• 05-19-2004, 01:45 PM
    Weister42
    Uneven speaker wire length
    I recently measured my home theater speakers with my SPL meter and receiver's test tone and found something interesting...all my front speakers have the same wire length(15 feet) and their SPL matched up, my left surround speaker have 23 feet and my right surround speaker has 32 feet, but their SPL didn't match up with neither the front channels or each other. The left surround is set at -3dB and the right surround is set at 0dB to maintain even SPL with all five speakers, my speakers are all idenical(JBL N24) except the center channel(N-Center), which is 4dB louder but I also adjusted accordingly. I'm ruling out the possibility of speaker defects and receiver malfunction b/c I've noticed this problem ever since I had this setup(with the same 12 guage Sound King speaker wire), so is uneven speaker length taxing my power?

    I've also heard about uneven speaker wire length can cause phase shift???
  • 05-19-2004, 02:18 PM
    IsmaVA
    Accoustics?
    The effect you describe probably has more to do with room accoustics than the difference in cable length.
  • 05-19-2004, 08:09 PM
    Weister42
    The room I was in before is a rectangle room with straight walls and even space, so I don't think acoustics have too much to do with it. The room I'm in now is a somewhat square with the speakers on the side wall slightly behind the listening position like it supposed to be. Let's say if acoustics has nothing to do with it, can uneven wire length be the cause of SPL difference between identical speakers?
  • 05-19-2004, 08:23 PM
    Tony_Montana
    Quote:

    Originally Posted by Weister42
    Let's say if acoustics has nothing to do with it, can uneven wire length be the cause of SPL difference between identical speakers?

    Not with the ten feet of wire difference you have in your setup. It will take longer than 10 feet of cable to cause a 4 dB difference between speakers :)
  • 05-19-2004, 08:51 PM
    mtrycraft
    Quote:

    Originally Posted by Weister42
    I recently measured my home theater speakers with my SPL meter and receiver's test tone and found something interesting...all my front speakers have the same wire length(15 feet) and their SPL matched up, my left surround speaker have 23 feet and my right surround speaker has 32 feet, but their SPL didn't match up with neither the front channels or each other. The left surround is set at -3dB and the right surround is set at 0dB to maintain even SPL with all five speakers, my speakers are all idenical(JBL N24) except the center channel(N-Center), which is 4dB louder but I also adjusted accordingly. I'm ruling out the possibility of speaker defects and receiver malfunction b/c I've noticed this problem ever since I had this setup(with the same 12 guage Sound King speaker wire), so is uneven speaker length taxing my power?

    I've also heard about uneven speaker wire length can cause phase shift???


    The electrical signa in a wire travels 1 ft in 1 nano seconds, pretty fast. 10 ft is 10 nano seconds.
    The time to complete 1 cycle at 20kHz is 50,000 nanoseconds or 100,000 nanoseconds at 10kHz. You think you will detect a phase shift at these frequencies of 10 nanoseconds, 5000th of a cycle at 20kHz or 10,000th at 10kHz. In air, the sound would travel .00012 inches in that time. You need to hold real still.
  • 05-20-2004, 05:58 AM
    IsmaVA
    Quote:

    Originally Posted by Weister42
    The room I was in before is a rectangle room with straight walls and even space, so I don't think acoustics have too much to do with it. The room I'm in now is a somewhat square with the speakers on the side wall slightly behind the listening position like it supposed to be.

    Accoustincs is very complicated stuff, I would not rule out accoustic that easily.

    Quote:

    Originally Posted by Weister42
    Let's say if acoustics has nothing to do with it, can uneven wire length be the cause of SPL difference between identical speakers?

    Highly unlikely (emphasis added) . . . .
  • 08-21-2004, 10:52 AM
    Thatch_Ear
    There is probably a fairly large level of tolerance allowed by the manufactorer of your componants. Differences that large if not caused by the acoustics of the room could be power transistors or even speaker crossover parts.

    I doubt that the resistance and capasitance of the different lengths of wire would vary as much as the parts used to make your gear.
  • 08-21-2004, 12:19 PM
    E-Stat
    Quote:

    Originally Posted by Weister42
    I recently measured my home theater speakers with my SPL meter... The left surround is set at -3dB and the right surround is set at 0dB to maintain even SPL with all five speakers...I've also heard about uneven speaker wire length can cause phase shift???

    I'm with everyone else - 10 feet shouldn't account for a 4 db drop unless you are using teeny tiny gauge wire. Try using 32' to both speakers and see if the issue resolves itself.

    rw
  • 08-21-2004, 02:19 PM
    Pat D
    Quote:

    Originally Posted by Weister42
    I recently measured my home theater speakers with my SPL meter and receiver's test tone and found something interesting...all my front speakers have the same wire length(15 feet) and their SPL matched up, my left surround speaker have 23 feet and my right surround speaker has 32 feet, but their SPL didn't match up with neither the front channels or each other. The left surround is set at -3dB and the right surround is set at 0dB to maintain even SPL with all five speakers, my speakers are all idenical(JBL N24) except the center channel(N-Center), which is 4dB louder but I also adjusted accordingly. I'm ruling out the possibility of speaker defects and receiver malfunction b/c I've noticed this problem ever since I had this setup(with the same 12 guage Sound King speaker wire), so is uneven speaker length taxing my power?

    I've also heard about uneven speaker wire length can cause phase shift???

    I can't see 9 feet of 12 gauge wire causing that kind of a drop and as mtry points out, phase shift is not an issue. Now, personally, I don't think that kind of level difference is a problem since you can easily adjust for it. I'm not even sure you can depend on all channels putting out the same voltage at any given setting. Are the wires and contacts clean and not oxidized? Anyway, have you switched the rear speakers to see if you get the same result? I suggest that because it is possible that something is amiss with a speaker. If not, I wouldn't worry about it.
  • 09-29-2004, 11:26 AM
    Weister42
    interesting...well thanks for all the input, I'm gonna go play with my setup and see if I can find the problem!
  • 09-29-2004, 11:49 AM
    tpcounty
    Quote:

    Originally Posted by Weister42
    interesting...well thanks for all the input, I'm gonna go play with my setup and see if I can find the problem!

    I doubt it's the wires but have you tried switching to wires of the same length. If you experience the same problem after switching cables, I would test your receiver and speakers separately to try and isolate the problem. My guess is the fault is in the receiver or speakers.
  • 10-08-2004, 04:53 AM
    JDaniel
    I Agree With IsmaVA
    Room acoustics most likely. Is your room identically furnished all around? Most are not. Do you have a sofa on one side, but not on the other? Identical things hanging on both walls? Is there a door/opening on one side versus the other? Is your listening chair exactly in the center of the two surrounds, or closer to one or the other? When you measured the SPL, were you closer to one surround than the other? Did you measure to be sure? Did you move around any during the measurements?

    I'm no expert, but it seems that any of the above would be a more likely cause than an extra 10' of speaker cable. I've never had all 5 speakers measure the same SPL before any adjustments.

    If you want to be scientific, go buy another 32' run and test it out for yourself.

    Bottom line though, since you have the SPL meter and are calibrating accordingly, it won't matter. Adjust it, and then just enjoy.

    JD