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RFL-3way in pre-test phase

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  • RFL-3way in pre-test phase

    Hi all,

    Below is a picture of the simulation of the version I plan to test ”full scale”.

    The critical part, perhaps worth waiting for as it had to be ordered separately from the manufacturer in Denmark, is the “monster-woofer- inductor” 8,2 mH, 0,25 ohms.
    Apart from a few quite expensive capacitors, I managed to find and unwind most of the components in my workshop.

    Will be back with the test results…

    By the way. Is using Jantzen “Permite”-core inductors a good idea??

    Regards//lasse
    Stockholm, Sweden

    Click image for larger version

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    Perry Mason talking to his dentist:

    "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

  • #2
    Hi all,



    For a few days, I´ve struggled with one aspect of XO design that I know many of you have done and that´s the delta-AC for the drivers, or rather the combination of drivers. I have measured and simulated the delta-AC for mid/tw a number of times and come up with results ranging from 0.3 to 0.7 inch.

    My chosen alignment on the mid/tw transitation, 2nd LR/2nd LR, is obviously quite sensitive to the correct delta if phase-tracking is an important design-criteria soo….



    I´ve decided to go to 3rd order alignment on the tweeter as this is capable to accept a wider range of delta-AC. Or rather accept larger errors from my side in order to predict the correct delta.



    The picture of the simulation below is for a delta-AC of 0.3”, which you can see seems to be close to “bulls eye” from a phase tracking point-of-wiew.



    On top of this, the new alignment offers added protection for the tweeter as the XO-point seems to have drifted to abt 2100 Hz from the intended 2500 Hz.



    Please feel free to comment on this, both my rationale for the new alignment and the design as a whole.



    Best regards//lasse

    Stockholm, Sweden







    PS// I can plague you even more now as I have been retired from the Swedish Armed Forces (Yes, they do exist!!) since a few weeks.



    Click image for larger version

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    Perry Mason talking to his dentist:

    "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

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    • #3
      G'day lasse,

      What drivers are you using again? the AC (Z) offset also depends on your distance you want to sum. For example - a 1m distance will place a great Z offset difference between the drivers than a 2m distance. So you can crudely alter your simulation "listening distance" by changing the Z offset.

      I'm using -3.6" for my 10" woofer and -0.81" for my 5 inch midrange. My 10" woofer is near the floor so the extra vertical distance takes over the close the "listening distance" is I am simulating. I think what I have works for 2m distance. My actual measurements show I'm very close as I was getting a pretty good reverse null (less noise) as shown.

      Post the drivers, position in the baffle and I'll work out the Z offsets I'd use so you can compare with your own. Click image for larger version

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      Click image for larger version

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      • #4
        Hi,



        I use:

        Woofer: Dayton RS-270-8
        Mid: Peerless 830991
        Tweeter: Seas 27TFFNCCG

        The picture below show why I state that the Delta-AC Woofer/Mid is (or can be )=zero

        Sorry, I have no scanner so I cannot give you the distances. Will be back on that.

        I also show the simulation with reversed polarity on the mid. Real life will show if this will be the case in reality….



        Regards//lasse




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        Attached Files
        Perry Mason talking to his dentist:

        "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

        Comment


        • #5
          Ah yes - sorry I forgot your design. it was in one of the other posts.

          The woofer will still be slightly behind the midrange - even if the voicecoils are vertically aligned. This is because I presume your listening axis is tweeter height - therefore there will be more distance to the voice coil centre of the woofer than midrange because it is simply further away from the listening position.

          In reality - at the lower wavelengths, the acoustic offset of a few millimetres won't matter much to phase tracking. It looks good to me

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          • #6
            Originally posted by Dave Bullet View Post
            Ah yes - sorry I forgot your design. it was in one of the other posts.

            The woofer will still be slightly behind the midrange - even if the voicecoils are vertically aligned. This is because I presume your listening axis is tweeter height - therefore there will be more distance to the voice coil centre of the woofer than midrange because it is simply further away from the listening position.

            In reality - at the lower wavelengths, the acoustic offset of a few millimetres won't matter much to phase tracking. It looks good to me
            Hi again,

            just a question: Do you use iron core inductors in the woofer XO-part? Any experience you want to share?

            Regards//lasse
            Perry Mason talking to his dentist:

            "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

            Comment


            • #7
              Originally posted by lasse View Post

              Hi again,

              just a question: Do you use iron core inductors in the woofer XO-part? Any experience you want to share?

              Regards//lasse
              Yes I used ircon core for the series Woofer inductor and aircore for all others. Reason for iron core is I needed 7mH and wanted as low DCR as possible with good power handling before saturation. I haven't measured inductor related distortion (I don't know how). I think the woofer will reach xmax anyway well before inductor issues occur.

              To me the sound is great. The LR2 acoustic target between woofer and mid sounds very smooth (transition).

              Comment


              • #8
                Hej Lasse,

                Looks like a very nice design. Do you have any listening impressions of the 830-991 drivers yet? I just pick up some because they look very cool, have good measurement curves, and they are on sale at PE right now!

                PS - my Farfar served in the Swedish military during WWII. He was a ski patrol watching for the Nazis to come over from Norway. Luckily that never happened.
                Craig

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                • #9
                  Originally posted by PWR RYD View Post
                  Hej Lasse,

                  Looks like a very nice design. Do you have any listening impressions of the 830-991 drivers yet? I just pick up some because they look very cool, have good measurement curves, and they are on sale at PE right now!

                  PS - my Farfar served in the Swedish military during WWII. He was a ski patrol watching for the Nazis to come over from Norway. Luckily that never happened.
                  Not Lasse, but I don't think he's heard them with a x-over yet. I've had a pair for years. I've used them sealed (with a sub at times), and as a midrange. They seem to sound really good to me on female vocals. Male vocals also. I'd suggest lots of dense fiberglass in the box, and an irregular box shape might help too. Try to absorb, or diffuse the back wave as much as practical, and I think that you will find that the mid range will be very good. I have no proof, but I believe that the cones might allow reflected sound in the box to be re-emitted through the cone. I've mostly paired mine with Morel tweeters in a speaker with a sloped baffle, and large round overs on the sides. Really nice with Nora Jones, Dianna Krall, Mark Knopfler, and new age type music that is played at 80dB or so. They can play rock too, but a 6.5" would be a little better once the spl gets a bit higher. I'd like to hear them in a transmission line. I think that would allow the back wave to be absorbed better. Try several x-over points. I've crossed as low as 1.5k I think. I'd stay below 2.5k LR4 if x-over part count is not a big concern. Many options, and compromises as is the norm for most drivers.

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                  • #10
                    Sorry Lasse for slightly side tracking your thread.

                    rpb, I am working on a MTM with them in a tall MLTL where the top 1/2 is stuffed. So I expect really good rear wave absorption.
                    Craig

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                    • #11
                      Originally posted by PWR RYD View Post
                      Sorry Lasse for slightly side tracking your thread.

                      rpb, I am working on a MTM with them in a tall MLTL where the top 1/2 is stuffed. So I expect really good rear wave absorption.
                      Wish I could hear them when you're done!

                      Comment


                      • #12
                        Originally posted by PWR RYD View Post
                        Sorry Lasse for slightly side tracking your thread.

                        rpb, I am working on a MTM with them in a tall MLTL where the top 1/2 is stuffed. So I expect really good rear wave absorption.
                        No worries! It is the nature of a discussion to let the associations take its own paths.....

                        regards// lasse
                        Perry Mason talking to his dentist:

                        "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

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