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How's this for a Rat Rod entry? (ND90 weekend boombox)

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  • How's this for a Rat Rod entry? (ND90 weekend boombox)

    Did you ever have a bunch of parts sitting around and your brain wants to find interesting ways of putting them together to make something new? Happens to me so much I can barely keep up with my other work!



    The Ingredients
    +an OSMTM cabinet from DIY sound group
    +a Dayton DTA-2, which I bought years ago and couldn't ever find the right use for
    +some leftover port tubes
    ... but what drivers to use? Well, I had a bunch of Dayton ND90-8 sitting around that weren't being used. And I was curious what kinds of things they would really be capable of if I pushed them.

    So I figured out a vented alignment using 1/2 of the OSMTM box... approx 4 Liters. I tuned it to 63 Hz, which gave an F3 around 51 Hz, but also a nice big push between 70-90 Hz. (This uses these port tubes, at a length of 5.75")

    I glued together the flat pack (most of it. I used a solid piece of MDF for the divider in the middle), and made a new baffle using the rear-mount method I discovered I liked for the pincushion frames. Oh, and I did a bit of roundover and chamfer on the box to give it a bit more style.

    The Filter
    I decided that my first listening to the ND90 would be full-range, without a filter. I figure that's what full-rangers are meant to do, right? Well, it sounded OK, but really a bit too congested in the midrange, and the bass was lacking. I decided a filter was in order. So I measured the driver and came up with a BSC/contour filter that really brings the whole FR into line. It's a night-and-day difference. Without the filter, it just sort of "made noise," like a boombox or computer speaker . But with the filter, I could actually get a HiFi sound out of it with a similar voicing to my designs.
    (as an aside, I am very curious how this filter would sound on a sealed ND90 or Aura NS3 like you see with Wolf's "PC" projects. If anyone is willing to give the filter a try, let us know how you like the sound)


    Listening Impressions

    Since this is a single-driver design, the ND90 is responsible for treble. It does better than I thought on-axis. Sounds a bit brittle, but seems to mesh well with today's compressed mixes (and since it's meant to be used by plugging in an ipod or smartphone, that was just fine with me) Off-axis, the treble rolls off, but that's to be expected. It's nothing tragic, and nothing unusual to this type of speaker. What IS surprising is that if you walk out of the room, the bass is STILL really pounding. This little guy has some serious low end for such a little thing. I think most people would be seriously surprised by the big sound put out.


    The Amp

    I knew I wanted a self-contained, plug-and-play speaker. But the DTA-1 needs some help in that area. The power and input jacks are right on the circuit board, and there's no practical way to mount it to the side of a box (without air leaks). So I went to radio shack and ace and got a couple parts, and put the input, volume, and power on a chrome wall switch plate. The amp is strapped down to some pegboard with zip ties. Kinda cheesy, but I oculdn't think of anything else off-hand. (it's all hidden inside anyway, right?)


    Bottom Line

    I think it took me about a total of 8 hours to put this thing together... the longest parts were figuring out how to mount the amp and jacks. I might give it to my daughter to put a "custom paint job" on; she's 2 and is colors compulsively. The end product should be pretty handy. You just plug in a wall wart, plug in your phone/ipod and let 'er rip. Should give most iHome/docking "schtuff" a serious run for its money... way more fun, too, to make one yourself than just go to the big box store and slap down your credit card.
    Attached Files
    Last edited by Paul Carmody; 02-24-2012, 11:32 PM.
    Isn't it about time we started answering rhetorical questions?

    Paul Carmody's DIY Audio Projects
    Twitter: @undefinition1

  • #2
    Re: How's this for a Rat Rod entry? (ND90 weekend boombox)

    Funny, I'm working on a project almost exactly like that, using the Lepai TA2020A+ and a pair of 4 ohm NS3's. Seems you beat me to it No filter as of yet, just using the bass and treble controls to bump up the low and high end. Sounds nice, but I agree, there is a bit of hash in the mid-range. What exactly is that filter, is it just a notch filter to knock down a peak in the response, or more of a shelf to knock down everything above a certain frequency? Any easy way I could model one for 4 ohms? (I really need to get excel so I can use PCD) I'd like to give it try but all my drivers are 4 ohm. I have a few of the ND91-4's that just came in, they were on backorder, I may try them out as well, see how they do.
    My modest builds:
    Armadillo TM, A.K.A. Lil' Dillo
    Tarkus/Armadillo build #2
    Armadillo Center Channel
    Au-Rock-O Sub
    Tarkus
    Staining MDF tutorial

    Comment


    • #3
      Re: How's this for a Rat Rod entry? (ND90 weekend boombox)

      The filter is mostly for Baffle Step Compensation, but it also does a bit of EQ. Take a look at the before and after.



      I would be curious how the 4 Ohm version of the driver would perform. Obviously, the filter would have to change. But the advantage would be more sensitivity, which is usually a good thing for boomboxes. The question is: can the DTA-2 (or Lepai, or whatever other TA2020 amp) handle the 4 Ohm load?
      Attached Files
      Isn't it about time we started answering rhetorical questions?

      Paul Carmody's DIY Audio Projects
      Twitter: @undefinition1

      Comment


      • #4
        Re: How's this for a Rat Rod entry? (ND90 weekend boombox)

        Tested it for about 2 hrs today at max volume before distortion, just a tad past half way on the volume knob. It didn't seem to even get warm, I'm guessing if it were going to fry anything it would have, it was pretty loud considering the amount of bass it was pushing out. Those NS3's really move, kinda neat to watch all that excursion happening on such a tiny driver. Any ideas for a finish? If it's going to be "rat rod" it can't be anything too nice, maybe spray bed liner on the baffle, and wrap the cab with duct tape, and seal it up with a couple coats of poly
        My modest builds:
        Armadillo TM, A.K.A. Lil' Dillo
        Tarkus/Armadillo build #2
        Armadillo Center Channel
        Au-Rock-O Sub
        Tarkus
        Staining MDF tutorial

        Comment


        • #5
          Re: How's this for a Rat Rod entry? (ND90 weekend boombox)

          Here's a shot of mine. I'm a sucker for fancy hardware :D
          Attached Files
          My modest builds:
          Armadillo TM, A.K.A. Lil' Dillo
          Tarkus/Armadillo build #2
          Armadillo Center Channel
          Au-Rock-O Sub
          Tarkus
          Staining MDF tutorial

          Comment


          • #6
            Re: How's this for a Rat Rod entry? (ND90 weekend boombox)

            Paul, is L1's gauge critical? 20 ga. OK? My 'puter speakers have the mid-range issue you mention, they aren't "clear". Not terrible, but not quite "there". Too much like a typical "boom box" radio in the mids. Fussed with damping...helped, but not enough.

            Comment


            • #7
              Re: How's this for a Rat Rod entry? (ND90 weekend boombox)

              I like!! Gives me some ideas about how to use the 4 ND105s I've got sitting here.
              https://www.facebook.com/Mosaic-Audi...7373763888294/

              Comment


              • #8
                Re: How's this for a Rat Rod entry? (ND90 weekend boombox)

                Originally posted by Whitneyville1 View Post
                Paul, is L1's gauge critical? 20 ga. OK? My 'puter speakers have the mid-range issue you mention, they aren't "clear". Not terrible, but not quite "there". Too much like a typical "boom box" radio in the mids. Fussed with damping...helped, but not enough.
                I think the inductor isn't going to be too critical of what the DCR is. 20 awg should be fine. For that matter, iron core would be fine, too.
                Isn't it about time we started answering rhetorical questions?

                Paul Carmody's DIY Audio Projects
                Twitter: @undefinition1

                Comment


                • #9
                  Re: How's this for a Rat Rod entry? (ND90 weekend boombox)

                  Originally posted by bolland83 View Post
                  Here's a shot of mine. I'm a sucker for fancy hardware :D
                  Dude, that's freaky! How did yours come out to look so much like mine, right down to the roundovers and chamfers?!?
                  Isn't it about time we started answering rhetorical questions?

                  Paul Carmody's DIY Audio Projects
                  Twitter: @undefinition1

                  Comment


                  • #10
                    Re: How's this for a Rat Rod entry? (ND90 weekend boombox)

                    Originally posted by isaeagle4031 View Post
                    I like!! Gives me some ideas about how to use the 4 ND105s I've got sitting here.
                    Yeah, the thought did cross my mind of doubling the woofers as in a 2.5-way. But the enclosure just got too big. (Maybe if it was an "add-on module"?)
                    Isn't it about time we started answering rhetorical questions?

                    Paul Carmody's DIY Audio Projects
                    Twitter: @undefinition1

                    Comment


                    • #11
                      Re: How's this for a Rat Rod entry? (ND90 weekend boombox)

                      Originally posted by Paul Carmody View Post
                      Dude, that's freaky! How did yours come out to look so much like mine, right down to the roundovers and chamfers?!?
                      Distant fraternal twins separated at birth? :D
                      Wolf
                      "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                      "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                      "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                      "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                      *InDIYana event website*

                      Photobucket pages:
                      http://photobucket.com/Wolf-Speakers_and_more

                      My blog/writeups/thoughts here at PE:
                      http://techtalk.parts-express.com/blog.php?u=4102

                      Comment


                      • #12
                        Re: How's this for a Rat Rod entry? (ND90 weekend boombox)

                        Originally posted by Paul Carmody View Post
                        Dude, that's freaky! How did yours come out to look so much like mine, right down to the roundovers and chamfers?!?
                        Very wierd...I have a very similar build on paper. I'm using the NS3's based on Wolf's PC design, DTA-2 and the MP3 module.

                        Comment


                        • #13
                          Re: How's this for a Rat Rod entry? (ND90 weekend boombox)

                          Paul, are the speakers separated in their own chamber or is open all the way inside?

                          Comment


                          • #14
                            Re: How's this for a Rat Rod entry? (ND90 weekend boombox)

                            They are each in their own chamber. There is a "divider" in the middle.
                            Isn't it about time we started answering rhetorical questions?

                            Paul Carmody's DIY Audio Projects
                            Twitter: @undefinition1

                            Comment


                            • #15
                              Re: How's this for a Rat Rod entry? (ND90 weekend boombox)

                              Originally posted by Wolf View Post
                              Distant fraternal twins separated at birth? :D
                              Wolf
                              Great minds think alike? I don't know, I just used the same vertical roundover/horizontal chamfer combo that I did on my tarkus build, I like the look. :D Also, update, the ND91's don't perform well in my cab, they are flatter overall, but the enclosure is actually way too large and tuned too low. I'll keep the NS3's in there. With a bit of stuffing I don't think I'm going to need a filter. The tone controls on the Lepai are sufficient, and the stuffing has tamed some of that midrange hash I was hearing.
                              My modest builds:
                              Armadillo TM, A.K.A. Lil' Dillo
                              Tarkus/Armadillo build #2
                              Armadillo Center Channel
                              Au-Rock-O Sub
                              Tarkus
                              Staining MDF tutorial

                              Comment

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