Blog Forums DIY Speakers and Subwoofers Dayton DS 135-8 project – nearfield measurements

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    • #14623
      lvx
      Member

      Hi, ladies and gents, 

       

      This is a next step of the same project in this topic. The project itself is combining the Dayton DS135-8 (paper cone) woofer and the Dayton ND28F-6 tweeter. Your help was excellent and I’m happy to say that this has been made absolutely clear. 

      Here in Belgium however, it’s been raining incessantly, so no chance yet to get some outside measurements.
      Instead, I have been taking nearfield measurements of the woofer response to have a look at what the woofer is doing at the moment.

      2852-nov-1-161021measurementwooferclosedaytondtapro.zip

       
      I was wondering if you could have a look at attached mdat file I generated and give me some feedback? 

      Some context, right now it sits in a rear-ported box with about 5,4l volume and a 9 cm port. I will also attach the zma file, note that for measuring this I paid special attention to making sure the vented pole piece was actually not obstructed, I’m not sure whether that is the correct procedure. 

      Specifically I wonder about:

      – Is the harmonic distortion acceptable? If I recall it should generally stay under 1%. Which it also does, unless below 75 Hz. 

      – Are there any optimizations I can still do?

      – With the current configuration, do you think I need to put in some protection against exceeding XMax? 

    • #14682
      123toid
      Keymaster
      Posted by: @lvx

      Hi, ladies and gents, 

       

      This is a next step of the same project in this topic. The project itself is combining the Dayton DS135-8 (paper cone) woofer and the Dayton ND28F-6 tweeter. Your help was excellent and I’m happy to say that this has been made absolutely clear. 

      Here in Belgium however, it’s been raining incessantly, so no chance yet to get some outside measurements.
      Instead, I have been taking nearfield measurements of the woofer response to have a look at what the woofer is doing at the moment.

      2852-nov-1-161021measurementwooferclosedaytondtapro.zip

       
      I was wondering if you could have a look at attached mdat file I generated and give me some feedback? 

      Some context, right now it sits in a rear-ported box with about 5,4l volume and a 9 cm port. I will also attach the zma file, note that for measuring this I paid special attention to making sure the vented pole piece was actually not obstructed, I’m not sure whether that is the correct procedure. 

      Specifically I wonder about:

      – Is the harmonic distortion acceptable? If I recall it should generally stay under 1%. Which it also does, unless below 75 Hz. 

      – Are there any optimizations I can still do?

      – With the current configuration, do you think I need to put in some protection against exceeding XMax? 

       

      Somehow I completely missed this topic.  I’ll try to have a look at this tomorrow for you.  Feel free to remind me if I don’t get to it in a few days.  I know tomorrow being veterans day, I’ll be spending of the time with my father honoring him and thanking him for his service. But I think I will still have some time for it. 


    • #14689
      lvx
      Member

      @123toid Thank you! And no worries, I’m not in any rush. I wish you a good veteran’s day!

    • #14766
      lvx
      Member

      @123toid Hope you’re having a good week. This post just serves as a quick reminder like you recommended. Did you have any time to review the above? If not, no problem. You have already helped me quite a bit in this project 🙂

    • #14783
      123toid
      Keymaster

      @lvx 

      First of all Thank You for the reminder.

      I believe you said this was a close mic of the woofer.  Just remember to also take a measurement of the port later to get a good idea of what the port tuning is actually doing.  So far, it looks really good.  

      Did you slow down your sweep when you tested for distortion? You typically want it a slower sweep to pick up distortion better.

      There is one area of concern. It is not showing anything on the distortion graph (which is also a concern), but you have cone breakup of 5Khz sneaking into your audible response.  

      This is only about 4dB down.  If it was me, I would work to get that much lower.  Even if it isn’t showing up in your distortion measurements, it will definitely affect your final response when you add your tweeter. I would take care of the 5Khz section, that will almost certainly be a problem. 

       


    • #14791
      lvx
      Member

      @123toid  I did in fact not slow down my sweep, so I’ll look into that. I’ll see if I can get rid of that 5 Khz breakup area. I assume the best way to go about is is to plot it in xsim and give it a try 🙂

      I really appreciate you for taking the time to look into this. It really keeps me from missing things, or from repeating the same mistakes. I’ll keep you posted!

       

    • #14795
      123toid
      Keymaster

      @lvx 

      You can throw a higher order crossover or even try a tank cap in parallel with the inductor. Either of those could be helpful. 


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