Teflon insulated speaker cable

dazed

Member
2005-08-23 12:01 pm
I'm sorry if this has been answered before, but here goes anyway.

I want to make a batch of speaker cables, but every cable I'm able to source, has PCV insulation and jackets. (Belden 5000-series, for instance.)

I'd prefer teflon or PE insulation. Can anybody recommend a good cable for making speaker cables, with about AWG 10 (or thicker) conductors?

It would be good if it could be bought in lengths of (considerably) less than your typical 1000 feet spools as well.

Thanks!
 

Pano

Administrator
Paid Member
2004-10-07 6:05 am
Panama
In the USA it is easy to find teflon insulated, silver plated copper wire in many sizes. Often in surplus houses at good prices. ApexJr., for example.
No idea if you can find the stuff way up north, where you are.

Teflon does have triboelectric effects Triboelectric effect - Wikipedia, the free encyclopedia, but at the low impedance of speaker drivers, it may not matter.
 
Teflon is good if you are planning to have a fire in your house. Burning PVC emits toxic fumes.

Better yet, when teflon is burned it produces phosgene gas. Much more toxic than PVC burning. Several workers lost their lives in the 60's in the US when teflon insulated wire became available for aerospace applications. Several deaths were associated with the space program. Workers were using thermal strippers, burning small amounts of insulation with each lead. For a few it reached toxic levels.

paul
 
Better yet, when teflon is burned it produces phosgene gas. Much more toxic than PVC burning. Several workers lost their lives in the 60's in the US when teflon insulated wire became available for aerospace applications. Several deaths were associated with the space program. Workers were using thermal strippers, burning small amounts of insulation with each lead. For a few it reached toxic levels.

paul

Hmm, never heard that one. Phosgene Gas is one of the chemical agents used as chemical warfare in WWI (invented and first used by the French).

It is extremely deadly ... accounting for 85% of all casualties due to chemical attack, despite not being the most widely used agent by a long shot. It prevents absorption of oxygen and thus it's method is suffocation.

It is very commonly used in industrial processes and is required for the manufacture of polyurethanes and polycarbonates. If you wear glasses, there's probably polycarbonate at the end of your nose right now.

Exposure badges are readily available. It is also relatively easy to generate accidentally, in the home, in welding, in HVAC systems.

I am very surprised to hear that deaths occurred due to inadvertent exposure in a workplace, especially when it's distinctive odour is noticeable below lethal concentrations. It kills quickly; if exposed to a deadly amount you will drop dead; it's not something that takes days to work.

Do you have any news reports or citations you could give me regarding death due to Teflon heating?

Now, if we're talking PVC, the industrial dangers to those who work in the manufacture it are well documented. Class action lawsuits; EPA regulations, workers compensation and long-term disability claims, the works.

Eats the liver; causes cancers, attacks the respiratory system, eats bone tissue, attacks blood vessels, skin, etc.

Somewhat back on topic, the reason PVC is not ideal for loudspeaker cable has nothing to do with electrical properties but instead its enviromental properties (ie not in the "tree hugger" sense of the word) ... it allows oxygen migration through the PVC dielectric which oxidizes (corrodes) copper.

I am sure everyone has seen examples of aged speaker cable with green conductors visible through the clear PVC jacket.
 
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As far as I could determine, Teflon releases PFIB when heated, not Phosgene. Although they are similar and are chemically related, they are not the same thing.

Now, PVC does actually release Phosgene Gas when heated between 300 and 600C; see:

Brown and Birky (1980)

... and:

Bjerre, Anders; HEALTH HAZARD ASSESSMENT OF PHOSGENE FORMATION IN GASES OF COMBUSTION OF POLYVINYL CHLORIDE USING A SIMPLIFIED METHOD OF MATHEMATICAL MODELLING; Annals of Occupational Hygiene; Oxford University Press; (1984) 28(1): 49-59.

The only references that I could find regarding Teflon and Phosgene came via unattributed allegations via nut-bar websites trying to get people to throw out their non-stick muffin pans. It was often repeated but never referenced to a citation. I attribute that to my suspicion that there are none.

My guess is that people just made the jump they wanted to make; ie similar to Phosgene equals identical to Phosgene equals Teflon is Poison, and then a call for the pitchforks and torchlit mobs.

But chemistry is funny sometimes ... a little molecule here or there and the entire nature of the chemical can change from benign to deadly, but that little molecule is still required ... this isn't "horseshoes and hand grenades" where "close is good enough".

Having said all that, PFIB is also a deadly toxin. Like a lot of things all around us every day; don't burn it and don't breathe it if you do.

The short answer is a lot simpler ... burning anything changes it chemically, and usually the result is something that if you breath enough, is toxic to fatal. So don't breathe smoke, which is itself potentially fatal, even if it's just plants from nature that are burning.
 
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So don't breathe smoke, which is itself potentially fatal, even if it's just plants from nature that are burning.

Well, hell, there goes my New Year's Eve plans.

Yes, you're correct, there's no phosgene in PTFE. Interestingly, there IS phosgene in polycarbonate (e.g., Lexan), but the chlorines are stripped off during polymerization with the notorious BPA so there's no phosgene when PC burns.

It takes a much lower temperature to get bad stuff to come out of PVC than PTFE, though, so the comparison is chalk to cheese.
 
I like numbers - we physicists are like that! Very boring, but instructive. Let's do a very rough calculation. Assume a speaker cable with poor dielectric (maybe PVC?). Let's assume 5m at 100pF/m, so 500pF in total. Most speaker cables will probably have lower capacitance than that. Assume an amplifier output impedance of 1 ohm (i.e. DF=8) - not very good (unless you are into valve SE). Assume that at peak bass voltage the capacitance varies by 10% due to the voltage swing across our poor dielectric - probably an overestimate. This means that the low pass filter formed by our output impedance and cable capacitance will modulate an HF signal and give intermodulation.

Do the sums (for 20kHz) and you find that the error signal is -104dB with respect to the music. I think this should be inaudible due to noise and masking. You can play with the figures and make different assumptions, but you have to have a very bad amplifier driving a long cable with very poor dielectric insulation before you get something which might be heard. My conclusion is that it really doesn't matter what you insulate speaker cables with.

It may matter what you insulate interconnects with, if they are long, your preamp has high output impedance and your main amp requires many volts of input signal. These conditions are more likely with 'high end' equipment, using something barmy like SRPP output from the preamp?