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Another small speaker build with the nd91

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  • Another small speaker build with the nd91

    Like alot of us, I decided I wanted to build a small "bang for the buck" speaker. A speaker that sounds larger than its size. I decided to use the nd91-4, and pair it with the low cost Dayton td20f-4. This will be rear ported, and due to that, and size constraints it will have a realistic tuning of about 70hz using .75" pvc. Most people seem to use the denovo flat pack paired with the nd91, but since the tweeter diameter is a bit large I built my own enclosures making them .5" taller than the flat pack. This increases the internal volume slightly to .048cf. I used a rabbit bit to slightly recess the tweeter, but it will stick out some to match the front mounted nd91. I also recessed the back of the woofer cutout to allow for some breathing room. Unfortunately this will be a boring square box. The tweeter placement just doesn't allow for a roundover.




  • #2

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    • #3
      The cossover I point I chose is 4600hz. This was chosen off of what would work, and availability of parts. The highpass is a second order Butterworth with a 3.3ohm and 1.5ohm L-pad. I prefer a more relaxed top end, so its pretty padded. The lowpass section is a second order Linkwitz. GIven the size of the tiny enclosures I had to hot glue the tweeter section of the crossover to the floor of the enclosure, and glue the woofer section to the side wide close to the tweeter.

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      • #4
        Finished the speakers tonight. Hooked them up and noticed something very wrong, I only could hear the highs. Removed the drivers and realized I wired up the lowpass section in the orientation of the highpass. 😭 I guess you shouldn't attempt to build when your sick and on cold medicine. Through all the fanangling I was about to reorient the crossover correctly with the tiny space alotted. Unfortunately, during that process the Cabinents got pretty dinged up, and one of the woofers got a small dent. So yeah, I'm pretty deflated. I'm considering a rebuild.
        Last edited by Jake; 03-08-2019, 01:34 PM.

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        • #5
          Looks good, Jake.

          How do you like what you're hearing? It is hard to get Xover parts in these tiny cabinets for sure. They look good. I always have a few boogers in my cabinets somewhere it seems. Sometimes others can see them, sometimes not, but I know they're there... so I feel 'ya. Those ND91-4's are cool little drivers, right?
          Looks good from the pic, though! Nice work.

          TomZ
          *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
          *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

          *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

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          • #6
            http://techtalk.parts-express.com/member/3901-tomzarbo
            Thanks for the kind words Tom. I initially thought I had the nd91 drivers pretty well broken in, but I believe they have a little to go. The speakers sound big. Those tweeters seem to really project throughout the house. The low end seems a tad behind, but I believe it will open up more. I'm not happy I had to jerry rig the lowpass. I'm considering a rebuild.

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            • #7
              I decided to do the rebuild. Some changes made to the crossover. I chose a higher cross at 5600hz for a little fraction more Bsc. I also went first order on the high pass with about 3db more off on the L-pad. I changed the port tune to 76Hz for more usable output. Got the crossovers in, and gluing the enclosures as we speak.

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              • #8
                During assembly today i noticed something I read about others mentioning. Inconsistencies regarding the Nd90's voice coil leads being too short. You can clearly see one of the Nd91's lead is much shorter than the others. Hopefully, it won't be a problem.

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