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Kapplite 3015LF Vented Cabinet Assistance Needed

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  • Kapplite 3015LF Vented Cabinet Assistance Needed

    I am working on building a light weight vented cabinet for a Eminence 3015LF based on the "Larger PA Subwoofer Cabinet" plan on Eminence's site here http://www.eminence.com/pdf/Kappalite_3015LF_cab.pdf

    I would like to use a slot or corner triangle ports instead of round tubes. I am working out the dimensions now and want to double check my ideas before I go any further. Here is a rough sketch using 4 corner ports.



    Am I going to run in to any issues with something with approximate dimensions shown above?

  • #2
    Re: Kapplite 3015LF Vented Cabinet Assistance Needed

    The only issues will be sizing the ports. As the port is near the side walls there's boundary effect that extends the effective length of the port. I don't have the correction factors in front of me but its close to 1 or .7 times the equivalent diameter added to the port physical length.
    John H

    BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim ,Aperivox,

    Comment


    • #3
      Re: Kapplite 3015LF Vented Cabinet Assistance Needed

      I'd think you'd be OK, if you're shooting for mid 40s.
      If the short sides of the triangle are 4", I'm guessin' the length would be about 6" (w/out any special corrections).

      Comment


      • #4
        Re: Kapplite 3015LF Vented Cabinet Assistance Needed

        Originally posted by Chris Roemer View Post
        I'd think you'd be OK, if you're shooting for mid 40s.
        If the short sides of the triangle are 4", I'm guessin' the length would be about 6" (w/out any special corrections).
        Yes, a lightweight mid 40s design is the goal. Multiples will be used for a live act with only 4 string bass.

        Eminence is recommending 5.11ft3 volume and four round vents, diameter 4" by 8.585". So if my math if correct, the cross sectional area of the recommended round port (pi*(r^2)) would come out to 12.56 sq in per port. So, if my 45/45/90 triangle ports were 5" on the base and height, area (1/2bh) would work out to an area 12.5 sq in.

        So four triangle ports 5" on the base/height and 8.585" long was my original assumption. I would greatly appreciate any assistance in correcting the length as needed.

        Thanks for the assistance.

        Comment


        • #5
          Re: Kapplite 3015LF Vented Cabinet Assistance Needed

          The Em-box @ 5.1cf is tuned to 47Hz.
          I figure your box is no larger than 4.5cf.
          My four 4" vents would use up .3cf, leaving you w/4.2. At 6" long, yuor Fb is 44Hz (which I like).
          Your four 5" vents use up at least .7cf, leaving you with 3.8. At 8.5" long, you end up w/an Fb of 47Hz. Pretty close to the E box. Your plan looks sound.

          Comment


          • #6
            Re: Kapplite 3015LF Vented Cabinet Assistance Needed

            Eminence changed some of their specs over the years, so maybe you should verify them against the latest spec sheet. I've been modeling various Eminence woofers recently and found some slight differences, which might affect how the box model turns out.

            Comment


            • #7
              Re: Kapplite 3015LF Vented Cabinet Assistance Needed

              End correction is subtracted from your port length without any end correction. I've use port length - equivalent port diameter times 1. This german pic says 1.7, which I've not verified. There was a thread where I believe Jeff B supported similar end correction factors.
              Attached Files
              John H

              BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim ,Aperivox,

              Comment


              • #8
                Re: Kapplite 3015LF Vented Cabinet Assistance Needed

                Originally posted by jhollander View Post
                I don't have the correction factors in front of me but its close to 1 or .7 times the equivalent diameter added to the port physical length.

                OK, so if the equivalent diameter is 4" we should add 2.8" (4*.7) to the original 8.585 length. to make the ports 11.385"?

                Originally posted by Chris Roemer View Post
                The Em-box @ 5.1cf is tuned to 47Hz.
                I figure your box is no larger than 4.5cf.
                My four 4" vents would use up .3cf, leaving you w/4.2. At 6"

                long, yuor Fb is 44Hz (which I like).
                Your four 5" vents use up at least .7cf, leaving you with 3.8. At 8.5" long, you end up w/an Fb of 47Hz. Pretty close to the E

                box. Your plan looks sound.

                Thanks for the info. the original 20x20x24" in the sketch was just a rough guess.

                So, in figuring how much internal volume the 5" base triangle ports are taking away, lets add a half inch to the base and height for the wood and set the

                corrected port length at 11.25". So the volume of one port (1/2 x base x height x length) would be (5.5 x 5.5 x 11.25)/2 , which comes out to 170.16 in3 per port for a

                grand total of 680in3 for all 4 ports.


                The original eminence box calls for 8830in3 volume so lets approximate 9500in3 with the added port volume. An option for internal dimensions could be 20" x 20" x 23.75. This isn't taking in to account any dowel bracing or the volume of the driver.

                Does this look correct to you?

                Comment


                • #9
                  Re: Kapplite 3015LF Vented Cabinet Assistance Needed

                  Originally posted by jims View Post
                  Eminence changed some of their specs over the years, so maybe you should verify them against the latest spec sheet. I've been modeling various Eminence woofers recently and found some slight differences, which might affect how the box model turns out.
                  I am using the latest specs of the site and the models are looking very close to the data in the eminence designer pdf. I also measured one of the drivers right out of the box in dats using a rough added mass method for vas. My sims are looking pretty good to my untrained eye. I will post that later.

                  Comment


                  • #10
                    Re: Kapplite 3015LF Vented Cabinet Assistance Needed

                    And here is the sim with 450w @8ohm, the latest eminence specs and the following variables from the discussion above. Everything looks right in line with the results in the Eminence spreadsheet.

                    Total Port Cross Section Area = 50 in2 (322.58 cm3)
                    Uncorrected port Length = 8.585 in (21.8cm)
                    Cabinet Volume = 5.11 ft3 (144.69L)




                    Last edited by DDG; 02-29-2016, 10:09 AM.

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                    • #11
                      Re: Kapplite 3015LF Vented Cabinet Assistance Needed

                      Yup.

                      Comment


                      • #12
                        Re: Kapplite 3015LF Vented Cabinet Assistance Needed

                        See my post #7. You subtract the end correction. The equivalent diameter is that of the ports next to the wall. If the ports are quantity of 4 at 1 inch diameters, 6 inches long the corrected port is between 5 and 4.3 inches long.
                        John H

                        BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim ,Aperivox,

                        Comment


                        • #13
                          Re: Kapplite 3015LF Vented Cabinet Assistance Needed

                          Originally posted by jhollander View Post
                          See my post #7. You subtract the end correction. The equivalent diameter is that of the ports next to the wall. If the ports are quantity of 4 at 1 inch diameters, 6 inches long the corrected port is between 5 and 4.3 inches long.
                          Sorry, I read that post in haste. So, If the eminence plans call for four 4" diameter ports 8.585" long I will end up subtracting approx. 4" from the ports with a result of four ports being 4" to 4.5" long.

                          That seems really short to me but I am willing to test it out. The good thing is they should be easy to add length to if the response doesn't measure out to the sim.

                          The last question I have is about the internal dimensions. I would like to keep the outer dimensions no longer than 24" so I was thinking about changing the internal dimensions to something like 21"W x 21"H x 22"D.

                          Would having similar xyz dimensions result in any problems? I am a rookie at speaker design but I thought I remember reading somewhere having equal dimensions for xyz inside a sub would cause issues with standing waves inside the box. But I also read if I keep my internal dimensions less than 1/4 of the wavelength of the frequencies in the pass band standing waves wont be an issue. If this is correct, if a 120Hz wave is 8.2 ft I should be OK if I keep internal dimensions under 24". Is this a correct assumption?

                          Thanks again.

                          Comment


                          • #14
                            Re: Kapplite 3015LF Vented Cabinet Assistance Needed

                            If you're really using them as "subs" (like, under 80 or 100Hz only), I've stopped lining my vented subs years ago w/no ill effects. OTOH, I don't build many that are cubes, and I don't know how thin your walls are, but several dowel (or sq.) braces should solve that issue.

                            Comment


                            • #15
                              Re: Kapplite 3015LF Vented Cabinet Assistance Needed

                              Originally posted by Chris Roemer View Post
                              If you're really using them as "subs" (like, under 80 or 100Hz only), I've stopped lining my vented subs years ago w/no ill effects. OTOH, I don't build many that are cubes, and I don't know how thin your walls are, but several dowel (or sq.) braces should solve that issue.
                              Yes. They will be used as PA "subs" so no lining. The plans are to use 1/2" ply heavily braced with Dowels.

                              Comment

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