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Alignment Delay

CybernaltCybernalt Posts: 22
edited May 2012 in PA General Discussion
What is actually adjusted .. I mean, if you "add delay" .. are you in effect moving the mains "back" towards the sub? ... in terms of feet if the mains are 8 feet in front of the sub' dou you start with a delay of 8 feet?

Comments

  • DraDra Posts: 3,777
    Give or take, in a nutshell, yes. If the tops are up high on stands or flown, be sure to take that geometry into account.

    DRA
  • GadgetGadget Posts: 4,915
    The THEORY is to line up the physical bottom of the cones/diaphragms using electronic delay.
  • EvolutionEvolution Posts: 14
    Hi All,
    We played a sunken cabaret style room last night that had a stage 4ft high and was semicircular in shape. Other than having the subs elevated on the stage with the tops, the only other option was to have the subs centred side by side at the end of the "D" on the floor. The tops were half way back towards the base line of the "D". So in effect the subs were 4ft lower and about 8ft in front of the tops. I tried the DRPA+ delay setting at max to see if there was any noticeable difference or if it tightened the sound, but could not pick any difference with my novice ear. I searched with Google prior to try and get some info on this situation, but did not find much, other than people recommending not to have the subs up elevated on the stage in these circumstances, hence getting them on the floor and the suggestion by someone that having subs in front of the tops is not as critical as the reverse when it comes to setting delays. Is this true :?:
    It was a show at short notice to help out the bar manager, so I didn't get to scope out the room and do some research on this, just do what I could.
    Thanks,
    E
  • DennisDennis Posts: 801
    Evolution wrote:
    and the suggestion by someone that having subs in front of the tops is not as critical as the reverse when it comes to setting delays. Is this true :?

    No, not true. 8ms ahead or 8ms behind is still 8ms. Aligning subs by ear is pretty much impossible. you could try doing it with a tape measure but the results would only put you in the correct zip code. Some form of Dual FFT program would be necessary for an accurate measurement.
  • GadgetGadget Posts: 4,915
    Well, there is the poor mans method which will probably be a better ballpark than strait measurement type delay. Reverse the polarity of one of the sources, play a tone that is equal to the LF/MF crossover point (say 100hz) and sweep the delay for maximum cancellation. It's not an earth shattering difference so don't expect total null, but there should be a point where you sense a null...

    The point that troubles me most is the 4' stage. Remember that boundary cancellation is a REAL problem, and the rule of thumb is "against the wall or more than 8' out.

    http://www.peavey.com/support/technotes ... lation.pdf
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