Announcement

Collapse
No announcement yet.

Am I on the right track? Bookshelf speaker Fountek FW146 / Dayton DC28F

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

  • crossbound
    replied
    What I learned tonight: As I was trying to reduce the impedance a little bit, I discovered that L1, C2, C9 and C11 had the biggest impact on reducing the impedance bump at 1500Hz. I reduced L1 just slightly, and increased C9 and C10. Also realized that R7 controlled the impedance bumps at 20Hz and 70Hz. And finally some other slight adjustments to keep the phase in line.
    Last edited by crossbound; 09-05-2016, 09:22 AM.

    Leave a comment:


  • WernerM
    replied
    You are doing fine. At this point anything else you decide to try will be for sheer learning and practicing. I can't tell you the number of Sims I have done just for experiments and learning. Wolf is definitely more versed at the terminology, some of the things that I mean aren't necessarily how I convey them... lol. If you chose to continue more experiments trying to flatten the impedance phase swings, then by all means do so. You aren't bothering any of us I'm sure. I personally like seeing these types of threads as they are great learning resources for more people than just yourself. I did the same thing when I first started. I also messaged Wolf and rpb plenty of times about theoretical builds and Sims to get their insight. For me it has been a pleasure trying to give you help and advice. Wouldn't you know it, I picked up a couple of tricks myself.

    Leave a comment:


  • Wolf
    replied
    It was just a statement and info to be aware of. Being that most Class D filters (some have another method that negates the effects by not having an output filter) are generally 1st order and 0.01-0.022mH in use. You can use the classic mH equation; L = [R/(2*pi*F) ]* 1000

    In general, lower impedance means lower Fc of the coil, and an earlier rolloff ensues. Most are meant for 4 - 8 ohms.

    Later,
    Wolf

    Leave a comment:


  • crossbound
    replied
    Once again thank you guys.
    I'm not planning on using a tube amp so no problem there.
    I guess my question now would be: is what I got acceptable, or are there any glaring issues I should take care of?
    I will try some more tweaks, but sure would like to wrap this up. :-)

    Wolf is there a certain impedance that you try to stay within to minimize the effects or are you designing for a certain type of amp in mind? I know next to nothing about amps.

    Leave a comment:


  • Wolf
    replied
    Keep in mind that a tube amp won't like the wild swings in impedance. A Class AB will be fine with it. A Class D might have altered response in the top-octave depending on tweeter impedance in this range due to the typically standard output filter they use to suppress the switching frequency at output.

    Later,
    Wolf

    Leave a comment:


  • rpb
    replied
    Originally posted by crossbound View Post
    My question is then, which impedance range should I shoot for?
    I don't know if it matters all that much. What I would probably shoot for is keeping the impedance peaks in the mids, and highs from exceeding 20 ohms, so yours looks fine to me. On my current speakers, I added a cap, coil, and resistor across the speaker input to reduce a peak down to about 8 ohms. I plan to compare the sound with, and without the added parts. I don't expect to hear much difference, but who knows. I'm keeping an open mind about it. The biggest potential advantage of adding the parallel resistor, is reducing the effect of the tweeters impedance on the filter. It's not always necessary, but sometimes it helps.

    Leave a comment:


  • crossbound
    replied
    My question is then, which impedance range should I shoot for?

    Leave a comment:


  • rpb
    replied
    There's a thousand ways you could design this x-over, so don't take my suggestions as an indication that you are doing something wrong. . Just as an experiment, try adding 1, 2 or 3 ohms for R12, and tweak the caps a little.

    If you put 6 ohms in parallel with the tweeter, it will tend to level the tweeter impedance. That sometimes makes it easier to get the desired roll off. It will probably change the top end too.

    Leave a comment:


  • crossbound
    replied
    After removing the large resistors in the highpass to start over, I tried again, but added resistors in series with the capacitors, which seemed to help to keep everything a little more even and more manageable. Currently the reversed null is not dipping all the way down. I could correct that by increasing the C9 and C10 capacitor 5.1uF, but it would elevate the SPL in the crossover regions just slightly.

    Leave a comment:


  • rpb
    replied
    Originally posted by crossbound View Post
    Here is version 3 of my Peerless tweeter response curve. It took a little while to figure out how to get the phase aligned better. What ultimately seemed to get me closer was adding the parallel resistor over the woofer. Is the high impedance at 5kHz an issue? And is the impedance phase okay?
    Thx
    Try replacing the 30 ohm R16 in the tweeter filter with about 6 ohms. Most of the other values will change as well, but you may find it easier to get the tweeter to roll off as desired. R10 will probably drop to about 4 ohms or so. This will reduce the impedance of the speaker above the x-over frequency.

    Leave a comment:


  • Wolf
    replied
    That is the place you have to put it in PCD, even if it's not the best place to put it. That's how I do it, since it's about the only place you can enter it for a notch.

    Later,
    Wolf

    Leave a comment:


  • crossbound
    replied
    Actually looking at it again. you are right. It doesn't have that much impact on the phase. What it did help with is dropping the reverse null.
    Also if you could look at my previous post again. I added an other image and was curious if I was placing the DCR value for the inductor in the RCL in the correct spot.

    Leave a comment:


  • Wolf
    replied
    Make sure that resistor is of sufficient wattage, and I'd shoot for a 25W resistor there. If you up the resistance to 50-60 ohms the power requirement can be reduced to using a 10-15W resistor. This may not be doing what you think it's doing. All that resistor is doing is reducing the magnitude at the inductive rise and Fs of the woofer, and minimally everywhere else. I'm not sure how it can affect the phase as you say. If you want to add a resistor, try using a 0.5-4 ohm resistor from C2 to ground instead of by itself. This will shift your phase, and affect the knee at rolloff. Honestly, the FR at xover is a bit bumped up, and this may help that as well.

    Later,
    Wolf

    Leave a comment:


  • crossbound
    replied
    Here you go. Also I just remembered that I meant to ask where I should put the DCR value for the 1.5mH inductor in the RCL notch filter. I put the 0.22Ohm value in the L2 section. Is that the correct way of doing it?

    Leave a comment:


  • Wolf
    replied
    Parallel resistor where at the woofer? Can you show the woofer circuit cells? I want to make sure what you have won't be cause for concern.

    Later,
    Wolf

    Leave a comment:

Working...
X