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Original Message

The Audio Cable FAQ

Posted by Jon Risch on May 16, 1999 at 15:58:07:

The Audio Cable FAQ
by Jon M. Risch

*Do both speaker cables need to be the same length?

This one often involves answers that the speed of the signal in the cable (near the speed of light) precludes any need to match lengths, and moving your speaker the space of a gnat's arse will change the sound more, and so on. What this simplistic answer overlooks, is that if the two speaker cables are not close to each other in DCR, and inductance, the damping will be different, and the high frequency roll-off will be different. These kinds of things can affect the stereo image and image depth, as the two channels delicate balance has been disrupted.

I recommend against any differences in length for shorter lengths of more than a 2 to 1 ratio, and preferably the closer to the same, the better. Long runs will be more critical, and would need a closer match still.

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*Can I coil any excess speaker cable up on the floor?

Not recommended due to increased inductance, and other interaction effects that may cause more than just an extra amount of high frequency roll-off. A snaking "S" pattern will avoid the worst of any interaction problems.

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*What is bi-wiring?

Bi-wiring is where the crossover inside the speaker has been separated into it's HF and LF sections, and separate pairs of connecting terminals provided to access those separate sections independently. Normally, the LF and HF crossover sections are in parallel, connected internally to the same single pair of binding posts.
For single cable use, a set of jumpers is provided to bridge the terminal pairs, paralleling the separated crossover sections outside the cabinet instead of inside.

Then, separate speaker cables are run from the same amp output to these separated pairs of terminals at the speaker.

*What good does bi-wiring do?

Some say that any improvement in the sound it makes is strictly due to the decreased total DCR, and this makes the speaker less prone to frequency response variations due to cable resistance. According to this view, simply running the two cables in parallel at both ends will do the same thing. In my opinion, this is a very simplistic and incomplete way of looking at the situation.

Once the crossovers have been electrically separated, they present different impedances (loads) to the power amp within their passbands and outside of their passbands. The woofer and corresponding low frequency crossover section will present a low impedance at low frequencies and a high impedance at HF, while the tweeter section will present a low impedance at high frequencies, and high one at LF's.

With the electrical separation, differing currents will flow within the two cables that make up a bi-wire set. For the separate cable feeding the woofer section, a lot of current will flow at LF's but not much current at HF's, and the tweeter cable will have some current flow at HF, but very little at LF's. A division of labor has occured with bi-wiring, whereby a single cable does not have have to carry the HF currents simultaneuously with the LF current.

Two things happen due to this:
1. The losses in the cable due to "eye-squared-are" losses (current squared time the resistance equals voltage drop) are reduced for each frequency band, so that any tendency for the woofer to modulate the tweeter due to current draw is greatly reduced. This form of IM would be in lock-step with the original signal.

2. The magnetic fields due to the HF and LF currents have also been separated out, and any tendency for them to intermodulate and cause sonic artifacts has been greatly reduced. This form of IM would be occuring both at the same time, and in a time delayed form due to mechanical resonances and motor/generator action.

See http://members.xoom.com/Jon_Risch/page7.htm for a more in depth discussion about the benefits of bi-wiring.

*Can I use the A and B outputs on my receiver to bi-wire?

While this would be very convenient, it can only be done if the outputs are placed in parallel, rather than series. Many receivers and integrated amps that have two speaker outputs will connect them in series when they are both selected at the same time, to protect the amplifier from an excessively low impedance. Check your owners manual to see how the A and B output are wired when they are both selected. A simple test would be to select them both with a speaker only hooked up normally to one of them, if the sound goes dead, then they are connected in series, and you will need to connect both of the bi-wire cables to one pair of output terminals.

*Should both cables be the same kind?

This is not absolutely necessary, although it can be argued that certain sensitive speakers need the same exact cable in order to minimize any discontinuities in the midrange (crossover region). However, as long as both cables are of a high quality, this is much less of a problem than it might seem. An extreme example would be to use heavy gauge zip cord for the woofer, and an exotic high performance cable for the highs. Some audiophiles have used this approach to great effect, and others found the zip cord on the woofer holding them back. It never hurts to try, and see how well a particular pairing will work for you.

*Should both cables be the same length?

This has already been answered above, but many people seem to feel that bi-wiring is even more critical, so the warnings in the answer above about matching length for electrical reasons are perhaps even more relevant.

*Are the bi-wire cables that are all in one jacket as good as separate cables?

Many cable manufacturer's offer an all-in-one bi-wire cable, primarily for convenience and a tidier wiring arrangement. If you read the explanation of how bi-wiring works, then you would realize that placing the cable's magnetic fields in close proximity within the same cable jacket may compromise the bi-wiring advantage to some degree. Most experienced audiophiles agree, totally physically separated bi-wire cables tend to sound better than those in a common jacket. The degree of compromise is going to depend on the spacing between the bi-wire sections within the common jacket, and how much magnetic coupling and motor/generator resonances are going on inside the common cable jacket.

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*How should I terminate my speaker cable?

First, if all your amp/receiver has those spring loaded terminals, there are not a whole lot of options. The gold plated pins that are available for such connectors are not an improvement over a good bare stripped wire connection. If you have spring loaded terminals, save your money and forget the gold-plated pins, use the bare wire, twist it hard and tight, and insert it naked. If the total wire thickness allows, double the wire over, and jam the doubled-up wire into the terminal opening, you want as much spring pressure on it as possible. I do not recommend tinning such a conection, and if you have some disposable speaker cable length, about every 6 months, cut off the oxidized exposed bare wire, and start fresh.

Those of you with gold-plated heavy duty 5-way binding posts, the choice here is clear: gold plated spades, preferably properly crimped. If you can not make a proper crimp via a crimping tool, then a proper solder joint will be very close in quality to a good crimp. Amazingly enough, the gold plated spades offered by RS are OK, one of the few RS parts I can recommend at all. The very best spades are the type with compression washers built into the spade fingers, such as the WBT and the Kimber Postmaster spades.

After spade lugs, the next best connection is a gold-plated expanding/locking banana plug. Standard non-expanding or non-locking banana plugs with a nickel plating are not very good at all, nor are the cheap gold-plated kinds at RS. Monster and WBT make the good types of banana plugs.

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*What RCA plugs should I use?

For DIY interconnects, one of the best is the Cardas RCA plug. Sonic Frontier's The Parts Connection offers the SF brand RCA's at a reasonable price for teflon insulated plugs, and Apature has some that are quite reasonable also. WBT has excellent plugs as well.

For all of the above, I recommend only the non-sliding non-spring loaded ground connection versions, as these compromise the ground connection too much. They should have teflon insulation, and a good grade fo gold plating.

--------------------------------------------------

*Can I bundle all my audio cables together with wire ties and stuff them under the rack/shelf?

Not a good idea. Power cords radiate a magnetic field and an electric field that is prone to carrying the interference that rides on all AC power lines to some extent. This RFI and EMI can get into the interconnects and into the unshielded speaker cables, and cause a low level fuzz or a less than totally silent background, even if it does not cause obvious hum. The interconencts are considered to be shielded in most cases (there are self-shielding types, such as the Kimbers, etc.), but even the most densely braided copper shield is only about 97 to 98 % coverage, and even if it is doubled up, or has a foil shield to aid it, 60 Hz and the associated garbage can leak in to some extent. 2% leakage is equivalent to only 34 dB down, although the likely hood of a full bore signal that close to the braid is not that high.

There is also the potential for digital devices such as a CD player to radiate internal RFI and clock noises into other components via the interconnected outputs, and there is also the possiblity of the speaker cable signal getting into the line level interconnects enough to cause signal deterioration.

So it is best to separate the line level interconnect cables from the speaker cables, and both of these from the AC cords, all as much as possible. Within these groups, separating the digital CDP interconnect from the others, and keeping a phono interconnect away from all others are also good ideas.

Finally, keeping all cables, but especially speaker cables, away from any metal, especially steel, is a good idea. Any conductive metal will tend to short out an electric field, and distort a magnetic one, while a ferrous metal will definitely affect and distort either type of field. A few inches to a 1/2 inch may be all that is needed to prevent the worst of any potential distortions.

--------------------------------------------------

*Should I raise my speaker cables up off the floor?

There has been a lot of debate over the more subtle aspects of cable dress, and one of those issues is whether or not speaker cables need to be kept up off of a wood or carpeted floor for better sound.

Consider that most carpeting is made from relatively poor dielectrics, and has a mat underneath it made from who-knows-what that is likely to be damp or hold moisture, while wooden floors may have nails near the cable, and can also hold moisture, then it is not as much of a stretch to consider reducing these bad influences on the speaker cables electric and magnetic fields. Even concrete can hold a significant amount of moisture, and these moist materials will tend to short out the electric field to some extent.

While not a must do kind of thing, it certainly can't hurt to get the speaker cables up off the floor, and keep them away from metal and steel.

*What should I use?

Everything from foam cups turned upside down to beanbags to string to little wooden fences have been proposed and touted. The main idea is to space the cables away from the floor using a dielectric that is better than the carpet or wood floor they were resting on.

The foam cups are decent candidates, but an even better solution is to use the foamed polyethylene pipe insulation available at hardware stores to keep heat loss from hot water heater pipes to a minimum. The PE is a better dielectric than carpet, and is foamed with a high proportion of air. You can either cut the pipe insulation in sections, and rest the speaker cable on top of the whole cylider formed by such a section, or slip the cable inside the slitted pipe insulation.

Personally, I would want to minimize the dielectric involvement of the PE pipe insulation, so I would go for the former approach.

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*Whats the best cable in the world?

What's the best car in the world? These are very personal and subective things, and can not be answered without consideration of your own personal tastes and the system the cable will be used in.


*Whats the best cheap cable in the world?

Similar situation as above, but compounded by the compromises and trade-offs that you find agreeable compared to someone else.

I can tell you that it is NOT zip cord, or the free OEM interconnects that come with a lot of audio components.

For those first upgrading from zip cord and the freebie interconnects, the vast array of choices is quite bewildering.

You can go homebrew, and see one of my DIY audio cable notes at http://members.xoom.com/Jon_Risch/ (or the notes of many others, such as Thorsten at TNT or others, see: http://www.tnt-audio.com/clinica/tweaks.html and also: http://www.msu.edu/user/churches/diy.htm ) to build your own high performance cables for a fraction of what many high end cables cost.

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*I read your DIY note on cables, and want to use some old doorbell wire I have laying around instead, will it sound as good as the cables in your note?

Dohhhh! One of the things I did to generate the information in my DIY notes was to listen critically and under controlled conditions to many different combinations of commercial cables, varying one aspect at a time. After literally hundreds of man hours, I was able to determine which cables, and which cable materials, gave the best sound.

If I had found door bell wire (or insert cable of your choice here) to sound best, I would have included it.

I even include cross-references to other cable manufacturers from the Belden wires in my notes, although I have not listened to all of these myself. West Penn Wire has a good reputation for the quality of their cable's and one of the reasons that I focused on Belden is their reputation for consistency and quality. Other brands may not have the same quality of copper or the same quality of insulators, so they may not perform as well as the Belden.

Aside from those kinds of issues, it is a forgone conclusion that tinned copper or PVC will not sound as good as bare copper or a superior dielectric (which includes just about everything else when compared to PVC).

If you want to try a different wire or cable, feel free, however, if you construct a cross-connected dual coaxial speaker cable using lesser insulations with a PVC jacket, tinned copper braid and steel core center wires, don't expect it to sound very good compared to the recommended Belden 89259 with it's bare copper braid and center wire and foamed teflon insulaton and teflon jacket. And please don't then post and say that "Jon Risch's speaker cable sucks!", because you really haven't constructed one of my recommended recipes.

Another example would be the CAT5 speaker cable recipe. In it, I call out specific CAT5 cables, ones that have the proper combination of conductors, insulators, etc. Just any old CAT5 cable will not give the same sonic results.

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*You recommend so many different cables in your notes, which one should I use?

I describe and write about a number of cables to allow some freedom of choice, and to allow those who may have access to one or the other of the recommeded cables to realize their DIY cable project without being forced to custom order a particular cable. All of the recommended and listed cables will handily outperform run of the mill coaxes and twisted pairs that have inferior materials in them. I do have my preferences, and I do call them out in my notes.

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*I can't find the cable/s you recommend OR I live in a foreign country, and Belden is not available, OR I can get brand X way cheaper than Belden, what should I use?

There are several possibilities here, one is to cross reference from the Belden part numbers, another is to obtain the full catalog for the brands and types that are available and match up the preffered materials and constructions, as outlined in my note. Finally, a last option is to order it from a US stocking distributor, such as Newark. The 100 foot spool of Belden 89259 only weighs about 5 lbs., and most US nationwide distributor also have an overseas office, or will ship overseas.

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*How can digital interconnect cables from a CD transport to an outboard DAC possibly affect the sound? Isn't digital audio just one's and zero's?

A very common misconception about digital signal
transmission with respect to audio is that if the signal does
not get corrupted to the point of losing or changing the 1's
and 0's, that nothing else can go wrong. If the transmission
system had been designed with cost no object, and by
engineers familiar with all the known foibles and problems
of digital transmission of audio signals, then this might
be subtantially true. No differences could rear their ugly
head.

Unfortunately, the systems we ended up with DO NOT remain
unaffected by such things as jitter, where the transistion
from a 1 to a 0 is modulated with respect to time. There are
many ways that jitter can affect the final digtial to analog
conversion at the DAC. Jitter on the transmitted signal can
bleed or feed through the input reciever, and affect the DAC.
How? Current drain on the power supplies due to the changing
signal content and the varying demands made on the power
supply to the logic chips and the DAC. Modulate the power
supply rails, and the DAC will convert at slightly different
times. This is due to the fact that a logical one or zero is detected by the signal swinging through a regoin from around zero volts to around 5 volts. The digital logic chips detect the change at a specific PERCENTAGE of that total voltage swing.

HOWEVER the power supply gets modulated, it will
affect the DAC. One version of this has been popularly
refered to as LIM or Logic Induced Modulation by the
audiophile press. See:
"Time Distortions Within Digital Audio Equipment Due to Integrated Circuit Logic Induced Modulation Products"
AES Preprint Number: 3105 Convention: 91 1991-10
Authors: Edmund Meitner & Robert Gendron

Many of the logic chips in a digital audio system behave
very poorly with respect to dumping garbage onto the rails
and even worse, onto the ground reference point. Even as I
post, logic manufacturers such as TI are advertising the
benefits of their latest generation of logic chips that
reduce ground bounce. The circuitry itself generates it's
own interference, and this can be modulated by almost
anything that also affects the power supply or ground.

The amount of jitter that it takes to affect the analog
output of the signal used to be thought of as fairly high,
somewhere on the order of 1,000 to 500 pS worth. Now, the
engineers on the cutting edge claim that in order for jitter
to be inaudible and not affect the sound of the signal, it
may have to be as low as 10 to 20 pS. That's for 16 bit
digital audio. That's a very tiny amount of jitter, and
easily below what most all current equipment is capable of.

Computer systems never convert the 1's and 0's to time
sensitive analog data, they only need to recover the 1's
or 0's, any timing accuracy only has to preserve the bits,
not how accurately they arrive or are delivered. So in this
regard, computer systems ARE completely different than
digital audio systems.

Look into digital audio more thouroughly, and realize that
the implementations are not perfect or ideal, and are
sensitive to outside influences. Just because they could
have been and should have been done better or more nearly
perfect does not mean they were! People are not hearing
things, they are experiencing the result of products designed
to a cost point that perform the way they do in a real
world because of design limitations imposed by the consumer
market price conciousness all the mid-fi companies live and
die by.

With digital cables, there are three things that are paramount:
proper impedance, proper cable termination, and wide bandwidth.
It may be that a particular cable more nearly matches a systems
actual impedance. The other factor, proper termination includes,
but is not limited to, the actual electrical termination inside
the components, as well as the connector on the end of the
cable. If the connector is NOT a perfect 75 ohm, 110 ohm, or
whatever, it will cause minor reflections in the cable, which
makes our old friend JITTER raise it's ugly head again.

The third factor, bandwidth, is only an issue because both the
AES/EBU and the SP/DIF interface formats were designed before
Sony/Phillips knew all there was to know about digital problems,
and they require PERFECT unlimited bandwidth cables in order for
the transimission systems to be free of jitter. The more you limit
the bandwidth, the more jitter. This is a known engineering
fact, and an AES paper was given about this very subject not
too long ago.

"Is the AES/EBU/SPDIF Digital Audio Interface Flawed?"
AES Preprint Number:3360 Convention: 93 1992-10,
Authors: Chris Dunn & Malcolm O. J. Hawksford

The effective data rate of SP/DIF is about 3 Mhz, and the
design of the transmitters and recievers is abysmal. Maybe
if everything else was done right, then cables, etc. wouldn't
matter. So much was done wrong or cost cut till it screwed
up that they do come into the picture.

A good web source for info on jitter is located at:
http://www.digido.com/jitteressay.html

AND:
http://www.audioprecision.com/publications/jan96.htm#Digital Audio Transmission

I recommend a couple of options for digital interconnect cables in my DIY Interconnect Note.

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*Where can I find the official newsgroup FAQ on wires?

http://www.faqs.org/faqs/AudioFAQ/part8/

It helps to keep in mind that this FAQ from the rec.audio newsgroups is a compilation of the opinion of a conservative few, primarily folks that until recently, would swear that audio cables could not possibly make a sonic difference. The more recent FAQ's on wire that have been put out are a bit more open to the possibility that there is something more to audio cables other than overly simplified high school physics.

I find it interesting that the newsgroup FAQ also recommends Belden 89182, as I do in my DIY Interconnect note, for use as a twisted pair.

Jon Risch