Announcement

Collapse
No announcement yet.

A couple crossover questions

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • A couple crossover questions

    Hi guys, just wanted to run a couple things past you. Is it ok to have a woofer/tweeter crossover that has the phase aligned in the crossover region, but where the two drivers phase wrap is in two very different places? I will attach the sims. This is just a prelim drawing board thing right now. The crossover produces an adequate reverse null and seems to track horizontally nicely, keeping phase in line and flattish response when moving. It just seems weird not having that nice lined up wrap.

    Also, I will attach a pic of the woofer circuit in PCD. It has two major breakups. The one closest to the pass band I want to notch out and then tame the second higher up one with a tank filter. My question is regarding the notch. Does it look right? I know I have to have some resistance to prevent a dead short, so when I put something like at least 4 ohms, which seems like the least I would want, it seems to render the notch useless as the spike still exists. The notch seems to be in the right place as when I zero out the resistor there is a nice cutout where the spike is. Any suggestions?

    Thanks Click image for larger version

Name:	prelim suns.gif
Views:	1
Size:	66.4 KB
ID:	1344329 Click image for larger version

Name:	prelim suns rev.gif
Views:	1
Size:	66.2 KB
ID:	1344330 Click image for larger version

Name:	prelim suns woofer section.JPG
Views:	1
Size:	78.3 KB
ID:	1344328
    Projects:

    transcenD: http://techtalk.parts-express.com/fo...5035-transcend
    Summits: http://techtalk.parts-express.com/sh...75-The-Summits
    References: http://techtalk.parts-express.com/sh...-My-References
    Vintage Style 2-way: http://techtalk.parts-express.com/sh...-vintage-2-way

  • #2
    Where the phase wraps is just a consequence of how it is graphed and has no bearing on anything. You should note, however that the phase of your 2 drivers does not track for more than a half-octave, which I would not consider good phase tracking even though it's dead nuts right at the xo point.

    The problem is that the graph shown is a snapshot measurement at a single point in space and as you move up or down, left or right, forward or backward in the room, that tiny stretch of perfect phase alignment will shift to misalignment. You can see this by playing with the listening distance and vertical and horizontal listening axes in PCD. When you have an octave or so of alignment on either side of the xo point, this alignment stays more intact at various listening distances and angles, keeping the FR intact as well.

    As for your notch, you can leave the 4 ohm resistor out of the circuit completely as there is no dead short there. There is potentially a short through the main inductor tank cap and the 16uf shunt cap, so some people opt to put a small (1 ohm) resistor in series with the tank cap for a warm fuzzy feeling. In practice, this short would be so high in frequency that there should be no energy there and the resistor should be unnecessary.

    Dan
    _____________________________
    Tall Boys
    NRNP Computer Sub
    The Boxers
    The Hurricanes
    The Baronettes
    Conneccentric
    UX3

    Comment


    • #3
      Thanks Dan. I did do panning left and right and it seemed to stay decent, but I didn't check the null at the extremes or watch how many degrees I went. Like I said this is only a prelim experiment based on models and factory traces, but I wanted to start to get an idea of what I will be looking at with this project. I'll work on getting a longer alignment based on your suggestion.

      Good to know on the notch, I wasn't sure if I could rely on the relatively small dcr of the parts alone to prevent issues, but now I know I can, thanks!
      Projects:

      transcenD: http://techtalk.parts-express.com/fo...5035-transcend
      Summits: http://techtalk.parts-express.com/sh...75-The-Summits
      References: http://techtalk.parts-express.com/sh...-My-References
      Vintage Style 2-way: http://techtalk.parts-express.com/sh...-vintage-2-way

      Comment


      • #4
        IMO until the drivers are measured on baffle, messing with the phase is not going to be meaningful (other than good practice). As Dan mentioned you can add a resistor in series with the capacitor on the parallel notch, the value can be adjusted to change the impedance at higher frequencies.
        John H

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

        Comment


        • #5
          I definitely plan to measure on baffle and redesign with that data. I just wanted to make sure I could get these two drivers to meet up, and when I saw the big gap between the phase wrap (where most two ways seem to wrap in the same place) but yet phase aligned it prompted curiosity enough to ask about it. I will likely leave at least one ohm in there as a feel good.
          Projects:

          transcenD: http://techtalk.parts-express.com/fo...5035-transcend
          Summits: http://techtalk.parts-express.com/sh...75-The-Summits
          References: http://techtalk.parts-express.com/sh...-My-References
          Vintage Style 2-way: http://techtalk.parts-express.com/sh...-vintage-2-way

          Comment


          • #6
            Unless you are shooting for a BW3 alignment, where the phase is not aligned and 90 degrees apart, you likely will have better phase alignment in your reverse polarity sim with some tweaking. You can see how they are relatively well aligned, just needing some adjustment. The knee at 1k on the woofer is a bit drooped as well.

            The reason the LC across a woofer is okay, even if minimal DCR from a large gauge wire or laminate core, is that the increasing impedance from the lowpass on the woofer brings the '0' impedance level back up. If you did not have a voltage divider before the LC-shunt, this would be death to your amplifier.

            Later,
            Wolf
            "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
            "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
            "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
            "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

            *InDIYana event website*

            Photobucket pages:
            http://photobucket.com/Wolf-Speakers_and_more

            My blog/writeups/thoughts here at PE:
            http://techtalk.parts-express.com/blog.php?u=4102

            Comment


            • #7
              Thanks, I have been tweaking on it for a while and have things closer. Unfortunately it is only a sim and I am guessing at the z measurement for now, so it will all change but was able to verify I can make it work. The project is an 8" two way with an M8N, so I also recently pulled up your Max project for guidance which is helping as well.
              Projects:

              transcenD: http://techtalk.parts-express.com/fo...5035-transcend
              Summits: http://techtalk.parts-express.com/sh...75-The-Summits
              References: http://techtalk.parts-express.com/sh...-My-References
              Vintage Style 2-way: http://techtalk.parts-express.com/sh...-vintage-2-way

              Comment


              • #8
                That was a dynamic, but difficult, design.
                Wolf
                "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                *InDIYana event website*

                Photobucket pages:
                http://photobucket.com/Wolf-Speakers_and_more

                My blog/writeups/thoughts here at PE:
                http://techtalk.parts-express.com/blog.php?u=4102

                Comment


                • #9
                  Seems worth the effort though, aside from the cone resonance that has to be dealt with, I've never heard anything bad said about the m8n. The ability for an f3 in the high 20s in a large stand mount that stays under xmax for over 50w is a nice addition as well. Planned tweeter is the seas h1212.

                  I've had the drivers forever, just getting around to revisiting the design..
                  Projects:

                  transcenD: http://techtalk.parts-express.com/fo...5035-transcend
                  Summits: http://techtalk.parts-express.com/sh...75-The-Summits
                  References: http://techtalk.parts-express.com/sh...-My-References
                  Vintage Style 2-way: http://techtalk.parts-express.com/sh...-vintage-2-way

                  Comment


                  • #10
                    Good luck! You'll need it!
                    Wolf
                    "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                    "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                    "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                    "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                    *InDIYana event website*

                    Photobucket pages:
                    http://photobucket.com/Wolf-Speakers_and_more

                    My blog/writeups/thoughts here at PE:
                    http://techtalk.parts-express.com/blog.php?u=4102

                    Comment

                    Working...
                    X