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    Vageta31's Avatar
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    Port correction factor...

    I just read on JL's site about port correction factor so let me see if I'm getting it right. Basically if you use a wall of the enclosure as a side of the port(slot design) then you effectively gain a bit of length to the port? Apparently because one side of the port doesn't end at the same place as the other, the speaker see's this as extra port length, half of the port height to be specific.

    So in essence this can be a bad thing for those tuning higher and don't take it into consideration as it will extend the port and cause the tune to go a bit lower than expected. For those like me however who want to tune low you can use it to your advantage by getting a free inch or so on the port without actually taking up displacement?

    Personally I want to tune my box low, but going as low as I'd like will take up gobs of space that I don't have. So when WinISD tells me to make a port length of 25.25" to accomplish a 29hz tune, then my 2" high slotted port design will add an extra 1" of effective port area giving me 26.25" and tuning a little bit lower? Assuming of course that I ingored the correction factor and built the actual port to 25.25".

    Just making sure I have the basic logic down to decide whether or not to actually build the port without the correction factor or not. If it will cause more harm then I will subtract that inch off of the design. Seems to me like a free way to get a longer port without taking any displacement away. May be miniscule in the larger scheme of things but hey it's free.







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    Trixter's Avatar
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    Never really looked at it like that. But yeah....makes sence to me. Anyone else have thoughts?



    2006 Jeep Liberty
    Adire Audio, Cadence, Clarion, MB Quart

    Lv = [(14630000 x R^2) / (Fb^2 x Vb)] - 1.463R
    *Vb = vol. in cu"
    **R = sq.rt. A / Pi (for square/slot port)

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    there was a thread at SIN awhile back about this verry thing.

    at the time i did not think about it.
    still have not
    but from what you are saying it makes sense.

    this could be why my note is not as i thought it to be.

    guess i will have to look into that tomorrow when i work on my box.

    Monty



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    F150Matt's Avatar
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    Use this website, it has a slot vent calculator. Tuning was right on the money last time I used this calculator. http://www.loudspeakers101.com/VentCal1.htm



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    Re: Port correction factor...

    Quote Originally Posted by F150Matt
    Use this website, it has a slot vent calculator. Tuning was right on the money last time I used this calculator. http://www.loudspeakers101.com/VentCal1.htm

    NEVER!! use that you're prolly tuned ~10hz higher than it say's



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    Re: Re: Port correction factor...

    Quote Originally Posted by slipknot87420
    NEVER!! use that you're prolly tuned ~10hz higher than it say's
    I have heard of people saying to tune it lower because you will be tuned ~10Hz higher. When I built my box I tuned it so it would peak at 38Hz (in WinISD). When I went to comp. with it I hit my max SPL at 38Hz. I don't know if it has to do with the vehicle or not but my tones were exactly where I tuned them to be.



    2006 Jeep Liberty
    Adire Audio, Cadence, Clarion, MB Quart

    Lv = [(14630000 x R^2) / (Fb^2 x Vb)] - 1.463R
    *Vb = vol. in cu"
    **R = sq.rt. A / Pi (for square/slot port)

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