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  • Please critique my first crossover design

    Hey,

    I have previously built sets of br-1's, overnight sensations, swope tm's, a powered subwoofer, and rebuilt crossovers on a pair of polk audio speakers with a proven design. This is my first crossover design and I would appreciate some critiquing before I order the parts. I am using the drivers from my br-1 speakers to keep costs low (DC160S-8 and DC28FS-8). I used Jeff Bagby's response modeler to model the frd and zma files I downloaded from audiodevelopers.com. I modeled the drivers in the PE br-1 cabinet, but left the zma file for the tweeter alone. After modeling the drivers' response in the box, I used WIN PCD to create the crossover. All of the parts I used are available at parts express. I know it may not be worth the money in upgrades, I just wanted some practice before I start a new design using more expensive drivers.

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    I plan to use these speakers on stands about 1.5' from the rear wall. Did I use an appropriate amount of BSC?

    Is there anything I may have missed while modeling the frd and zma files?

    I will appreciate any advice.

    Thanks,

    Matt A

  • #2
    Re: Please critique my first crossover design

    Response and phase angle look good. The inductor on the tweeter is pretty big, and there's a lot of series resistance to pad the tweeter down. Try a resistor in parallel with the tweeter, and a smaller value inductor should work. The woofer inductor has a decent amount of resistance, you could get away with an iron core there. You may need a zobel on the tweeter to lower the top end. I'd try listening to it with and without. BSC is easier to judge with speakers in place, using ears/measurements, but it looks fine. If you have measured zma files try those in the simulation too. Did you extract phase after simulating the drivers on baffle? I can't think of anything else, it looks pretty good.

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    • #3
      Re: Please critique my first crossover design

      Your woofer's .frd file looks W-A-A-Y too smooth. Where'd the "hump" at 1.4kHz go (compared to Dayton's spec sheet)?

      W/out THAT, it looks pretty good. Runnin' around 80dB +/-2dB w/+6dBSC, . . .
      EXCEPT it's got a peak from: 81dB @ 800Hz to 88dB @ 1.4k, then back down to 81dB by 2k.

      It could be better than your stock kit IF you model that woofer's peak (and treat it). The stock woofer LP filter handles it better. I know some guys are "anti-Zobel", but if you add one (like in the stock XO) you can cut your inductor size by half probably.

      You MIGHT have cut the tweeter down a "tad" too far, but maybe not.

      Have you modeled the stock filters? Using an L-pad to drop the tweeter's level has the added benefit of also squelching its Z-peak at Fs a bit.

      I'd say "as-is" that it's probably not an improvement over stock, but is more complex and probably a bit more expensive.

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      • #4
        Re: Please critique my first crossover design

        Thanks for the responses. To answer your question, I did extract phase after simulating the drivers on the baffle. Per your recommendations, I lowered the values of the inductors on the tweeter and woofer. I added a zobel to the woofer and moved a resistor from series to parallel before the tweeter. I also played around with the values until I got a relatively flat response with decent phase tracking.

        The frd file I used in the model does show a spike at 1.4kHz similar to the one posted by PE. After modeling the file on a baffle and changing the crossover values, I think I tamed it pretty well. I have attached a picture to show the raw response of the woofer on the baffle too.

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        Lowering the inductor values definitely helped reduce the price. Which of the capacitors can I get away with using electrolytic on.

        Also, other than dc resistance, are there any pros and cons to air core inductors vs iron core?

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        • #5
          Re: Please critique my first crossover design

          Both caps on the woofer can be npe without a problem. And really ALL could be. Polys wouldn't be that much on the tweet.

          you should be able to get away with using a damped second order on the woofer. Meaning rolling the zobel and the 2mf cap together. You will have to play with the values. Maybe a 15uf and 2-4 ohm resistor.
          https://www.facebook.com/Mosaic-Audi...7373763888294/

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          • #6
            Re: Please critique my first crossover design

            PE's iron cores are all pretty good. When you hear talk about BAD iron cores (the ones that would saturate fairly easily) it's mostly about the tons of teeny iron cores used in commercial systems over the years. They were VERY small, either wrapped around a ferrite "bar" (or rod) - about the size of a power resistor, or ones that looked like a bobbin off a sewing machine. VERY small wire (maybe in the #28 - #32 range).

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            • #7
              Re: Please critique my first crossover design

              I'd add a notch on the woofer peak at 2.7k.

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              • #8
                Re: Please critique my first crossover design

                Thanks guys, this is great advice. I rolled the zobel and the 2uf cap together and created a damped 2nd order on the woofer. I started with a 15uf cap and a 3 ohm resister, but upped the values to create a steeper roll off. I played around with notch filters, but I couldn't get anything to work on PCD above 2k hz. I also used less dampening on the tweeter as suggested in previous posts. I am very happy with what I have now. By reducing the inductor values and changing two of my caps to electrolytic, the total cost is less than half of what I started with.

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                I am going to be in Dayton this weekend and am ready to order the parts. Please let me know if you have any suggestions before I do.

                Thanks,

                Matt A

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                • #9
                  Re: Please critique my first crossover design

                  Go with what you have and compare. You can create a notch that will aid in the roll off or even go to 3rd order on the woofer. But honestly with these drivers I am not convinced the expense would be worth it. Nice work!
                  https://www.facebook.com/Mosaic-Audi...7373763888294/

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                  • #10
                    Re: Please critique my first crossover design

                    I really appreciate you're help. I put the crossovers together and they sound great! It may just be wishful thinking, but I think they sound better than the original kit. I was really just trying to see if I could making something work from scratch, so I'll call it a success either way.

                    -Matt

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