Re: Re: Re: Re: Re: Re: Here we go again
The point Pavel is that even if I do not hear a difference, this does prove nothing. Put it another way, if the estimated error had been in the order or -120 dB to say something, I shouldn't bother a split millisecond about the coil issue.
I may as well make a test, but to ease things I should select a square wave and a coil/no-coil switch. Perhaps subtle differences not obvious within the confussion of actual musical passages stand out more clearly.
Rodolfo
PMA said:
....
I do cordially suggest for you to try it and make your own point of view ...
The point Pavel is that even if I do not hear a difference, this does prove nothing. Put it another way, if the estimated error had been in the order or -120 dB to say something, I shouldn't bother a split millisecond about the coil issue.
I may as well make a test, but to ease things I should select a square wave and a coil/no-coil switch. Perhaps subtle differences not obvious within the confussion of actual musical passages stand out more clearly.
Rodolfo
Re: Re: Re: Re: Re: Here we go again
Hi Rodolfo,
We should not disregard linear frequency response "distortions" or deviations, but we should put them in the proper context. Suppose, for the moment, that the audibility of coils had only to do with linear effects, such as frequency response. So, for the moment, we are not talking about nonlinearities, etc.
While it is true that we should not ignore such linear frequency response deviations, it would seem that their effect would be no different, or more or less important, than differences in frequency response from one amplifier to another. In other words, from this perspective, the high-frequency bandlimiting of the amplifier plays the same kind of role as that of the inductor.
In this case, an amplifier with a wider inherent bandwidth, but which uses a coil, might be expected to sound the same as an amplifier of somewhat less inherent bandwidth that does not use a coil (i.e., their frequency and phase responses, as seen at the speaker, might be identical, even though arrived at differently).
For me, if coils can cause an audible degradation (and I do not rule that out), I do not think it is because of linear frequency response effects, but rather as a consequence of some nonlinear or coupling effect going on, or something that falls in the X-factor category where we just don't yet understand it.
Cheers,
Bob
ingrast said:
Hi Rodolfo,
We should not disregard linear frequency response "distortions" or deviations, but we should put them in the proper context. Suppose, for the moment, that the audibility of coils had only to do with linear effects, such as frequency response. So, for the moment, we are not talking about nonlinearities, etc.
While it is true that we should not ignore such linear frequency response deviations, it would seem that their effect would be no different, or more or less important, than differences in frequency response from one amplifier to another. In other words, from this perspective, the high-frequency bandlimiting of the amplifier plays the same kind of role as that of the inductor.
In this case, an amplifier with a wider inherent bandwidth, but which uses a coil, might be expected to sound the same as an amplifier of somewhat less inherent bandwidth that does not use a coil (i.e., their frequency and phase responses, as seen at the speaker, might be identical, even though arrived at differently).
For me, if coils can cause an audible degradation (and I do not rule that out), I do not think it is because of linear frequency response effects, but rather as a consequence of some nonlinear or coupling effect going on, or something that falls in the X-factor category where we just don't yet understand it.
Cheers,
Bob
Speaker cable inductance
Well, after reviewing my files, I have found it. Some 4 years ago, we made a measurement of respectable set of speaker cables, of their inductance and capacitance. With a good, bridge instrument. An inductance of the speaker cables was in range from 0.19 to 0.83 uH per 1m length. OK, 1uH coil might not be negligible in value compared to that of a cable.
Well, after reviewing my files, I have found it. Some 4 years ago, we made a measurement of respectable set of speaker cables, of their inductance and capacitance. With a good, bridge instrument. An inductance of the speaker cables was in range from 0.19 to 0.83 uH per 1m length. OK, 1uH coil might not be negligible in value compared to that of a cable.
john curl said:
This is a complete nonsense for a zip cord.
I would guess that this was a "well respected source":
http://www.empiricalaudio.com/frclarity7.html
andy_c said:Just to put some numbers to this, I'm reposting a chart from an article reviewing speaker cables, where they measured the R, L and C of the cables. These numbers are per foot. The article was at audioholics.com
If the amps used were monoblocks and placed right behind the speakers using a very short length of the Goertz wire and no output coil, it seems like one could get some pretty low series inductance values between the amp output and the speaker. Would the improvement be audible? Dunno.
Hi Andy,
Thanks for posting this valuable information. I do, however, think that it may be subject to some mis-interpretation by those not familiar with transmission line theory.
The inductances here are the implicit inductances that go into making up the impedance of the transmission line. The impedance of a transmission line is SQRT (L/C). So, for example, if you have 40 pf/ft and 0.1 uH/ft, you end up with an impedance of 50 ohms.
BUT, the implicit inductance is NOT the same as a series inductance that would mitigate destabilizing effects of a capacitor at the far end. The mitigating inductance of a transmission line (i.e., speaker cable) is more akin to the leakage inductance of a transformer, and will typically be much less.
Take a one-ft length of this stuff and short the end, then measure the inductance as seen at the open end. You will get a much smaller number.
Bob
Hi John,
Remember we were talking earlier about the apparent discrepancy in the Bryston output inductor values between their schematics and the Stereophile output impedance measurements? I asked James Tanner about this over in another forum. Here is the thread. Looks like schematics of the 7B and 14B are in error. They actually use 1uH rather than 2uH. But the 4B we were discussing earlier is really 2uH. So this suggests the Stereophile output impedance measurement of the 4B may be incorrect (actually too low, strangely enough).
Remember we were talking earlier about the apparent discrepancy in the Bryston output inductor values between their schematics and the Stereophile output impedance measurements? I asked James Tanner about this over in another forum. Here is the thread. Looks like schematics of the 7B and 14B are in error. They actually use 1uH rather than 2uH. But the 4B we were discussing earlier is really 2uH. So this suggests the Stereophile output impedance measurement of the 4B may be incorrect (actually too low, strangely enough).
No, it was 'Audioholics' Online AV Magazine. I simply 'Googled' "inductance zip cord" and this was the first thing that came up. I must admit that I read through it quickly, and Jneutron only PEER REVIEWED this paper.
What is says is: " LTOT (sounds like total inductance to me)= .0304uH/ft for Zip Cord. "
Now, is it a misprint? Is it the REAL total L? or is it only 1/2 of total L? Inquiring minds need to know and understand this.
What is says is: " LTOT (sounds like total inductance to me)= .0304uH/ft for Zip Cord. "
Now, is it a misprint? Is it the REAL total L? or is it only 1/2 of total L? Inquiring minds need to know and understand this.
john curl said:
Where did you get those figures John? The formulas in this link
http://www.audioholics.com/education/cables/calculating-cable-inductance-of-zip-cord
is part of the article somebody linked to earlier and are supposedly reviewed by John Escallier, who I understand to be jneutron. Using these forumula for extreme case where where the conductors touch each other (ie. B/A = 2), we get the theoretical minimum inductance for zip cord, the value being 0.11 uH/feet. Any practical zip cord would thus have a higher value. (The figure 0.03 uH/feet is mentioned, but that is not the total inductance).
(It should be noted, however, that the article is not quite clear about definitions, so have assumed B to be the distance between conductors centres, not the minumum distance between their surfaces, since that is the usual definition. )
Edit: I saw your new post after writing mine and you seem to have used the same article. I don't think it is a misprint, but you seem to have misread it. The article says "Li1 + Li2 = .0304 uH/ft for Zip Cord". That is the internal impedance, and if you read the beginning of the same line you see that to get the total inductance you must also add the mutual inductance which is .281*Log(B/A).
john curl said:
Hi John,
What I saw was this:
"LTOT = .281*Log(B/A) + Li1 + Li2 where Li1 + Li2 = .0304 uH/ft for Zip Cord"
So it looks like there are three terms, and the .0304 uH/ft is only the sum of the last two of the three terms (Li1 and Li2).
Edit: Oops, it looks like I just repeated what Christer said
Bob Cordell said:
Hi Bob,
I agree that trying to equate these parameters to lumped parameters, even at low frequencies, can be dicey.
I've been playing around with this in SPICE using the LTRA model, which is a true distributed transmission line model. Its limitations are that R, L, C and G must be constant with frequency (so skin effect can't be modeled for example). There are some neat articles about LTRA by some Berkeley guys here and here. I've attached a sim that shows how to use this model in LTSpice. The circuit on the right is the Stereophile simulated speaker from Ken Kantor.
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