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Re: Not Just a Review, but

Posted by twest820 (A) on March 16, 2006 at 22:06:27

In Reply to: Not Just a Review, but posted by Jon Risch on March 16, 2006 at 16:59:15:

In general, I'd say any sort of review is a matter of opinion; you're welcome to object to my diction.

> You pepper your review with personal opinion, but state it as if it were factual:
>> On the low end MI2 has no advantage over any other AWG 10 copper cable ...

At low frequencies (say below 500Hz) inductive and capacitive impedances in the nH/pH or nF/pF range are small compared to the resistance of ~AWG10 worth of copper. Since the resistance is dominant the electrical behavior of two AWG 10 cables will be functionally identical (assuming other things such as termination are held equal).

>> "Air aside, Teflon's about the best dielectric around at RF frequencies but the difference between it and something with a larger loss tangent like vinyl is basically negligible at audio frequencies; in a speaker cable Teflon adds cost but not really any value."

Both materials vary depending on exact composition, but PVC usually has a loss tangent around 10% and Teflon of 0.05% for frequencies below 1MHz or so. This translates into a shunt impedance of something like 5GOhms/foot in MI2 for PCV and 5TOhms/foot for teflon.

>> Used MI2 bi-wires are pretty easy to find on audiogon and are often close enough to DIY costs to be worth the savings in hassle.
> This is also a bit of opinion, but in point of fact, you contradict yourself on this one.

Yep, it's an opinion. A further opinion of mine is the question of whether or not cables are overpriced is orthogonal to how much you value your time. So I personally don't think I'm being particularly contradictory.

> It also means you spent over $400 for your speaker cables alone.
> Your bi-wire 10 foot pair will end up at 18,900 pF total capacitive load per channel.

Actually, I bought a biwire pair a bit over 8 feet long for $175 (actually closer to $11 a foot than $10 if you want to be particular). I wired my bi-amp using one half of the pair and gave the other half to a friend who cut it apart and used it to monowire his bookshelves.

The $10/foot I mentioned for a bi-wire includes both cables, so a 10 foot bi-wire would run to $200. I agree with your capacitance numbers for a 10 foot bi-wire, but in my case it's more like 7nF per channel.

> Yes, the L is a little smaller on the Goertz, and slightly smaller on the CAT5, but at a tremendous increase in capacitance.

> I do not consider bare wires or a strip of 10 mil copper to be a proper termination.

I've wondered about the contact resistance of bare wire verus bananas or spades but don't happen to have access to a set of Kelvin probes to make accurate resistance measurements. If you have any comparative figures for the contact resistances of different terminations I'd be quite interested in seeing them.

Deformation of bare wire as the binding post is tightened definitely loosens the connection. However, I've found you can get a mechanically stable connection if you go through a few iterations of wiggling the cable and retightening the post. Another potential drawback of bare wire (or direct foil connection) is the risk of oxidization increasing contact resistance over time.

> These can be effective for most of the affected amps, but there are still a significant number that would not be stable, even with the Zobel networks.

Yes, it's a risk. However, the only data point I have to work with is my Parasounds, which work just fine with doubled MI2 without Zoebels.

> Many DIYer's have found that PVC in a speaker cable sucks, that it can be heard as a detriment, and that low inductance is only one of several traits that a speaker cable should have to provide the very best sound.

Interesting observation. The dielctric properties of polymer compounds vary widely based on composition. Since you're quoted in another fork of this thread as recommending Kimber TC let us take 8VS and 8TC as examples. 8VS uses polyethylene insulation---there's plenty of overlap in the dielectric property ranges of polyethelene and PVC so the two are basically equivalent unless you have information about the exact materials used---and 8TC uses teflon information. Kimber's published RLC parameters for these two cables are quite similar with 8TC being slightly more capacitive and slightly less inductive. 8TC therefore has somewhat lower impedance than 8VS. For an 66 cm cable this translates into a 0.06dB reduction in cable loss at 1kHz and about 0.76 dB at 20kHz. If you shorten the cable to 60 cm then the 8VS figures are very close to the 8TC figures at 66 cm.

How would you say the listening experience with 8TC cables compares to 8VS cables which are about 10% shorter?

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