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Thread: Positioning of ports and driver?

  1. #91
    Member Greg_M's Avatar
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    If you believe WinISD, there is nothing to be gained by changing the vent size from 4" to 5"
    My enclosure net size is 10,702.1 cubic inches and if using the insulation boosts it by 20%, it is 12,842.5 cubic inches.

    Tuning this enclosure to 28hz will give me pretty much flat response to 40hz and a slight bump up after that. If the insulation trick works it will be a slightly bigger bump but not much.
    I have nothing to lose if it does not work and not much to gain if it does.

    Why worry?
    A 4-string 20-fret bass (like a standard Fender Precision) goes from E1 (41.203 Hz, second E below middle C) to Eb5 (622.25 Hz, second Eb above middle C).
    https://www.quora.com/Whats-the-rang...guitar?share=1

    The lowest note of a double bass is an E1 (on standard four-string basses) at approximately 41 Hz or a C1 (≈33 Hz), or sometimes B0 (≈31 Hz), when five strings are used.
    https://en.wikipedia.org/wiki/Double_bass


    This all hinges on WinISD being accurate.
    I have uploaded my WinISD file, so if you want to play with the figures you certainly can.
    It is here
    http://www.datilcam.com/GregsBox.wpr

    Let me know if you find some figures that are in error and I will run them on my version of WinISD.
    Thanks
    G

  2. #92
    Senior Member RMC's Avatar
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    When dealing with vent size one must remember speaker sound level impact on this, therefore keep an eye on power input data. Many softwares use 1 watt level for speaker modeling . At that level vent size doesn't matter much. But as power increases markedly then it does matter.

    I have played with this software power level thing in the past and saw the impact on vent size, it was eye opening. The software suggested vent size did vary based on input power number fed in the program. I don't remember if it was with Winspeakerz or Win ISD or both.

    For the last few years I've been using mostly Winspeakez, though I still have Win ISD and use it once in a while only because its driver database is pretty poor compared to Winspeakerz.

    Some softwares allow you to change driver input power level to model at higher or lower SPL, and some use as default the driver's power capacity number for suggested vent. Can't remember which power number ISD uses and if it can be modified since I use it less often.

    In any case, at the end of the day its still your project, not mine, so you decide what vent suits you best. Amen.

  3. #93
    Member Greg_M's Avatar
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    Quote Originally Posted by Ian Mackenzie View Post
    What method did you use to obtain the TL parameters?
    Not sure what TL parameters are.

  4. #94
    Member Greg_M's Avatar
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    I think it is time to put the speakers back on the shelf and terminate this project again.
    This just isn't fun.

  5. #95
    Senior Member Ian Mackenzie's Avatar
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    For anyone reading this thread l can confirm from my DATSv3 measurements the issue with the data is a user error.

    When setting up the VAS measurements the piston diameter must be measured correctly. With a foam surround the piston diameter needs include half or more of the surround.

    I used three or four 36 gram lead sinkers and got a VAS of 459 LT.

    My T/L data was close the Jbl data. The driver must be rigidly clamped with clear space under the driver.

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