audio cable versus coat hangers

[A. J. deLange]

The distinction is as to whether the circuit looks like a transmission line or not and that is a function of the frequency of the energy being carried. A piece of RG/8 (coax) is a transmission line at any frequency but for 20KHz audio frequency a meter of it represents about 2/15000ths of a wavelength i.e. .05 electrical degrees. If you analyze it as a transmission line you won't find much impedance transformation (transmission line behavior) in that much of a rotation and so engineers don't treat cables that short as transmission lines. There is no need to. Monster's main marketing pitch seems to emphasize the use of materials and manufacturing techniques which are important features of the design of transmission lines but speaker wires simply aren't and so it doesn't make any difference. None of the engineers I have known to try to measure any differences between monster cables and any other have been able to find anything unusual about them at audio frequencies.

Digressing a bit: "Skin effect" causes currents at high frequencies to be confined to near the surface of a conductor. This is why tubing is often used at r.f. where large currents are involved. Tubing also conveniently forms coax and that is why coax is frequently seen at modest r.f. frequencies. The problem with it is that the center conductor has to be held in the center. The supports must be made of some type of insulating material and this is lossy. At higher frequencies thus waveguides (no center conductor) are used.

Skin effect causes the resistance of a conductor to go up with frequency. The strategy for keeping resistive losses down is to make the biggest diameter tube practical with thickness approximately the same as the thickness of the "skin". At audio frequencies there is no skin effect so the strategy is to get as much metal as possible in there e.g. 4/0 is a better conductor (less resistance per foot) than 22 ga.

There is one application at low frequency at which tubing is used and that is where voltages are very high. The intensity of the electric field surrounding a charged conductor is inversely proportional to it's radius. Fat conductor means a lower field with less chance of breakdown (arcing).

I hope everyone has enjoyed this little dip into the pool of electrical engineering trivia.

[Vic Owen]

To add a little to this...

In many radar systems, I've seen the use of copper tubing to carry the "skin effect" currents, as well as just the large DC currents in the HV cage. The introduction of waveguide, however, opens up a whole new field of "magic" (FM). The behavior of RF signals traveling down a waveguide exhibit significantly different characteristics. The RF is comprised of E & H fields, in quadrature, and actually bounce off the inside of the waveguide walls during their travels. The rectangular dimensions of the waveguide are critical to a specific range of frequencies. It's considered virtually lossless over the normal distances used in radar systems.

[A. J. deLange]

A waveguide may seem to work by "FM" but is actually just another form of a transmission line (above the cutoff frequency). It follows exactly the same rules as a coax or a pair of parallel wires. In reality even the pair of coat hangers forms a transmission line though, as noted above, they are too short to exhibit the behaviour to a noticeable extent.

One of the most interesting paradoxes here is that no energy is actually conveyed within the wires, tubing of a coax or walls of a waveguide but rather in the space surrounding the wires, the space beween the conductors in a coax or the space inside a waveguide. People may find the latter case intuitive but the wire case counterintuitive with the coax pehaps midway between.

[Vic Owen]

I think that I can agree with some of that, in general terms, regarding electromagnetic fields, however, the physical characteristics play a much more significant role in a waveguide. For example, the cross-sectional dimension of a waveguide must be greater than 1/2 wavelength to contain an electromagnetic field properly; fields below the cut-off frequency will not propagate. A waveguide is much simpler to construct, since it has no center conductor. Wavelength, however, becomes much more significant; a waveguide for 200 MHz, for example, would have to be around four feet wide. Interestingly, metal walls are not necessary, since the fields will be reflected whenever they encounter a different dielectric than the material through which they're traveling. Fields can be made to travel through a ceramic rod, for example, since, when they encounter air, they are reflected back into the rod. Not real practical, though.

Obviously, an in-depth discussion of waveguide theory is well beyond the scope of this forum; as I recall, this started out with coat hangars!

[Allen Plowman]

aren't we getting a little off topic here? isn't this thread about coat hangars?

(just kidding)

[A. J. deLange]

Originally Posted by Vic Owen

Fields can be made to travel through a ceramic rod, for example, since, when they encounter air, they are reflected back into the rod. Not real practical, though.

Optical Fiber! Monster has those that supposedly work better than other peoples', too. And thus we got it back on topic.

[Petri Kaipiainen]

As far as I know there are also many $$$$ digital connection cables which make the signal more musical and pictures more true to life...

A good optical link cable certainly makes the signal more transparent???

[John DeLuca]

The quality and thickness of the wire will matter if you have long runs (did they even mention how long the run was in the article?). Check this out-

http://www.bcae1.com/images/swfs/spe...rassistant.swf

[Gints Klimanis]

I'm willing to pay more for connectors that last and wires that don't fray. Sure, we laugh at Monster for their claims, but the cables are well-built in my experience. There are some mid-grade cables by Phillips that are also better than the cheapie consumer grade cables but not as much as the Monster cables.

[Kevin Randolph]

Just to throw in my 2 cents...

Once upon a time I worked at a consumer electronics store that sold Monster Cable and one day a Monster Cable Phone Cable came in on the truck to use with your computer modem. Yes, it was a few years back. My natural instinct was, "Are you kidding me?" So I took one of them into the store manager's office and hooked up his computer using the cable. Transmission speed for the modem went from 33.6kbps to 48kbps just by switching out the phone cable.

So do I think the expensive cables are that much better? I'm sure that you can prove it on some type of monitor with some type of test equipment. But for me, I buy high quality enough to get an RF shield in the cable and let it go at that.

Kevin

[John DeLuca]

The article is misleading. It should say- ‘High quality short run cables are a waste of money for the average consumer’.

-John