6-Channel Interconnects--What cables?

Discussion in 'Archived Threads 2001-2004' started by MikeWieda, Dec 8, 2001.

  1. MikeWieda

    MikeWieda Auditioning

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    Hello,
    Real quick: I'm new here, but I've been lurking for a little while and I'm impressed with the knowledge, professionalism and respect that the members of this forum possess; qualities often lacking in internet forums. It's good to be here.
    On to my question...
    (I've tried searching the active forums and the archives and didn't find anything that really helped me out.)
    I will soon be installing a multi-channel SACD player in my stack. As you all may well know, SACD signals are output only in analog (in my player's case, via RCA jacks). While five of the six channels are full bandwidth, the LFE channel is, of course, not (it's low frequency stuff only).
    I plan on using full-bandwidth-capable interconnects for five of the six channels. What sort of cable should I use for that ".1" channel? Should I use a cable specifically engineered for low frequencies? I figure I'm using LFE-specific cables to connect to my subs, shouldn't I use one "all the way through?"
    My current installation uses Monster Cable M550i audio interconnects throughout. I will continue to use M550i interconnects for the five "regular" channels, but I'm stumped as to how to connect that LFE channel. [​IMG]
    Thanks in advance for your help!
    -Mike
     
  2. MikeWieda

    MikeWieda Auditioning

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    Rajee,
    Thanks for the thoughts. I checked Outlaw's site and it looks like their 6-channel solution is simply three pairs of their regular interconnects ("PCA...Analog"). At least that's all I saw on their order page. I didn't see anything that said "6-channel cable..."
    Well, that's pretty much what I have in mind at the moment: To use three 2-channel cables (although from Monster Cable because I can get a deal on them from a buddy in Texas!).
    Although I still have this crazy notion that I should be using a base-specific cable for ".1" audio channels. Am I off base here?
    -Mike
     
  3. Andrew Pratt

    Andrew Pratt Producer

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    Mike there's nothing special about the .1 track that it needs anything different for an interconnect. If you are talking about long runs to a sub across the room then yes better shielding etc comes into play but for an interconnect between SACD player and the pre amp etc then a regular interconnect will do fine. Of course this leads to the question of sonic differences in interconnects etc that often gets rather heated between the believers and the non believers. In any case there are a variety of companies out there that offer cables that will suit your needs. Some of the better companies can even make cables that are custom made to the lenght you need so you don't have slack and keep cable lenght to a minimum. One such company that I deal with is www.catcables.com since I like their build quality but there are others as well should to choose to try something other the Monster
     
  4. Martice

    Martice Screenwriter

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    Go to Parts Express and look at their new line of Dayton Cables.
    Parts Express
     
  5. Bob McElfresh

    Bob McElfresh Producer

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    Mike: I'm afraid you have a misconception that you need some special coax for the subwoofer cable. You dont.
    Let me try and explain a few coax concepts:
    Coax tends to be defined by it's upper frequency limit. The frequency for subwoofers is between 20 and 120 hz - a trivial challenge for any coax.
    Coax is rated by a "charastic Impedence". This is like resistance, but this works against analog signals. The impedence does not depend upon length. A 1 foot and a 20 foot length of coax has the same impedence.
    Coax can be bought in 50/75/110 and 300 ohm impedences. The 75 ohm coax is the most common.
    All Video cables are made with 75 ohm coax. (This is why the specification for the Coaxial-Digital connector on your DVD player calls for a 75 ohm cable - it's very common.) Your CATV and DSS coax (called RG59 and RG6) is also 75 ohm.
    A coax cable is really 2 wires: the center conductor which typically carries the signal, and the outer shield. The outer shield is usually the ground reference and is connected to the ground on your equipment.
    Important points for a subwoofer cable
    People often buy a self-powerd sub and hook it up. But to their suprise, the sub starts making a low hummm. This is because that outer-shield on the coax ties the ground from the receiver and the amp in the sub together.
    To solve this, some companies make a special "subwoofer cable" with little arrows on it. The destination end does not have the outer shield connected to the RCA plug. This can prevent the humm.
    Most people use a cable with the shield connected all the way through and then use a electrical "cheater plug" on the sub to solve the humm.
    (Now for a personal opinion): We have seen a good sub initially sound bad, but sound much better when a different cable is used. The new cable was not more expensive/higher-end, but it had tighter RCA connectors!
    Subwoofers seem to sound better with tight RCA connections. This may be the true reason one sub cable sounds different from the other - not the coax at all.
    Hope this helps.
     
  6. MikeWieda

    MikeWieda Auditioning

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    Bob,
    Thank you for the enlightening explanation of subwoofer cables. I didn't know about the hum-to-ground relationship you described. Very interesting.
    So this is to say that the reason some people use a subwoofer-specifc cable is more for hum and grounding reasons than for the cable's particular sonic abilities?!
    So then, the coax cable doesn't convey low frequencies better than, say, stranded cable?
    Indeed, I did have a misconception! I thought it was "better" to use a cable that is designed for subwoofers for sonic reasons, not for grounding reasons! My misconception is undoubtedly propaganda-induced by the cable manufacturers! [​IMG]
    Here is the Monster Cable M351 Subwoofer Interconnect:
    http://products.monstercable.com/por...key=35511&-img
    Okay just for arument's sake, suppose the above cable is not coax (I can't tell, anyway!). Let's assume it is a specialized subwoofer cable for some other reason than grounding and hum suppression; The cable is, then, designed for sonic reasons.
    Supposing that Monster did, indeed, engineer a cable that specializes in the conveyance of low-frequency information, would I need such a cable for the .1 channel of my SACD 6-channel audio?
    Even though it's slowly becoming apparent that a "normal" (although, "good") interconnect will work fine, isn't this what audiophiles are supposed to do...obsess about fringe stuff like this?! [​IMG]
    Sorry to be beating a dead horse, but this is really very interesting.
    Thanks.
    -Mike
     
  7. Bob McElfresh

    Bob McElfresh Producer

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    Most people dont buy a sub cable knowing that one end of the shield is connected/not connected. They buy a cable because:
    - A salesman sold it to them with the sub
    - They like the look and perceive a good looking cable will sound "better".
    And in truth, a good looking cable will be made with some quality coax, good construction technique and good RCA plugs.
    We have seen the "not-connected" shield CAUSE humm in one system and solve it in another. (It depends a lot upon how new the wireing is in your house).
    These cables SHOULD all be coax. Your SACD player is producing what is called "line-level" signals. These are weak, low-current, low-voltage signals. They NEED the shielding of a coaxial cable to protect the weak signals. Remember that you are running a mass of them next to both power cords and speaker wires (which carry watts of power). Without shielding, you would be injecting lots of 60 hz and other signals into the interconnects.
    This is why you use Coax - for the shielding.
    Now coax can be made with solid or stranded center, the center can be all copper, or aluminum-tinted copper.
    The outer-shield can be foil, braded wire and the braid can be copper, aluminum, or an alloy.
    Look at the picture of the Monster cable: From the outside you see what looks like copper mesh - this is part of the shield. The silver part is another foil shield. The black part is the insulator that keeps the center-conductor from touching the shield. Then there is the copper center conductor (it looks stranded from the picture).
    Now look at the "fringe" looking stuff. This is nylon rope that takes the strain if you pull the coax through a wall/floor. See the blue wire - this is an extra shield concept called a "drain wire". For most HT applications this is over-kill, but it does announce that this is some high-end wire.
    So this would be a good sub/audio and probably even a good video cable (if it's made with 75 ohm coax).
    If you want this cable, go for it. But....keep in mind that this quality of cable sells for about $0.50/ft. And that the RCA plugs sell for about $2-$3.50 each.
    I'll bet you spent a LOT more than that for your existing Monster cables. This is because:
    - The cost of a cable is in the labor, not the materials
    - Cables are a high-markup/high-profit item at most stores
    My Advice
    Do you already know where you are placing your sub and how long of a cable you need? If not: go to Radio Shack and buy one of their 20-foot interconnects. Use this to start playing with positions for that sub. If you need more than 20 feet, buy some RG6 CATV coax and slap some RCA plugs on the end to start.
    Once you know how long of a sub cable you need, do this:
    - Contact your local store and ask for a quote on a Monster M351 cable in your length.
    - Go to the following sites: www.bettercables.com, www.wickedcables.com, www.catcables.com and get quotes for their cables in the length you need.
    (These web sites are guys who buy the high-quality components - the stuff production studios use - and custom build cables for people. It is usually more expensive than the low-end Monster, but a LOT cheaper than the high-end, but you are getting high-end materials and hand-built construction.)
    If the web-sites are more than 50% cheaper than the Monster, order from the web sites. Otherwise get the Monster cable and you will have the bonus of having matched-sets of cables. (There IS an astetic/pride part of this hobby). But my guess is that the web sites will be a major savings.
    Some final thoughts: As a human, your hearing is best at around 10 khz. Subwoofer frequencies are almost subliminal to you.
    In fact: many LFE ports produce 1-8% THD (Total Harmonic Distortion). This is when L/R channels are rated at 0.03 or 0.08% THD. But human hearing is SO INSENSITIVE at subwoofer frequencies, that they get away with 5% THD on the LFE. It takes some distortion-analysis equipment to even detect this much distortion at subwoofer frequencies.
    Throw in the fact that much of the subwoofer sound you experience is INDIRECT - thats right, you mainly bounce the sound off of your walls, and it starts to seem a bit silly to spend $120+ for a "high-end" subwoofer cable.
    Opinion Alert:Of all the cables in your system, this is NOT the cable to spend $$$ on. Good quality - Yes, but you are not going to realize much sonic benifit with a $120 over a $60 subwoofer cable. Save the money for some of those SACD disks.
    (My advice would be different if we were talking about VIDEO cables, and perhaps different for the full-range audio interconnects. But not for the sub cable.)
    You should know that there ARE people here, who's opinion I respect on other issues, that will disagree with this. So keep an open mind.[​IMG]
    Hope this helps.
     
  8. MikeWieda

    MikeWieda Auditioning

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    Bob,
    Thank you very much for the time and effort you put into that last (and the previous) post. Your write up is informative and much appreciated!
    I think I found the answer I've been looking for in the following quote:
     
  9. Bob McElfresh

    Bob McElfresh Producer

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    Ok. You caught me.

    This cable is the "other" kind. It IS shielded similar to Coax, but instead of a single center conductor, it has 2. They are called "twisted-pair".

    This type of cable is used in computer networks.

    Here is the trick: if you had 2 wires in parallel and sent a signal down one, when it reached the end the other wire will have a small signal induced in it and the original signal will be reduced a bit. But if you twist the wires around each other, a funny thing happens: there is very little signal jump. You can run a twisted-pair wire hundreds of times longer than a parallel wire.

    Will it work for your LFE cable: yes. Is twisted-pair cable better than coaxial for LFE or full-range audio - not that I know of. (While twisted pair is better for 100+ feet of cable, this does not make it superior for a 10 foot run in your home. And computer networks run at 10 Million or 100 Million hz. Your sub woofer tops out at 120 hz - very different situation).

    Monster has those "turbine-grip-of-death" RCA plugs which subs seem to want. So it would be a good choice for you.
     

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