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Driver Specs and Port Types

Discussion in 'Amps [BG]' started by chienmort, Dec 30, 2012.

  1. chienmort

    chienmort

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    OK please bear with me on these questions but like many others I find a lot of conflicting advice around.

    #1 How good is WinIsd at helping to design a good cabinet for bass. What are it's limitations and are there better programs out there? Also which version is best? Beta or Pro alpha.

    #2 I have always believed that it is best to get the most efficient driver possible. However some of the speakers recommended on here and elsewhere have great XMax figures but poor sensitivity. I realise that sensitivity is measured at 1KHz usually but even looking at the response graphs the sensitivity of many highly regarded drivers is in the mid 80s at 50Hz. Discuss!

    #3 Vents/Ports. I am happy to have any type of port but I am
    confused. Is a shelf port different to a slot port? I thought that ports should be kept away from the cabinet edge but a shelf port uses the edge. Can anyone shed some light (sound) here?

    #4 Driver unloading. I think this is where the tuning stops working and the drivers sees an open baffle. It sounds dangerous for the driver so is there a formula or rule of thumb that says what frequencies are affected?

    #5 Xmax. I assume that this is the maximum linear travel of the cone/voice coil. At what power is this reached? Again is there a formula or way of calculating this?

    Sorry for the long post but the more I look into this the . more confused I get.:D
  2. vishuddha

    vishuddha 100% Mediocre Supporting Member

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    I'd love to learn more about this as well...
  3. bassmeknik

    bassmeknik

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    #1 I have some experience with WINISD and have used both versions, I agree with other posters here on TB that recommend the Beta version. I have had very pleasing results from the cabs I have designed with WINISD but it is the only program I have used. It's freeware so that was a big reason I used it, and the paid programs weren't any easier to use according to the reviews I read. WINISD will take a bit to get comfortable with so do a few simulations first and get a feel for what changing parameters does to the response.

    #2 IMO there is no "best/most efficient" driver for bass or MI use. Pick a well respected driver manufacturer and determine which model fits your needs/likes. Such as do you like 10's 12's or 15's. A great cab can be built from any of these.

    #3 nothing I can contribute here.

    #4 Design the box to fit the drivers at any useful frequency. Then use of a filter to roll off the unwanted lows (below the unload frequency) will protect your drivers from destruction.

    #5 I think Xmax is the cones safe limit of travel but this is another area where I am not sure as some drivers give both Xmax and Xlim (limit) so I am looking forward to being educated myself... I have read here on TB that most drivers reach Xmax at about half of their rated power, but I do not know how to calculate this. Anyone?


    Good questions I am looking forward to learning more about this too.
  4. Codger

    Codger Bradley Baker Supporting Member

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    I don't use it anymore because it isn't friendly with Windows 7. As I recall you can choose to display things other than the magnitude response, e.g. cone excursion, port velocity, maximum limited power (excursion, thermal). Set your signal power to your maximum for these views.
  5. 1958Bassman

    1958Bassman

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    How is it not Windows 7 friendly? I use 7 and it works fine.
  6. 1958Bassman

    1958Bassman

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    Bass Box Pro is more full-featured but it's not free. Both work, Bass Box Pro includes electrical power limit, phase response (more detailed than WinISD) and is more flexible. I used Term Pro (distributed by Rockford Fosgate, as well as Wayne Harris Enterprises) when I did car audio and it worked very well. I have used WinISD quite a bit and it works well too, but I really liked the full-featured Bass Box Pro designs that were done for me. BB Pro also does much more elaborate crossover designs, which is good for anyone who wants to do home speaker design.

    Bass Box Lite and Pro are available from Parts Express, too. Eminence has their own box design software and several others are out there, but some are incredibly putzy, which makes them a PITA, IMO.

    They all take some getting used to, especially for someone who has never designed boxes before. If I was paying for a program, it would be Bass Box Pro.
  7. 1958Bassman

    1958Bassman

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    Xmax is linear excursion, not total power. Xlim is physical limit, which shouldn't be reached for anything other than destructive testing.

    You could look for The Speaker Design Cookbook, by Vance Dickason. He has also designed speakers for kits sold by Parts Express and has a tutorial available.
  8. Codger

    Codger Bradley Baker Supporting Member

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    Should have said 64-bit. It errors when closing the program and requires the process to be killed manually. A report on the forum said it was because it was developed on an old Delphi platform (or some such). I now usually use BoxSim.
  9. bassmeknik

    bassmeknik

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    So Xmax is the maximum safe/workable amount of excursion the driver can produce repeatedly and Xlim is the point at which the cone/spider/voice coil assembly becomes physically damaged? Thanks 1958Bassman
  10. DukeLeJeune

    DukeLeJeune Only immortal for a limited time Gold Supporting Member

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    Disclosures:
    Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
    I don't use WinISD so can't help there.

    Generally speaking, fartout (exceeding x-max) is more likely to the the limiting factor for a bass cab than thermal overload, such that a lower-efficiency speaker with greater x-max often gives you more useable SPL than a higher-efficiency speaker with modest x-max.

    Say you have a decent woofer in a cab tuned to 50 Hz. Cone movement will be minimal near that 50 Hz tuning frequency, but will rise very rapidly below it. While you might not get fartout from a strong low-E (41 Hz) fundamental, you might well get fartout from a strong low-B (31 Hz) fundamental. Now we get into the juggling of tradeoffs. Let's say you drop the tuning frequency down to 40 Hz to better protect against fartout from the fundamental of low-B. Two other things happen: You increase susceptibility to fartout from strong signals in the 55-70 Hz region (roughly a half-octave above the tuning frequency), and you decrease the amount of energy the cab puts out north of 50 Hz as well. There is no one "right" tuning frequency that does everything best; you have to take into account as much as you can and make your best educated guess.

    As a ballpark first approximation, tuning frequencies in the mid to upper 40's generally are a good starting point. But there are lots of excellent cabs out there that are tuned somewhere else, depending on the woofer's capabilities and where the goal posts are.
  11. Passinwind

    Passinwind Charlie Escher Supporting Member

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    There's a newer version of WinISD that runs fine on Win7 64 bit - my version is 0.7.0.900. Look for it on their Facebook page, or use this link: http://www.linearteam.org/download/winisd-07x.exe.

    I like BoxSim too though.
  12. T-Bird

    T-Bird

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    Hi.

    And unfortunately creating a thread about it won't assure a conflicting advice free information ;).

    Pro alpha is the best...If You are an engineer, and/or can think like one. Hellishly difficult if You want to inport T/S specs, but unbelievably versatile if one knows how to use it.

    Beta is a magnitudes easier to use, and for the average user "close enough for rock'n roll".

    For me, the availability of the driver (or the re-cone kit) comes first.
    No use to design something around something that won't be available if the oldie bits the dust. Or if there's no local distributor and the manufacturer won't sell directly. Or the driver is a OEM driver and not for sale separately.

    Designing the cab for multiple driver choices is always a good idea though.


    Unless You're shooting for the smallest possible footprint, or the least drivers in the cab, sensitivity doesn't mean much nowadays. Watts are cheap.

    Better to look at other specs rather than the efficiency if a balanced operation is the goal. Especially if it's a one-way design.



    Usually shelf ports are used for increased rigdity, killing two birds with one stone.
    OTOH, a lot of the desire to use shelf ports can probably be credited for the EV TL designs.

    There's a whole a lot more freedom in placing round ports though.

    Definitely dangerous.
    The "better" enclosure designing software do calculate that, but generally an octave below the tuning frequency is considered very thin ice.

    Different manufacturers use different methods for displaying the Xmax. For some it's PP, for some list it as the one way travel, ie PP/2. AFAIK for most manufacturer it (PP) is the VC height minus twice the air gap height though.

    Again, the "better" enclosure designing software do calculate that, the power needed for over excursion is a function of frequency, not a fixed value.

    :D indeed.

    Prepare to be even more confused the more You dig into it.
    The key is to draw the line somewhere.
    A lot of the science behind sound reproduction is outside the normal MI/PA SR needs anyway.
    No practical need to use a Bugatti if a Volvo will do ;).

    Regards
    Sam
  13. Codger

    Codger Bradley Baker Supporting Member

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    Yup. Works good, thanks.:hyper:
  14. 1958Bassman

    1958Bassman

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    Unloading is a good case for using an amp/preamp with a HP filter, to keep the speaker(s) from puking.
  15. chienmort

    chienmort

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    Thanks to every one that responded. It has cleared my head. I have two cabs to build and will post again when I have decided on the drivers.

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