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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: RE: Objective Measurement Results for Cables posted by andy19191 on October 2, 2007 at 01:58:00:
...or is this an 'a priori' rejection?
andy19191 wrote:
"I was referring to the later unlabelled graphs and in the context of my post the point was that measured minute differences are inaudible and the text was not overly reliable."
Which unlabeled graphs?
Minute differences? I wouldn't think that distortion that is at -38 to -48 dB is 'minute', especially since there are more than one distortion product showing at or near those levels. If there were just 4 products at that level, then the total distortion would be in the range of approx. -32 to -42 dB, hardly something that one could call 'minute' or wish away as if it were insignificant.
And what in the world does "text not overly reliable" mean? Is this just another way of saying "I don't believe these people, and refuse to even entertain their data or arguments? How scientific is that?
andy19191 wrote:
"Anyway, if the CV engineers have provided a model for the effect then the physics is presumably understood. What is it?"
They modeled the amount of distortion that would occur with a particular multitone pattern due to the air and due to the horn placed on the driver (not including the driver's own distortions), and then compared that to an actual measurement of a typical driver, and an experimental one they were working on. Other work has modeled what the distortion pattern would look like with a certain (very low) amount of distortion, such as with a power amp. Finally, the measurements in the Newell and Howard paper show what the distortion levels are for a load resistor, and this provides a residual distortion level that is very similar to that of the previously modeled low amount of distortion.
No one has yet proposed a model for the distortion created by the amplifier/cable/loudspeaker combinations (that I am aware of). I would suspect that some one at CV or JBL might be working on it, and I have a few ideas myself, as well as having tried taking my own measurements of similar and related conditions, and seeing levels of distortion higher than load resistors and very short lengths of cable/wire.
Keep in mind that the length of the speaker cable under test in the Newell and Howard paper is 6M, or almost 20 feet.
Jon Risch
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Follow Ups
- Answer really wanted... - Jon Risch 17:06:06 10/02/07 (2)
- RE: Answer really wanted... - andy19191 05:09:42 10/04/07 (1)
- Another imaginative Objectivist! - bjh 14:28:12 10/04/07 (0)
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