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Cabinet builders: WinISD questions

Discussion in 'Amps and Cabs [BG]' started by basstrader, Feb 26, 2004.


  1. Joris, BGavin, et. al. -

    I've been playing around with WinISD for a while now. My first question is can you find out how much power/volume it will take to get to the mechanical limit of the driver? (Xmax) The power graph seems to take into account only the thermal limit of the driver, that is the rated wattage of the driver.

    Second question: how much group delay is acceptable? I know that's kind of vague, but is there a rule of thumb to use?

    Have I stopped making sense?
     
  2. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    The graph you need is "Max Power". This graph does indeed take the driver's suspension and non-linear behaviour into account. The "Cone Excursion" graph doesn't.

    I enlisted the help of the guys who whote the program via the Linear team online forum. The graphs mentioned are only available on WinISD Pro. It's only in alpha testing phase at the moment but it seems to be working well. You can download it from their website in basic form, but a more advanced version is available to people registered on the forums with a list of upgrades as long as your arm (including the choice of several different alignments finally).
     
  3. I don't use WinISD at all for this, because I cannot see the calculations being done. I use a spread sheet instead, so I can understand exactly what is being calculated, and how it is done.

    I have no experience with WinISD Pro.

    I'd use LEAP if it came down to a commercial venture.
     
  4. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Sorry I forgot to answer this question.

    You want to keep group delay as low as possible. As a general rule, 20ms would be an upper limit.
     
  5. Cool guys, thanks.

    So Bruce, is that formula available? I mean the one for max power that will include the xmax/suspension stuff.
     
  6. Don't put too much emphasis on the xmax figure. It's cool to have a box with linear cone movement across the frequency spectrum. But the fact is: at the volume levels where this comes into play, you won't be able to discern the distortion caused by the xmax limit, and you will hardly ever be using the max power level at all. I wouldn't worry if you exceed xmax by 30% or so. It's always cool to design within the limits, but you must ask yourself how big an issue it is if you don't.

    My Eur 0,02
     
  7. The formulas are readily available on the net, and in publication.

    Vance Dickason's book, "The Loudspeaker Cookbook" has them. Do a net search for "Brian Steele" as he has them on his site.

    The formulas are multi-tiered, and dependent on many intermediate results to reach the final measurement.

    Yes, there is a substantial difference between Xmax and Xmech. But... it is beyond the scope of most design programs to accurate predict response beyond linear motor control. And yes, in a live venue nobody will hear the distortion anyway. The Delta 10 is a prime example: tiny Xmax and very large Xmech. Designed to be overdriven and sound like merde, but without suffering mechanical damage.

    Also... there is a sufficient number of folks who blow drivers by first exceeding Xmax, then exceeding Xmech.