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  • Prel measurements RFL-3way

    Hello,

    I started the "build threads" with this:

    http://techtalk.parts-express.com/fo...-classic-3-way

    Attached is a summary of the prel measurement. You can se pic´s of the system in the abovementioned thread.

    What do you think?

    Will 2-nd order at 3000 be OK? Or 2nd/3rd at 3000?
    There is a disturbance at 400, detectable in both drivers but not there in the nearfield. What can this be?

    Regards//lasse


    Click image for larger version

Name:	Summary prel measurements RFL-3way 180926.JPG
Views:	47
Size:	121.3 KB
ID:	1388879
    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?"

  • #2
    Originally posted by lasse View Post
    There is a disturbance at 400, detectable in both drivers but not there in the nearfield. What can this be?
    Most likely, floor bounce, which would also explain why the notch is slightly higher in frequency on the mid than the tweeter. I'm assuming you're not time-gating your 60cm measurements. How high was your tweeter off the floor during testing?

    Comment


    • #3
      Originally posted by lasse View Post
      Hello,

      I started the "build threads" with this:

      http://techtalk.parts-express.com/fo...-classic-3-way

      Attached is a summary of the prel measurement. You can se pic´s of the system in the abovementioned thread.

      What do you think?

      Will 2-nd order at 3000 be OK? Or 2nd/3rd at 3000?
      There is a disturbance at 400, detectable in both drivers but not there in the nearfield. What can this be?

      Regards//lasse


      Click image for larger version

Name:	Summary prel measurements RFL-3way 180926.JPG
Views:	47
Size:	121.3 KB
ID:	1388879
      For the crossover point, I'd probably want a little more data. The woofer appears pretty tame, no breakup peaks but is there any evidence in the impedance sweep of a blip? Also, where's the tweeter Fs? Lastly, did you do a distortion sweep to see where that tweeter starts losing it a bit?
      Electronics engineer, woofer enthusiast, and musician.
      Wogg Music
      Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

      Comment


      • #4
        Hi and thanks for the feedback.

        I attach a more complete Picture from the SIRP-software I use fore measurements. This time, the program has extracted the distorsion information from the signal. It seems that the tweeter is starting to distort below 1000 Hz. The Fs is 1155 and 1318 Hz respectively for my two "speciments"

        The tweeter height is abt 90 cm and I agree, the anomality at 400 is probably a floor Bounce


        Regards//lasse



        Click image for larger version

Name:	Tweeter distorsion measurements RFL-3way 180926.JPG
Views:	55
Size:	200.3 KB
ID:	1388926
        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
          If the mid is the 830991, I'd shoot for 2.5k as a design starting point.

          Comment


          • #6
            Originally posted by rpb View Post
            If the mid is the 830991, I'd shoot for 2.5k as a design starting point.
            Hi, is this due to the beaming of the driver at higher freq´s or is it the behaviour over 5-6000 Hz?

            Oh, by the way.
            I realized that I posted a not-so-very-readable Picture of the distortion plots. Honestly, I don´t know which distortion is more interesting so if you want a new Picture with a specific "order" of distortion, just say so

            Best 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, is this due to the beaming of the driver at higher freq´s or is it the behaviour over 5-6000 Hz?

              Oh, by the way.
              I realized that I posted a not-so-very-readable Picture of the distortion plots. Honestly, I don´t know which distortion is more interesting so if you want a new Picture with a specific "order" of distortion, just say so

              Best regards//lasse
              I based the comment on two things. First, on using the driver, and hearing it with many x-overs, and secondly because you don't want to use a lot of parts in the x-over. You could still try other x-over points, but for the first shot, I'd try 2.5k. If your lowpass is second order at 2.5k, the tweeter needs to be time aligned, or possibly 3rd order. The higher you cross, the harder (I think) it will be to get a good summation.

              I've recently used it with a 5 part x-over 2-way. I should check to see where the x-over point is. I think it was below 2k. It sounded really good. The 5 part x-over was due to a contest that will be in Indiana this spring.

              I'll see what I can come up with on a filter. What sensitivity are you shooting for?

              Comment


              • #8
                I just hooked up the x-over, and remeasured. The x-over point is a hair above 2.5k, and is basically second order. There is a bump in the response that might give you trouble if you cross much higher. If you want to cross higher, a notch at 5k should help. (3 more parts)

                Click image for larger version  Name:	gfc at 2.5k.JPG Views:	1 Size:	206.2 KB ID:	1389048

                Comment


                • #9
                  Well, my x-over mojo must be working tonight. I made a simple x-over for the GFC mid. The sensitivity matches my previous post x-over. Nothing changed on the tweeter. The mid gets two resistors for padding, and 2 caps, 2 coils. The baffle is sloped, so this would not necessarily work for you. If you want to know values, let me know. Here are the measurements. The high pass is 400hz.

                  Click image for larger version  Name:	gfc at 400 to 2.3k.JPG Views:	1 Size:	194.3 KB ID:	1389055

                  Comment


                  • #10
                    Hi rbp,

                    I think that it all adds up to a XO- point of 2500 Hz and 2nd/3rd order alignment.

                    will be back!

                    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

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