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In Reply to: RE: Drawing the line posted by Joe Roberts on September 20, 2015 at 21:56:43
Pierre called Dave and said he thinks Dave labeled one of the wires wrong. In other words, he got caught.
Indeed I was caught but the comment was that the "spool" from the reversed wire must have gone through an extra de-reeling procedure.
I do know that pierre and ron (bauman) have a series of very specific test tracks they use to listen for direction and iirc the differences they hear is all in the attack of the notes. Sure some will argue that a real engineer should be able to measure this and it is important to note that both Pierre and Ron are top level real engineers.
I have another friend Johannes who could nail the relative phase of a SE amp to a speaker. This doesn't have anything to do with absolute phase but rather the idea that air is harder to compress than it is to rarify which sets up a situation to create an even order distortion. When you combine this even order distortion generator with another (a SE tube output stage) suddenly you get very different distortion spectra based on phase. Johannes would simply instruct me to listen to the bass and it was easy to hear. I admit I heard differences but in no way could I ever nail it like Johannes could.
(important thing to note for all you absolute phase junkies is simply swappping speaker cables polarity is not a fair way to reverse phase)
dave
Follow Ups:
"I have another friend Johannes who could nail the relative phase of a SE amp to a speaker. This doesn't have anything to do with absolute phase but rather the idea that air is harder to compress than it is to rarify which sets up a situation to create an even order distortion. When you combine this even order distortion generator with another (a SE tube output stage) suddenly you get very different distortion spectra based on phase. Johannes would simply instruct me to listen to the bass and it was easy to hear."
This is an interesting point, since indeed there must be some degree of asymmetry in a sound wave, since air pressures can increase arbitrarily high, but they cannot decrease below zero. On the other hand, as I learned from a Wiki page, a sound level of 94dB corresponds to a fluctuation of about 1 part in 100,000 around atmospheric pressure, so one would have thought any non-linearities associated with this effect would be really tiny; at something like the 0.001% level or so. This looks as if it could be rather negligible in comparison to the order of magnitude of distortions from the amplifier, and from the speaker itself.
In fact, I think I have seen astonishingly large distortion figures quoted for loudspeakers. Isn't it possible that, if there is some audible effect associated with the phase choice for the connection of the amplifier to the speaker, it is much more likely to be associated with asymmetries in the way the loudspeaker itself responds to being driven outwards, as opposed to being driven inwards? I would have thought that such kinds of mechanical asymmetries in the behaviour of the loudspeaker cone would be overwhelmingly more important than non-linearities in the way the acoustic wave propagates in the air.
I was a bit puzzled by you final remark: "important thing to note for all you absolute phase junkies is simply swappping speaker cables polarity is not a fair way to reverse phase". Until I reached that point in your message, I thought that you precisely were talking about what happens if you reverse the two speaker wires? What did you mean, if not that?
Just to make sure we don't go off on a complete tangent, this discussion has absolutely nothing to do with the discussion of the phase of one speaker relative to the other in a stereo system! The effect you are wanting to talk about is, I believe, what is normally called "absolute phase," and could be discussed purely in a mono audio system. It is concerned with the issue of whether a transient attack at the beginning of an impulsive sound will drive the speaker cone forwards, towards the listener, or instead drive the cone backwards, away from the listener. This effect would precisely be reversed if one switched over the two wires going to the speaker. Thus I am puzzled by your sentence apparently saying that that is not what you were talking about.
Anyway, in summary, I could believe that absolute phase has a chance to be an audible phenomenon, because of non-linearities and asymmetries in the system. But I would have thought non-linearities and asymmetries in the mechanical response of the speaker cone would be far more likely to be at play here than non-linearities in the propagation of sound waves in air.
Chris
By absolute phase I indeed meant swapping polarity of both channels at the same time and not one channel in relation to the other.
The air thing was under the assumption of mainly bass (due to the large amounts of air movement) and an asymmetrical design (not an open baffle) where there is a pressure build up in a back chamber. I was using lowthers in rear loaded horn at the time.
dave
"By absolute phase I indeed meant swapping polarity of both channels at the same time and not one channel in relation to the other."
OK, good...we are on the same wavelength (so to speak)!
I think, though, that the percentage change in air pressure around the quiescent 1 atmosphere is still absolutely tiny, even for loud low-frequency sounds.
But the asymmetry of the loudspeaker response, together with the asymmetry of the SET amplifier response (because of its predominant 2nd harmonic distortion) would certainly, I imagine, lead to the possibility of either addition, or subtraction, of the two asymmetries, depending on the polarity of the connection to the speaker. I'd put my money on that, rather than asymmetry in the acoustic propagation of the air wave itself.
Chris
It was presented to me as the non-linearity of air as being the cause. What other aspect of a speaker design could generate even distortion?
A slightly off center voice coil in the gap?
suspension / spider?
dave
"It was presented to me as the non-linearity of air as being the cause. What other aspect of a speaker design could generate even distortion?
A slightly off center voice coil in the gap? suspension / spider?"
Quite possibly.
I tried quickly googling around a bit, and distortion figures for loudspeakers seem to be commonly up to the order of several percent, especially at low frequencies (presumably because the amplitude of the cone movement gets larger at low frequencies). These distortions include substantial second harmonic, which implies asymmetry.
So if the second harmonic distortion of the speaker were comparable with the second harmonic distortion of the amplifier, then I suppose there could be a significant and audible difference if the two asymmetries were combining on the one hand in unison, versus on the other hand in opposition.
By contrast, I think the non-linearities in the acoustic propagation in air will be way down, for any kind of realistic sound pressure level. (The "maximum possible" sound level in air at standard ambient pressure, based on supposing the pressure reaches down to zero in the troughs, is about 194 dB. which is pretty loud!!!. A loudspeaker, on the other hand, will be hitting one or other of its end-of-range mechanical movement limitations at hugely lower sound levels. Thus asymmetries at normal listening levels will be likely to be much bigger for speakers than for air, since the ratio of typical cone movement over maximum possible cone movement is a much bigger fraction than the ratio of air pressure change over ambient air pressure.)
Chris
Silly wabbits...It would never happen with the UPOCC copper or silver wires. Less Grainy so it solved the directional issues.
megasat16
It is the Neotech UP-OCC hook-up wire I use the most in my projects and it's highly directional.
Neotech UP-OCC
Highly recommend, this is some of my favorite, best sounding wire I have encountered. I can not hear if it is directional or not.
Indeed I was caught but the comment was that the "spool" from the reversed
wire must have gone through an extra de-reeling procedure.
============
Slick footwork, Slagle!
But obviously they did not need your silly labels anyway.
JR
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Free your mind and your ass will follow -- Parliament/Funkadelic
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