Flared port length question

Discussion in 'Amps [BG]' started by thebassbuilder, Apr 4, 2014.


  1. thebassbuilder

    thebassbuilder

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    I am in the process of getting the parts picked out to build a cab. I am wanting to use a flared port for this. I am on parts express site and they have Precision Sound link to calculate the proper port length. It gave a shorter length then winISd. Is this normal? I do not have winISd in front of me but it gave 6.xxx" long and this flared port calculator gave me total length of 5.07" long. Let me know what you think.
  2. thebassbuilder

    thebassbuilder

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    Duke anyone?
  3. DukeLeJeune

    DukeLeJeune Only immortal for a limited time Gold Supporting Member

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    I don't use WinISD so I don't know how its port length calculator compares with others, sorry.

    Perhaps the calculator on the Precision Sound website includes end correction, and WinISD does not? That would be my first guess.

    Given that the minimum port length with most PRecision Ports is 6.0" (outer flare + inner flare), you might want to make sure that still results in a tuning that works for your application. To a certain extent, I design my bass cabs with that minimum port length in mind, just because I like those flared ports so much.
  4. thebassbuilder

    thebassbuilder

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    running that faital pro 10fe200 in winisd tuned to 44hz gives one port 4'' dia by 5.65" length. The mach is 0.08. I know you have to account for the flares, so do you think it would still be a good idea to run the flared port? Also using a 6" length would the difference be huge when talking 3/8" in deference in port length?
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  6. DukeLeJeune

    DukeLeJeune Only immortal for a limited time Gold Supporting Member

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    What is your internal volume, before subtracting for woofer and port?

    Also, if you don't mind, is that the 4 ohm or 8 ohm version of the 10FE200?
  7. bobcruz

    bobcruz

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    I can't comment on the specifics of your port but the answer to your general question is yes, flared ports need to be a little shorter than nonflared ports for the same tuning frequency because there is more air in the flared port at each end compared to a nonflared port.
  8. fdeck

    fdeck Supporting Member

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    Here's an idea stolen from mainstream engineering, called "sensitivity analysis." Basically, you change each parameter in a design by a little bit, run it through the modeling software, and see what happens to the results. For a speaker, at the very least I would compare two designs varying by 1 liter in box volume, and 1 Hz in port frequency (look at the response graphs, and also what happens to the port length).

    It is not a fancy "multi factor" analysis, but is pretty useful. I think it will show for most designs, that bass speakers are quite forgiving.

    WinISD lets you graph two designs at once. You can just have two copies of the same design, with a small difference in one parameter. My modeling spreadsheet has space for entering two designs at once, for the same purpose.
  9. DukeLeJeune

    DukeLeJeune Only immortal for a limited time Gold Supporting Member

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    While that makes intuitive sense, it's not the actually mass of the air in the port that determines the tuning frequency (along with the box volume); rather, it's the shape of that mass of air. Assuming equal internal volumes, the longer and thinner column of air will give you the lower tuning frequency.

    Think of blowing across the top of a beer bottle. Ignoring for now how much beer is left in the bottle, the longer and thinner the neck, the lower the pitch (tuning frequency).

    In my experience, flared ports need to be a bit longer than non-flared ports, because the effective diameter of the flared section is larger.
  10. DukeLeJeune

    DukeLeJeune Only immortal for a limited time Gold Supporting Member

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    Thank you! I didn't know what that process is called; I do it for crossover designs, and also look at changes of multiple parameters when it's logical to do so (like changing a cap and inductor simultaneously to change the shape of a second order filter - sometimes unexpected benefit or detriment occurs due to phase rotation). And as the name implies, this process tells me which component values need to be kept within tight tolerances, and which ones don't - though I've done it enough now that I can usually predict that in advance.
  11. Arjank

    Arjank

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    +1

    I use the following end-correction.
    add 1/2 of the flare-radius to the total port lenght.

    Btw. what's also important is the position of the port. I use Boxsim to calculate the port lenght. It takes the position of the port into it's calculation so it's a bit more accurate then most of the other free programs.

    Attached Files:

  12. thebassbuilder

    thebassbuilder

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    I am going with one 8ohm 10fe200 in a 2ft box before subtracting anything.
  13. bobcruz

    bobcruz

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    Thanks for clearing that up since I had it exactly backwards. Seems like that's happening more and more these days....
  14. Arjank

    Arjank

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    What is your design-goal(other then it's smooth midrange) to choose the 10fe200 and put it in a ported 2cu ft enclosure? There are several 12" drivers that "feel" happy in a 2cu ft enclosure and outperform the 10fe200 with ease. It's also a driver that's not well suited for a ported design. Better put two of 'm in the 2cu ft cab, leave it closed and orientate the cab vertically to get good off-axis dispersion.
    Just askin' / suggestin' :ninja:
  15. DukeLeJeune

    DukeLeJeune Only immortal for a limited time Gold Supporting Member

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    I second arjank's reservations about the 10FE200 in a two cubic foot vented box, but it could work well for low-power applications.

    If you do not have a protective highpass filter in your amp, I suggest tuning quite low, like in the lower 30's if you tune to low-B, and in the lower 40's if you tune to E. That translates to a single flared 3" port, or a single flared 4" port, respectively. Or if you use two 3" ports, try plugging one, and see how you like that.
  16. thebassbuilder

    thebassbuilder

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    I have put this speaker up against a ton of 12 and 15's in winisd and it out performs most of them and all of them in this price range. I have thought about getting a 12 and running it as the low end and the 10 as the mid and up. My amp is stereo/ biampable with a 2 way active crossover. The only 12 I have found that beets it in winisd is the PRV 12". My goal is something that can do it all. I am not in a band so max volume is not a big deal even though I like to jam loud when I can. If you have any better ideas I am open to them. I do not want to spend a ton, so non of the other faital pro's are needed. I want something that is smooth and not super flat or say mid heavy/forward. If these 10fe200 are that way let me know. I like fat bass that you can eq kids in when needed but I want it to have a nice sparkle top end regardless. I like the way gk, amp tech and ebs sound.
  17. Arjank

    Arjank

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    Nothing in the 53 bucks price range that can outperfrom the 10FE200?
    Hmmm.
    Btw. I think that xmax of 4.7mm is rather high for a voice-coil overhang of only 2mm.... (xlim peak-peak is 10.4mm)

    Yes, put the 10Fe200 in a Transmissionline enclosure :) , that'll give you a nice ol' school bass sound.
    Duke may help you with that :smug: he's a TL lover (like me)
    I can also help you with the design for that, at least I can simulate a TL in AJhorn :D
  18. thebassbuilder

    thebassbuilder

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    At 8ohms I will be pushing 220 watts per channel. My amp is bi amp able.
  19. DukeLeJeune

    DukeLeJeune Only immortal for a limited time Gold Supporting Member

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    I think the 10FE200 in that big ported box will go non-linear (get mushy and/or fartout) well before you run out of amplifier power.
  20. Arjank

    Arjank

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    Btw. I just fiddled around with AJhorn a bit.
    I could sqeeze out a TL with a size of approx 2 cu ft :)
  21. thebassbuilder

    thebassbuilder

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    Then I may need to think of another option here. I am going to try and up load an image of 3 speakers I am looking at.

    Speakers 1&2 are both the 8ohm Faital 10" 1: is in the sealed box and 2: is in the vented box.

    Speaker 3: Dayton Audio 8" in a vented box. These can handle a lot of power based off the specks but are only at 92db, all the other are 97db.

    Speaker 4 is the PRV 12" Which has the best over all graph (I think?)

    I would not mind using both the Dayton 8" and the PRV 12" together and use the by amp in my amp to cross them both over. I have a level control for both channels, so that could help with difference in SPL, correct?

    I hope this works. I will post the image in a moment. I need to free up some space.

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