Sexy speaker cables

I realised that a lot of audio system buffs have fat, well finished speaker cables with what looks like layers and layers of cladding. The Darbari, being 3-way active speakers, requires six cables emanating from my multi-channel amp to the four boxes. That's a lot of cables. It would be nice to invest in making sexy speaker cables.

I looked at various DIY speaker cables recommended by various builders. I saw the braided or plaited speaker cables, and speaker cables made by (many cores of) solid-core copper pulled out of UTP Ethernet cables. I calculated how many cores of UTP cable conductors I would need to arrive at some significant cross-section area of copper, and realised that a lot of cores would be needed. I went back to basics from Linkwitz and Doug Self and realised that it's unlikely that any well-made electrical cable would improve the sound of the audio system. It was all about durability and looks now. And in the looks department, I discovered sleeves, sheaths, termination techniques, all of which would make a finished product look much sexier.

So, I poked around at the kind of cable sheaths and sleeves and tubings available, and then imported small quantities of various things from a fabulous source: CableOrganizer.Com. I built one or two test stretches of cable, and fixed my errors in the sizes of various types of sleevings and tubings. I bought myself a hot air gun, since heat-shrink technology is key to building sexy speaker cables. These were the days before started stocking lovely Black and Decker hot-air guns for paltry sums -- I bought a cheap, unbranded Chinese product, which, luckily, worked.

And then, with the lessons thus learned, I built six cables for the Darbari.

My terminology

A logical speaker cable is a cable which conducts current to one of the terminals of a terminal block. Therefore, to connect one conventional passive speaker to a normal stereo amp, you need two logical speaker cables, one for the "plus" or red terminal, and one for the "minus" or black terminal. A normal stereo setup needs four logical speaker cables.

A physical electrical cable is something which carries electrical current. It could be a single thick copper strand, or a thousand hair-thin copper strands inside polyethylene insulating sheath. I built each of my logical speaker cables by putting three physical electrical cables in parallel, to get a good balance of physical flexibility and low impedance.

A finished speaker cable made by my process contains two logical speaker cables, for the red and the black terminals. Therefore, each finished speaker cable is for one passive conventional speaker enclosure. For a typical stereo setup with passive speakers, you need two of my finished speaker cables.

Step-by-step build process

  1. Wind the raw electrical cables into twisted pairs. Procure good Finolex or Polycab cable (choose something suitable if you are outside India) from a genuine dealer. Fake cables which poor copper or even copper plated aluminium abound in India. Good, high quality genuine electrical copper cables are all oxygen-free copper. Buy cables of 2.5 sqmm cross-section area. Make each twisted pair by winding one black and one red physical cable. I bought boxes of 90 metres of Polycab cable of this thickness for Rs.1,300 (about USD 20) per box. One box of red cable and one box of black cable was more than sufficient for all my Darbari cables, with 20% left over. If you just have a passive stereo pair, your cable requirements will be much shorter.

    If you want to make a 3-meter speaker cable, you must cut a black cable of 3 metre length, a red cable of 3 metres, and wind the two together. I used a hand drill for the winding -- manual winding without a drilling machine is absolute hell on the hands. My drill has speed controls, and a gun-like trigger to control the speed precisely. My assistant (shown in photo) learned how to control the speed very well. I stood 3 metres away from him holding the other ends of the two cables. He started the drill and slowly let the strands rotate, till they twisted tight. With a bit of practice, it is very easy and quite quick.

    I made each logical speaker cable by combining three physical electrical cables each of cross-section 2.5 sqmm. In order to do this, I created three twisted pairs, and this collection together formed two logical speaker cables. The three twisted pairs gave me three red physical electrical cables which formed one logical speaker cable and three black physical electrical cables which formed the other logical speaker cable. Since they were all bunched together, I got two logical speaker cables to hook up both the speaker terminals in one neat bunch. More details below.

    Remember that the act of twisting shortens the effective length of the twisted pair. If you start with a black cable and a red cable each of 3 metres, the final twisted pair will be a few inches short of 3 metres.

    For a conventional setup, you will need three twisted pairs of physical electrical cables for the left speaker and three more pairs for the right speaker. That's six twisted pairs. This means you will need six lengths of black electrical cable and six lengths of red cable to start with.

  2. Slide transparent heat-shrink tubing pieces onto PET sleeves. These PET sleeves from CableOrganizer are used here, half-inch diameter. If you are building for a stereo setup with passive pair of speakers, you will need two pieces of this sleeve of the right length. The sleeves will need to be about a foot shorter than the physical electrical cable pairs. The reason for this will be apparent later -- you will need the physical electrical cables to jut out six inches or so at either end. So, you may think that if your twisted pairs of electrical cables are 10 feet long, your PET sleeves should be 9 feet long, and you will go and order 9 feet of sleeve for each speaker. That would be WRONG. These PET sleeves are like expandable pipes made of netting. They expand when you shove the electrical cables in them. As they expand in diameter, they shrink in length. Therefore, if you need 9 feet of PET sleeve after expansion, you should start with something like 9 feet 6 inches of raw PET sleeving. Be careful, order accordingly.

    The transparent heat-shrink tubing I used was 2:1 shrinking 3/4" diameter tube, again from CableOrganizer. It will shrink to 3/8" afterwards. Use the clear (transparent) type for this piece. Each piece is six inches long, and you need two of these for each PET sleeve. Cut two pieces of 6" each and slide them onto the PET sleeve, as shown in the photo.

  3. Insert twisted pairs into PET sleeves. In my experience, three twisted pairs of physical electrical cable slipped into one PET sleeve rated at half-inch diameter happily. The end of the PET sleeve will fray and expand a bit, but don't worry about it. It will get tied down nicely later.

  4. Straighten the ends of the physical wires projecting out of the PET sleeve. If you've done everything right, about six inches of physical twisted pairs must be projecting out of the PET sleeve at each end. Untwist the cables for these six inches. After untwisting, bunch the three red cables together and the three black ends together, in preparation for the next step. The photo shows how they look after untwisting. The lengths of cable inside the PET sleeve still remain twisted, of course.

    Each PET sleeve has three twisted pairs, or three red and three black cables. That's six physical cables at each end of the PET sleeve, or 12 physical cable lengths in all. You need to untwist and straighten these 12 physical cable lengths. This is just for one PET sleeve.

  5. Slide heat-shrink tubing on the ends of the physical cables. Bunch together the three black physical cables and slide one piece of heat-shrink tubing, 6" long and black in colour, onto this set of three. Then bunch together the three red cables and slide a piece of red heat shrink tubing, 6" long, on them.

    The heat-shrink tubing used here is 3/8-inch pre-shrink diameter, 2:1 shrinkage. This diameter is just right to shove in three physical untwisted cable lengths.

  6. Shrink the tubings at the ends. Fire up the hot air gun and shrink the six-inch lengths of red and black tubings at the ends of each cable. Once these are shrunk and tight, move the clear length of tubing (which is also six inches long) on the PET sleeve so that it covers the fraying end of the PET sleeve and just a bit of the ends of the thinner red and black tubings. Then shrink that too.

    Doing heat-shrinking is a slow process -- you need to turn the cable round and ensure that hot air hits the tubings from all sides for a sufficient length of time for it to get hot and shrink properly. Take your time. My estimate is that each end of each cable will take two minutes or so.

    The photo shows the transparent tubing now tightly gripping the frayed end of the PET sleeve, and the red and black tubing pieces have now acquired a twisted, gnarled look as they clamp down tightly on the cables inside them. The cable end in the foreground has been shrunk, but the other red-and-black pair behind it has not yet been heat-shrunk.

  7. Put on your boots. This is where you slide the cable boots, one at each end of the cable, and lock them down with the hot air gun.

    Each boot I used is rated as two-core, 0.9" boot size, which implies 0.35" cores and 2.2" length. See these products from CableOrganizer. You will see all sorts of sizes. Select the one I mentioned.

    Once this is done, the boots will securely clamp down on the PET sleeving and the clear transparent heat-shrink tubing and the two branches of red and white cables very tightly, and there's an internal lining of hot glue which melts and re-solidifies, thus sealing everything down in a total weather-tight seal for life.

    Each cable boot is fairly thick, and so the hot air gun takes time to do its job and shrink it properly. Budget two minutes for each cable boot.

    You now have finished speaker cables which look very sexy and professional. If you have a conventional stereo pair of passive speakers, you will have two of these thick cables lying on the floor by now. Each finished cable has the red conductor and black conductor to connect to the two terminals of one physical speaker.

  8. Prepare the cable ends. I needed bare copper to connect to the amplifier, and wanted gold-plated spade lugs to connect to the speakers. So, I now did this bit. For the amplifier ends, I stripped the insulation of each end for about one inch, and twisted the three bunches of copper from the three black cables into one bunch. Similarly, the three bunches of copper strands from the three red electrical cables became one twisted bunch for the red terminal.

    For the speaker end, I stripped the insulation again from the cable ends, pushed them into crimp-type spade lugs, and used a crimping tool to fix the lugs to the copper.

Job done, bar the hooking up and listening. The final photo shows how tightly the transparent heat-shrink tubing clamps down on the PET sleeve.

A summary bill of materials

This is the summary of everything you may need, per nominal metre of finished speaker cable:

  • Good electrical cable: 2.5 sqmm in cross-section, in two colours, red and black. You will need a little more than three metres of red and three metres of black.
  • PET sleeves: half-inch diameter, a little less than a metre. (Order one whole metre.)
  • Transparent heat-shrink tubing: 2:1 shrinkage, 3/4 inch diameter. Order one foot for each finished speaker cable, irrespective of length of finished cable.
  • Red and black heat-shrink tubing: 2:1 shrinkage, 3/8 inch diameter. Order one foot of each colour for each finished speaker cable, irrespective of length of finished cable.
  • Cable boots: two core, 0.9" boot size, which gives (in my case) more than 2" length and 0.35" diameter for each core's opening. Order two boots for each finished speaker cable.
  • Cable terminating lugs: I used spade lugs, which are my favourite type of termination. Choose your poison.

A summary of tools:

  • A good wire snipper and stripper
  • A pair of scissors: to cut heat-shrink tubing and PET sleeves
  • A drilling machine: to wind twisted pairs of electrical cables
  • A hot air gun: You get superb ones these days, like this one from Stanley and this one from Black and Decker. I didn't get these two years ago, so I bought a cheap Chinese thing which works just as well for me.
  • A crimping tool: if you are going to use crimp type connectors. I have two of these tools, for small and large connectors respectively.

What would I do differently the next time

The crimping of the spade lugs is exposed. This is about half-inch long, and you can see bare copper wire shoved inside the crimping end, and so on, as with any crimped connection. This crimping part should have been sheathed. I would add the following two steps to the whole process.

  • Between step 7 and step 8: slide small heat-shrink tubing pieces onto the cable ends. These will be the same 3/8" red and black heat-shrink tubing used for the cable ends earlier. Cut a one-inch piece of black tubing, slide it onto the already-shrunk black cable end. Cut another one-inch piece of red tubing, slide it onto the already-shrunk red cable end. Leave these pieces there. This needs to be done only for those cable ends where we will add spade lugs or other crimp-type terminals later.
  • After step 8: position the small pieces and heat-shrink. These small pieces of tubing should be positioned to cover the crimping, and then heat-shrunk. This will neatly hide the crimping and odd bits of bare wire.

A variation

It may be a good idea to extend the transparent outer heat-shrink sheath all along the full length of each cable, instead of just keeping them for six inches at each end. This would make it a tough cover to protect the PET sleeving from cuts and abrasion without taking away from the looks. A second reason would be to provide a smooth, easy-to-wipe surface when removing dust. As things stand now, the PET sleeve is like fine nylon netting, and attracts dust.

How do they sound?

Good speaker cables don't sound anything. Only faulty electrical connections or electrically poor cables (high impedance, or high capacitance, or high inductance, in really exceptional cases) impact sound. My earlier cables were simply thick electrical cables bought from a hardware stores -- they were 4 sqmm or 6 sqmm per physical electrical cable. The system sounded the same with those cables, but the cables were ugly looking.

I built these cables for their looks, solid electrical properties, and solid mechanical strength. I did not expect, nor get, any impact on the sound of the system.

People who have the science and/or engg education which I have, and who believe the things I do about audio systems, but who do not want to build speaker cables themselves, have two choices:

  • use good quality, branded electrical cable from a reputed hardware store, at least 4 sqmm in cross-section.
  • buy speaker cables made by Blue Jeans. These chaps are the only sensibly priced, excellent quality, no-snake-oil cable makers I know. (Yes, this is a tiny minority of manufacturers.) Their cables, needless to say, are better built than my DIY creations, though they don't have my neon-bright colours.

I know that these options will all give you transparent sounding speaker cables. However, you may believe otherwise.

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