Flat cables vs round cables?

Zilch510

AVForums Super Veteran
Joined
Feb 24, 2019
Messages
1,019
Reaction score
174
Location
Durbanville, Cape Town
I think I read somewhere that flat cables are better than round cables, iirc something about the natural flat shape having less inductance or some rubbish.  Was a long time ago.

Really interested to know if there are any technical reasons as to why one should consider flat cables.  They certainly are very eye-catching.
 

DeonC

AVForums Super Veteran
Joined
Feb 4, 2010
Messages
1,995
Reaction score
126
Location
Kimberley, South-Africa
Zilch said:
... the natural flat shape having less inductance...

Yes, but they have much greater capacitance IIRC (which some amps mighy not like very much). Gain some, lose some. TBH, I think Kimber with their braided cable and XLO with their unique construction is better. But there are others much more experienced and more knowledgeable then me that can cast greater light on this matter.
 

chrisc

AVForums Grandmaster
Joined
Dec 24, 2008
Messages
14,145
Reaction score
1,247
Location
Cape Town
A braided cable is easy to make on your own and the advantages can outweigh using relatively inexpensive wire

https://youtu.be/O9X3R2Ukhf4

8-way:  https://youtu.be/5-ShuLHnB7k

rS85d9n.png
 

handsome

AVForums Super Veteran
Joined
Jan 23, 2009
Messages
1,354
Reaction score
352
Thin, wide conductors have lower inductance. Inductance increases in a wire if you coil it like a spring (it is now an air-cored inductor - wrap the wire round a magnetic metal and you have a traditional inductor). Capacitance results from how close the conductors are to one another.

Braided cables have low inductance because because the three or more cable braiding makes the wires zig-zag across one another, as opposed to two cables being twisted together would which make two coils increasing inductance. However braiding multiple cables increases capacitance.

Three-wire braiding is easy?but not fun and painful on the hands - you will probably only want to do it once. 4 and 8 wire braiding is harder as you have to keep track of which strand is which. However you can easily and cheaply make yourself some very good-looking and capable speaker cables. Get yourself some CAT network cable that uses solid-core conductors - usually marked ?plenum? for CAT5. Then either strip the outer insulation and directly braid the inner conductor pairs or braid three or more complete CAT cables directly. CAT 5 has four twisted pairs of 24 AWG conductors, twelve 24AWG conductors equals one 13AWG conductor and thats about as large as you need to go!
 

Cuco

AVForums Member
Joined
Feb 6, 2017
Messages
201
Reaction score
38
Location
Johannesburg
Flat cables can contain small amount of different type of snake oil in parallel. It depends on the type of snake oil and interaction between these, which sometimes is referred as capacitance. 
 

d0dja

AVForums Grandmaster
Joined
Nov 26, 2010
Messages
2,952
Reaction score
68
Location
Johannesburg
+1 on what handsome said.

Flat cables would have lower capacitance as the narrow bits are facing each other. Capacitance comes from how close conductors are and the surface area presented by each to the other.

Flat cables are normally a minor second down on regular cables.
 

chrisc

AVForums Grandmaster
Joined
Dec 24, 2008
Messages
14,145
Reaction score
1,247
Location
Cape Town
I've seen speaker cables with the same design as FM tape - conductors quite widely spaced.  van der Hul's premium cables are like this.  I am sure this was not an accident that they were designed like this

9xNW1Wq.png
 

jlaubza

AVForums Member
Joined
May 28, 2019
Messages
178
Reaction score
24
Location
Gauteng
chrisc said:
I've seen speaker cables with the same design as FM tape - conductors quite widely spaced.  van der Hul's premium cables are like this.  I am sure this was not an accident that they were designed like this

9xNW1Wq.png

The flat cable in your illustration has very low capacitance but high inductance, relative to zip cord type cables. The effect of this cable will be very dependent on the amplifier output circuit but one can expect an early bass roll off due to the high inductance.

I've actually tried using FM tape wire as a loudspeaker cable (over a short distance and the sound was distinctly of a manure nature.
 

chrisc

AVForums Grandmaster
Joined
Dec 24, 2008
Messages
14,145
Reaction score
1,247
Location
Cape Town
How can a widely spaced cable have high inductance?  Surely an inductor needs to be designed in a coil format to be effective.

Reviews of this very expensive vdH cable extol it?s neutral effect
 

handsome

AVForums Super Veteran
Joined
Jan 23, 2009
Messages
1,354
Reaction score
352
Capacitance is a byproduct of 2 (or more) conductors whilst inductance is a property of a single conductor.

Sent from my SM-A715F using Tapatalk

 

chrisc

AVForums Grandmaster
Joined
Dec 24, 2008
Messages
14,145
Reaction score
1,247
Location
Cape Town
Yes it is, I know that

The size of a magnetic field generated by an AC current (not voltage) in a cable diminishes by the square of the distance from the cable.  It is a scalar quantity

The magnetic field density can be calculated using B-u*(NI/I) but would really only apply with much larger currents.  (u = magnetic permeability of air)

Lets assume that the current through speaker cables is 5 amps.  The subsequent magnetic field will be so weak that any voltage in the adjacent spaced cable would not be measurable by consumer instruments and be overwhelmed by the signal (music in our instance)

You can also read this text:  http://www.phys.uri.edu/~gerhard/PHY204/tsl216.pdf
 

handsome

AVForums Super Veteran
Joined
Jan 23, 2009
Messages
1,354
Reaction score
352
Indeed but the ability for two pieces of conductive material to behave like a capacitor is entirely based on their physical size, the spacing between them and the kind of insulator that separates them. Currents and/or voltages through them does not play a role. Any conductor possesses inductance: thin, wide conductors have less inductance than round conductors of the same cross-sectional area and coiling up any conductor will increase its inductance; the inductance of a conductor has nothing at all  to do with a second conductor (unless of course you are quantifying a transformer but that is two or more inductors in one package)
 
Top