IPB

Welcome Guest ( Log In | Register )

3 Pages V  < 1 2 3  
Reply to this topicStart new topic
A collection of anti-hifi [ripoff] information, cables, tweaks, expensive equipment...
Pio2001
post Sep 19 2003, 22:06
Post #51


Moderator


Group: Super Moderator
Posts: 3936
Joined: 29-September 01
Member No.: 73



Skin Effect Summary.

The skin effect in a cylindrical conductor has two components :

The resistance is increased because the usable section is reduced.
The inductance is also changed.

I calculated the effect on the resistance.
Here is the formula giving the resistivity R' in IS units (ohms per meter). Note it, it is very difficult to find ! It comes from the "Traité d'éléctromagnétisme" de l'Ecole Polytechnique de Lausanne.

R=1/(2*Pi*radius^2*gamma)*RE(k*radius*J0(k*radius)/J1(k*radius))

Where
Radius is the radius of the cable in meters
Gamma the conductivity of the metal in ohm^-1*Meters^-1
RE (x) is the real part of x
plus or minus k = (1-j)/d
j is the imaginary number such as j^2=-1
d is the penetration depht in meters defined as
d= square root of (2/(omega*µ*gamma))
omega is 2*Pi*f where f is the frequency in Hertz
µ is the magnetic permeability in Henrys per meter

JN(kr) (N integer from 0 to infinite) is the Bessel function of order N defined as
JN(kr) = (kr/2)^N * [1/N!-1/(1!(N+1)!)(kr/2)^2+1/(2!(N+2)!)(kr/2)^4-1/(3!(N+3)!)(kr/2)^6+ ......]

For a speaker cable of 3 meters (6 meters the two ways), this gives

Section / R at 20 Hz / R at 20 kHz
0.75 mm2 / 0.128 Ohm / 0.132 Ohm
1.5 mm2 / 0.0640 Ohm / 0.0703 Ohm
2.5 mm2 / 0.0384 Ohm / 0.0484 Ohm
4 mm2 / 0.0239 Ohm / 0.0362 Ohm
6 mm2 / 0.0160 Ohm / 0.0287 Ohm
12 mm2 / 0.00804 Ohm / 0.0196 Ohm

075 mm2 is your standard 1200 W zip cord
2.5 mm2 is the big zip cord (must be rated around 3600 W)
4 and 6 mm2 are common in audiophile speaker cables.
I gave 12 mm2 a shot because I used some 12 mm2 cables in my tests (to be published after this), though it is quite impossible to find.

I then computer the treble loss, between 20 Hz and 20 kHz, if the speaker is 8 Ohm at any frequency, and the ampli 0.08 Ohm.

0.75 mm2 : -0.0042 dB
1.5 mm2 : -0.0067 dB
2.5 mm2 : -0.011 dB
4 mm2 : -0.013 dB
6 mm2 : -0.014 dB
12 mm2 : -0.012 dB

The loss is maximal at 6 mm2. Below, the skin effect is decreses because the cable is so small that the current fills its section completely even at 20 kHz. Above, the effect decreases, because the resistance of the cable becomes negligible at any frequency. This maximal loss, about on hundredth of a dB, is completely inaudible.

This page came to a similar conclusion : http://www.audioholics.com/techtips/audiop...fect_Cables.htm, using different methods.
Go to the top of the page
+Quote Post
Audible!
post Sep 19 2003, 23:29
Post #52





Group: Members
Posts: 533
Joined: 28-June 03
From: CA, USA
Member No.: 7426



Very informative post Pio!

QUOTE
The usual rec.audio excuse from those who claim differences is that blind testing doesn't work because there is too much pressure to perform. On the other hand many of the same folks say that they can easlily tell the difference between hearing cable A in one store and cable B in another store.


Bwahahahahahaha!!! That's hilarious! edit: Pio is not all caps

This post has been edited by Audible!: Sep 20 2003, 01:32
Go to the top of the page
+Quote Post
ChrisGranger
post Sep 20 2003, 01:01
Post #53





Group: Members
Posts: 50
Joined: 31-March 03
From: Winnipeg, Canada
Member No.: 5772



QUOTE (Audible! @ Sep 19 2003, 05:29 PM)
QUOTE
The usual rec.audio excuse from those who claim differences is that blind testing doesn't work because there is too much pressure to perform. On the other hand many of the same folks say that they can easlily tell the difference between hearing cable A in one store and cable B in another store.

Good god, that's just idiotic. smile.gif Comparing different systems in different store listening rooms and using that to make a claim that you can hear the differences between cables? laugh.gif The expensive cable makers need people this foolish in order to sell their $100+ /m stuff.

As an aside, auditioning stereos in a dealer's showroom is just plain pointless too. The only way to tell if you'll be happy with a piece of gear is to take it home and use it in your room, in your system. The differences between a dealer's room acoustics and your own listening room's probably outweigh the differences in the sound of two pieces of equipment.


--------------------
Folding@Home HydrogenAudio.org Team ID# 32639
http://folding.stanford.edu/
Go to the top of the page
+Quote Post
Pio2001
post Sep 20 2003, 01:23
Post #54


Moderator


Group: Super Moderator
Posts: 3936
Joined: 29-September 01
Member No.: 73



Speaker cables recordings.

Don't try this at home unless you have a diploma about electric engineering !!!

I recorded the speaker signal delivered by my ampli at the ampli plugs and at the speaker plugs, with three different speaker cables, with a coaxial cable connecting the speaker plugs into the line in of my DAT deck (47 kOhm standard line in).
The tricky part : if you mistake the + for the -, you fry your amplifier connecting the positive speaker out to the ground of your recorder !

The samples are mono, because I didn't have enough coax to reach both speakers.
They are available at http://www.hydrogenaudio.org/forums/index....=13401&st=0
I made 4 samples.
-Recorded from the ampli (Arcam Diva A85), with double A2 cable (12 mm2 solid core copper), about 4 meters long, with a Dynaudio Gemini speaker (4 ohm).
-Same thing recorded from the speaker
-QED Qudos cable (4 mm2 stranded copper), 4.5 meters, speaker side
-Same thing with 6.5 meters of cable

The RMS levels (over 123 seconds of recordings, while you have only 20 seconds samples) are :
Ampli : -16.64 dB
Speaker / A2 : -16.64 dB
Speaker / QED short : -16.68 dB
Speaker / QED long : -16.70 dB


Compared spectrum analysis.

I made Samplitude draw the spectrums over the 123 seconds recordings, with the same settings. I then superimposed them in additive mode and colors inverted.
As a result, you get the A2, QED long and QED short spectrums compared to the ampli spectrum.
White lines are identical levels. When you see red pixels at the top, then the speaker signal is louder (the cable emphasizes this frequency). If you can see cyan pixels, the ampli signal is louder (the cable attenuates this frequency). Look closely in order to see the tiny pixels !
One pixel equals 0.1 dB. I counted the pixels moving the layers step by step until the pixels change colors in Corel Photopaint.



Above, the A2 cable gives up to +0.15 dB between 3 and 8 kHz, and up to -0.2 dB above 8 kHz



Above, the short QED gives up to -0.2 dB above 8 kHz



Above, the long QED gives up to -0.3 dB above 8 kHz

If we assume that the speaker impedance can fall as low as 3 Ohm, and that the ampli impedance is 0.08 Ohm, then, the long QED cable being about 0.07 Ohm ,skin effect (20 kHz) taken into account (4mm2, 13 meters), just to get an idea (anyway the real speaker impedance is unknown), it should give
U'/U=(3+0.08)/(3+0.07+0.08)=0.98
Loss = 20 log (0.98) = -0.2 dB

Thus the differences measured can be explained by the speaker impedance and the cable resistance only.

ABX Listening tests on the samples (8 sessions each ) :
Long Qed vs Ampli signal : failure (I don't remember my bad score)
A2 vs ampli signal : failure (5/8).


Edit : pictures links

This post has been edited by Pio2001: Nov 17 2008, 21:35
Go to the top of the page
+Quote Post
Audible!
post Sep 20 2003, 01:37
Post #55





Group: Members
Posts: 533
Joined: 28-June 03
From: CA, USA
Member No.: 7426



QUOTE
Loss = 20 log (0.98) = -0.2 dB

But, but, but, but, my psychic chihuahua hear a 0.2dB drop easy!!!!
wink.gif rolleyes.gif biggrin.gif laugh.gif
Go to the top of the page
+Quote Post
Pio2001
post Sep 20 2003, 03:10
Post #56


Moderator


Group: Super Moderator
Posts: 3936
Joined: 29-September 01
Member No.: 73



Then, looking at him you can ABX ?
Go to the top of the page
+Quote Post
Audible!
post Sep 20 2003, 03:37
Post #57





Group: Members
Posts: 533
Joined: 28-June 03
From: CA, USA
Member No.: 7426



QUOTE
Then, looking at him you can ABX ?

Well, not under controlled conditions and only when I'm not looking at him. Then he tilts his head slightly to the side to indicate to me which cable he prefers. Of course, if I look back to see which side he meant, he straightens up and I can't tell.
I know for sure that he does though, because he told me in a dream.
Go to the top of the page
+Quote Post
ger@co
post Sep 20 2003, 06:01
Post #58





Group: Members
Posts: 110
Joined: 20-January 02
From: Canada
Member No.: 1088



QUOTE (sthayashi @ Sep 17 2003, 10:38 PM .)
Most of my speaker hookups are using what I think is a copper/aluminum hybrid wire. One wire is silver in color (and I suspect it's aluminum), the other is copper.


If you hook the copper wire to the positive pole and the silver wire to the negative pole, I don't think the quality of the sound will be affected, because one of the wires (the silver one) is the ground.

Later

This post has been edited by ger@co: Sep 20 2003, 06:07


--------------------
"Did you just say he contacts you through a bird? Did I just hear you say that?" Sonny Valerio (Cliff Gorman). Ghost Dog: The Way of the Samurai.
Go to the top of the page
+Quote Post
lucpes
post Sep 20 2003, 19:27
Post #59





Group: Members
Posts: 517
Joined: 9-October 01
Member No.: 254



The audio signal is alternative current, so it doesn't matter what good conductive material (decent gauge) you hook the speakers on the ground/active with as long as the speakers are in the proper phase.

also check this link: http://www.pcavtech.com/abx/abx_wire.htm

Another link: http://sound.westhost.com/cables.htm

However, the "warm fuzzy feeling" is non ABX-able, and costs a lot in some situations... maybe a head wire check is required smile.gif

edit: added 'good conductive' to material

This post has been edited by lucpes: Sep 20 2003, 21:23
Go to the top of the page
+Quote Post
Audible!
post Sep 20 2003, 21:27
Post #60





Group: Members
Posts: 533
Joined: 28-June 03
From: CA, USA
Member No.: 7426



QUOTE
However, the "warm fuzzy feeling" is non ABX-able, and costs a lot in some situations... maybe a head wire check is required

laugh.gif Comedy Gold!
Go to the top of the page
+Quote Post
Pio2001
post Sep 20 2003, 21:50
Post #61


Moderator


Group: Super Moderator
Posts: 3936
Joined: 29-September 01
Member No.: 73



QUOTE (lucpes @ Sep 20 2003, 09:27 PM)
The audio signal is alternative current, so it doesn't matter what good conductive material (decent gauge) you hook the speakers on the ground/active with as long as the speakers are in the proper phase.

The fact that the current is alternative is not a good argument, because in line connections, the current is alternative too, and the choice of the wire (core or shield) to plug is crucial.
The main argument for speaker cable immunity is the extremely low output impedance of the power amplifier : around 0.08 Ohm, compared to the 470 Ohm standard of line outputs...
I realised, recording the speaker output into the line input, that I had to push the volume quite loud in order to get a decent line level into the speaker output. Audio amplifiers are mostly current amplifiers, that can be interpreted as "impedance decreasers". They can amplify the voltage too, but that's not what makes them "power" amplifiers.
Go to the top of the page
+Quote Post
lucpes
post Sep 20 2003, 22:05
Post #62





Group: Members
Posts: 517
Joined: 9-October 01
Member No.: 254



QUOTE (ger@co @ Sep 20 2003, 05:01 AM)
If you hook the copper wire to the positive pole and the silver wire to the negative pole, I don't think the quality of the sound will be affected, because one of the wires (the silver one) is the ground.

@Pio2001
QUOTE
The fact that the current is alternative is not a good argument, because in line connections, the current is alternative too, and the choice of the wire (core or shield) to plug is crucial.


Sorry, I was trying to counter the 'quality won't change if you use the silver wire to the ground' post.

This post has been edited by lucpes: Sep 20 2003, 22:06
Go to the top of the page
+Quote Post
Welly Wu
post Sep 20 2003, 22:10
Post #63





Group: Banned
Posts: 22
Joined: 3-January 03
Member No.: 4384



I certainly respect the opinions of my fellow HA members on matters relating to cross-platform / cross-format psychoacoustic audio compression. I agree with the notion that spending more capital resources to acquire "better" audio equipment does not necessarily mean "better" sound quality. However, I agree to disagree that with respect to "audiophile" cables: juxstaposing a $20 dollar Radio Shack IC versus my $170 dollar DiMarzio M-PATH IC does produce a dramatic increase in sound quality. Furthermore, I am a proponent of carefully defining one's specific audio goals prior to investing any capital; thus research is critical. I do believe that more carefully thought out and constructed cables do deliver beneficial increases in sound quality. I just do not want to quantify these perceptual "gains" in cold, hard, monetary figures. I listen to music to relax and to be entertained. If there is to be had a "better" cable that can help me to achieve that level of satisfaction, then I will commit my time to research it and I may possibly commit my own money to acquire it. These are just my opinions.

By the way, I compared two power cords with my recently acquired and refurbished Denon DVD 2900 universal player. I listened to "cheap" stock power cord for one week. The results were very good but I felt that my music was a bit "congested" and "dry." So, I did my research into power cords al la Head-Fi, AudioAsylum, and AudioGon. I came to the conclusion that the PS Audio XStream Plus power cords could help me eliminate those sonic imperfections. I ordered them and I have noticed an ever growing and dramatic improvement in sound reproduction qualities with my Denon DVD 2900. I am very happy with the results delivered by the PS Audio XStream Plus power cord.
Go to the top of the page
+Quote Post
lucpes
post Sep 20 2003, 22:25
Post #64





Group: Members
Posts: 517
Joined: 9-October 01
Member No.: 254



QUOTE (Welly Wu @ Sep 20 2003, 09:10 PM)
Furthermore, I am a proponent of carefully defining one's specific audio goals prior to investing any capital; thus research is critical.  I do believe that more carefully thought out and constructed cables do deliver beneficial increases in sound quality.

Here are some themes to research: http://www.audiotweaks.com/collection_ascend.htm ph34r.gif
Go to the top of the page
+Quote Post
fewtch
post Sep 20 2003, 22:25
Post #65





Group: Members
Posts: 1460
Joined: 5-February 02
From: Seattle WA. USA
Member No.: 1261



Welly Wu,

I'll allow that cables may make a difference in some cases (probably due to capacitance issues, better shielding, etc. that could be interpreted as improvements). However, how the hell do you think a power cord will make a difference? I'm not sure you realize what the current is traveling through before it hits the wall socket -- are you? You think it's "audiophile grade" wiring in there?

If you rewired your house completely from the transformer outside to the wall sockets, you get my respect. Otherwise, I have to say "complete BS" as far as power cords go... you're imagining it, period.

This post has been edited by fewtch: Sep 20 2003, 22:39


--------------------
Bring back dynamic range... www.loudnessrace.net
Go to the top of the page
+Quote Post
lucpes
post Sep 20 2003, 22:29
Post #66





Group: Members
Posts: 517
Joined: 9-October 01
Member No.: 254



QUOTE (Welly Wu @ Sep 20 2003, 09:10 PM)
...I have noticed an ever growing and dramatic improvement in sound reproduction qualities with my Denon DVD 2900.  I am very happy with the results delivered by the PS Audio XStream Plus power cord.

Listening to the emotional audio platitudes is such great sport!! So mild, yet flaccid, with warm buttery overtones, eh? Such precipitous velvety fuzzylicious bass too!
Go to the top of the page
+Quote Post
Audible!
post Sep 20 2003, 22:35
Post #67





Group: Members
Posts: 533
Joined: 28-June 03
From: CA, USA
Member No.: 7426



QUOTE
However, I agree to disagree that with respect to "audiophile" cables: juxstaposing a $20 dollar Radio Shack IC versus my $170 dollar DiMarzio M-PATH IC does produce a dramatic increase in sound quality.


That's a pretty bold claim, but not particularly unusual.
What length of cable are we talking about here, and have you ever subjected yourself to blind or double blind conditions to see if you can verify this claim with cables sight unseen?

I have never witnessed or read about a situation where individuals could distinguish a difference in audio quality when subjected to verifiably stringent conditions. In fact, quite the contrary - every test of this type that I have ever seen has shown exactly the opposite.
Go to the top of the page
+Quote Post
Pio2001
post Sep 21 2003, 00:04
Post #68


Moderator


Group: Super Moderator
Posts: 3936
Joined: 29-September 01
Member No.: 73



QUOTE (Welly Wu @ Sep 21 2003, 12:10 AM)
juxstaposing a $20 dollar Radio Shack IC versus my $170 dollar DiMarzio M-PATH IC does produce a dramatic increase in sound quality.

To Welly Wu and all who answered : the basic and absolute rule in HydrogenAudio.org is to only make statements that are backuped by a scientific proof.
See the two links at the top of the FAQ, under "Hydrogenaudio.org's basic rules on listening tests".

Statements are divided into two categories.
1- Statements that have been tested in the past and became part of HydrogenAudio recommendations, like "Lame provides better quality than Fronhaufer encoders at high bitrates", or "joint stereo provides better quality than pure stereo". For these ones, it is admitted to restate them without providing other proof than a suggestion to read the FAQ.
2 - Statemens that either go against previous ones (like "Lame APS gives me a better result than MPC Standard"), or that are new and untested (like "a power cable improved the sound of my CD Player").

The second category of statement is only admitted with a proof, that is usually a double blind test with statistically valid results (example: recognition of the right source 8 times out of 8). It may also be a measurment showing an obviously audioble difference (-20 dB noise, +5 dB medium boost, etc).

The placebo effect has been proven, read for example http://www.nytimes.com/library/tech/99/12/...les/23down.html

QUOTE
"They describe huge changes and they say, 'Oh my God, John, tell me you can hear that difference,'" Mr. Dunlavy said. The trick is the technicians never actually change the cables, he said, adding, "It's the placebo effect."


So we can't think anythink about someone claiming he can hear "huge differences". I myself already thought that I could hear "huge differences" between some devices (24/96 vs 44.1/16 recording of a vinyl), and changed my mind later, no hearing anymore any difference. This is also true for professionnal people, like sound engineers ( http://www.hydrogenaudio.org/forums/index....t=75#entry48032 ), or audiophile critics (quote above).

Therefore the only way to gather information is to test the audible differences. Perform a blind test and see if you can recognize your cable not knowing if it is plugged or not, at least 7 times out of 8 (only one mistake allowed).
I also thought I could tell the recordings of my cables, posted above from each other. I tried in blind, I failed. I though I heard one while it was the other playing etc...
Most audiophile say that all differences vanish in blind tests because of the stress caused by the test. But in your case, a "dramatic increase in sound quality" can't be masked by "stress", and should turn the blind test very easy and fast.

Please HA members, when someone makes an unsupported statement about sound, recall the term of service number 8, until we setup a short and informative article about blind tests. Just answering that they are wrong won't help. The fact that blind tests are compulsory here must be recalled at once in order to avoid flaming...

EDIT : ...people don't know it and thus naturally discuss their impressions about sound, like in any other forum. The real point is that the rule is different here. The point that this is a valid approach was discussed elsewhere and is off topic in this thread. Here, the pertinent information is that it is the rule.
Go to the top of the page
+Quote Post

3 Pages V  < 1 2 3
Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 



RSS Lo-Fi Version Time is now: 21st November 2014 - 10:04