RG6 for sub cable? Does it muddy the sound?

Discussion in 'Archived Threads 2001-2004' started by Steve Morgan, Feb 16, 2002.

  1. Steve Morgan

    Steve Morgan Second Unit

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    Have heard different opinions that it does muddy the sound and the bass is not as clean and precise as custom sub cables then again their is the camp that says its fine? Your thoughts.

    Thanks,

    Steve M.
     
  2. Mark Austin

    Mark Austin Supporting Actor

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    It's not my first choice.
     
  3. Bob McElfresh

    Bob McElfresh Producer

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    My personal pet theory is that its the tightness of the RCA plug that causes the funny sound.

    The frequency response charts indicate that ordinary CATV coax is find for subwoofers. The guys at SVS who design/build/test their own subs have said that CATV coax is fine. An early purchaser of SVS was disapointed in the sound. (He was using a generic Radio Shack cable). When he used a similar cable (also Radio Shack) from his junk-box, the sound tightened up and he started to be impressed. The difference? The second cable had tighter plugs.

    So my usual advice is to use CATV coax to "rough in" the placement of the sub (or run RG6 through the walls), and then later buy a inexpensive, but nicer looking/softer cable for the perminent connection.
     
  4. Lee Bailey

    Lee Bailey Second Unit

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    I would think that if one wants to use RG6 cable for audio, make sure the shield is copper, not aluminum. Also remember that RG6 is rated for 75ohm at very high frequencies, your sub amp is probably 47k ohm at audio frequencies. You'd have to A/B compare some cables to see if you can hear the difference.
     
  5. Brian Schucher

    Brian Schucher Supporting Actor

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    It was my understanding that a quality RG6 terminated with true 750hm (canare) connectors are IDEAL for this type of appplication... Anyone else??
     
  6. brucek

    brucek Second Unit

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    Brian,

    I don't know about "muddy", but RG-6 makes an ideal cable for your sub interconnect. Its only problem I see is that it's a little stiff to work with and a little difficult to terminate.

    Certainly, the fixation that some audiophiles seem to have with regard to a perfect 75 ohm cable for audio interconnects is unfounded. It's a very common engineering practice to ignore characteristic impedance and consider only the DC resistance of a cable (transmission line) when the line is short in comparison with the wavelength of the electrical energy that it conducts.

    In that regard, I would consider a typical subs 5 meter cable very short in comparison to a couple thousand kilometer wavelength for 100Hz audio frequency. In fact, in very short cables, in relation to the wavelength of the signal, the resistance of the line is considered completely insignificant and the energy transferred is considered lossless. This would be the case for an audio interconnect with regard to impedance matching.

    This is considered a line level, high impedance connection where the input impedance of the sub power amp will be in the order of 50Kohms with the output impedance of the preamp being in the order of 100 ohms. This is a voltage bridge type high impedance connection where the preamp acts as a voltage source and almost no current is drawn. We are not interested in power transfer in this interface.

    We want to present a relatively low voltage to the sub amplifier input with as low a noise floor as possible. A properly shielded cable is important. RG-6 coaxial cable certainly fits this bill. Wouldn't matter if it was 50 ohms or 100 ohms characteristic impedance. The characteristic impedance of an audio cable is of little concern here. In fact the characteristic impedance of a piece of coax is only valid at higher frequencies - audio doesn't qualify, and certainly not at sub frequencies.

    brucek
     
  7. Earl Simpson

    Earl Simpson Supporting Actor

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    So/ can we use rg-6 for all our cable needs=rca, digital coax, video etc.????
     
  8. Bob McElfresh

    Bob McElfresh Producer

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  9. Steve Morgan

    Steve Morgan Second Unit

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    Thanks for the input. I ended up ordering a 40ft. cable from Cat Cables and took the RG6 back.

    Thanks,

    Steve
     

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