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"Rock Its" Build Thread

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  • #91
    Re: "Rock Its" Build Thread

    You are right Dave. The Salk speaker was meticulously finished. If you are going for that look, then I think they will look good. Whatever you do will end up looking good. You're one of the many wood whisperers on these boards!

    Darren

    Comment


    • #92
      Re: "Rock Its" Build Thread

      That's an excellent way ("wood whisperer") to describe Dave's wood-working skills. I'm always envious of his work.
      Paul

      Originally posted by dian1511 View Post
      You are right Dave. The Salk speaker was meticulously finished. If you are going for that look, then I think they will look good. Whatever you do will end up looking good. You're one of the many wood whisperers on these boards!

      Darren

      Comment


      • #93
        Re: "Rock Its" Build Thread

        Originally posted by Paul K. View Post
        That's an excellent way ("wood whisperer") to describe Dave's wood-working skills. I'm always envious of his work.
        Paul
        Thanks guys unfortunately my skills are coming to a quick end as I start into the real parts that make a great loud speaker. I will probably be needing some advice on the TL as soon as I get things properly set up. Paul, in one of your emails you said to stuff the line .75 lbs. per sq. ft. and to stuff the first 26". So if my line is 7"x7" then add the 26" that makes .74 cu. ft. so that converts to 12oz. of stuffing correct? All I had was 7 oz. of pillow stuffing so I put it in. As of now measuring with arta the woofer is rolling off around 50 Hz and I have a few decibel hump at 125 Hz then about a 4 db dip around 400 Hz. Am I correct in assuming the early roll off is the port and the hump and dip is stuffing. I also did not break the woofer in at all I just hooked it up and took measurements. I was working more on getting my set up correct. I haven't taken any Impedance measurements yet. Not sure if I can even get any accurate measurements inside either. See what I meant about my skills coming to a quick end.
        Dave
        http://www.pellegreneacoustics.com/

        Trench Seam Method for MDF
        https://picasaweb.google.com/101632266659473725850

        Comment


        • #94
          Re: "Rock Its" Build Thread

          Hi Dave,

          What did you do for the dye or stain, Dave - or did I miss it?

          Maynard

          Comment


          • #95
            Re: "Rock Its" Build Thread

            You would need ~9 ounces of stuffing uniformly distributed by weight in the first 26" of the line's total length to achieve a uniform density of 0.75 lb/cu.ft. within that 26" length. Regarding your measurements, the email I sent you on May 3 had several graphs. The second one shows how the woofer should be responding with the red line, and how the port should be responding with the dashed blue line. The woofer's response actually starts rolling off around 200 Hz and will be 8-10 dB down at 50 Hz, with a notch at 40 Hz which is the system tuning frequency. The port's response peaks at just above 40 Hz. The third graph shows the impedance characteristic. If you no longer have that email I should be able to resend it.
            Paul

            Originally posted by davepellegrene View Post
            Thanks guys unfortunately my skills are coming to a quick end as I start into the real parts that make a great loud speaker. I will probably be needing some advice on the TL as soon as I get things properly set up. Paul, in one of your emails you said to stuff the line .75 lbs. per sq. ft. and to stuff the first 26". So if my line is 7"x7" then add the 26" that makes .74 cu. ft. so that converts to 12oz. of stuffing correct? All I had was 7 oz. of pillow stuffing so I put it in. As of now measuring with arta the woofer is rolling off around 50 Hz and I have a few decibel hump at 125 Hz then about a 4 db dip around 400 Hz. Am I correct in assuming the early roll off is the port and the hump and dip is stuffing. I also did not break the woofer in at all I just hooked it up and took measurements. I was working more on getting my set up correct. I haven't taken any Impedance measurements yet. Not sure if I can even get any accurate measurements inside either. See what I meant about my skills coming to a quick end.
            Dave

            Comment


            • #96
              Re: "Rock Its" Build Thread

              Originally posted by maynardg View Post
              Hi Dave,

              What did you do for the dye or stain, Dave - or did I miss it?

              Maynard
              I used Min Wax Red Mahogany.
              http://www.pellegreneacoustics.com/

              Trench Seam Method for MDF
              https://picasaweb.google.com/101632266659473725850

              Comment


              • #97
                Re: "Rock Its" Build Thread

                Originally posted by Paul K. View Post
                You would need ~9 ounces of stuffing uniformly distributed by weight in the first 26" of the line's total length to achieve a uniform density of 0.75 lb/cu.ft. within that 26" length. Regarding your measurements, the email I sent you on May 3 had several graphs. The second one shows how the woofer should be responding with the red line, and how the port should be responding with the dashed blue line. The woofer's response actually starts rolling off around 200 Hz and will be 8-10 dB down at 50 Hz, with a notch at 40 Hz which is the system tuning frequency. The port's response peaks at just above 40 Hz. The third graph shows the impedance characteristic. If you no longer have that email I should be able to resend it.
                Paul
                I have all the emails I will go back through and find those thanks.
                http://www.pellegreneacoustics.com/

                Trench Seam Method for MDF
                https://picasaweb.google.com/101632266659473725850

                Comment


                • #98
                  Re: "Rock Its" Build Thread

                  Just to simplify the stuffing requirements, you need approximately 1 ounce of stuffing in each 3 inches of line length for the first 26 inches. When you go back and look at those graphs sort of represent a "perfect" driver, one whose response is absolutely smooth, which obviously ain't never gonna be true.
                  Paul

                  Originally posted by davepellegrene View Post
                  I have all the emails I will go back through and find those thanks.

                  Comment


                  • #99
                    Re: "Rock Its" Build Thread

                    I must have the density correct. I have 7 ounces in 20 inches. That is to the bottom of the line. If I turn 90 degree do I then make the next 6" from the center of the line. That would go to about the center of the next 90 degree turn. Or am I over complicating it. Just put the next 2 ounces on the rest of the bottom towards the back before it turns up.
                    Here is my measured impedance. Looks like it is tuned to 45 Hz. I believe it should be 40 Hz. Wonder if this is because of the flared ends on the port. Should I lengthen it to lower the tuning? An inch maybe? Can a lack of stuffing cause this?
                    Dave

                    http://www.pellegreneacoustics.com/

                    Trench Seam Method for MDF
                    https://picasaweb.google.com/101632266659473725850

                    Comment


                    • Re: "Rock Its" Build Thread

                      The ends of your port are rounded over more than they are flared, but the roundovers will have the same effect as being flared just not as much, so you will need to lengthen the port. How much I don't know but an inch may just do it. Stuffing has a small effect on the tuning frequency and since you have less stuffing than I modeled with, the tuning frequency will possibly be a little higher than desired.
                      Paul

                      Originally posted by davepellegrene View Post
                      Here is my measured impedance. Looks like it is tuned to 45 Hz. I believe it should be 40 Hz. Wonder if this is because of the flared ends on the port. Should I lengthen it to lower the tuning? An inch maybe? Can a lack of stuffing cause this?
                      Dave

                      Comment


                      • Re: "Rock Its" Build Thread

                        Originally posted by Paul K. View Post
                        The ends of your port are rounded over more than they are flared, but the roundovers will have the same effect as being flared just not as much, so you will need to lengthen the port. How much I don't know but an inch may just do it. Stuffing has a small effect on the tuning frequency and since you have less stuffing than I modeled with, the tuning frequency will possibly be a little higher than desired.
                        Paul
                        I'll go ahead and get the rest of the stuffing before I do anything with the port.
                        http://www.pellegreneacoustics.com/

                        Trench Seam Method for MDF
                        https://picasaweb.google.com/101632266659473725850

                        Comment


                        • Re: "Rock Its" Build Thread

                          Got a bag of stuffing today. I decided to pull all the old stuffing since it was a little different from the new stuff. It's kind of nice stuffing the line with the three inch hole that I had to cut though the center divider of the line so I could access the screws on the baffle. Then it dawned on me. this is were I need a smiley of a light bulb. I forgot to put the plug over the hole in the divider when I closed up the cabinet.
                          I did a new Impedance test with the modeled amount of stuffing and the hole plugged and I got an almost identical graph as what Paul modeled. Even the peaks on the double humps match.

                          Dave

                          http://www.pellegreneacoustics.com/

                          Trench Seam Method for MDF
                          https://picasaweb.google.com/101632266659473725850

                          Comment


                          • Re: "Rock Its" Build Thread

                            Oops!:p We all have done something similar, like wiring one driver of the two in an MTM with reverse polarity, and not being able to understand why there's no bass to speak of.

                            After correcting your oops, you were able to confirm this: Using Martin's worksheets, if your model is accurate and you build what you modeled, you will get the predicted results! What kind of stuffing are you using?
                            Paul

                            Originally posted by davepellegrene View Post
                            Got a bag of stuffing today. I decided to pull all the old stuffing since it was a little different from the new stuff. It's kind of nice stuffing the line with the three inch hole that I had to cut though the center divider of the line so I could access the screws on the baffle. Then it dawned on me. this is were I need a smiley of a light bulb. I forgot to put the plug over the hole in the divider when I closed up the cabinet.
                            I did a new Impedance test with the modeled amount of stuffing and the hole plugged and I got an almost identical graph as what Paul modeled. Even the peaks on the double humps match.

                            Dave

                            Comment


                            • Re: "Rock Its" Build Thread

                              Originally posted by Paul K. View Post
                              Oops!:p We all have done something similar, like wiring one driver of the two in an MTM with reverse polarity, and not being able to understand why there's no bass to speak of.

                              After correcting your oops, you were able to confirm this: Using Martin's worksheets, if your model is accurate and you build what you modeled, you will get the predicted results! What kind of stuffing are you using?
                              Paul
                              100% premium polyester fiberfill from Walmart. Is this ok or should I buy something else?

                              Thank Dave
                              http://www.pellegreneacoustics.com/

                              Trench Seam Method for MDF
                              https://picasaweb.google.com/101632266659473725850

                              Comment


                              • Re: "Rock Its" Build Thread

                                The Walmart polyester fiberfill is just fine. BTW what is the length of the port representing the impedance measurement you made most recently? Is it the length I modeled or have you increased the length?
                                Paul

                                Originally posted by davepellegrene View Post
                                100% premium polyester fiberfill from Walmart. Is this ok or should I buy something else?

                                Thank Dave

                                Comment

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