HDTV Forum

Originally the title of this thread was

I found this site and thought it was interesting enough to pass along. I still think you get what you pay for and that a sucker is born every minute


http://home.earthlink.net/~rogerr7/wire.htm

JZ

This is true for zip cord. Zip cord is not speaker wire.

Speaker wire should be a coaxial product designed for 8 or 4 ohms. Zip cord is anywhere from 150-300 ohms.

Richard

Richard - what is your rationale? Coaxial construction and characteristic impedance pertain to unbalanced systems operating at frequencies where transmission line effects occur. Audio frequencies are too low to take advantage of the self-shielding properties of coax, and its controlled impedance. If anything, a shielded twisted-pair cable would be more appropriate for a speaker cable. But speaker impedance is so low, and levels are so high, there's no advantage to having the shield. Two conductor cable like zip cord is just fine.

Are we getting into another 'power conditioner' thread?


emc guy

EMC Guy's got the coaxial requirement for speaker cable pretty well covered. I'll ask about the other half.

Zip Cord is a pretty generic term and the product comes in a variety of configurations.

http://www.therfc.com/zipcord.htm provides examples

Excluding the fiber optic stuff, most of what we are (IMHO) talking about here is twin conductor copper cable from maybe #8 down to maybe #18 AWG.

Richard, when you say:

Zip cord is anywhere from 150-300 ohms.

Under what conditions would this be true? Last time I measured a piece of copper wire, the resistance was pretty low. Without some kind of statement about frequency or length, the statement is meaningless.

Are you just checking to see if we're reading this stuff?

Toddk

I don't know how deep I want to get into this because I will discuss standards when none exist. It will be difficult to apply the knowledge. If we are to have any kind of a serious discussion then much of it will be theory since there are very few products in the world that actually follow any kind of real world engineering standards. As an example there is not an industry standard for input and output impedances of line level signals nor the cables and connectors for those impedances. The same goes for the amp/speaker interface. There is a true 8/4 ohm coaxial speaker cable out there from Sumiko called Ocos, very pricey but accurate in this regard.

Do you transmit power to anything that is sensitive to small variations in response using zip cord? We are not driving a fan motor here folks. Think of how an audio amplifier works and the fact that regardless of roll off the active components themselves are typically in the 1-10 Mhz range. Has it ever occured to anybody that hanging a wire completely open to RF connected to a speaker completely open to RF is just like connecting an antenna to your amplifier which is monitoring the output by the way for VERY small differences between the output and input. Regardless of the lower frequency response it still matters and we need to move ahead beyond the science of the 50's.

Zip cord is anywhere from 150-300 ohms.

Under what conditions would this be true? Last time I measured a piece of copper wire, the resistance was pretty low. Without some kind of statement about frequency or length, the statement is meaningless.

That is AC impedance using audio frequencies.

Richard

That is AC impedance using audio frequencies

OK Richard, you believe speaker cables should be considered transmission lines, correct? You are bringing to attention 'AC impedance' which I assume you mean the same as 'characteristic impedance'.

Well, let's look at the wavelengths of some audio frequencies. 1000 Hz is 300 km. 1 MHz (well above audio) is 300 m. Most speaker wire lengths around the home are what, maybe 5 m - 10 m max? (up to about 30 feet).

Your transmission line theory simply does not apply. At these frequencies the cable simply looks like lumped elements - capacitors, inductors, resistors. That's all. And it turns out that resistance is the predominant factor. Capacitance and inductance are insigificant compared to the load (speaker) and source (amplifier) impedances.

Now to shielding to RF. Speakers and amps are way too low impedance and have too high signal levels to be susceptible to RF. Speakers and amps don't have shielded RF connectors and internal wiring anyway to make a shielded cable effective. Also, coax does not work to provide shielding at audio frequencies as with RF. Think of it this way: If you put a load on the end of a coax and run DC through it, all the current on the center conductor returns on the shield. However, if you provide an external ground return path outside the cable, the current will return on that also. Same is true at audio frequencies. But at 'RF' frequencies, almost all the current will return on the shield regardless of the external path. And the fields cancel outside the coax. A coax does not work at audio like at RF, for preventing radiation off the cable or protecting it from outside radiation. They do use shielded wiring for low-level, high-impedance audio circuits. But his is not coax. And you have to be careful how you terminate the shields to prevent 'ground loops'.

This is not the science of the 50's. It's the science of today and it's basic electromagnetic theory. There are some good books on the subject and I can suggest a few, perhaps you should read up on it.

emc guy

EMC Guy,

Go get a TDR, a real amplifier and I will tell you how to make some cheap 8 ohm cables and a couple of dummy speaker loads using caps, inductors and resistors and then you can see it all for yourself.

Richard

I've got a TDR and use it once in a while. It puts out some nice picosecond risetime pulses. Great for checking characteristic impedance, load matching, and cable faults (discontinuities). Not used for audio but mainly for RF and digital with fast rise/fall times. LCR lumped element circuits are often used for computer modeling of cables up to several MHz. Meters that measure RLC directly are better than TDRs for low freq work.

If you had 8 ohm cables, something I doubt could be made because the impedance is way too low, they would be highly capacitive. Do you want your amp pumping all that current into that capacitive load? Really, all you need are for the cable's resistance, inductance, and capacitance to be no more than about one-tenth of that of the speaker. Most zip cord or inexpensive speaker wire will do that. Go back to the top of this thread - that link tells the real story.


emc guy

Since you have the most expensive part of what's necessary then why not give it a try. You do not login and therefore I cannot e-mail you. If you are serious send me a private note.

The purpose of my response is the same as everyone elses - common sense and logic. I could write a novel of the trials and tribulations of my audio journey through "nobody seems to KNOW just what the hell they are doing" to end up with "and nobody really cares to KNOW what the hell they are doing" and "who ever said this has anything to do with science". I nearly started manufacturing and was stopped stone cold when it became obvious that my sales would end up being directly related to how much money I made you spend on the cosmetics. Yes, they were right, science means little.

Here we have this Hi-End Audio community that seeks to resolve the most miniscule of differences and improvement yet THERE ARE NO STANDARDS!?!? Go and find a book telling you what the standards are for an audio circuit and you will be greeted with 1950's mentallity. Research it further and you will find everybody does what ever they want as long as it passes sinewaves at a reasonable distortion level and doesn't blow up with some of the wierd combos out there. This is one of the reasons Mark Levinson did Red Rose Music - all his equipment is designed to work together properly and he can replicate his sonic signature anywhere in the world. Yes, it is expensive.

So what about the wire? The engineer who researched this with equipment and his ears had a eureka moment 18 years ago and used a common industry coax to create an 8 ohm wire. He gave this wire to the lead engineer and owner who played with it for months delighted with the results. They turned on a couple of dealers to the wire and they tried it on some other equipment. What they found out was that their products loved it but some other hi-end products blew up - poor design. I have tested it on a number of mid-fi products succesfully with out any implosions. It is difficult to recommend because it is one part of the chain and the end results were not always positive. Correcting one thing can lead to negative results until you correct the other stuff. Another way to say this is the wire is accurate on an accurate system in terms of engineering from the CD player output through all your stuff to the speaker terminals.

Richard