Reply
 
Thread Tools Display Modes
  #1   Report Post  
Midlant
 
Posts: n/a
Default cabling explained

Mr Lampen of Belden Electronics Division answered this posts on
"rec.audio.high-end" some time back. I hope this answers your questions
in regards to cable quality and length of runs whether interconnect or
speaker.
John


In article , Lou Anschuetz

writes:

OTOH, I can understand how he comes to the conclusions he
comes to. As someone with 25 years in IT, I have thrown away dozens
of supposedly competently designed SCSI/serial
cables that don't work. SCSI cables in particular are darn
hard to to get right for the newer higher speeds - and it
all seems to come down to how the cable(s) is insulated.

I also agree that this doesn't necessarily have anything to do
with audio transmission. However, IMHO, this business about
insulation continues to bedevil me. Since it does play havoc
with digital signal transmission, it seems to me hard to leap
to an absolute conclusion that it has no effect in the analog
audio world. No hard science on this yet, but it is a very active
field of research...


Well, I'm on a plane flying from Beijing to Hong Kong (and on to
Melbourne,
Australia) listening to Chinese Pop music in my headphones, and nothing
to do,
so I thought I would just jump in here!

Why do some cables work on signal X but not with signal Y? The answer
is
simple: wavelength. (The answer is simple, the explanation is a little
more
complicated.) Every signal, data, audio, video, etc, etc. occupies one
or more
frequencies. Each frequency has a wavelength, that is, there is an
electromagnetic wave moving down the cable that has a specific length.
This
can be calculated by dividing 300,000,000 by that frequency. (The
answer comes
out in meters, so us backwards USA types have to multiply by 3.28 to get
to
feet.)

If you look at 20 kHz (or you can pick any frequency you want), that
gives you
a wavelength of 15,000 meters (about 9 miles). What that means is that
the
impedance of the cable (how it reacts to frequencies) is of no
consequence.
Most engineers agree that the ACTUAL critical distance is 1/4 wavelength
which
is, in this case 2.25 miles, still too far to have any effect. This
distance is
also affect by the plastic around the conductors. This affects the
speed
"velocity" of the signal. (Signals only move at the speed of light in a
vaccum,
i.e. outer space. If you ever have a chance to check out your speakers
there,
be sure and give me a complete test report!)

Let's say your interconnect cables were the worst ever made (a "velocity
of
propagation" of 50%). You would multiply the wavelength by 50% so we're
down
to 1.12 miles. Anybody with one mile speaker cables? data cable? mic
cables?
video cables? audio cable? Well, yes, there are people with AUDIO
cables of
that length or more. They call themselves the TELEPHONE COMPANY. And
the
maximum distance between your home and your central office is 13,000 ft.
(over
2 miles).

But the twisted pairs they use (even fancy new ones, Category 3) are not
the
correct impedance (too expensive). Luckily, the audio on your phone
ends at
3500 Hz. You can calculate the bandwidth and see you can go VERY far
before
you need to have impedance-specific twisted pairs. I'll be honest and
tell you
that I don't know the actual occupied bandwidth of a 56k data signal. (I
think
it's NRZI Manchester Coded, that would make it 28kHz bandwidth.) I'm
sure you
note that this puts it on the edge for performance if you are far from
the
central office, and you can't always get dialup that fast. And you'll
understand why in the USA, the FCC now mandates that all telephone
wiring must
be Category 3 or better. Category 3 is impedance-specific (100 ohms)
data
cable. But there are other reasons the FCC made this a standard besides
distance. The signals either go back to the source or simply stop in the
cable
(called "standing waves") and then radiate all that reflected energegy
into
cables around them. That's why the phone company is trying to use data
cable,
to avoid "alien crosstalk" (between cables).

That's why you can use crappy interconnect cables that come free with
your
receiver and it all sounds pretty good. They aren't long enough to make
a
difference. As long as you have continuity (electrical signal flow),
you'll be
just fine. But what if you use that cable for DIGITAL (i.e. S/PDIF).
Suddenly
we're sampling that audio at 44.1kHz (like a CD), and the bandwidth is
defined
as 128 times the sampling (5.6448 MHz, if memory serves). Let's just
use 6 MHz
to make it easy. (If you don't want easy, do it yourself.)

300,000,000 divided by 6,000,000 = 50 meters. 1/4-wavelength = 12.5
meters or
about 44 feet. How long is your cable? 3 ft? 6 ft? No problem. It's
still
not LONG enough to make a difference. Now, if you want to send S/PDIF
to the
other end of the house, that might be 40 ft. or even more. What would
you do?
Be sure and use cable which is the correct impedance. S/PDIF requires
75 ohm
cable (75 ohm cable has the lowest signal loss "attenuation" so it is
used for
many applications where low loss is required).

What if you get a really long piece of crappy cable? What impedance is
it?
Who knows!! And what will happen is that the signal, which will require
a 75
ohm "transmission line" and not see it. The farther it is away from 75
ohm the
more the signal will be REFLECTED back to the source and not get to the
other
end. This is called "return loss" in the cable world. You send me the
actual
impedance of your cable and I can calculate the mismatch and the return
loss.

But, if you get the right 75 ohm cable, how far can you go? It depends
on the
size of the wire (gage) in the middle. Let's assume it is a 20 AWG
center
(such as Belden 1505A, the world's most popular coax cable and a nice
generic
size).. Then the cable could go 716 ft. (This is based on a source
voltage of
0.5v and a minimum received voltage of 0.2v, at a bandwidth of 5.6448
MHz.)
Yup, 700 feet!!! (Snippy aside: try going 700 ft. on a piece of toslink
plastic fiber!)

And in the digital format, you can be real close to the maximum and the
signal
(i.e. data/audio) sounds just perfect. But add in one patch cord, or
one less
than perfect connector, or just a few more feet of cable, and you could
be down
the slippery slope of the "digital cliff". So, how many of you have to
run 700
ft.??? Not many, I assume.

This is not to say you shouldn't have cable with low capacitance.
Digital
signals need low capacitance to keep their sharp edges (i.e. the clock).
But
(amazing fact that no cable manufacturer ever told you) once you choose
the
construction (i.e. plastic/dielectric/velocity) and the impedance (i.e.
75
ohms) the capacitance is AUTOMATIC. High velocity foam coax 75 ohm = 15
pF/ft.
Old solid polyethylene 75 ohm coax = 20 pF/ft. And this is why you
should
avoid CATV coax, because it's not all copper in that center conductor
(it's
copper-clad steel for high-frequency-only applications where only the
skin of
the conductor is working.) This means the resistance is 5 to 7 times
higher
than an all-copper center and the distance you can go is 5 to 7 times
shorter.
(OK, we're down to 100 ft. and you're going 6 ft., but I wouldn't use
it.)

And all those SCSI cables (at the beginning of this thread) suffer from
the
same problem. Most of them use generic multiconductors (just pull one
apart if
you don't believe me). The impedance of a pair of wires is determined
by their
size (gage), the distance between them and the quality (dielectric
contact) of
the material inbetween. So, while the plastic is important, these
cables fail
at high frequencies because of the DISTANCE between conductors, which
varies
all over the place. Open up a SCSI 2 or 3 cable, what do you see?
Ahhhh,
twisted pairs!!! And the better the pairs (tighter impedance specs) the
less
the mismatch, the less the return loss, the greater the received signal
strength, the less the bit errors. Flat cable can also help maintain
impedance
specs, at least better than just a bunch of loose wires.

As frequencies go higher and higher, every dimension becomes more
critical.
Just take your car on a racetrack if you don't believe me. You need a
race car?
Buy a race car! You need a high-frequency cable? Buy one made,
tested,
verified, and guaranteed for whatever frequency band you wish.

OK, class, how did I do?

Steve Lampen
Belden Electronics Division


  #2   Report Post  
Adair Winter
 
Posts: n/a
Default cabling explained

Very nice..
Adair


  #3   Report Post  
EFFENDI
 
Posts: n/a
Default cabling explained

Midlant wrote:
Mr Lampen of Belden Electronics Division answered this posts on
"rec.audio.high-end" some time back. I hope this answers your questions
in regards to cable quality and length of runs whether interconnect or
speaker.
John


In article , Lou Anschuetz

writes:


OTOH, I can understand how he comes to the conclusions he
comes to. As someone with 25 years in IT, I have thrown away dozens
of supposedly competently designed SCSI/serial
cables that don't work. SCSI cables in particular are darn
hard to to get right for the newer higher speeds - and it
all seems to come down to how the cable(s) is insulated.

I also agree that this doesn't necessarily have anything to do
with audio transmission. However, IMHO, this business about
insulation continues to bedevil me. Since it does play havoc
with digital signal transmission, it seems to me hard to leap
to an absolute conclusion that it has no effect in the analog
audio world. No hard science on this yet, but it is a very active
field of research...



Well, I'm on a plane flying from Beijing to Hong Kong (and on to
Melbourne,
Australia) listening to Chinese Pop music in my headphones, and nothing
to do,
so I thought I would just jump in here!

Why do some cables work on signal X but not with signal Y? The answer
is
simple: wavelength. (The answer is simple, the explanation is a little
more
complicated.) Every signal, data, audio, video, etc, etc. occupies one
or more
frequencies. Each frequency has a wavelength, that is, there is an
electromagnetic wave moving down the cable that has a specific length.
This
can be calculated by dividing 300,000,000 by that frequency. (The
answer comes
out in meters, so us backwards USA types have to multiply by 3.28 to get
to
feet.)

If you look at 20 kHz (or you can pick any frequency you want), that
gives you
a wavelength of 15,000 meters (about 9 miles). What that means is that
the
impedance of the cable (how it reacts to frequencies) is of no
consequence.
Most engineers agree that the ACTUAL critical distance is 1/4 wavelength
which
is, in this case 2.25 miles, still too far to have any effect. This
distance is
also affect by the plastic around the conductors. This affects the
speed
"velocity" of the signal. (Signals only move at the speed of light in a
vaccum,
i.e. outer space. If you ever have a chance to check out your speakers
there,
be sure and give me a complete test report!)

Let's say your interconnect cables were the worst ever made (a "velocity
of
propagation" of 50%). You would multiply the wavelength by 50% so we're
down
to 1.12 miles. Anybody with one mile speaker cables? data cable? mic
cables?
video cables? audio cable? Well, yes, there are people with AUDIO
cables of
that length or more. They call themselves the TELEPHONE COMPANY. And
the
maximum distance between your home and your central office is 13,000 ft.
(over
2 miles).

But the twisted pairs they use (even fancy new ones, Category 3) are not
the
correct impedance (too expensive). Luckily, the audio on your phone
ends at
3500 Hz. You can calculate the bandwidth and see you can go VERY far
before
you need to have impedance-specific twisted pairs. I'll be honest and
tell you
that I don't know the actual occupied bandwidth of a 56k data signal. (I
think
it's NRZI Manchester Coded, that would make it 28kHz bandwidth.) I'm
sure you
note that this puts it on the edge for performance if you are far from
the
central office, and you can't always get dialup that fast. And you'll
understand why in the USA, the FCC now mandates that all telephone
wiring must
be Category 3 or better. Category 3 is impedance-specific (100 ohms)
data
cable. But there are other reasons the FCC made this a standard besides
distance. The signals either go back to the source or simply stop in the
cable
(called "standing waves") and then radiate all that reflected energegy
into
cables around them. That's why the phone company is trying to use data
cable,
to avoid "alien crosstalk" (between cables).

That's why you can use crappy interconnect cables that come free with
your
receiver and it all sounds pretty good. They aren't long enough to make
a
difference. As long as you have continuity (electrical signal flow),
you'll be
just fine. But what if you use that cable for DIGITAL (i.e. S/PDIF).
Suddenly
we're sampling that audio at 44.1kHz (like a CD), and the bandwidth is
defined
as 128 times the sampling (5.6448 MHz, if memory serves). Let's just
use 6 MHz
to make it easy. (If you don't want easy, do it yourself.)

300,000,000 divided by 6,000,000 = 50 meters. 1/4-wavelength = 12.5
meters or
about 44 feet. How long is your cable? 3 ft? 6 ft? No problem. It's
still
not LONG enough to make a difference. Now, if you want to send S/PDIF
to the
other end of the house, that might be 40 ft. or even more. What would
you do?
Be sure and use cable which is the correct impedance. S/PDIF requires
75 ohm
cable (75 ohm cable has the lowest signal loss "attenuation" so it is
used for
many applications where low loss is required).

What if you get a really long piece of crappy cable? What impedance is
it?
Who knows!! And what will happen is that the signal, which will require
a 75
ohm "transmission line" and not see it. The farther it is away from 75
ohm the
more the signal will be REFLECTED back to the source and not get to the
other
end. This is called "return loss" in the cable world. You send me the
actual
impedance of your cable and I can calculate the mismatch and the return
loss.

But, if you get the right 75 ohm cable, how far can you go? It depends
on the
size of the wire (gage) in the middle. Let's assume it is a 20 AWG
center
(such as Belden 1505A, the world's most popular coax cable and a nice
generic
size).. Then the cable could go 716 ft. (This is based on a source
voltage of
0.5v and a minimum received voltage of 0.2v, at a bandwidth of 5.6448
MHz.)
Yup, 700 feet!!! (Snippy aside: try going 700 ft. on a piece of toslink
plastic fiber!)

And in the digital format, you can be real close to the maximum and the
signal
(i.e. data/audio) sounds just perfect. But add in one patch cord, or
one less
than perfect connector, or just a few more feet of cable, and you could
be down
the slippery slope of the "digital cliff". So, how many of you have to
run 700
ft.??? Not many, I assume.

This is not to say you shouldn't have cable with low capacitance.
Digital
signals need low capacitance to keep their sharp edges (i.e. the clock).
But
(amazing fact that no cable manufacturer ever told you) once you choose
the
construction (i.e. plastic/dielectric/velocity) and the impedance (i.e.
75
ohms) the capacitance is AUTOMATIC. High velocity foam coax 75 ohm = 15
pF/ft.
Old solid polyethylene 75 ohm coax = 20 pF/ft. And this is why you
should
avoid CATV coax, because it's not all copper in that center conductor
(it's
copper-clad steel for high-frequency-only applications where only the
skin of
the conductor is working.) This means the resistance is 5 to 7 times
higher
than an all-copper center and the distance you can go is 5 to 7 times
shorter.
(OK, we're down to 100 ft. and you're going 6 ft., but I wouldn't use
it.)

And all those SCSI cables (at the beginning of this thread) suffer from
the
same problem. Most of them use generic multiconductors (just pull one
apart if
you don't believe me). The impedance of a pair of wires is determined
by their
size (gage), the distance between them and the quality (dielectric
contact) of
the material inbetween. So, while the plastic is important, these
cables fail
at high frequencies because of the DISTANCE between conductors, which
varies
all over the place. Open up a SCSI 2 or 3 cable, what do you see?
Ahhhh,
twisted pairs!!! And the better the pairs (tighter impedance specs) the
less
the mismatch, the less the return loss, the greater the received signal
strength, the less the bit errors. Flat cable can also help maintain
impedance
specs, at least better than just a bunch of loose wires.

As frequencies go higher and higher, every dimension becomes more
critical.
Just take your car on a racetrack if you don't believe me. You need a
race car?
Buy a race car! You need a high-frequency cable? Buy one made,
tested,
verified, and guaranteed for whatever frequency band you wish.

OK, class, how did I do?

Steve Lampen
Belden Electronics Division



THANK YOU FOR THIS GREAT POST!

You are deserving of a great thank-you man. I was trying to figure out
cabling and wiring and was going to post about it before I know it you
post it all here together. Great information and very easy to
understand. You should be a teacher if it pays better.

EFFENDI
  #4   Report Post  
Bill Pallies
 
Posts: n/a
Default cabling explained

Very good explanation. Thank you.

-Bill

"Midlant" wrote in message
news:v_fsb.20629$oB3.15068@lakeread03...
Mr Lampen of Belden Electronics Division answered this posts on
"rec.audio.high-end" some time back. I hope this answers your questions
in regards to cable quality and length of runs whether interconnect or
speaker.
John


In article , Lou Anschuetz

writes:

OTOH, I can understand how he comes to the conclusions he
comes to. As someone with 25 years in IT, I have thrown away dozens
of supposedly competently designed SCSI/serial
cables that don't work. SCSI cables in particular are darn
hard to to get right for the newer higher speeds - and it
all seems to come down to how the cable(s) is insulated.

I also agree that this doesn't necessarily have anything to do
with audio transmission. However, IMHO, this business about
insulation continues to bedevil me. Since it does play havoc
with digital signal transmission, it seems to me hard to leap
to an absolute conclusion that it has no effect in the analog
audio world. No hard science on this yet, but it is a very active
field of research...


Well, I'm on a plane flying from Beijing to Hong Kong (and on to
Melbourne,
Australia) listening to Chinese Pop music in my headphones, and nothing
to do,
so I thought I would just jump in here!

Why do some cables work on signal X but not with signal Y? The answer
is
simple: wavelength. (The answer is simple, the explanation is a little
more
complicated.) Every signal, data, audio, video, etc, etc. occupies one
or more
frequencies. Each frequency has a wavelength, that is, there is an
electromagnetic wave moving down the cable that has a specific length.
This
can be calculated by dividing 300,000,000 by that frequency. (The
answer comes
out in meters, so us backwards USA types have to multiply by 3.28 to get
to
feet.)

If you look at 20 kHz (or you can pick any frequency you want), that
gives you
a wavelength of 15,000 meters (about 9 miles). What that means is that
the
impedance of the cable (how it reacts to frequencies) is of no
consequence.
Most engineers agree that the ACTUAL critical distance is 1/4 wavelength
which
is, in this case 2.25 miles, still too far to have any effect. This
distance is
also affect by the plastic around the conductors. This affects the
speed
"velocity" of the signal. (Signals only move at the speed of light in a
vaccum,
i.e. outer space. If you ever have a chance to check out your speakers
there,
be sure and give me a complete test report!)

Let's say your interconnect cables were the worst ever made (a "velocity
of
propagation" of 50%). You would multiply the wavelength by 50% so we're
down
to 1.12 miles. Anybody with one mile speaker cables? data cable? mic
cables?
video cables? audio cable? Well, yes, there are people with AUDIO
cables of
that length or more. They call themselves the TELEPHONE COMPANY. And
the
maximum distance between your home and your central office is 13,000 ft.
(over
2 miles).

But the twisted pairs they use (even fancy new ones, Category 3) are not
the
correct impedance (too expensive). Luckily, the audio on your phone
ends at
3500 Hz. You can calculate the bandwidth and see you can go VERY far
before
you need to have impedance-specific twisted pairs. I'll be honest and
tell you
that I don't know the actual occupied bandwidth of a 56k data signal. (I
think
it's NRZI Manchester Coded, that would make it 28kHz bandwidth.) I'm
sure you
note that this puts it on the edge for performance if you are far from
the
central office, and you can't always get dialup that fast. And you'll
understand why in the USA, the FCC now mandates that all telephone
wiring must
be Category 3 or better. Category 3 is impedance-specific (100 ohms)
data
cable. But there are other reasons the FCC made this a standard besides
distance. The signals either go back to the source or simply stop in the
cable
(called "standing waves") and then radiate all that reflected energegy
into
cables around them. That's why the phone company is trying to use data
cable,
to avoid "alien crosstalk" (between cables).

That's why you can use crappy interconnect cables that come free with
your
receiver and it all sounds pretty good. They aren't long enough to make
a
difference. As long as you have continuity (electrical signal flow),
you'll be
just fine. But what if you use that cable for DIGITAL (i.e. S/PDIF).
Suddenly
we're sampling that audio at 44.1kHz (like a CD), and the bandwidth is
defined
as 128 times the sampling (5.6448 MHz, if memory serves). Let's just
use 6 MHz
to make it easy. (If you don't want easy, do it yourself.)

300,000,000 divided by 6,000,000 = 50 meters. 1/4-wavelength = 12.5
meters or
about 44 feet. How long is your cable? 3 ft? 6 ft? No problem. It's
still
not LONG enough to make a difference. Now, if you want to send S/PDIF
to the
other end of the house, that might be 40 ft. or even more. What would
you do?
Be sure and use cable which is the correct impedance. S/PDIF requires
75 ohm
cable (75 ohm cable has the lowest signal loss "attenuation" so it is
used for
many applications where low loss is required).

What if you get a really long piece of crappy cable? What impedance is
it?
Who knows!! And what will happen is that the signal, which will require
a 75
ohm "transmission line" and not see it. The farther it is away from 75
ohm the
more the signal will be REFLECTED back to the source and not get to the
other
end. This is called "return loss" in the cable world. You send me the
actual
impedance of your cable and I can calculate the mismatch and the return
loss.

But, if you get the right 75 ohm cable, how far can you go? It depends
on the
size of the wire (gage) in the middle. Let's assume it is a 20 AWG
center
(such as Belden 1505A, the world's most popular coax cable and a nice
generic
size).. Then the cable could go 716 ft. (This is based on a source
voltage of
0.5v and a minimum received voltage of 0.2v, at a bandwidth of 5.6448
MHz.)
Yup, 700 feet!!! (Snippy aside: try going 700 ft. on a piece of toslink
plastic fiber!)

And in the digital format, you can be real close to the maximum and the
signal
(i.e. data/audio) sounds just perfect. But add in one patch cord, or
one less
than perfect connector, or just a few more feet of cable, and you could
be down
the slippery slope of the "digital cliff". So, how many of you have to
run 700
ft.??? Not many, I assume.

This is not to say you shouldn't have cable with low capacitance.
Digital
signals need low capacitance to keep their sharp edges (i.e. the clock).
But
(amazing fact that no cable manufacturer ever told you) once you choose
the
construction (i.e. plastic/dielectric/velocity) and the impedance (i.e.
75
ohms) the capacitance is AUTOMATIC. High velocity foam coax 75 ohm = 15
pF/ft.
Old solid polyethylene 75 ohm coax = 20 pF/ft. And this is why you
should
avoid CATV coax, because it's not all copper in that center conductor
(it's
copper-clad steel for high-frequency-only applications where only the
skin of
the conductor is working.) This means the resistance is 5 to 7 times
higher
than an all-copper center and the distance you can go is 5 to 7 times
shorter.
(OK, we're down to 100 ft. and you're going 6 ft., but I wouldn't use
it.)

And all those SCSI cables (at the beginning of this thread) suffer from
the
same problem. Most of them use generic multiconductors (just pull one
apart if
you don't believe me). The impedance of a pair of wires is determined
by their
size (gage), the distance between them and the quality (dielectric
contact) of
the material inbetween. So, while the plastic is important, these
cables fail
at high frequencies because of the DISTANCE between conductors, which
varies
all over the place. Open up a SCSI 2 or 3 cable, what do you see?
Ahhhh,
twisted pairs!!! And the better the pairs (tighter impedance specs) the
less
the mismatch, the less the return loss, the greater the received signal
strength, the less the bit errors. Flat cable can also help maintain
impedance
specs, at least better than just a bunch of loose wires.

As frequencies go higher and higher, every dimension becomes more
critical.
Just take your car on a racetrack if you don't believe me. You need a
race car?
Buy a race car! You need a high-frequency cable? Buy one made,
tested,
verified, and guaranteed for whatever frequency band you wish.

OK, class, how did I do?

Steve Lampen
Belden Electronics Division





  #5   Report Post  
Mark Zarella
 
Posts: n/a
Default cabling explained

Unfortunately, I can't share the enthusiasm of the other posters
responding in this thread.

The post says absolutely nothing to us in the audio world, and is in
fact completely irrelevant. He's looking at the issue from a microwave
transmission line perspective which, as he pointed out in his first
paragraph, doesn't apply to audio.

One of the most comprehensive articles I've read on the subject of
speaker cables was written by Fred Davis in the '80s and published by
the Journal of the Audio Engineering Society. I've placed a reprint at
the following website:

http://www.geocities.com/audiotechpa...ractions. pdf

Davis essentially examines the relevant electrical properties of several
different cables (everything from $100/meter cables to jumper cables he
found in his garage to lamp cord) and performs an analysis of their
interactions with loudspeakers and amplifiers. Also noteworthy is that
Davis looks at capacitance and inductance properties in the cables and
compares them to various aspects of their construction which, unlike the
assertion made in the original post, depends on many more factors than
just the dielectric properties. Rather, the geometrical properties and
other electrical properties come into play.


Midlant wrote:
Mr Lampen of Belden Electronics Division answered this posts on
"rec.audio.high-end" some time back. I hope this answers your questions
in regards to cable quality and length of runs whether interconnect or
speaker.
John


In article , Lou Anschuetz

writes:


OTOH, I can understand how he comes to the conclusions he
comes to. As someone with 25 years in IT, I have thrown away dozens
of supposedly competently designed SCSI/serial
cables that don't work. SCSI cables in particular are darn
hard to to get right for the newer higher speeds - and it
all seems to come down to how the cable(s) is insulated.

I also agree that this doesn't necessarily have anything to do
with audio transmission. However, IMHO, this business about
insulation continues to bedevil me. Since it does play havoc
with digital signal transmission, it seems to me hard to leap
to an absolute conclusion that it has no effect in the analog
audio world. No hard science on this yet, but it is a very active
field of research...



Well, I'm on a plane flying from Beijing to Hong Kong (and on to
Melbourne,
Australia) listening to Chinese Pop music in my headphones, and nothing
to do,
so I thought I would just jump in here!

Why do some cables work on signal X but not with signal Y? The answer
is
simple: wavelength. (The answer is simple, the explanation is a little
more
complicated.) Every signal, data, audio, video, etc, etc. occupies one
or more
frequencies. Each frequency has a wavelength, that is, there is an
electromagnetic wave moving down the cable that has a specific length.
This
can be calculated by dividing 300,000,000 by that frequency. (The
answer comes
out in meters, so us backwards USA types have to multiply by 3.28 to get
to
feet.)

If you look at 20 kHz (or you can pick any frequency you want), that
gives you
a wavelength of 15,000 meters (about 9 miles). What that means is that
the
impedance of the cable (how it reacts to frequencies) is of no
consequence.
Most engineers agree that the ACTUAL critical distance is 1/4 wavelength
which
is, in this case 2.25 miles, still too far to have any effect. This
distance is
also affect by the plastic around the conductors. This affects the
speed
"velocity" of the signal. (Signals only move at the speed of light in a
vaccum,
i.e. outer space. If you ever have a chance to check out your speakers
there,
be sure and give me a complete test report!)

Let's say your interconnect cables were the worst ever made (a "velocity
of
propagation" of 50%). You would multiply the wavelength by 50% so we're
down
to 1.12 miles. Anybody with one mile speaker cables? data cable? mic
cables?
video cables? audio cable? Well, yes, there are people with AUDIO
cables of
that length or more. They call themselves the TELEPHONE COMPANY. And
the
maximum distance between your home and your central office is 13,000 ft.
(over
2 miles).

But the twisted pairs they use (even fancy new ones, Category 3) are not
the
correct impedance (too expensive). Luckily, the audio on your phone
ends at
3500 Hz. You can calculate the bandwidth and see you can go VERY far
before
you need to have impedance-specific twisted pairs. I'll be honest and
tell you
that I don't know the actual occupied bandwidth of a 56k data signal. (I
think
it's NRZI Manchester Coded, that would make it 28kHz bandwidth.) I'm
sure you
note that this puts it on the edge for performance if you are far from
the
central office, and you can't always get dialup that fast. And you'll
understand why in the USA, the FCC now mandates that all telephone
wiring must
be Category 3 or better. Category 3 is impedance-specific (100 ohms)
data
cable. But there are other reasons the FCC made this a standard besides
distance. The signals either go back to the source or simply stop in the
cable
(called "standing waves") and then radiate all that reflected energegy
into
cables around them. That's why the phone company is trying to use data
cable,
to avoid "alien crosstalk" (between cables).

That's why you can use crappy interconnect cables that come free with
your
receiver and it all sounds pretty good. They aren't long enough to make
a
difference. As long as you have continuity (electrical signal flow),
you'll be
just fine. But what if you use that cable for DIGITAL (i.e. S/PDIF).
Suddenly
we're sampling that audio at 44.1kHz (like a CD), and the bandwidth is
defined
as 128 times the sampling (5.6448 MHz, if memory serves). Let's just
use 6 MHz
to make it easy. (If you don't want easy, do it yourself.)

300,000,000 divided by 6,000,000 = 50 meters. 1/4-wavelength = 12.5
meters or
about 44 feet. How long is your cable? 3 ft? 6 ft? No problem. It's
still
not LONG enough to make a difference. Now, if you want to send S/PDIF
to the
other end of the house, that might be 40 ft. or even more. What would
you do?
Be sure and use cable which is the correct impedance. S/PDIF requires
75 ohm
cable (75 ohm cable has the lowest signal loss "attenuation" so it is
used for
many applications where low loss is required).

What if you get a really long piece of crappy cable? What impedance is
it?
Who knows!! And what will happen is that the signal, which will require
a 75
ohm "transmission line" and not see it. The farther it is away from 75
ohm the
more the signal will be REFLECTED back to the source and not get to the
other
end. This is called "return loss" in the cable world. You send me the
actual
impedance of your cable and I can calculate the mismatch and the return
loss.

But, if you get the right 75 ohm cable, how far can you go? It depends
on the
size of the wire (gage) in the middle. Let's assume it is a 20 AWG
center
(such as Belden 1505A, the world's most popular coax cable and a nice
generic
size).. Then the cable could go 716 ft. (This is based on a source
voltage of
0.5v and a minimum received voltage of 0.2v, at a bandwidth of 5.6448
MHz.)
Yup, 700 feet!!! (Snippy aside: try going 700 ft. on a piece of toslink
plastic fiber!)

And in the digital format, you can be real close to the maximum and the
signal
(i.e. data/audio) sounds just perfect. But add in one patch cord, or
one less
than perfect connector, or just a few more feet of cable, and you could
be down
the slippery slope of the "digital cliff". So, how many of you have to
run 700
ft.??? Not many, I assume.

This is not to say you shouldn't have cable with low capacitance.
Digital
signals need low capacitance to keep their sharp edges (i.e. the clock).
But
(amazing fact that no cable manufacturer ever told you) once you choose
the
construction (i.e. plastic/dielectric/velocity) and the impedance (i.e.
75
ohms) the capacitance is AUTOMATIC. High velocity foam coax 75 ohm = 15
pF/ft.
Old solid polyethylene 75 ohm coax = 20 pF/ft. And this is why you
should
avoid CATV coax, because it's not all copper in that center conductor
(it's
copper-clad steel for high-frequency-only applications where only the
skin of
the conductor is working.) This means the resistance is 5 to 7 times
higher
than an all-copper center and the distance you can go is 5 to 7 times
shorter.
(OK, we're down to 100 ft. and you're going 6 ft., but I wouldn't use
it.)

And all those SCSI cables (at the beginning of this thread) suffer from
the
same problem. Most of them use generic multiconductors (just pull one
apart if
you don't believe me). The impedance of a pair of wires is determined
by their
size (gage), the distance between them and the quality (dielectric
contact) of
the material inbetween. So, while the plastic is important, these
cables fail
at high frequencies because of the DISTANCE between conductors, which
varies
all over the place. Open up a SCSI 2 or 3 cable, what do you see?
Ahhhh,
twisted pairs!!! And the better the pairs (tighter impedance specs) the
less
the mismatch, the less the return loss, the greater the received signal
strength, the less the bit errors. Flat cable can also help maintain
impedance
specs, at least better than just a bunch of loose wires.

As frequencies go higher and higher, every dimension becomes more
critical.
Just take your car on a racetrack if you don't believe me. You need a
race car?
Buy a race car! You need a high-frequency cable? Buy one made,
tested,
verified, and guaranteed for whatever frequency band you wish.

OK, class, how did I do?

Steve Lampen
Belden Electronics Division






  #6   Report Post  
Midlant
 
Posts: n/a
Default cabling explained

No, he set out the needs for RF then compared it to audio to make his
point. Audio is not as high frequency as RF so don't use CATV coax and
since the wavelengths are so long, don't worry too much about cable
properties having a majore impact on the system. We run cabling in such
short lenghts that it really doesn't matter. I read the link you posted
and he summed it up the same way.

"12 AWG seems more than adequate, even for demanding systems, high power
Speaker levels, and reasonable lengths.
The effects of 3.1-m cables are subtle, so many situations may not
warrant the use of special cables. Low-inductance cables will provide
the best performance when driving reactive loads, especially with
amplifiers having low damping factor, and when flat response is
critical, when long cable lengths are required, or when perfection is
sought. Though not as linear as flat cables, 12 AWG wire works well and
exceeds the high frequency performance of other two-conductor cables
tested."

Remember, he's writing in the context of home audio which some customers
are very demanding of and even go to such lenghts as building listening
rooms desinged around Cardas' principle among others. A very quiet
listening environment, unlike car audio. And, home audio speakers aren't
pressed into car doors, rear shelves, etc. They reveal a whole lot more
that even the best car audio set up can deliver due to acoustics. Room
interaction is a major player when it comes to great sound.
John



"Mark Zarella" wrote in message
...
Unfortunately, I can't share the enthusiasm of the other posters
responding in this thread.

The post says absolutely nothing to us in the audio world, and is in
fact completely irrelevant. He's looking at the issue from a

microwave
transmission line perspective which, as he pointed out in his first
paragraph, doesn't apply to audio.

One of the most comprehensive articles I've read on the subject of
speaker cables was written by Fred Davis in the '80s and published by
the Journal of the Audio Engineering Society. I've placed a reprint

at
the following website:


http://www.geocities.com/audiotechpa...ractions. pdf

Davis essentially examines the relevant electrical properties of

several
different cables (everything from $100/meter cables to jumper cables

he
found in his garage to lamp cord) and performs an analysis of their
interactions with loudspeakers and amplifiers. Also noteworthy is

that
Davis looks at capacitance and inductance properties in the cables and
compares them to various aspects of their construction which, unlike

the
assertion made in the original post, depends on many more factors than
just the dielectric properties. Rather, the geometrical properties

and
other electrical properties come into play.


Midlant wrote:
Mr Lampen of Belden Electronics Division answered this posts on
"rec.audio.high-end" some time back. I hope this answers your

questions
in regards to cable quality and length of runs whether interconnect

or
speaker.
John


In article , Lou Anschuetz

writes:


OTOH, I can understand how he comes to the conclusions he
comes to. As someone with 25 years in IT, I have thrown away dozens
of supposedly competently designed SCSI/serial
cables that don't work. SCSI cables in particular are darn
hard to to get right for the newer higher speeds - and it
all seems to come down to how the cable(s) is insulated.

I also agree that this doesn't necessarily have anything to do
with audio transmission. However, IMHO, this business about
insulation continues to bedevil me. Since it does play havoc
with digital signal transmission, it seems to me hard to leap
to an absolute conclusion that it has no effect in the analog
audio world. No hard science on this yet, but it is a very active
field of research...



Well, I'm on a plane flying from Beijing to Hong Kong (and on to
Melbourne,
Australia) listening to Chinese Pop music in my headphones, and

nothing
to do,
so I thought I would just jump in here!

Why do some cables work on signal X but not with signal Y? The

answer
is
simple: wavelength. (The answer is simple, the explanation is a

little
more
complicated.) Every signal, data, audio, video, etc, etc. occupies

one
or more
frequencies. Each frequency has a wavelength, that is, there is an
electromagnetic wave moving down the cable that has a specific

length.
This
can be calculated by dividing 300,000,000 by that frequency. (The
answer comes
out in meters, so us backwards USA types have to multiply by 3.28 to

get
to
feet.)

If you look at 20 kHz (or you can pick any frequency you want), that
gives you
a wavelength of 15,000 meters (about 9 miles). What that means is

that
the
impedance of the cable (how it reacts to frequencies) is of no
consequence.
Most engineers agree that the ACTUAL critical distance is 1/4

wavelength
which
is, in this case 2.25 miles, still too far to have any effect. This
distance is
also affect by the plastic around the conductors. This affects the
speed
"velocity" of the signal. (Signals only move at the speed of light

in a
vaccum,
i.e. outer space. If you ever have a chance to check out your

speakers
there,
be sure and give me a complete test report!)

Let's say your interconnect cables were the worst ever made (a

"velocity
of
propagation" of 50%). You would multiply the wavelength by 50% so

we're
down
to 1.12 miles. Anybody with one mile speaker cables? data cable?

mic
cables?
video cables? audio cable? Well, yes, there are people with AUDIO
cables of
that length or more. They call themselves the TELEPHONE COMPANY.

And
the
maximum distance between your home and your central office is 13,000

ft.
(over
2 miles).

But the twisted pairs they use (even fancy new ones, Category 3) are

not
the
correct impedance (too expensive). Luckily, the audio on your phone
ends at
3500 Hz. You can calculate the bandwidth and see you can go VERY

far
before
you need to have impedance-specific twisted pairs. I'll be honest

and
tell you
that I don't know the actual occupied bandwidth of a 56k data

signal. (I
think
it's NRZI Manchester Coded, that would make it 28kHz bandwidth.)

I'm
sure you
note that this puts it on the edge for performance if you are far

from
the
central office, and you can't always get dialup that fast. And

you'll
understand why in the USA, the FCC now mandates that all telephone
wiring must
be Category 3 or better. Category 3 is impedance-specific (100

ohms)
data
cable. But there are other reasons the FCC made this a standard

besides
distance. The signals either go back to the source or simply stop in

the
cable
(called "standing waves") and then radiate all that reflected

energegy
into
cables around them. That's why the phone company is trying to use

data
cable,
to avoid "alien crosstalk" (between cables).

That's why you can use crappy interconnect cables that come free

with
your
receiver and it all sounds pretty good. They aren't long enough to

make
a
difference. As long as you have continuity (electrical signal

flow),
you'll be
just fine. But what if you use that cable for DIGITAL (i.e. S/PDIF).
Suddenly
we're sampling that audio at 44.1kHz (like a CD), and the bandwidth

is
defined
as 128 times the sampling (5.6448 MHz, if memory serves). Let's

just
use 6 MHz
to make it easy. (If you don't want easy, do it yourself.)

300,000,000 divided by 6,000,000 = 50 meters. 1/4-wavelength = 12.5
meters or
about 44 feet. How long is your cable? 3 ft? 6 ft? No problem.

It's
still
not LONG enough to make a difference. Now, if you want to send

S/PDIF
to the
other end of the house, that might be 40 ft. or even more. What

would
you do?
Be sure and use cable which is the correct impedance. S/PDIF

requires
75 ohm
cable (75 ohm cable has the lowest signal loss "attenuation" so it

is
used for
many applications where low loss is required).

What if you get a really long piece of crappy cable? What impedance

is
it?
Who knows!! And what will happen is that the signal, which will

require
a 75
ohm "transmission line" and not see it. The farther it is away from

75
ohm the
more the signal will be REFLECTED back to the source and not get to

the
other
end. This is called "return loss" in the cable world. You send me

the
actual
impedance of your cable and I can calculate the mismatch and the

return
loss.

But, if you get the right 75 ohm cable, how far can you go? It

depends
on the
size of the wire (gage) in the middle. Let's assume it is a 20 AWG
center
(such as Belden 1505A, the world's most popular coax cable and a

nice
generic
size).. Then the cable could go 716 ft. (This is based on a source
voltage of
0.5v and a minimum received voltage of 0.2v, at a bandwidth of

5.6448
MHz.)
Yup, 700 feet!!! (Snippy aside: try going 700 ft. on a piece of

toslink
plastic fiber!)

And in the digital format, you can be real close to the maximum and

the
signal
(i.e. data/audio) sounds just perfect. But add in one patch cord,

or
one less
than perfect connector, or just a few more feet of cable, and you

could
be down
the slippery slope of the "digital cliff". So, how many of you have

to
run 700
ft.??? Not many, I assume.

This is not to say you shouldn't have cable with low capacitance.
Digital
signals need low capacitance to keep their sharp edges (i.e. the

clock).
But
(amazing fact that no cable manufacturer ever told you) once you

choose
the
construction (i.e. plastic/dielectric/velocity) and the impedance

(i.e.
75
ohms) the capacitance is AUTOMATIC. High velocity foam coax 75 ohm

= 15
pF/ft.
Old solid polyethylene 75 ohm coax = 20 pF/ft. And this is why you
should
avoid CATV coax, because it's not all copper in that center

conductor
(it's
copper-clad steel for high-frequency-only applications where only

the
skin of
the conductor is working.) This means the resistance is 5 to 7

times
higher
than an all-copper center and the distance you can go is 5 to 7

times
shorter.
(OK, we're down to 100 ft. and you're going 6 ft., but I wouldn't

use
it.)

And all those SCSI cables (at the beginning of this thread) suffer

from
the
same problem. Most of them use generic multiconductors (just pull

one
apart if
you don't believe me). The impedance of a pair of wires is

determined
by their
size (gage), the distance between them and the quality (dielectric
contact) of
the material inbetween. So, while the plastic is important, these
cables fail
at high frequencies because of the DISTANCE between conductors,

which
varies
all over the place. Open up a SCSI 2 or 3 cable, what do you see?
Ahhhh,
twisted pairs!!! And the better the pairs (tighter impedance specs)

the
less
the mismatch, the less the return loss, the greater the received

signal
strength, the less the bit errors. Flat cable can also help

maintain
impedance
specs, at least better than just a bunch of loose wires.

As frequencies go higher and higher, every dimension becomes more
critical.
Just take your car on a racetrack if you don't believe me. You need

a
race car?
Buy a race car! You need a high-frequency cable? Buy one made,
tested,
verified, and guaranteed for whatever frequency band you wish.

OK, class, how did I do?

Steve Lampen
Belden Electronics Division






  #7   Report Post  
Mark Zarella
 
Posts: n/a
Default cabling explained

No, he set out the needs for RF then compared it to audio to make his
point.


But what point is that exactly? He's comparing apples and oranges. Or
rather, contrasting apples and oranges.

Audio is not as high frequency as RF so don't use CATV coax


There's nothing wrong with coax. Many people use coax for their preamp
signal cables. The input impedance of amplifiers and processors are
high enough to make any effects of increased capacitance negligible.
I've yet to see a practical application where it can be used for speaker
wiring - where capacitance can actually be relevant.

and
since the wavelengths are so long, don't worry too much about cable
properties having a majore impact on the system. We run cabling in such
short lenghts that it really doesn't matter. I read the link you posted
and he summed it up the same way.


Yes, transmission line theory can be neglected in car audio. I don't
know of anyone using any elements of microwave theory to support using
different kinds of wire in car audio though, so I don't know why the
author insisted on addressing this.

"12 AWG seems more than adequate, even for demanding systems, high power
Speaker levels, and reasonable lengths.
The effects of 3.1-m cables are subtle, so many situations may not
warrant the use of special cables. Low-inductance cables will provide
the best performance when driving reactive loads, especially with
amplifiers having low damping factor, and when flat response is
critical, when long cable lengths are required, or when perfection is
sought. Though not as linear as flat cables, 12 AWG wire works well and
exceeds the high frequency performance of other two-conductor cables
tested."


How did the author come to these conclusions? None of what he said
prior to this statement was relevant to it. He said little about the
reactance of the cable and its effect on the output.

Remember, he's writing in the context of home audio which some customers
are very demanding of and even go to such lenghts as building listening
rooms desinged around Cardas' principle among others. A very quiet
listening environment, unlike car audio. And, home audio speakers aren't
pressed into car doors, rear shelves, etc. They reveal a whole lot more
that even the best car audio set up can deliver due to acoustics. Room
interaction is a major player when it comes to great sound.


I realize this, which makes me wonder even further why he addressed the
issue like he did. Yes, home users are demanding. So what does this
have to do with telling people about the differences between two cables?

If I were to explain the differences, it would be as Fred Davis did: an
impedance explanation of attenuation. That is, how a voltage drop
occurs, and then compare the relative magnitudes based on the electrical
properties of the cable. The author you posted did not do this, but
instead talked about transmission line theory. Since virtually no one
was citing transmission line theory as a reason for using one cable over
another, I find that it was completely unnecessary to do so. Therefore,
it hardly serves as a comprehensive explanation of why cables are
different, and more importantly, what the relative magnitude of these
differences are.

I don't mean to criticize your posting this on here, because I think
it's an interesting analysis probably worth reading by anyone who wants
to know one of the differences between the requirements for transmission
of a very high frequency and very low frequency signal (though a bit
misleading in a couple other areas). However, I just wanted to point
out that it's not an explanation of what the differences between cables
are and how such differences may or may not be significant.

  #8   Report Post  
Midlant
 
Posts: n/a
Default cabling explained


"Mark Zarella" wrote in message
.. .
No, he set out the needs for RF then compared it to audio to make

his
point.


But what point is that exactly? He's comparing apples and oranges.

Or
rather, contrasting apples and oranges.

Audio is not as high frequency as RF so don't use CATV coax


There's nothing wrong with coax. Many people use coax for their

preamp
signal cables. The input impedance of amplifiers and processors are
high enough to make any effects of increased capacitance negligible.
I've yet to see a practical application where it can be used for

speaker
wiring - where capacitance can actually be relevant.


CATV Coax is only copper clad steal (or maybe only some of it is).
That's why Belden doesn't recommend it. Other coax where the center
conductor is solid copper is fine for audio. The difference for them is
that RF is of such high frequency that it only travels on the outer most
portion of the wire where audio uses much more of the conductor since
it's in a lower frequency range.
I do have an email from Belden stating wire part numbers for analog
IC's, digital IC's, and speaker cabling, the latter surprised me as it
isn't all that thick which is more in line with Mr Davis's article. I
can email it to you or post it here for the ng if anyone is interested
in building their own. (personaly I'm cheap and use www.knukonceptz.com
cables.)

About a year and a half ago, I came across and EE who happened to enjoy
music and had a pretty decent system. He used nothing but coax for his
IC"s. He stated the same as everyone else, we use such short lengths
that it doesn't matter what we use as long as its well built. He
accidentally pinched his turntable's IC so built another one out of
boredom one day. He was shocked at the way the music sounded with the
new one. All his highs were back. I guess the pinched dielectric caused
havoc with the cables capacitance or other property.



Yes, transmission line theory can be neglected in car audio. I don't
know of anyone using any elements of microwave theory to support using
different kinds of wire in car audio though, so I don't know why the
author insisted on addressing this.


Beats me. Mr Davis wrote it in 1991. I don't think theory has changed
since then. From what I gathered reading the article, I think Mr Davis
went from known fact into opinion, then back again, switching several
times. His brain was probably working faster than his fingers could type
and he got ahead of himself. Proofreading it, his mind filled in the
blanks for him. I've seen that happen many times at work. (Lots of PhD
types.)

"12 AWG seems more than adequate, even for demanding systems, high

power
Speaker levels, and reasonable lengths.
The effects of 3.1-m cables are subtle, so many situations may not
warrant the use of special cables. Low-inductance cables will

provide
the best performance when driving reactive loads, especially with
amplifiers having low damping factor, and when flat response is
critical, when long cable lengths are required, or when perfection

is
sought. Though not as linear as flat cables, 12 AWG wire works well

and
exceeds the high frequency performance of other two-conductor cables
tested."


How did the author come to these conclusions? None of what he said
prior to this statement was relevant to it. He said little about the
reactance of the cable and its effect on the output.


Like I said above, I don't know. It's from Mr Davis' article that you
posted.
I snipped the rest. Honestly, both authors were wrote about transmission
line IRT amp through cable to speaker. He has quite a formula set up.
I appreciate you stating you weren't intending to flame me. Thanks. I
posted the article since I thought there was a need for it. One thing
about audio is it is full of people waiting to take our money. Mark up
on cables is ridiculous. A salesman of an audio shop (which shall remain
anon) said that the stores customer were following cable mfg's advice on
allocating a certain % on cables when buying a system that the store
wasn't selling its higher end gear but more mid-fi which had less profit
margin. So the owner contacted one of the cable companies who agreed to
build him cables with his name on it for a per unit cost of $14.65.
These were the same cables they were selling for $695.00! He could sell
them for anything he wanted to (cheap) and get people to spend money on
better equipment, where it mattered the most. The store was able to sell
higher quality gear making its customers appreciate what it was they
were spending thier hard earned money on, turn a profit, stay in
business and continue selling good quality audio instead of the lower
end mass market Circuit City stuff. As much as I hate it, there is a
difference.
Spend as much as you can on speakers then go from there. Some say start
with the source, but it's still only as good as the speakers. I have
been blown away by pretty medicore gear when hooked up to really great
speakers.

On AudioQuest's site, in their FAQ section, they state speaker cable
length differences of 25% will make a difference. I don't know how since
the signal is traveling so fast and with the various other problems we
face with acoustics, I think any difference there may be measurable but
not discernable.

John



  #9   Report Post  
Mark Zarella
 
Posts: n/a
Default cabling explained

CATV Coax is only copper clad steal (or maybe only some of it is).
That's why Belden doesn't recommend it. Other coax where the center
conductor is solid copper is fine for audio.


So what? It doesn't matter. The input impedance of a typical amplifier
is between 10k to 50k ohms. You could add a 100 ohm resistor in there
and it wouldn't make any difference. It's a simple voltage divider.
Attenuation is roughly proportional to the ratio between wire impedance
and input impedance. As you can see, a 100 ohm wire impedance would
present attenuation of the signal of less than 1%. You can simply
compensate for this with the gain adjustment, or just ignore it as it's
indetectable to humans anyway, and in fact would probably be within the
noise level. And this is with a 100 ohm resistor! If you were to truly
go from solid copper wire to solid steel wire, you'd be increasing the
resistance of a 20 foot wire from somewhere on the order of 0.1 ohms to
0.2 ohms. In other words, resistivity of the wire does not matter.

The difference for them is
that RF is of such high frequency that it only travels on the outer most
portion of the wire where audio uses much more of the conductor since
it's in a lower frequency range.


But who cares about RF?

I do have an email from Belden stating wire part numbers for analog
IC's, digital IC's, and speaker cabling, the latter surprised me as it
isn't all that thick which is more in line with Mr Davis's article. I
can email it to you or post it here for the ng if anyone is interested
in building their own. (personaly I'm cheap and use www.knukonceptz.com
cables.)

About a year and a half ago, I came across and EE who happened to enjoy
music and had a pretty decent system. He used nothing but coax for his
IC"s.


I'd never use typical CATV coax in a car just because it's a pain to
work with - solid wire breaks rather easily and isn't very bendable.


He stated the same as everyone else, we use such short lengths
that it doesn't matter what we use as long as its well built. He
accidentally pinched his turntable's IC so built another one out of
boredom one day. He was shocked at the way the music sounded with the
new one. All his highs were back. I guess the pinched dielectric caused
havoc with the cables capacitance or other property.


It's the power of suggestion. Even if the cable was pinched, it would
have little bearing on the capacitance of the wire - just the
resistance. If the resistance skyrocketed, it would not differentially
attenuate the highs.

Yes, transmission line theory can be neglected in car audio. I don't
know of anyone using any elements of microwave theory to support using
different kinds of wire in car audio though, so I don't know why the
author insisted on addressing this.



Beats me. Mr Davis wrote it in 1991. I don't think theory has changed
since then.


Ah, I thought the quote you provided was from the post written by the
other guy. That's why it made no sense in his context.

From what I gathered reading the article, I think Mr Davis
went from known fact into opinion, then back again, switching several
times. His brain was probably working faster than his fingers could type
and he got ahead of himself. Proofreading it, his mind filled in the
blanks for him. I've seen that happen many times at work. (Lots of PhD
types.)


Well, some of what he said was purely conjecture. I actually disagree
with Davis' interpretation of his results as it applies to audio since
it doesn't address detectability by humans. The part of the article
worth reading is the part where he measured the electrical properties of
the cables and noted their interactions with amplifiers. That's the
purely scientific aspect of the article. Like most scientific articles,
the interpretation at the end of the paper is subject to debate, but the
results aren't unless you take issue with his methodology.

On AudioQuest's site, in their FAQ section, they state speaker cable
length differences of 25% will make a difference. I don't know how since
the signal is traveling so fast and with the various other problems we
face with acoustics, I think any difference there may be measurable but
not discernable.


I've spent a considerable amount of time criticizing Audioquest's FAQ in
here. I think they're also the company that tries to convince people
that the skin effect is relevant in audio and comes up with some bogus
claims. I won't buy from them. But I probably wouldn't buy that
overpriced crap anyway.

Reply
Thread Tools
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
bipolar, dipolar, monopolar speakers explained Norris Watkins General 1 April 12th 04 05:14 PM


All times are GMT +1. The time now is 11:30 AM.

Powered by: vBulletin
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AudioBanter.com.
The comments are property of their posters.
 

About Us

"It's about Audio and hi-fi"