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HiVi M8a helper woofer ML-TL design

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  • HiVi M8a helper woofer ML-TL design

    Hi All,

    This is my first post here but I'm a member over at diyaudio and a similar post can be found here:

    http://www.diyaudio.com/forums/full-...-woofer-3.html

    a member over there suggested I pot here and get some sage advice from this speaker building crew.

    I have built (still finishing) a set of uFonkens employing the fostex 108eZ sigma drivers.

    http://www.diyaudio.com/forums/full-...ken-build.html


    They are quite lovely in the mid and high end but are obviously lacking in the bass department. As such I set out to design and build some helper woofers to be crossed somewhere in the ~150Hz range (maybe even higher to keep the 108's from getting into excursion trouble) and I settled on using a pair of HiVi M8a's in a Pensil inspired cabinent to set the uFonken's atop. Attached are my latest plans using MJK's matcad sheets and WinISD. Any suggestions would be greatly appreciated!

    Click image for larger version

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  • #2
    Re: HiVi M8a helper woofer ML-TL design

    You may want to consider a folded line. Putting uFonkens closer to ear level (center of the driver around 36-38" or so will greatly help in creating a more realistic soundstage. JMO, seems to work fairly well.
    https://www.facebook.com/Mosaic-Audi...7373763888294/

    Comment


    • #3
      Re: HiVi M8a helper woofer ML-TL design

      Just eyeballing the volume and cross sectional area seem high. What are the areas and volumes you are using? Folding also put the driver in the middle of the line which helps with harmonics.

      If Paul K chimes in he can also tell if the end of the line port is ideal. I can't see that when I use Horn Response.
      John H

      Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

      Comment


      • #4
        Re: HiVi M8a helper woofer ML-TL design

        the dimensions are 10x14" as stands and the volume ~60L

        I would be happy to scale down a bit though there is a table that they are going to be sitting on either side of that is around ~30" high. How would I go about modeling the folded horn design? I don't mind them getting deeper.

        Comment


        • #5
          Re: HiVi M8a helper woofer ML-TL design

          Correct me if I'm wrong, but it seems like to have a real 1/4 wave style transmission line for this woofer would need a quite long TL like this?

          Click image for larger version

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          I'm not sure I know how to sim that in the MJK sheets, looks like a good bit of the tinkering with the geometry inputs.. Also that's going to be a good bit deeper...

          Comment


          • #6
            Re: HiVi M8a helper woofer ML-TL design

            Looks like you are tuning to the Fs of the driver. While that is one way to do it, that is usually not necessary. My suggestion is to contact PaulK for assistance in designing a TL or MLTL for the driver. Do you have measured T/S parameters? This will go a long way in getting an accurate design.
            https://www.facebook.com/Mosaic-Audi...7373763888294/

            Comment


            • #7
              Re: HiVi M8a helper woofer ML-TL design

              I've not done as many as Paul but I typically start with a decent box design and extend the response by shaping the volume into a line. My quick look yesterday was a 45 liter enclosure tuned to about 30 with a line length of about 100 to 110 cm. It was pretty close to my Aperivox design in my sig, which is just a single fold.

              +1 on the measurements, I used the PE posted measurements (in the driver description page) over HiVi's.
              John H

              Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

              Comment


              • #8
                Re: HiVi M8a helper woofer ML-TL design

                I used PE's published specs for some ML-TL modeling, not HiVi's specs that PE links to. Very similar to what John saw, I found the optimum tuning frequency to be 31 Hz. I modeled two different ML-TLs, one 40" long with a cross-section of 8.5" X 7", and the other one 60" long with a cross-section of 8.5"W x 5". Both ended up with a predicted f3 of 31-32 Hz. A 10:1 tapered TL that's 60" long and having about the same line volume as the 60" non-tapered ML-TL would also work. Obviously the 60-inch lines would need to be folded, perhaps also the 40" ML-TL.
                Paul

                Comment


                • #9
                  Re: HiVi M8a helper woofer ML-TL design

                  Originally posted by Paul K. View Post
                  I used PE's published specs for some ML-TL modeling, not HiVi's specs that PE links to. Very similar to what John saw, I found the optimum tuning frequency to be 31 Hz. I modeled two different ML-TLs, one 40" long with a cross-section of 8.5" X 7", and the other one 60" long with a cross-section of 8.5"W x 5". Both ended up with a predicted f3 of 31-32 Hz. A 10:1 tapered TL that's 60" long and having about the same line volume as the 60" non-tapered ML-TL would also work. Obviously the 60-inch lines would need to be folded, perhaps also the 40" ML-TL.
                  Paul
                  Paul, how about the 60" ML-TL (non-tapered) folded box you modeled for me
                  using this same driver had a cross section of 9"x7" I believe,I have to look it up. That was
                  with measured T/S from Jason P,would that be more accurate?

                  Comment


                  • #10
                    Re: HiVi M8a helper woofer ML-TL design

                    Thanks for weighing in Paul. I like the sound (no pun intended) of the folded no taper line that squidspeak is referring to, any way those plans could be posted?

                    Also PE's T/S parameters and HiVi's seem to be in good agreement plus or minus a hundredth on the Q's

                    Comment


                    • #11
                      Re: HiVi M8a helper woofer ML-TL design

                      Yes, those T/S measurements and what I modeled for you would definitely be more accurate. I knew I had modeled a TL for this driver but didn't remember for whom or when and didn't take the time to look for that information.
                      Paul

                      Originally posted by Squidspeak View Post
                      Paul, how about the 60" ML-TL (non-tapered) folded box you modeled for me
                      using this same driver had a cross section of 9"x7" I believe,I have to look it up. That was
                      with measured T/S from Jason P,would that be more accurate?

                      Comment


                      • #12
                        Re: HiVi M8a helper woofer ML-TL design

                        I'd have to see the T/S values I used for squidspeak's ML-TL to know for sure how well they do or do not compare to PE's and HiVi's published values. Squidspeak should be able to provide the details on what I modeled for him.
                        Paul

                        Originally posted by vapemaster View Post
                        Thanks for weighing in Paul. I like the sound (no pun intended) of the folded no taper line that squidspeak is referring to, any way those plans could be posted?

                        Also PE's T/S parameters and HiVi's seem to be in good agreement plus or minus a hundredth on the Q's

                        Comment


                        • #13
                          Re: HiVi M8a helper woofer ML-TL design

                          Great, I pm'ed him. I'll also look in the forum more rigorously though I didn't see it mentioned in my cursory searches..

                          Comment


                          • #14
                            Re: HiVi M8a helper woofer ML-TL design

                            If Mike can't help you, I've found the emails I sent him with all of the modeling graphs as well as a cabinet drawing I made up and can send them to you if you contact me at the email address I gave you privately. But not until tomorrow because I'm shutting my computer down for today.
                            Paul

                            Originally posted by vapemaster View Post
                            Great, I pm'ed him. I'll also look in the forum more rigorously though I didn't see it mentioned in my cursory searches..

                            Comment

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