Testing the Quality of Cables

Discussion in 'Accessories, Cables, and Remotes' started by CarlosGH, Jul 31, 2004.

  1. CarlosGH

    CarlosGH Stunt Coordinator

    Joined:
    Jan 11, 2004
    Messages:
    74
    Likes Received:
    0
    I have heard many people dispute whether cable X is better than cable Y because of various properties. I just wanted to know if any one hard a simple(or complex) hardware device that sends a test signal and determines if there was any loss on the opposite end?
     
  2. Chu Gai

    Chu Gai Lead Actor

    Joined:
    Jun 29, 2001
    Messages:
    7,270
    Likes Received:
    1
    what kind of cable?
     
  3. CarlosGH

    CarlosGH Stunt Coordinator

    Joined:
    Jan 11, 2004
    Messages:
    74
    Likes Received:
    0
    well all of them: video, audio, digital, optical, etc...
     
  4. Chu Gai

    Chu Gai Lead Actor

    Joined:
    Jun 29, 2001
    Messages:
    7,270
    Likes Received:
    1
    What seems to be a fairly simple question has no simple answer and any attempt at a simple answer might sound dismissive and would leave you feeling that your question hasn't been answered.

    A cable, be it digital, speaker wire, or analog interconnects between a preamp and amp, or video cable, is part of an electrical circuit. As a result the cable itself has an inductance, capacitance, and resistance commonly referred to as LCR parameters. Further the equipment that it connects also has its own set of parameters and characteristics such as impedance that dictate just how that wire will behave when a signal passes through it. To further complicate matters, the signal may or may not be susceptible to outside interference from EMI or RFI which dictates just how that cable can be constructed in the sense is shielding required or some sort of twisted/braided approach in order to mitigate the effects of EMI or RFI.

    Hence there is no simple device that one can use in order to determine how much loss there will be at one end since this device would need to be loaded if you will with the correct (whatever that may mean) impedance.

    Further, one must consider the nature of human hearing in the aforementioned cases and determine just how much of a loss can be detected. While some speaker cables can be down only 0.1 dB at say 20kHz, others may be down 0.4 dB depending upon length, gauge, etc. While either cable would not have an audible effect, one can be stated to be technically better however it does not translate to an audible difference.

    So far this sounds remarkably complicated. For a complete characterization it does involve some math since the answers to a large part of your question can simply be answered by considering the engineering mathematics that relate to the problem. This was covered some time ago in a paper presented to the AES by a Mr. Fred Davis.

    Let's simplify the matter tremendously and I'll touch upon speaker cables for now. If time and energy permits, I'll talk about some of the others you mentioned.

    If one chooses their speaker cables so that the total loop resistance is about 0.1 ohms, which you can calculate from the gauge of the wire times 2 (its a loop, right?), then this will result in two important benefits.
    1) The overall resistance will be such that the signal drop around 20 kHz is somewhere in the vicinity of 0.1 dB. It is impossible to hear this so it satisfies the arbitrary criteria that the wire pass the signal faithfully and without acting as a tone control.
    2) The overall resistance is low enough so that it does not cause the amplifier to behave in a fashion similar to an equalizer whose output mimics the impedance curve of your speaker. This means it does not act euphonically.

    For virtually everyone, this reduces down to the simple generalization that 12 gauge speaker wire covers just about every scenario that's out there allowing you to simply buy a 100 foot spool, enjoy the economic benefits or a 'bulk' purchase, and wire your entire system, front, rears, sides, with it.
     
  5. Leo Kerr

    Leo Kerr Screenwriter

    Joined:
    May 10, 1999
    Messages:
    1,698
    Likes Received:
    0
    (plus, if you've anything left over, 12ga makes excellent extension cords for AC power. No house can ever have enough extension cords or duct-tape. [​IMG] )
     

Share This Page