1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

does speaker cable need to be the same lenght?

Discussion in 'Cables & Switches' started by pickle, Mar 13, 2004.

  1. pickle

    pickle
    Standard Member

    Joined:
    Feb 21, 2003
    Messages:
    30
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Location:
    N ireland
    Ratings:
    +0
    as title really.

    is it ok to use different lenghts to left and right speakers?

    im talking pretty long runs of cable too, im looking at ~5m to one speaker and ~7m to the other so the ratio wouldnt be that far off.

    will this case an imbalance? or have any other wierd effects?

    ive got 12m here which i could use if this is ok, before any1 tells me not to be so tight and just buy an extra 2m :p

    thanks in advance :)
     
  2. CARLOS

    CARLOS
    Well-known Member

    Joined:
    Feb 11, 2001
    Messages:
    5,907
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    WEST MIDLANDS
    Ratings:
    +1,200
    Ideally they should be the same length as the signal will reach one speaker before the other, Though how much difference a couple of metres will make is debatable ?
     
  3. pickle

    pickle
    Standard Member

    Joined:
    Feb 21, 2003
    Messages:
    30
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Location:
    N ireland
    Ratings:
    +0
    just made some better measurements.

    7m one side, 5.5m the other

    to explain my situation a little better...

    i have 12.5m of QED SA biwire. i see two options:

    1. run it 7m - 5.5m biwired.
    2. rip it in half, and run 7m each side of single cable.

    anybody like to advise me as to what direction i should go? :smoke:
     
  4. CARLOS

    CARLOS
    Well-known Member

    Joined:
    Feb 11, 2001
    Messages:
    5,907
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    WEST MIDLANDS
    Ratings:
    +1,200
    I would deffinately go with the biwire, As i said above 1.5 m difference in length isn`t going to make any audiable difference !
     
  5. gmt steve

    gmt steve
    Active Member

    Joined:
    Aug 19, 2002
    Messages:
    648
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    Manchester
    Ratings:
    +6
    It's not just about the timing of the signals, different lengths of cable will exhibit different inductance and capacitance characteristics. This in turn will put different demands on the relevant amp sections, so all in all I'd avoid it if at all possible. Differences of a few cm won't matter, but several metres isn't ideal. I would go with equal lengths of single wire and upgrade to bi-wire later when funds recover, although you don't mention what the speakers are. Sorry if this contradicts CARLOS, but then he's a jackel isn't he?:devil: :D
     
  6. Ajax

    Ajax
    Standard Member

    Joined:
    Feb 4, 2004
    Messages:
    169
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    21
    Ratings:
    +1
    Hello,

    Does the rear speaker cables need to be the same as the front or can you get away with longer lengths for the rear and short ones for the front?

    Ajax.
     
  7. pickle

    pickle
    Standard Member

    Joined:
    Feb 21, 2003
    Messages:
    30
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Location:
    N ireland
    Ratings:
    +0
    humm.. thanks for the replies, altho, now i still dont know what to do... :suicide:

    speakers are B&W 604s3's

    i dont really understand how biwiring actually helps (from my limited engineering knowledge) altho ive never tried it before so i cant say wether it makes a difference or not :rolleyes:

    so i might just go with single wiring, the same lenght, waiting for a 3rd vote to swing it one way or the other... :smoke:
     
  8. gmt steve

    gmt steve
    Active Member

    Joined:
    Aug 19, 2002
    Messages:
    648
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    Manchester
    Ratings:
    +6
    Like I said, it's nothing to do with a signal arriving at each speaker at differing times, we are talking of propogation speeds of approx 80-90% the speed of light. It's about differing electrical properties of differing lengths of cable. So it's ok (and thank goodness from a cost point of view) to have different lengths on the rears or the centre, than the fronts, as long as each pair are the same length. Of course absolute fidelity on the rear channels isn't as much of an issue with film material as it is with music, so from a cost /practicality point of view, differing lengths at the rear shouldn't be a problem.

    .

    Bi-wiring "works" by keeping "delicate" treble signals apart from the signals intended for the mid/bass driver. Some speakers respond to bi-wiring better than others. Bear in mind that one of the best manufacturers of speakers, Dynaudio(among others) never have a bi-wiring option
     
  9. pickle

    pickle
    Standard Member

    Joined:
    Feb 21, 2003
    Messages:
    30
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Location:
    N ireland
    Ratings:
    +0

    how are these signals kept apart tho? surely all the signals (bass/mid/treble) are still being sent down the cable from the amp?

    theres nothing (as far as i know) on an amp that seperates one type of signal to another?
     
  10. gmt steve

    gmt steve
    Active Member

    Joined:
    Aug 19, 2002
    Messages:
    648
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    Manchester
    Ratings:
    +6
    The crossover is in the speaker. So the seperate signals run down the doubled up lengths of cable.
    It helps to analogise the signal with water flow. bearing that in mind remember that contrary to what you might imagine, the amplifier doesn't pump the signal/water to the loudspeaker, the loudspeaker "sucks" the signal from the amp. The amp keeps the "resovior" topped up. That's why a 4ohm loudspeaker is tougher for an amp to drive that an 8ohm loudspeaker. Logically you would think that the lower impedance of 4ohms would be easier, but a 4ohm loudspeaker is "sucking" much more signal from the "resovoir" and the amp must work harder to keep it topped up. Going back to your original point about how the signals are kept seperate, kepping in mind what I've just explained; the separate drivers (via the passive crossover in the loudspeaker) suck the signal they need along each length of pipe/cable)
    I hope that very basic and simplified explanation helps.
     
  11. pickle

    pickle
    Standard Member

    Joined:
    Feb 21, 2003
    Messages:
    30
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Location:
    N ireland
    Ratings:
    +0
    whoa, all of a sudden it all makes sense! really hope i wasnt being daft as a brush before! :blush:

    ill think differently the next time i hear someone talking about an amp driving speakers.

    many thanks for that :)
     
  12. gmt steve

    gmt steve
    Active Member

    Joined:
    Aug 19, 2002
    Messages:
    648
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    Manchester
    Ratings:
    +6
    To be honest I'm still waiting for some very informed person to correct me. I know I'm basically right, but my explanation is about as deep as my own understanding goes. The water analogy always helps though. I think they use it when training electricians.
     
  13. eviljohn2

    eviljohn2
    Well-known Member

    Joined:
    Jul 8, 2002
    Messages:
    7,529
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    86
    Location:
    Near London.
    Ratings:
    +208
    For biwiring, unless the amplifier sections are seperate (biamplifying) then the amplifier, speakers and cables "see" exactly the same signal since at one point or another there will be a bottleneck.

    Biwiring does double the effective CSA of the speaker cable though and thus halves the resistance which may well have an audible effect.
     
  14. CJROSS

    CJROSS
    Well-known Member

    Joined:
    Nov 16, 2000
    Messages:
    5,070
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    106
    Ratings:
    +343
    We had an inetresting discussion about “velocity of propogation of electrical current” dudes over at HFC recently, I have copied the quotes which are verifiable “velocity” measurements and they range from 13Km to 300Km per second, anyone thinking they can hear a difference with different length cables is clearly “hearing things” due to pre belief in the cables being different lengths. The human ear is getting close to bat status with some claims made about what it can “hear” anyway some interesting reading :

    ******
    Ref 1 : Typical results are presented for Al (10 µ m-thick), Pt (10 µ m), Au (5 µ m) and Cu (5 µ m) foil plates at laser intensities ranging from 20 to 400 GW/cm2. For the 10 µ m-thick Al, velocities over 13 km/s within about 30 ns have been detected with a time resolution of ~300 ps and ~2% error for the peak velocity. ©2002 American Institute of Physics

    Ref 2: A Text Book of Electrical Technolgy : B.L Theraja & A.K Theraja

    Page 4 : 1-2 Current Velocity and Velocity of Energy Propogation

    I emailed a sparky friend and he told me that this book is a good reference bible : states a “velocity of propogation of electrical energy” (in his words a “charge”) of 300,000,000 m/s (3 x 10-8 m/s) for electrical charge thru copper. This is the actual charge ie not the speed of which charge drfits in a conductor which is called “velocity of current” FWIW. A lot of these terms are new to me but they explain how even differing terms for “drift” or “charge” are termed and the speed or velocity of these (apologies to those who know this stuff to this level anyway).

    Thats 300,000 Km/second (Edit Courtesy of MH - you cant get the staff these days eh ?) so maybe 13 Km / second is tad low Here is the chapter for those interested.

    1-2 Current Velocity and Velocity of Energy Propogation

    The speed with which charge drifts in a conductor is called the “velocity of current”. As seen from above, its value is quite low, typically a fraction of a metre per second. Its value depends on the value of the current, conductor cross section & free electron density in the conductor etc.

    However the speed with which the effect of e.m.f is experienced at all parts of the conductor resulting in the flow of current is called the “velocity of propogation of electrical energy”. Its is independent of current and voltage and has a high but constant value of nearly 3 x 10-8 m/s”

    Interesting stuff.

    ******

    http://forum.hifichoice.co.uk/viewtopic.php?t=9233
     
  15. eviljohn2

    eviljohn2
    Well-known Member

    Joined:
    Jul 8, 2002
    Messages:
    7,529
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    86
    Location:
    Near London.
    Ratings:
    +208
    Reference books will tell you that an electron (the "charge" mentioned above) propagates through pure copper with a velocity of 3x10^7m/s.

    This is indeed independent of current and voltage, and subsequently resistance (for those that remember Ohm's law ;) )

    As has been described in more detail above, the differences in length of speaker cable - there would be a difference of 1s for every difference of 30,000,000m of cable.

    If you're interested, the speed of light in a vacuum is 3x10^8m/s. :)

    More details available if you're interested, but essentially, a few metres WILL make a difference, but only by fractions of a microsecond (or a few hundred nanoseconds, they're both the same but one sounds much smaller).
     
  16. pickle

    pickle
    Standard Member

    Joined:
    Feb 21, 2003
    Messages:
    30
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Location:
    N ireland
    Ratings:
    +0
    does anybody know how this delay compares to delays in timing in a cd player? i presume timing errors in a cd player are also in the microsecond region, and it seems to make a difference. (i say seems cause i dont know how you could ever do a test of good timing against poor timing, as if u change cd player ur changing everything)

    anyway, i went the biwire route, and i dont notice a difference from left / right speaker. might try to beg/borrow/steal a spl meter to see if it can pick up a difference but as i said, my ears cant, and thats what matters. :)
     

Share This Page

Loading...