By David Gibbons
Revised April 2007
Wiring and cabling is the plumbing of your home theater.
If a plumbing salesman came to your house and told you that all your plumbing was inadequate and had to be replaced with $100 per running foot gold-plated, high-pressure, six inch-diameter piping, you would tell that salesman to go and (your favorite impolite phrase)
Don't be hustled by audio/video salesmen trying to sell you over-specified and super-expensive wiring and cabling. Here's some information to help you understand what is important and unimportant about wiring and cabling:
Let's start with a little bit about wires and electricity. Wires and electricity go together much like pipes and water go together.
For plumbing, pipe is chosen on the basis of the pressure of the water, and how much water has to flow through the pipe. Corrosion resistance is also important. This is common sense, plus there are lots of building codes to make sure that the right type of pipe is chosen and installed in your home. The material, thickness, and diameter all need to be correct so that the water stays inside the pipe, and so that enough water can get to where it needs to go.
The same things are true of wires and electricity. Electricity is not exactly the same as water, but the same sort of ideas apply.
A pipe has to be able to hold the pressure of the water inside it.
A wire has to be able to handle the voltage that is applied to it.
The highest voltage in home theater system cables and wires is actually the voltage on the AC main power cords. All the other voltages are much, much lower and super fancy or thick insulation is therefore not required.
A pipe has to be big enough to carry the desired flow of water.
A wire has to be big enough to carry the desired flow of electricity.
The highest current flow in home theater system cabling and wiring is usually the speaker wire current. It is not much current, and thumb-thick copper conductors are not required.
Water does not like to stop or change direction suddenly. Water hammer in plumbing systems is prevented by putting together the piping correctly.
The direction of flow of electrical current can be changed very rapidly. However, cables, wires, and connectors that carry that electricity must be designed to handle the rate of change of flow of electricity (frequency) that is being carried by those wires, cables, and connectors. If these items are not designed, manufactured and installed correctly, they can mess up (speaking technically) the proper change of flow of electricity through them.
As the rate of change of flow (frequency) of the electricity goes up, the cable and connector design and material must be chosen to carry the flow without problems. Almost any sort of solid connection works for audio frequencies. The frequencies coming from a broadcast cable system these days can be over 100,000 times higher than the highest audio frequencies, and connectors and cable suited to handle those frequencies are required. Video frequencies are intermediate to the previous two, and thus cable for video frequencies need not be quite as good as the cabling required for the broadcast cable wiring.
Corrosion or contamination of a water pipe can either cause a blockage or leak.
Corrosion or contamination of a wire or cable can reduce the amount of flow of electricity, or mess up (again speaking technically) the proper change of flow of electricity through that wire or cable.
A shield wrapped around a cable's center conductor keeps the signal on the cable's center conductor free from interference, and also keeps the cable's signal from leaking out and interfering with other equipment.
The low frequency and high power level in the speaker wires make shielding unnecessary for those wires. All other connections require shielded cables.
An electrical signal is just a change in flow and/or direction of flow of electricity, which we use to carry a message . You could even do this in a plumbing system.
Let's go back to that plumbing salesman who was trying to sell you a pipe-upgrade job for your house. He told you that 6 in. diameter gold-plated pipe will never corrode, will be sure to carry all of the water you'll ever need, and will never affect the taste of your water.
He's telling you the truth!
So why did you tell this salesman to take a hike? Because you know that the plumbing you have is good enough. You know it would be better to spend your plumbing upgrade money on a better bathtub or a better sink.
IT IS THE SAME EXACT THING FOR WIRING AND CABLING ON HOME THEATERS!!!!
For the ordinary home theater money spent on extra-fancy cabling and speaker wires is a waste.
The salesmen in the home theater store will try to sell you wire and cable which is the electrical equivalent of the insanely expensive pipe mentioned in the example above. Yes, the wire he's trying to sell you will carry lots of electricity. Yes, the cable is more corrosion resistant, and will carry high-frequency signals better.
He will even show you articles in fancy home theater or audio magazines which praise the wire or cable the salesman is trying to sell you. (Ask yourself where those magazines get their advertising dollars from. Ask how profitable the "high-end" wire and cable can be for the home electronics stores)
You need to remember the phrase "gold-plated pipes" when reading or listening to these pitches.
Enough theory. I'm going to make some recommendations on the right amount of quality you should pay for in the wiring and cables for your home theater.
Type SPT Lamp Cord is plenty good. 18 gauge is heavy enough unless you have long runs, say over 20 feet. Then you could use 16 or (go wild!) 14 gauge wire. I specify this type of wire because it is very durable. You can step on it, set furniture on it, and bend it back and forth a lot before the wire will fail. You can buy good quality type SPT lamp cord in bulk at your local hardware or electrical store for cheap. (like 25 cents per foot). Watch out! Really cheap stuff sold as "speaker wire" is typically inflexible, and will fail quickly if it is bent back and forth a few times. Further, the insulation quality of "speaker wire" is sometimes poor, and can actually contribute to corrosion of the wire. Stay with the type SPT cord.
Reliability can be a problem where the speaker wire attaches to the amplifier and the speaker. Putting connectors on the end of the wires can help.
Expensive hook-up connectors of various types can be purchased, but inexpensive crimp-type solderless spade tongue terminals of various sizes are available at your local hardware store which will work well to make a good connection to the terminals on the speakers and amp. Get a matching crimp tool from the hardware store, and securely crimp a connector on each wire end, taking care that no bare wire is exposed outside of the crimp connector. Having no exposed bare wire avoids short circuits.
If your equipment has the little spring-clamp type connectors, you can cut off one of the two prongs on a spade tongue terminal, and stick the remaining prong into the hole where the wire goes. However, the Thomas & Betts company makes a crimp terminal especially suited for connecting speaker wires - ask for their type TV14-18BL blade crimp terminal at electrical supply houses.
Single or dual Banana-type connectors are a somewhat more expensive, but convenient, option where the speaker and amplifier terminals will accept them. Again, look for good quality commercial ones, such as those sold by Pomona Electronics, and avoid the bulky, triple gold-plated, "high end" versions. Note that the bodies of the connectors shown are fully insulated, which helps prevent shorts.
Whatever connections you make, ensure they are clean and tight.
Audio frequencies do not require fancy cables either. Good quality shielded cabling with decent RCA (phono) connectors will do the job. Gold plating is not required, although these days you may not able to avoid it. The L-Com company (www.l-com.com ) offers excellent value in their RCA cable assemblies, found in the Video/Monitor cable section of their website. Radio Shack is probably the nearest local place to get the cables you need to carry the audio signals between the different pieces of gear in your system. Watch out! Radio Shack is now offering "high end" audio/video cables too, so go for the less-expensive stuff.
We are caught in a interesting situation on the subject of the cables and connectors used to carry the video signals used in home theater systems.
A long time ago some unknown engineer, probably working for the RCA company, designed a little connector for connecting up cables to (it is said) phonographs. Supposedly this is why the connectors are also known as "phono" connectors. This type of connector is inexpensive, and is not a precision connector designed to carry radio frequency signals. Unfortunately, the manufacturers of television and consumer audio/video equipment somehow ended up using this inexpensive connector for carrying low-level video signals. (Gee, could it have anything to do with the connector being really inexpensive?)
The phono connector obviously works. Millions of home theaters have them carrying video signals. People get decent pictures. Still, Audio/Video cable marketers tell us that if we spend lots of money on fancy cables to carry the video signals, our pictures will be much better.
The problem is that EVERY piece of wire and connector between a video source and a video signal receiver affects the signal. When I talk about a signal source, I am talking about the actual integrated circuit buried inside your DVD player which is creating the video signal. When I am talking about the signal receiver, I am talking about the integrated circuit in your receiver which takes the video signal from your DVD so it can be passed on to the TV. The circuit board traces, jumper wires, jacks, plugs, interconnect cabling, etc. all affect the signal going from the one integrated circuit to the other.
Think of a chain--the weakest link determines the strength of the chain. If you increase the strength of SOME of the links in the chain, the chain is not much stronger. With the RCA connector being what it is, spending big dollars on a fancy cable which connects to those connectors may not be the best use of your money.
The other weak link in cable assemblies asked to carry video signals is how the cable actually connects to the phono connector. The cable is co-axial. That is, the cable consists of a center wire running through insulation, with a woven or solid metal shield all around the insulation. An RCA connector is arranged the same way as you can see when you look at the end of the plug. The center pin is surrounded all the way around by the outer part of the connector. What you usually cannot see is if the cable connection to the RCA connector is also co-axial. That is, the cable shield should connect securely to the outer body of the RCA connector all the way around. This helps assure the effectiveness of the shielding.
In 'shielded' cable assemblies for audio with RCA connectors, this is often not done, and so shielded audio cables preferably should not be used for video, even if the cable type is good. Here are picture of some cable assemblies, some truly coaxial, and some where the center conductor is not fully shielded on it's way into the connector. Look at the top two connectors in the top picture - see the bare copper center conductor? If the outer body of the connector is metal, this can help reduce the effect of the non-optimum connection method. The springy strain reliefs shown in the top picture are useless for home theater cabling unless you plan to regularly dance with the equipment in your arms.
The cable type used in the cable assembly does matter for coaxial cables used to carry video signals. RG-59 type '75 Ohm' cable is appropriate for the frequencies used for video signals. You may see some cheap video cables which are only about 1/8" thick, and these should be avoided. Ask for cable assemblies that are made from RG-59 type cable. There are much better cable types offered, but RG-59 type cable will do a fine job, unless your cable runs start to get over, say, 50 feet.
Once again, using regular RG-59 cable assemblies to carry the video between the different pieces of gear in your home theater will deliver very good pictures. If you would rather spend $300 just for one video cable, (Solid silver conductors, triple shielding, super-duper connectors, high-spec cable, etc.) go for it, but spending the $300 to help buy a new television which costs $280 more than the one you were going to buy and a plain $20 video cable will probably improve your picture far more.
As with the video signals, various problems make interconnect cable replacement with top-dollar cables an unlikely route to a perfect picture.
Consider the following:
In these cases, super-duper connection cables again may not make a big improvement, except to the bank accounts of the people who make and sell those types of cables.
Even so, let's look a little at the type-F connector, as it does perhaps justify considering somewhat better cable assemblies for more reliable connections.
Even more than the phono connector, the type-F connector is a miserable "consumer-grade" connector. (It is favored by the cable companies because it is cheap and quick to install.) Due to the low performance of the typical F-connector the best interconnect cables in the world won't fix all of the F-connector's problems.
That being said, a somewhat better interconnect cable with better connectors featuring properly shaped gold-plated center pins can improve contact reliability. (One problem is that the female F-connectors mounted on televisions and other home theater equipment have a cheap internal center contact that is prone to damage and corrosion.) Once again, L-Com offers very good RG-6 cable assemblies fitted with better quality F connectors at good prices. The image below shows F-connectors, and a cable prepared for installation of a connector. Note that the center conductor of the cable actually is the center pin for the connection once the typical F-connector is installed on the cable.
FINAL THOUGHTS:
Here's to spending your home entertainment dollars wisely!
