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Some cable measurments

post #1 of 31
Thread Starter 

 

 

Cables arrived


All cables



Audioquest



Audioquest-unboxed


Blue jeans


Tartan (Belden)


Stocky


Monoprice


Audioquest-Blue-jeans-AR



So the first order of business was to see how flat the response of each cable was.

First I generated a 40 second clip of white noise , I saved this as a Wav file and ran it through a spectrum analyser,
this is the reference point.

Then I burned the sample to CD and tested each of my CD players by playing it back and recording the analog
output to find the one most like the reference in shape and overall level. I settled on a Denon DCD910 analog
output which had the lowest deviation from the reference from 20 - 20K using stock cables.

Now I set about more critically measuring the response for the 4 cables I bought plus my own 77c specials.

To do this I played back the white noise sample and recorded it to my PC. To cater for random variations
I did each recording with each cable **10** times.

Each resulting wav file (70 of them, I tested the AQ cables aligned by the arrows and unaligned to test for the claimed directionality) was clipped to exactly 24.003628 seconds, each file is precisely
4.03 MB (4,234,284 bytes) all white noise. Due to careful editting ( the same protocol used for each file)
no wav file can differ from any other wav file in alignment by more than 1/1000th of a second.

Each file was then run through a spectrium analyser with 1024 sample points. Each spectrum was exported as a text file.

Then I started up Excel and I loaded each set of ten trials into a separate worksheet. This allowed me to see the Min, Max and Average levels for any frequency. Also it allowed me to see how much variation there was in any set of trials.

For instance the biggest difference between any two trials for any frequency with the Stock cables was 0.056db, the average difference between the max and min value for all frequencies for stock cables was 0.032 db.

Tartan cable 0.032 and 0.014
BlueJeans 0.047 and 0.016
AQ G-Snake Not Aligned 0.061 and 0.016
AQ G-Snake Aligned 0.038 and 0.013
AQ Sidewinder Not 0.050 and 0.014
AQ Sidewinder Aligned 0.044 and 0.014



The way that the recording was set up meant that each recoding was always at a slightly lower absolute level than the reference. Thus the best cable by definition at any frequency would have the highest value or the lowest attenuation from the reference. This made life easy.

In no case did any cable boost any frequency above the reference level.

Each set of 10 trials for each cable was averaged and the results fed into the worksheet with the reference values.

The maximum difference found between any two cables at any frequency point was 0.029db. The average difference between the best and worst cable across all frequencies was 0.012db. Note that the identity of best and worst cable did differ between frequencies.



Two of the cables I purchased are supposed to be directional. I recorded samples using the Audioquest G-Snake and Audioquest Sidewinder both correctly aligned and incorrectly aligned. I recorded 10 samples with each of the 4 combinations.

The G-Snake correctly aligned was in fact measurably different from the G-Snake incorrectly aligned. When I fed the results into SPSS the result was significant.

the maximum difference at any frequency was 0.022db and the average difference was 0.001db. For the Sidewinder the maximum difference was 0.011db and the average difference at all frequencies was 0.002db.


 


Do any of these cables roll off any more than any others. I tested the differences in level between 1K and 20K, 2K and 20K, 3K and 20K, 4K and 20K, 5K and 20K, 6K and 20K, 7K and 20K, 8K and 20K, 9K and 20K, 10K and 20K, 11K and 20K, 12K and 20K, 13K and 20K, 14K and 20K , 15K and 20K and finally between 16K and 20K.

The maximum difference in roll-offs between any two cables for any two frequencies was 0.016db



Stock(77c) vs Sidewinder ($60) , max diff 0.020db, ave difference 0.009 db
Stock(77c) vs G-Snake ($35) , max diff 0.013db, ave difference 0.003 db
Stock(77c) vs Blue Jeans($26.75), max diff 0.014db, ave difference 0.004 db
Stock(77c) vs Tartan ($5) , max diff 0.009db, ave difference 0.003 db

Tartan ($5) vs Sidewinder ($60) , max diff 0.014 , ave difference 0.006db
Tartan ($5) vs G-Snake ($35) , max diff 0.009 , ave difference 0.003db
Tartan ($5) vs BJC ($26.75) , max diff 0.007 , ave difference 0.002db

BJC($26.75) vs Sidewinder($60), max diff 0.011 , ave difference 0.005db
BJC($26.75) vs G-Snake ($35), max diff 0.012 , ave difference 0.004db

Sidewinder vs G-Snake max diff 0.018 , ave difference 0.009db


 


I just loaded my dataset up into SPSS and ran a repeated measures ANOVA with cable type as a covariate and some ANOVAs between cables.

The results show that for these cables there was no significant effect on changing cable, no cable was significantly different from any other. Frequency also did not alter the result, no cable was significantly different at any frequency.

The other result was that there was much more variation between trials than between cables, this is entirely predictable as a cable is a passive device and and ADC is not, so my decision to average 10 trials was justified. Amusingly the repeated measures variation was significant. Remember this was a variation of no more than 0.056db between any two trials for any given cable at any frequency, but when you have 4600+ data points little differences become statistically significant.



 


I just tested the Sidewinder vs the stock cable using a cymbal crash with lots of harmonics and transients.


Originally Posted by nick_charles View Post

Stock and Sidewinder

Complex set of square waves from 10hz to 10000hz, maximum difference 0.027, average diference 0.0028


 

New test of Sidewinder vs Stock cable with cymbal crash
-------------------------------------------------------

Max difference 0.102340db average difference 0.003539db

Average overall signal
Stock------------ Sidey ------------ difference
-37.743888 ******-37.742651 ****-0.001237







This graph shows the stock cable with the sidewinder dropped by 20db so you can see the patterns




For the Anoraks - the distribution of differences against frequency




And finally difference vs signal level


 

With many thanks to Maxvla I have a 0.5m Zu Oxyfuel on loan for testing. I ran the cymbals test and compared the results against the stock cable.

The max variation was 0.08db at 129hz and -54db, the average difference is 0.001408db.


 
These were done using a five second sample of digital silence and recorded back via the ADC. I ran the tests ( 10 trials) for both stocky and the Zu Oxyfuel.

Average Noise levels Stock -95.7975db.........Zu Oxyfuel -95.8598db

This is quite close to the theoretical noise levels for 16 bit systems



Low frequency noise pattern
---------------------------



I also did a few tests on my $2.11 Monoprice and the $60 Sidewinder. Interestingly each cable has a distinct noise pattern with specific low level spikes at different frequencies.

To place these noise figures in context, here is the noise juxtaposed against the cymbals crash.




In absolute terms the stock cable is the worst for noise with three low frequency spikes between -78 and -76db ,- Monoprice is as good as the most expensive cables for noise, but I will need to run 10 trials.



This text is between a DH labs BL-1 Series II Silver Plated Copper cable and the solid copper Sidewinder with the cymbals sample.

Maximum difference is at 19488hz where the difference is -75.3254db to
-75.3695db i.e a difference of 0.0441db, average difference from 20 to 20K is 0.0014 db. See graph below



 

Noise pattern fro DH Labs cable -  low levels of background noise at an average of -95.63db and a few spikes at ~ -86db

 

White Noise tests 20 - 20K
-------------------------
Maximum difference at any frequency = -0.00436 db , the Monoprice cable has less attenuation at all frequencies, the average difference = - 0.00266 db.

No graph posted, no point , impossible to see the deviations.


 


For these tests I made a slight change to my protocol I used a 16K FFT analysis which translates to 7K sample points. Since I have all the original wav files I may redo them with a smaller FFT later if it is a bust.

Noise differences ranged from
Freq (Hz)SilverCopperdiff
1418-101.0146-92.8366-8.1781
1421-100.8319-95.2206-5.6112
1416-100.7780-95.2324-5.5456
541-99.8670-96.9008-2.9662
15111-97.3906-95.1398-2.2508
538-99.8972-97.7621-2.1351

to

Freq (Hz)SilverCopperdiff
721-79.8842-95.098515.2143
301-80.4885-95.816915.3284
299-79.8153-95.577015.7617
719-79.4283-95.246215.8179
121-65.8202-82.408316.5881
600-79.7158-96.373216.6574
118-66.7071-83.371416.6642
363-80.7216-98.865118.1435
358-73.5922-99.016525.4243
361-70.9139-98.449627.5356


Silver Average Noise level = -97.8339 db
Copper Average Noise level = -99.5085 db
Average difference = 1.6746 db


 

Averages
silvercopperdiff
-35.1717-35.19860.0269


Range of differences from

Freq (Hz)silvercopperdiff
10864-31.2361-31.1511-0.0850
12037-34.3904-34.3113-0.0791
19598-64.2617-64.1956-0.0661
17821-60.0233-59.9590-0.0643
18050-53.2547-53.2003-0.0544
19668-64.8693-64.8172-0.0521


to

Freq (Hz) silvercopperdiff

17870-58.5000-58.59830.0983
12029-32.1039-32.20500.1011
19679-68.4469-68.55140.1045
19663-66.2487-66.38070.1321
121-53.2967-53.58550.2888
118-55.8897-56.20280.3131





Differences vs frequency

 

Average difference levels from 3hz to 20Khz

Silver copper diff
-12.2418-12.26050.0188


Range of differences
Freq(Hz)Silvercopperdiff
19237-12.7538-12.76280.0090
19902-13.4680-13.47800.0100
19862-13.2093-13.21950.0102
19657-13.5434-13.55390.0105

to
Freq(Hz)Silvercopperdiff
12880-12.7116-12.73470.0231
16422-13.0786-13.10170.0232
8454-12.6774-12.70070.0233
8064-11.8652-11.88850.0233
18594-13.4783-13.50170.0234
17286-13.2584-13.28180.0234
11666-13.2417-13.26540.0237
7580-11.4654-11.48910.0237
19113-13.3649-13.38870.0238
10933-12.7789-12.80300.0241

Differences vs frequency
-----------------------




Pattern of Frs against Frequency




 



 


Edited by nick_charles - 3/1/11 at 3:56pm
post #2 of 31
Thread Starter 

..

post #3 of 31

It sounds like you're saying the difference between cables is completely and measurably insignificant. 

post #4 of 31

Thanks nick_charles. Wasn't this thread locked?

post #5 of 31

Clearly your audio interfaces and measurement tools do not have golden ears - try putting a shakti stone on them

post #6 of 31
Thread Starter 
Quote:
Originally Posted by dan1son View Post

It sounds like you're saying the difference between cables is completely and measurably insignificant. 



 For those cables measured under a specific set of conditions the differences were very small and unlikely to be audible

post #7 of 31
Thread Starter 

It was - I asked for it to be unlocked as it had been moved to this subforum and the admin kindly obliged .

 

Quote:
Originally Posted by xnor View Post

Thanks nick_charles. Wasn't this thread locked?



 


Edited by nick_charles - 3/3/11 at 2:49pm
post #8 of 31

Thank you, solid data on such a debated subject is always a good thing.

post #9 of 31

I auditioned a few cables for my home system many years ago.  I decided to go by what I can hear, not what I read.

 

I listened to mainly Straightwire brand cables.  From the bottom of the line to the $150 for 3' RCA interconnect (about 10 years ago).

 

They were connected to the best equipment the sound store had.  The store personel were very obliging.

 

Much to my surprise, the sound did improve as you went up the price scale!  Very subtle but audible differences.  After the "$100" pair, the sound difference was less noticable (with my ears).  So I went with the $100 cabling, and have been very happy with it over the years.

 

Different brands of color tvs can have identical specs, but the picture can be quite different.

 

If you can't hear a difference between components, buy what is reasonable.  But try out stuff, you just may hear a difference that will enhance your enjoyment of your music.

post #10 of 31
Quote:
Originally Posted by fredpb View Post

Different brands of color tvs can have identical specs, but the picture can be quite different.

 



This is irrelevant, I think. The TV specs are not "measured" as in the way the cables were... an equal analogy would be a test involving pointing a camera at two different televisions with the same specs in equal lighting/room conditions and measuring the output (which would, if graphed, show very measurable differences). Let's not forget that TVs are so much more complex, even two of the exact model can have big variations. (even if their "specs" are the same!)

post #11 of 31
TV specs are not a good comparison. It's the same as with amps - you can get different sounds with the same output specs, but that means that you haven't considered all potential measurements. For instance, the output impedance curve makes a significant difference, but you rarely see that included. Two 50W amps with different output impedance curves will sound different. Because the only published spec is the 50W of power does not mean that there are paranormal influences at play. It simply means that you haven't considered everything. I am certain that two TVs with different pictures could be quantified if you measure other things.

Cables have been analyzed every which way for more than a century. You will find differences in high power applications as well as with high frequencies. However, no significant difference has ever been found at audio frequencies.

That raises the odd proposition that science sometimes applies to cables, like in high power transmission lines, but then doesn't apply at all for audio frequencies. Even worse for believers, this plays out in the real world. You can use science and measurements for a cable that carries gigahertz radio frequencies to an antenna. It works as predicted. But then you have to turn around and claim that science doesn't work.

All the cables "differences" are adequately explained by psychological phenomena. This is why no one has ever passed a blinded listening test. Placebo is real, in a sense. People have felt better when given sugar pills. Recently, it was shown that placebo aided healing. Those who believe really do hear a difference. I think they're sincere. But it does not follow that a psychological difference means a difference in the real world. This is why unsighted listening tests always show no difference.
post #12 of 31

Nick, that is a lot of tests that you have done in the interest of audio science.  Thanks.  Some aspects of your test are very interesting while others need to read with a caution.  I really do not like the average number as they always have a tendency to hide the truth or present the wrong picture as can be seen all of the average numbers are very very minimal as compare to other stats.  This is specially true in wave science as they can cancel each other and present a normal picture.  I use this analogy before to illustrate this point:  if I put your head in an oven and your feet in a freezer, will you average out to feel warm and fussy?  Also, all of you cables are basically in the same price range.  It would be very interesting to see some really high end cable to see if they do vary, like some transparent reference or Kimble reference etc.

 

Uncle Erik, I think you made a good point with regard to the measurement science.  Sometimes if we haven't consider everything, then to draw conclusion that there is no difference in terms of overall cable difference is a scientific mistake.  However, based on the samples that Nick used, he can still draw some limited conclusions that there are very little difference in term of frequency among certain cable that he uses.

 

However, I have to disagree with you on the subject of placebo effect.  I agree that placebo is real but just because it is real it doesn't account for all observed experimental effect (i.e. IV or independent variable).  A good experimental design always consider and control for all other non IV effects including placebo effect, experimenter bias, other dv or dependent variables.  A good experimental design will allow a researcher to draw conclusion that changes are due to the subject of interest and in this case sound difference in cable and not other variables including placebo.  I have done many research in neuroscience, brain wave, P300, evoke potential etc.  The human brain is very good at noticing differences.  It can notice changes in brainwave that machine cannot detect.  So precise that I can alter changes in the Delta frequency by 0.1 hertz and the human brain can notice the difference immediately.  My point is when our brain notices sound difference in cable, I doubted that we at present has that science of measurement to measure things like PRat, sound stage, attacks, dynamics, warm/cold, decay etc.  The frequency measurement is only one aspect of sound but it doesn't reveal all characteristics of what we hear in audiophile.  And you really cannot just simple attribute any perceived changes in sound to placebo.

 

post #13 of 31
Thread Starter 
Quote:
Originally Posted by Jalo View Post

Nick, that is a lot of tests that you have done in the interest of audio science.  Thanks.  Some aspects of your test are very interesting while others need to read with a caution.  I really do not like the average number as they always have a tendency to hide the truth or present the wrong picture as can be seen all of the average numbers are very very minimal as compare to other stats.  

 

I used averages to adjust for inter-measurement variation, any measurement system has a certain amount of random error. If I did just one test on each the random error could easily distort the conclusions. Averaging across 10 trials for each cable makes the data much more reliable. I am working on the assumption that the cables behave more consistently across trials. If we do not accept that assumption then we cannot do any sensible tests on cables of any sort ever.

 

 

The frequency measurement is only one aspect of sound but it doesn't reveal all characteristics of what we hear in audiophile.  

 

FR is however the most important audio parameter, it is the most defining element of tone.

post #14 of 31

First thanks a lot Nick_Charles, as said above this kind of test is too rare not to be praised when we actually have some done properly.

 

Second, I was wondering if that would be a problem to give an indication of the variation's range. Averaging sounds reasonable, but an indication of the delta could be interesting. Given the average difference displayed by your tests, it would probably only corroborate your results anyway. 
 

EDIT : Nevermind, I reread the graphs and you've done just what I was suggesting. My bad for the lack of attention.

 

Quote:
Originally Posted by nick_charles View Post
I used averages to adjust for inter-measurement variation, any measurement system has a certain amount of random error. If I did just one test on each the random error could easily distort the conclusions. Averaging across 10 trials for each cable makes the data much more reliable. I am working on the assumption that the cables behave more consistently across trials. If we do not accept that assumption then we cannot do any sensible tests on cables of any sort ever.

 


 


Edited by frenchbat - 3/6/11 at 11:37pm
post #15 of 31
Quote:
Originally Posted by nick_charles View Post
Quote:
Originally Posted by Jalo View Post

Nick, that is a lot of tests that you have done in the interest of audio science.  Thanks.  Some aspects of your test are very interesting while others need to read with a caution.  I really do not like the average number as they always have a tendency to hide the truth or present the wrong picture as can be seen all of the average numbers are very very minimal as compare to other stats.  

 

I used averages to adjust for inter-measurement variation, any measurement system has a certain amount of random error. If I did just one test on each the random error could easily distort the conclusions. Averaging across 10 trials for each cable makes the data much more reliable. I am working on the assumption that the cables behave more consistently across trials. If we do not accept that assumption then we cannot do any sensible tests on cables of any sort ever.

 

 

The frequency measurement is only one aspect of sound but it doesn't reveal all characteristics of what we hear in audiophile.  

 

FR is however the most important audio parameter, it is the most defining element of tone.


 


Nick, the problem is inherent in the design of this study, as you decided to do multiple sampling (i.e 10x) you are going to incur inter-measurement variation and other random errors that has to be control for.  So you are forced to use averaging to minimize any random errors.  And unfortunately in this case, the actual variations of the inter and intra value for each cable and between cables may be much smaller than the inter-measurement and random errors and by doing averaging to adjust for the error, you are destroying the actual value also.  It is like if a measurement has a mean of 50 and a max/min value of 0 and 100.  And if you have a standard error of +/- 100, that will make any number meaningless.  Or if you have a measurement of 100 and the standard deviation is also 100, then there will be no meaning to any numbers measured.

 

In fact, I really do not think you need to do multiple sampling.  You are right to assume that cables behave more consistent and as such, you could have a single trial design (ABAB) with much longer recordings with multiple sampling points.  This way, you can avoid introducing inter-measurement variation and other random errors and at the same time you can establish internal consistency by comparing a cable performance over time at the same frequency point.  Once you can establish experimental reliability/internal consistency for each cable, then when you compare across cables, the value will be more meaningful.  

 

Anyway, I do respect your care in each step you take in your exercise.

 

 

 

 

 

 

 

 

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