure resistive loads, in the sense that their impedance varies
with frequency, being this impedance higher than the nominal in most
part of the spectrum. So, this 1.8 ohm in series with a real world
speaker would definitely result in an attenuation below 1.76 dB over
the whole audible spectrum on a wideband signal. Also, the attenuation
will vary with frequency, so that max attenuation will be at the
frequencies where the speaker impedance is minimum, and there will be
little attenuation at frequencies where speaker impedance is maximum.
So, the whole attenuation will depend on the spectrum of music used.
There's a possibility that choral music has most of its content at
frequencies where attenuation was not high, but it's difficult to know
without having access to the actual music used and the speaker
impedance curve.

Said, that, I tried yesterday to ABX an 1.7 dB wideband (frequency
constant) level attenuation on a musical sample. Result: 60/60 on a
couple of minutes, Not a single miss. It is obvious to hear, but one
could argue I'm trained.

Despite that, I claim that, any person that does not have serious
auditive problems, would be able to ABX a 1.7 dB wideband level
difference on any kind of real-world music, being trained or not in
ABX testing, just taking a couple of minutes to explain him the basics
of ABX testing.

Now, you make a point in that you have to be trained in ABXing to be
good at it. I say that you have to be trained in *any* method you use
to be good at it. Also, ABX testing per se requires little training.
What takes more training is to learn to detect reliabily some kind of
differences, whether you use ABX or not. Serious ABX training is
required just for detecting very subtle differences, just like in
every other area where high performance is required.

And finally, an analogy: you can't evaluate driving comfort in cars
without driving them, so you have to learn how to drive in order to
evaluate driving comfort. Driving a car is the only reliable way to
evaluate driving confort, whether you are good at it or not. And
such...