What is the minimum distance to prevent induction in looped speaker cable?

What is a prevention of induction ?  Wether it might spontaneously combust ! Why should it be eliminated ?  Is it more harmful for a Naim system to suffer from too much induction than not enough length/ induction/capacitance ? Is this a design artefact that comes from using din - din ?

Was this intended as a brainteaser? Of course the width of the spacer will be dependent on the material used.

When electric current flows through a conductor, it creates a magnetic field around the conductor. That field will, in turn, create an electric current in another conductor placed within the field. That's induction. It's how transformers work.

In a speaker cable (a pair of parallel conductors), when current is flowing down one conductor, an opposite and equal current is flowing back through the other conductor. Since the current is opposite, the magnetic field will also be opposite in direction. The two magnetic fields will tend to cancel and, presumably, minimise induction of current in the conductors.

Nac A5 cable is designed as a spaced pair of conductors. If I understand correctly, the spacing - which is about 12 mm - was chosen to provide the ideal inductance for Naim amps. 

So, back to my question. If the cable is tied together in concertina fashion, the spacing between conductors (at the points where tie-wraps hold the cables together) is reduced to about half of the 12 mm spacing. Also, since each conductor is doubled back onto itself, the magnetic field is not opposite, so no cancellation occurs. 

Depending on the magnitude of the induction, what we could have is a slight smearing, where the audio signal picks up a trace image of itself at the cable-tie points.

The effect (if any) is probably too small for the brain to register (or is it?). A hunch tells me that doubling Naim's 12 mm spacing for parallel conductors with opposite current would be a good place to start for conductors with identical current direction, but I wonder if anyone has done the calculations?

Thanks for bearing with me

Jan

Thinking a bit more about this, it might be better to twist the Nac A5 at the tie-wrap points, so that current flow is opposite in the closely spaced conductors. Magnetic fields will then also be opposite, improving cancellation and, presumably, any effects of induction.

Jan - 

unless you twist the pair of wires at each bend so that the bottom wire goes to the top and the top wire goes to the bottom (not done in your photo), the currents in the two adjacent wires where they touch are, in fact, in opposite directions: that would be the obvious rationale for your concertina pattern. Draw an arrow for the current on a wire if your goal is to minimize mutual inductance: it zigs and zags as you point the wire first upwards in the photo then (after your bend) back downwards. You would maximize inductance by winding the wire in a spiral coil - that is the geometry where the adjacent wires carry current in the same direction. Indeed, that is how you would wind a transformer... 

I have no idea (not having done any math here) what the change in inductance will be, but your pattern would minimize this effect  

I hope this is clear enough to help!

Regards alan

Good luck with twisting the Nac A5! If it was me I'd space it out. I like to keep my cables well apart from each other and I'm furtunate enough that I don't have any cable coiled up. Can you get shorter cables? Or shorten the ones you have? 

Our messages crossed, Jan.

think of only one wire, not a vertical pair. Winding in a spiral has a continuous (say clockwise) arrow for the current; winding zig zag has alternating arrows going up then down then up. 

Twisting the pair of wires would swap this over and undo your strategy. A Google search on bifilar windings might produce diagrams that would help you visualize this.

Regards alan

If you have 250DR it seams that it is not an issue according to steve sells chief designer  at naim 

http://www.the-ear.net/review-...0-dr-power-amplifier

and interestingly neither is the 250.2 according to that article... 

However with regard to the OP clear;y it is best to avoid adding too much inductance or capacitance to a speaker cable run as it will interact with the amplified  power signal and the speaker crossover... and at least try and keep both channels reasonably consistent..

I would say adding proper instead of adding to much The design of POA is designed optimised for a load to give the best performance . I think that is what Naim is trying to state with their 3,5 m cable length 

Hpw20001 posted:

I would say adding proper instead of adding to much The design of POA is designed optimised for a load to give the best performance

Have you considered a career writing instruction manuals? 

It was not the purpose to be, as suggested a manual writer. It was an experience. Everything is not maximise or minimise my old friends amplifier was hot, egg frying tem. when he had the wrong cable length. But since you are trying to say my comments is not imprtant maybe you are the manual writer

Stop it I'm crying! 

Are you serious? You are making this way more complicated than it really is

 Don't overthink this stuff. Just connect the cables to  your amp and listen to your music and enjoy it. It's just a stereo for heavens sake.

Sorry I don't se how I am involved 

Not wanting to add a spanner to the thread but the Naim recommended zigzag arrangement worked superb for creating an aerial to pick up local radio. I couldn't find any location for the zigzag arrangement where this didn't happen. 

The best compromise I could come up with was to commit the sin of coiling. However, I've attempted to mitigate this by arranging it as a concentric coil where the cable only meets itself at the apex of the circle and each loop puts another 2cm of air between it and the previous loop at the point oppose the apex.

Other than having 2 different lengths of cable, I really can't see another suitable arrangement. After speaking with my dealer he also confirmed the Naim zigzag doesn't work well for some other users (himself included) due to picking up radio stations. The 250 and 135s appear particular sensitive to this.

alan33 posted:

Jan - 

unless you twist the pair of wires at each bend so that the bottom wire goes to the top and the top wire goes to the bottom (not done in your photo), the currents in the two adjacent wires where they touch are, in fact, in opposite directions: that would be the obvious rationale for your concertina pattern.

Thanks Alan for pointing this out ; quite obvious, now that you mention it...

I'll tie-wrap the cables with some foam spacers and see if I can notice any difference, without, I hope adding an aerial to the system.

Jan