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Opinions welcome: XO for my current build

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  • Opinions welcome: XO for my current build

    My current design goal is to create a passive XO speaker with >4Ohm minimum impedance, an 83dB or higher sensitivity, and that sounds full-range (down to 35Hz) at low volume (like 50dB). I realize there are human perception issues in this realm and I'm willing to EQ around that for low volume listening. Although high volume isn't my goal I would still like to be able to play them up towards 90dB without damaging the woofers . The main use for these will be to listen to electronic ambient, electronic chill, classical, instrumental, jazz, vocal, and rock while my family is sleeping.

    The current prototype is an MT tower with a Dynavox LW6004PRM and a Peerless XT25GB30-04 in a 39l ported enclosure tuned at 39Hz. The tweeter is centered at 38" from the floor and the baffle is 8 11/16" wide. My goal for this was a fairly low crossover point so, to limit the amount of energy in the tweeter near its resonance, I went with an acoustic LR4 at 1650Hz. The crossover that I've prototyped is shown in the attached drawing. My listening impressions for these speakers, as prototyped, are mostly negative: the bass is thin and the mid through upper is lifeless. As a cross-check I coded up a mini-DSP to simulate the transfer function that I expect and am running the prototype speakers in a fully active configuration: they sound fantastic (and easily handle my SPL requirements). Being a novice designer, I'm confident there are glaring errors in the passive XO.

    Any folks who are inclined, would you please give this design a once-over and share your opinions?

    Thanks.
    Judd

  • #2
    Do you have the sims to go with your schematic? Even with an fs comp and 4th order that tweeter may be crabby that low.

    I actually am doing this exact driver combo in a 15L box (the BR1 cabs) right now. I am so close to done with them but the wife tasked me with some huge projects I must finish first.. just need to do a little more tweeeter level adjustments and solder up the crossovers.

    Click image for larger version

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    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


    • #3
      That's a lot of series resistance on the tweeter, 25 ohms total. How did you arrive at the current crossover?

      Comment


      • #4
        Originally posted by chrisn
        That's a lot of series resistance on the tweeter, 25 ohms total. How did you arrive at the current crossover?
        There's only 7Ohms inline with tweeter. Sent from my 7040T using Tapatalk

        Comment


        • #5
          Not to say your LCR comp is wrong, but I used 1.0mH(20awq)/150uF/3.3 ohm on my Scandivifias. I measured to verify the flattened impedance on my particular tweeters. If the Fs is different on yours, YMMV.

          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


          • #6
            Not sure what to say . . . . In an independent study (using mfr. curves and a different sim program) I see a system running around 81-82dB +/-2dB (VERY close to your targeted 83dB) w/a 3w power limit at Xmax @ 35Hz (yielding 92dB - close to your SPL goal). Your box sim looks like it should reach your F3 goal. Your Fc looks to be 1.6k, and the system seems to have about+4dBSC. Nothing looks bad here (to me anyway).

            Phase summing looks good. W/a Zmin of 5-1/2 ohms near Fc, I'd call it a nominal 8ohm system. -9 to -10dB of tweeter attenuation. Tank (notch) at 4kHz (right on). Tweeter's LCR is right at Fs, but you COULD add about 2ohms resistance there (it's slightly overcomping the Fs peak - based on MY mfr. curves, but doubt that's doing any harm). Hard to believe it doesn't sound fairly great.

            Did you try flipping tweeter polarity? Are you SURE the XO is wired properly? A DATS (or other impedance) sweep on the finished system could tell the tale (IF something amiss in the wiring).

            Comment


            • #7
              I am embarrassed to say that, despite hundreds of snapshots and limp saves, I don't have an image of the LIMP impedance measurement of the prototype system. I'll snag one and post it later this week along with some front/back photos of the prototype XO.

              Comment


              • #8
                Hi Judd, what did you use to sim the XO? Could you post the actual TS specs and the frd of the drivers? The files can help others try a sim for you. I end up sending/posting PCD files for help or review.

                Comment


                • #9
                  Attached are my files for my project with the same drivers for reference. Keep in mind our offsets are likely different I'm sure some more experienced guys here could do it better, but just throwing it out there for comparison sake. I had to do a notch on the woofer due to an odd shelf the response made preventing a proper crossover point above 1500hz. I also didn't notch the problematic fs of the xt25, and am not picking up on any harshness without it.

                  Click image for larger version

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                  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
                    Originally posted by juddwilcox View Post
                    There's only 7Ohms inline with tweeter. Sent from my 7040T using Tapatalk

                    I misread the 1 ohm resistors as 10 ohms, derp:/

                    Comment

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