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  • First Build! Feedback wanted

    Hello! This is my first real speaker build and I was absolutely stoked to throw the drivers in and hear them for the first time yesterday. They still need veneering, but I couldn't wait to give them a try.

    They sound great to me, but I thought I'd ask if anyone had any advice in modifications or interpreting the frequency response. I do have some polyfill, and am planning on reinforcing the enclosure a little more on the sides. I also have a bunch of capacitors between 7 and 15 uF that I could swap out.


    Driver Specifications
    Woofer - Dayton Audio DC300-8 12" Classic Woofer
    Mid/Hi - Dayton Audio PC83-8 3" Full-Range Poly Cone Driver

    Enclosure
    Baffle, Top, Bottom 3/4" MDF, Sides, Back 1/2" MDF
    Mid Volume - 0.83 ft^3 CORRECTION 0.083 ft^3
    Woofer Volume - 1.34 ft^3

    Crossover
    First Order at 2000 Hz - 1.6 mH Inductor on the Woofer, 10 uF Cap on the Mid

    Measurement
    Measurements made in a 20x20ft room with a good amount of furniture, using REW and a Tascam DR-05 recorder positioned 1 yard away centered between woofer and mid.

    Thank you for looking!

    Last edited by BikesAndRain; 09-10-2018, 12:43 PM.

  • #2
    They sound great to me, but I thought I'd ask if anyone had any advice in modifications or interpreting the frequency response.
    20x20ft room with a good amount of furniture, using REW and a Tascam DR-05 recorder positioned 1 yard away centered between woofer and mid.
    I'm guessing you are not listening 1 yard away however
    My interpretation of the graph may not necessarily represent the sound at your ears, considering your initial impression.
    "Not a Speaker Designer - Not even on the Internet"
    “Pride is your greatest enemy, humility is your greatest friend.”
    "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

    Comment


    • #3
      Sorry, but you asked:
      Why such a large volume for the mid? 0.25cf would be about right.
      How do you feel about only mid 50s from a 12" woofer?
      Your box is too small, and has little bass w/out a port.
      The 8" "Classic" would do mid 30s in 1.3cf, vented.

      If you gave me your speaker (and I couldn't change drivers), I'd move 0.6 cf from the mid box to the woofer box (so, 0.23 for the mid - STUFFED, and 1.94 for the woofer). Then I'd add a 4"id x 12" long port (out the back) so the bass could then hit 40Hz.
      That coil doesn't pull the woofer down -6dB until 6000Hz. IF you throw a Zobel across the woofer terms (8ohms+50uF), then you'll be -6dB around 1.1kHz, and -19dB down @ 6k. (It COULD be that unfiltered top end on the woofer adding to the 3"er's output making your top octave so high!) The raw 3" response doesn't look that bad.

      Sort of confused now (just looked at your box diag.)? Says "Sealed Box", but then you list a tuning freq. of 55Hz? Did you port it? THAT tuning in that box w/that woofer makes a +6dB "hump" around 80Hz. It LooKs like I can see that in your response curve?

      Comment


      • #4
        First off - cool cabinet! Pretty daring to go for curves on your first speaker. That will look great once the veneer is finished up.

        Second - take what Chris said and run with it. He knows his stuff. I'll add that you'll be much better served with some accurate measurements & software modeling. Maybe there's a forum member in your area with measurement gear who could help you out. You'll be surprised how much clearer everything will sound once you have everything dialed in.
        Co-conspirator in the development of the "CR Gnarly Fidelity Reduction Unit" - Registered Trademark, Patent Pending.

        Comment


        • #5
          Sydney - Thanks for your advice! I'm not unhappy with how they turned out, but I'm always looking to see if I can improve the sound more.


          Chris - Thanks for taking the time to look over it and your critique is absolutely welcome. You caught a typo - the mid enclosure section is only 0.08 ft^3, it's a 12x3x4" sub-section in the enclosure.

          Regarding the bass, you're absolutely right, I'm somewhat disappointed that the 12" woofer isn't reaching lower, especially when I moved them into a larger room. The low-pass coil also doesn't seem to do much as you noted. Thanks for the crossover suggestions - I was trying to play it easy with a first order, but perhaps it needs to be a little more complex.

          That peak between 10 and 20 kHz does appear in the parts express spec sheet, but yeah, it is a little more pronounced on mine. Do you think adding polyfill would lower this?

          The box is indeed sealed - I got the calculations from here, not sure how they get the turning frequency https://www.diyaudioandvideo.com/Cal...rBoxEnclosure/

          Thanks for your port suggestion - it seems a shame to have such large woofers and still feel like I need to add a subwoofer. I will look into that.


          Tom - Thanks also! I have a little bit of woodworking experience, though this was my first time with MDF - that stuff cuts and shapes like butter! Dusty, but fun to work with.

          Comment


          • #6
            Originally posted by BikesAndRain View Post
            Sydney - Thanks for your advice! I'm not unhappy with how they turned out, but I'm always looking to see if I can improve the sound more....
            As the others pointed out there were some unusual design decisions.
            The FR graph is worrisome.
            That woofer is better suited for a reflex design.
            Rooms with 2 or more similar dimensions are often problematic.
            Height?

            First Order at 2000 Hz - 1.6 mH Inductor on the Woofer,
            Does not agree with other 1st order calculators.
            Last edited by Sydney; 09-10-2018, 05:04 PM.
            "Not a Speaker Designer - Not even on the Internet"
            “Pride is your greatest enemy, humility is your greatest friend.”
            "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

            Comment


            • #7
              I just had a thought - you could gain more cabinet volume for your woofer by building integrated stands/bases that are actually part of the cabinet. Spica did that with the Angelus design. It still doesn't solve the crossover issue, but at least you wouldn't have to find a different woofer or start from scratch.

              Where are you located? Unless you're out in the middle of nowhere, I'm sure there's somebody on the forum nearby.
              Co-conspirator in the development of the "CR Gnarly Fidelity Reduction Unit" - Registered Trademark, Patent Pending.

              Comment


              • #8
                Can I make a suggestion on your cabinet? You're going to experience some significant 'telegraphing' of those seams through your veneer - even paperbacked veneer. You could seal and sand, and seal and sand, and seal and sand....or you could go down to the HD and buy a 1/8" High Density fiberboard sheet for under $7.00. Glue it to the top and bottom to cover the seams and you've eliminated the telegraph problem. You may want to do the front baffle too.

                Comment


                • #9
                  Tom - That's a neat idea! I actually remembered I had an equalizer in the basement, so I've been playing around with that. Might be cheating, but we'll see how much I can correct the response. I'll post an update with that. I'd rather not make the speakers any larger. I'm thinking for my next build, I'll stick with smaller drivers and see how low I can get them in a proper enclosure. I'm located in Madison, WI though frequent/might be moving to Milwaukee soon.

                  Marty - Thanks for the suggestion- I actually do have some 1/8" plywood that I'll be putting on the top and bottom, should help protect the corners too, I think!

                  Comment


                  • #10
                    Looks like a nice design to me, I like the idea of the 12" woofer in a sealed box. I would recommend not changing anything too drastic until the woofers have broken in for at least a few hours. You may find that the overall bass response ends up sounding rather good.

                    Comment


                    • #11
                      Originally posted by BikesAndRain View Post
                      [B] I'm located in Madison, WI
                      You have a local speaker building resource, no need to wander in the wilderness.

                      Comment


                      • #12
                        "I'm located in Madison, WI..."

                        Madison? My wallet would be empty most of the time if I lived closer to Madison!

                        You are within a short drive of a warehouse filled with nice drivers - and probably some good advice if you buy from them.
                        Co-conspirator in the development of the "CR Gnarly Fidelity Reduction Unit" - Registered Trademark, Patent Pending.

                        Comment


                        • #13
                          LOL, I have actually heard of that particular warehouse before, but I never made the connection, I live very close. I will definitely pay them a visit!

                          Comment


                          • #14
                            First, props for an unusual combination that I think shows some creativity. My guess is they will/can sound pretty good.

                            Second, I agree with what Chris said. Modify the woofer crossover as he said with a zobal. I might add a cap in series with the coil and zobal on woofer circuit, maybe a 22 uf cap (but do what Chris says, not me, he knows much more). That brings down woofer. Move some cabinet volume to woofer from mid/tweeter as Chris suggested and port box as he says.

                            With those modifications I think you may have pretty good speaker, especially for cost of drivers.

                            Comment


                            • #15
                              If you are planning to play any vinyl records without a subsonic filter, the sealed box would be less likely to feedback and oscillate at higher volumes.

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