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Old 1st June 2010, 10:19 PM   #11
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Some of the heaver RG-8 and RG-11 would make good but stiff speaker cables. Capacitance ranges from 55 to 100 pF/m. Cable diameter is about 10mm.

For twisting two wire cables, I put one end in a vise and a battery drill at the other.
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Old 2nd June 2010, 03:20 AM   #12
star882 is offline star882  United States
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Use coax for unbalanced signals and shielded CAT5 or CAT6 for balanced signals. And fiber offers the very best EMI immunity.
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Old 5th June 2010, 10:48 PM   #13
Xoc1 is offline Xoc1  United Kingdom
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I have a personal preference for using woven cables like the designs by Kimber Cable
These cables were designed to cope with high EMI.
The story behind Kimber Kable
I have no idea if this really has a performance gain over twisted pairs, but I like the way that the cables hold together.
The tricky bit is the braiding process, but I have made bi wire cables of 8 metre long for my PA (with some difficulty!).
3 wire braid is easy. 4 wire takes some practice but a quick google search will get you some info on braiding.
If you are really suffering with EMI problems, You might also concider filtering the input to your amplifier and improved grounding.
Ben Duncan has a done a lot of work on EMI, and you can find some of his products here.
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Old 9th June 2010, 11:44 AM   #14
Galgo is offline Galgo  Israel
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Quote:
Originally Posted by Xoc1 View Post
I have a personal preference for using woven cables like the designs by Kimber Cable
These cables were designed to cope with high EMI.
The story behind Kimber Kable
I have no idea if this really has a performance gain over twisted pairs, but I like the way that the cables hold together.
I also liked the design of these cables and would probably experiment with these and twisted pairs as well.

I'm talking about SPEAKER wires currently not interconnects or internal wirings (which I already have good results with CANARE StarQuad and shielded twisted pairs cables).

I've got some info regarding the shielded wires I considered using - they are multi-stranded silver plated cooper with PTFE and plated cooper wire shield + PTFE again:
1X26AWG 37pf/ft
1X24AWG 41pf/ft
1X22AWG 50pf/ft
1X20AWG 54pf/ft

It seems WAY too high considering I'll need to braid/twist few of them together (it's in capacitance for ft...) - right?
So no shielded cables for speakers...

I'm waiting for same data for the unshielded and twisted pairs variants which I expect to be better...

any insights?

Gal
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Old 11th June 2010, 11:01 AM   #15
Galgo is offline Galgo  Israel
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Hello again,
I decided to go for twisted/braided design (will experiment with both).
Wires will be PTFE covered Silver plated copper - 19strands wires.
Any recommendations for required AWG ?
(I'm talking ~50W RMS, 91db, 50Hz-25kHz speakers).
I don't want to go to extremities - just some experimentations - so I'll look for something around 2mm inductors cross section per each lead (4 of these per speaker).

How many wires to combine for each Biwire cable?
As much as possible with smaller gage (high AWG)? or one thick multi-stranded wire 18-20AWG is enough?
Combine various AWG within each lead?
Making the ground thicker than signal?
Making the LF thicker than HF (I'll probably do that anyhow).

Please share your "recipe" with me
Gal
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Old 11th June 2010, 11:02 AM   #16
Galgo is offline Galgo  Israel
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BTW - any reason to use other insulators instead of PTFE?
Silk/Cotton etc.? or is it going too far !?
Gal
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Old 11th June 2010, 01:26 PM   #17
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The geometry of the cable is insignificant compared with the way most speakers are wired up inside, unless you have a really wide spaced pair like DNM. Too many speakers have widely separated wires to the drivers creating huge loops
If you don't want to fix bad speaker layout, you could try putting 100R in series with 1nF across the speaker terminals to reduce rf going into the amp
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Old 11th June 2010, 02:47 PM   #18
Sheldon is offline Sheldon  United States
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Quote:
Originally Posted by richie00boy View Post
Just take a pair of wires and keep the end in one hand. Have your writing hand about 5cm further along holding the wires free. Now twist both hands in opposite direction like you would be wrapping a sweet (candy). You should find the wire has a tendency to twist at a 'natural' rate. The twist should stay in place by itself, but you could heatshrink segments or all if you wish.

It helps if you can work on the floor or other big clear space where the wires are free to flap around and will remain supported and level.

CAT5 cable is too thin and messy, having lots of terminations to do. A screened cable would be OK but for the screen to be any good it must be earthed (grounded) at both ends, something which you probably can't do. Earthing one end only is worse than no shield as it creates an antenna.
The best method I've found for twisting (which I think came from Morgan Jone's tube amp construction methods), is to take the two wires of the same length, put the one ends in a vise or clamp them to a sturdy support. Stretch the wires straight and tighten the other two ends in a power drill chuck. Start winding with the drill, keeping modest tension on the wires. At first, the twisting wires will pull in slowly. At some point, they will start to pull in quickly, and if you continue, will bunch. Just at the point where they start to pull in quickly, stop twisting and give the wires an extra pull to "set" the twist. Unclamp the wires and let them relax. Done.

BTW, in the environment described by the thread starter, I'd be more worried about the stuff coming through the mains, than stuff coming through the air.

Sheldon
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Old 12th June 2010, 04:19 AM   #19
star882 is offline star882  United States
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Quote:
Originally Posted by Galgo View Post
I also liked the design of these cables and would probably experiment with these and twisted pairs as well.

I'm talking about SPEAKER wires currently not interconnects or internal wirings (which I already have good results with CANARE StarQuad and shielded twisted pairs cables).

I've got some info regarding the shielded wires I considered using - they are multi-stranded silver plated cooper with PTFE and plated cooper wire shield + PTFE again:
1X26AWG 37pf/ft
1X24AWG 41pf/ft
1X22AWG 50pf/ft
1X20AWG 54pf/ft

It seems WAY too high considering I'll need to braid/twist few of them together (it's in capacitance for ft...) - right?
So no shielded cables for speakers...

I'm waiting for same data for the unshielded and twisted pairs variants which I expect to be better...

any insights?

Gal
I would suggest coax, two per channel if you're running BTL. Common RG6 can carry plenty of current (7A or so). Also note that modern amplifier designs often have a few hundred nF in the output filter, so a few hundred pF is not going to be significant.
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