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RFL-3way in test & tweak mode

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  • RFL-3way in test & tweak mode

    Hi all,



    The project has moved forward a bit since my latest post. One unit including XO is now in test-mode and initial measurements show promising results.



    At first, I thought that the sound was a bit on the ”thin” side but when I studied the measurements, the explanation came to me: (Remember, it´s been like ten years since my last passive system design) I hav geatly underestimated the baffle-step effect on the system. When I cranked up the 50Hz and 320 Hz pots on the Cit11 abt 4-6 dB, the speaker (I have only one) started to sing.



    The two attached measurement-pictures show that:

    - in ”nearfield 40 cm in between the Woofer and Mid, the integration seems to work fine W-M

    - in farfield 300-20000, the integration Mid-Tweeter seems to work as predicted.



    I will now install the XOs in the speakers and make new measurements and longterm listening tests on the complete system but I predict that this will end with me padding down Mid and Tweeter abt 4-6 dB



    (Now, I´m glad that the L-pads ar placed in the ”foot” under the upper unit…

    Regards//lasse



    Click image for larger version

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    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
    The padding will most likely alter the shape of the pass band, and will change the cap and coil values needed..

    Comment


    • #3
      Originally posted by rpb View Post
      The padding will most likely alter the shape of the pass band, and will change the cap and coil values needed..
      Hi,

      OK, after a few minutes of tweaking in Speaker Workshop, I realize that there is no "Quick-Fix" to solve this…

      A complete redesign will be made with new targets, Woofer 6 dB above Mid and Tweeter, which seems to be well aligned as-is.

      I just hope I can keep the gold-plated 8,2 mH Woofer-coils….

      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


      • #4
        Hi again,



        Is this a valid method to pad down both mid and tweeter in a 3-way system at the same time and with the same ”amount”? (I spent a few hours, trying to tweak the individual L-pads for mid and tweeter, running into all sorts of trouble with the other parts of the XO)

        After I corrected the woofer SPL according to my measurement of woofer and mid (previous post, pic nr 2), I introduced a L-pad so that both mid and tweeter came down abt 6 dB.

        I think that the impedance curve was smoothed out quite nicely at the same time.

        Does anyone see a problem with this??



        Regards//lasse
        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?"

        Comment


        • #5
          The padding resistors are going to carry too much current in that location.

          You can try this in your sim if you want. It's a filter I came up with when you started this project. What I have is not a sim. It's a filter that I assembled, and measured. My baffle size is different than yours, but this could be in the ballpark. I added padding while I designed the filter. Take a look if you want to. This is just a filter for the mid.

          90uf_ 3.4mH_ .6mH_ 15uf. I think you know where these go.

          Two resistors for padding. In front of the x-over, a 2.2 ohm resistor. In parallel with the woofer, at the woofer, a 5.6 ohm resistor.
          Last edited by rpb; 12-01-2018, 03:50 PM.

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          • #6
            Can you please upload your .swd file (hopefully my version of SW can open it - SW can be fussy between O/S versions/ PCs).

            NB: you might have to rename it to .TXT or other supported file extension so it will upload. SW can also be greedy on file size - so you may need to export and re-import data into a clean project file.

            I'm happy to take a look.

            Can you please also post your raw driver FR curves?

            Comment


            • #7
              Click image for larger version

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ID:	1395822 Here's my 3 way xo if it helps with a topology. You may need to go higher order on mid or tweeter - or change / add the value of shunt resistors with the parallel capacitors or inductors to shape the slope. Ignore / remove the following components (I have to have them because my system is all metal drivers to kill breakup). C2, L2, C8, C5, L6.

              Impedance here is a min. 4.3 ohms in the midbass and 4.2 in the lower treble

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              • #8
                Hello, and thanks for all the feedback and suggestions.



                As I think that I have a system with reasonably flat frequency response and good phasetracking, I am thinking of perhaps a different way of solving the problem with the lack of BSC:



                What do you think of solving the baffle-step problem with this approach, installed between the pre- and poweramps?



                From this website:



                http://sound.whsites.net/bafflestep.htm



                It states that it is essential that the compensation circuit is driven by a ”low impedance source” (<100 ohms) but the manual for my preamp (Citation 11) states the output impedance to be ”less than 500 ohms”. Will this be a problem?? And, if so, is there a way around this without adding buffer stages to the compensation unit and with that, adding a lot of complexity??



                Please, chime in you electronics-knowing people.



                Best regards//lasse


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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?"

                Comment

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