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The validity of ABX testing - Page 8

post #106 of 109
7/24/09 at 12:44pm
Quote:
Originally Posted by mike1127 View Post
I don't think you are aware what "linear" means. "Linear" does not refer to the shape of the frequency response plot. Any RLC network is linear. Refer to any textbook about "Linear Systems and Signals." Amazon.com: Linear Systems and Signals (The Oxford Series in Electrical and Computer Engineering) (9780195158335): B. P. Lathi: Books
You are arguing a useless point. Cables as such are very well known systems. If you want to claim that there might be some non-linearity in cables then fine - state the nature and the reasons why it does not show up in thd+n or frequency response measurements. After all, such are extremely easy to measure and harmonic distortion directly relates to (non-)linearity of circuits.

Just continuing to say "there might be some non-linearity or difference to transient response" is just babble.

Quote:
Originally Posted by mike1127 View Post
It's a model. Nothing exactly matches the model.
Fine. To the extent that we can measure the parameters of cables, the measurements match the theory.

Quote:
Originally Posted by mike1127 View Post
In a linear system, transient and frequency response have equivalent information, so your statement that transients "match the models" is meaningless. Of course they match the model. In the model. Not in reality. (Not exactly.)
Again, to the extent of measurements. oh, and <citation needed> as far as cables are concerned!

Quote:
Originally Posted by mike1127 View Post
Why do you assume I'm not?
Lack of posted measurements?

You are just making up strawmen of doubt of what is or might not be known about very simple physical systems. This is called FUD-ing.
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post #107 of 109
7/24/09 at 1:43pm
Quote:
Originally Posted by sanderx View Post

Just continuing to say "there might be some non-linearity or difference to transient response" is just babble.
No, it's serious thinking about an issue. What is the deal with you? It's like you want to shoot down everything we say, point by point, so you demand a list of references after each statement that makes you uncomfortable. My statement was not given as proof. Most of us are exploring this issue from different angles and have various areas of expertise. Some things we are just learning about. If your only interest in joining this discussion is to take pot shots at individual statements, then I respectfully ask you to leave it.

Quote:
Fine. To the extent that we can measure the parameters of cables, the measurements match the theory.
You don't write like an engineer or scientist. Of course the "measurements of the parameters match the theory" because the measurements are the parameters of the theory.

There's an important philosophical point here. Nothing completely matches the model. Work as an engineer for 20 years and you'll start to appreciate that more. Do statistical spacecraft navigation, which depends on the tenuous nature of the link between models and reality, and learn a few things.
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post #108 of 109
7/24/09 at 4:10pm
A couple of comments.

1) Nobody is going to agree on the best way to "expose" subjects to the different cables. This is why the subject should have the OPTION to listen however he/she chooses. If he wants his Bose 9000 speakers and to listen for 1 week to each, then fine. The only thing the experiment needs to do is ensure blinding.

2) If you have sensitive/accurate enough equipment, then you can find differences in ANY cable. You can find miniscule differences in resistance, capacitance, and inductance in cables of the same make/model! So the question is how much is actually audible? AFAIK, there is no table that equates A mohms, B uF, and C mH to audibility. So I'm not sure how useful it is to argue that cables do or don't measure differently.

To someone who is experienced with these types of measurements with respect to audio, the differences in SPL, low-pass, and high-pass characteristics created by differences in cable LCR woud likely be interpreted as insignificant. to someone who wants to believe that cables make a difference, a difference of 100 nanofarads is HUGE. 100!!!
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post #109 of 109
7/24/09 at 7:58pm
Quote:
Originally Posted by sanderx View Post
Actually, all audio cables measure the same. As an example, lets compare an ideal wire (which has no impedance and hence no attenuation at any frequency) to a clearly inadequate and bad joice of interconnect. Like say 20 meters of AWG 28 wire (R=213ohm/km) with shunt capacity of 160pf/m. So the cable has a resistance of 4.26 ohm and capacitance of 3.2nF. As a low-pass filter its corner frequency is 11.675MHz. Voltage gain Av=1/sqrt(1-(f/f0)^2), so at 20Khz the gain difference between the ideal cable and our "cleary inadequate" cable would be 1-1/sqrt(1+(20000/11675000)^2) = ~ 1.467 * 10^-6 . This is -116dB. For a more realistic, AWG14 cable with capacitance of 100pf/m @ 20m this will be -180 dB.

Cable testing is all about "Physics says there is no difference, but we can hear it!"

Physics is all WRONG!

Of course I'm absolutely kidding. I agree with you completely. My apologies everyone for this useless post.
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