Blog Forums DIY Speakers and Subwoofers I could use some advice…

3 voices
17 replies
  • Author
    Posts
    • #25174
      rich
      Participant

      I was watching a Toids DIY Audio YouTube video tutorial on the proper way to input the T-S parameters in winisd. After entering the required fields for my own subwoofer build I noticed that I was getting outrageously high numbers for port air velocity. And, no matter what I did, no matter what adjustments I made, the problem persisted. Thanks to Toids’ videos I learned that these high port air velocity numbers meant that I would get significant chuffing from the speaker port. After posting my question onto the YouTube comment board, Mr. Toids (no disrespect, I just don’t know his real name) suggested that I post some screenshots in the forum and get input from the community. So, here ya go. If you good folks could help me resolve this chuffing problem, I would most certainly appreciate it.

      Just so you know, the box is 4 cubic feet, tuned to 20Hz, and the HP filter is set at 20Hz. And, it’s not two different speakers. I just have the same speaker twice (superimposed) so that I can you y’all more speaker stuff.

    • #25178
      123toid
      Keymaster

      @Rich glad to have you on board. I think we can definitely help you with this. It looks like the port that you have right now is only about two and a half inches. That’s going to be too small. The typical Port size is going to be between 1/3 to one half the size of the driver. Obviously most people aren’t going to want to put a 6-in port on a 12-in driver. So I would recommend trying a slot port. Maybe something about 12″ wide x 1.5″ and see how long it is. Also pay attention to the first Port resonance. Do you have any idea of where you want to cross this over at? Typically you want your first Port resonance to be twice wherever you cross it over at. So if you’re subble for only place 80 hertz and below, you’d want a first Port resonance of 160 HZ or higher. We’ll see where we are when we get some results from that. But I think that would be closer to what you’re going to be looking for.


    • #25235
      rich
      Participant

      Hi 123toid,

      Thank you for your reply. I went ahead and did what you suggested. I changed the port from round to slotted. Even after making the port 2″ X 12″, winisd calculated that my port would have to be 42″ long to maintain the tuning while bringing the port air velocity under 30ft/sec. Did I buy the wrong driver? Or, is there something else I’m doing wrong, or forgetting to do? Again, thank you very much for your help. I appreciate it.

    • #25239
      tvor-ceasar
      Moderator

      I think I may have found it.

      Set BL to tm instead of N/A. Always check your units.

      So, I put the driver in, gave it a 4 Ft^3 At 20 Hz box, 20 Hz highpass (2nd order Butterworth), and put in 400W:
      14″x1.5″x36.5″ long port puts you at 16 M/S and you’ll just be exceeding XMax. That’s at ~380W (full XMax).


    • #25241
      123toid
      Keymaster

      @tvor-ceasar I completely agree. I just got back from vacation so I haven’t been able to run the numbers, but it does appear that the data in WinISD is off. When I did check this driver earlier, I was getting some similar results to yours.

      @Rich try to re input the driver data because I think you put it in incorrectly. If I get a chance to tomorrow I’ll send you over my driver data so you can load it. Maybe you can see where the differences lie within the data so that you can correct your file.


    • #25243
      rich
      Participant

      First off, I really appreciate both of you taking the time to help me with my problem. I’m grateful.

      I cleared the fields and re-entered all of the values according to the Dayton spec sheet (not the Parts Express specs) and triple checked my units. Nothing changed. The port air velocity is still ridiculous. Plus, I watched more tutorials on winisd to make sure I wasn’t missing anything. But, I think I’m still missing something. Again, this has got to be user error. Here’s the spec sheet for the subwoofer.

    • #25289
      rich
      Participant

      Hi Tvor-Ceasar,

      I really appreciate you being involved in my nightmare. Please be advised, I am a technology moron. So, the only thing I really noticed was that you numbers (and maybe your units?) were different than mine. Beyond that, I’m clueless. I cleared all of my entries for the driver, then entered your numbers into the appropriate fields in the proper units. All I got was error messages. So, I did the only thing I know how to do and re-entered the numbers from the Dayton spec sheet. Nothing works no matter what I do. What will it cost me to have you figure this out for me? I’m lost and crawling around in the weeds.

      Also, I cannot seem to paste any more pictures to the forum. Maybe there’s a limit? I have NO idea. Thank you for your time, Sir.

      • #25296
        tvor-ceasar
        Moderator

        I’m not aware of any limitation. @123toid do you have any idea why?

        I believe you are only inputting the numbers in Green, all else is auto-calculated. If you are doing that and the units are correct, then it SHOULD work. If that doesn’t work, download my driver file above (the .txt file) and change its extension to .wpr and move it to where your other driver files are located. You can then go into the driver editor and check the units to make sure the units are correct. Reference my last screen cap above.

        I’ll be back later.


    • #25293
      rich
      Participant

      Hi Tvor-Ceasar,

      I really appreciate you being involved in my nightmare. Please be advised, I am a technology moron. So, the only thing I really noticed was that you numbers (and maybe your units?) were different than mine. Beyond that, I’m clueless. I cleared all of my entries for the driver, then entered your numbers into the appropriate fields in the proper units. All I got was error messages. So, I did the only thing I know how to do and re-entered the numbers from the Dayton spec sheet. Nothing works no matter what I do. What will it cost me to have you figure this out for me? I’m lost and crawling around in the weeds.

      BTW, I cannot seem to paste more pics to this thread. There’s a limit maybe? I have no idea. Thank you very much for your time, Sir.

    • #25314
      rich
      Participant

      Remember when I said that I was a technology moron? Well, now I can prove it. I just discovered that I had my rear port air velocity set to feet/sec. So, I was seeing numbers like 60 to 70 feet/sec. I watched Toids ported speaker tutorial probably 10 times. Then, by the 10th time, I finally caught the missing piece of the puzzle. He said, “You you should try to keep your port air velocity at or below 17 METERS/SECOND. For Christ sake! See? Moron!

      I’m really sorry for dragging everyone through this. But, at least I now know that my speaker will work. I wanna thank Toids and Tvor-ceasar for being amazing moderators and awesome people.

      • #25315
        tvor-ceasar
        Moderator

        @Rich I have a confession: I saw that. I didn’t mention that because, as the son of a teacher, and having teaching going way back in my lineage, I recognized your dogged determination to master what’s in front of you. If I had told you outright, I doubt it would stick as well as it will since you’ve found it yourself. And you did find it, so a moron “you ain’t.” (Love the 3 Stooges)

        Congratulations and welcome to the next step. Onward and upward!


      • #25328
        123toid
        Keymaster

        @Rich Glad you got it figured out! We would love to see pictures of the build as you build it. Would you be willing to create a build log? P.S. in order to add more pictures, just click the button that looks like a camera underneath the text box (the box you are typing in). It should allow you to upload photos.


      • #25384
        rich
        Participant

        A build log? Absolutely! That would be fun.

        So, now that I have the whole winisd thing handled, I’m still struggling over plate amp choice. Since the subwoofer driver is a 12″ Dayton Audio 400w (RMS) @ 8 ohms (RSS315HFA-8). The best option I could find, based on functionality and affordability, is the Dayton Audio SPA500. Is this a good choice for the driver that I have?

        BTW, have any of you seen the prices for plywood or MDF these days? Holy Christ!

      • #25387
        123toid
        Keymaster

        @Rich The Dayton SPA500 is great amplifier for sure. ANd if you want a plate amplifier, then that is probably the way to go. Another option would be to buy the Behringer NX1000D. That amplifier is about the same price, but offers DSP (although it is a standalone unit). However there are a few caveats to this, one you will want to replace the fans with Noctua otherwise it runs too loud. You will also want to bridge the amplifier as the bridged output is closer to 650w – not 1000w. WIlliston Audio LAbs tested the model before this and those were the results and there is no reason to think it would be any different.

        https://www.youtube.com/watch?v=Ibsvu1xownw

        Another option would be the NX3000D, if you ever think you will run a second one. It should run two just fine. You will also need to replace the fans though.


    • #25409
      rich
      Participant

      Thank you for the awesome suggestions. But, two questions: what the heck is “bridge mode”? And, my speaker is 8 ohms. Won’t there be some sort of compatibility issues? The info on the NX3000D only talks about 2 and 4 ohms.

      If you’re pounding your head against your desk right now, I totally get it. My wife finds my lack of tech savviness very frustrating.

      • #25751
        tvor-ceasar
        Moderator

        Bridge mode is special way of dealing with the inputs and outputs.

        Background:
        Many (read that as most) amplifiers are what you call single ended, ie they run between a certain voltage and ground (0 volts). Many of those take the supply voltage, split that in half, and then the amplifier can only go a certain amount above and below that 1/2 way point, pushing through an output capacitor, into the speaker, and out to ground. So your output is limited to a percentage of 1/2 the supply voltage. Yes, there are other amps that run + and – power supplies in order to get that much more voltage swing, but that’s another post.
        Now, if you reconfigure things a bit by adding a second part to the input where you get both a “positive” (upward going to start) and “negative” (downward going to start) signal, then apply that to 2 of your power amplifier sections, connecting the output of the amps to the speaker + & – (no ground reference is used), you get twice the voltage swing as before. Say you had 4 volts RMS output before (single ended), now you have 8 volts RMS (bridged). What you have done is actually quadrupled your power output.

        Formula:

        (RMS V)^2 / Impedance

        (4^2) / 8 = 16 / 8 = 2 watts

        (8^2) / 8 = 64 / 8 = 8 watts

        (^2) is “squared” or “raised to the power of 2”

        As for the impedance of the bridged mode being rated @ 2 or 4 ohm, you will be fine with 8 ohm, generally, since it is solid state (transistor) which has no real problem seeing greater and greater impedances. Granted, the higher the impedance mismatch, the more it affects the bandwidth (shrinks). But 8 ohm should be no problem. Just know that the power will be about 1/2 the 4 ohm rating.


You must be logged in to reply to this topic.

©2022 KLEO Template a premium and multipurpose theme from Seventh Queen

CONTACT US

We're not around right now. But you can send us an email and we'll get back to you, asap.

Sending

Log in with your credentials

or    

Forgot your details?

Create Account