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  • Spot-check first timer's design?

    I'm building a desktop boombox bluetooth setup using two Daton Audio RS75-4 3" 4 ohm drivers. I've used BassBox to create a design with each speaker housed in its own cabinet with internal dimensions of (in inches) 4 x 4 x 4. Boombox suggests a port tube .75 inches internal diameter by 2.812" long. I don't see any port tubes on parts express smaller than 1.125" in diameter, so either I'd be chancing port noise, or, what, PVC painted black? When I change the tube to 1" diameter, it's 5+ inches long, which doesn't fit. I'm building the cabinet out of 1/4" hard maple glued to 1/4" of MDF. BassBox suggests a minimal fill. Based on the image, I'd guess a 1/2" of polyfill? I don't really know.

    Any glaring problems jump out at you?

    Happy thanksgiving to those celebrating, and a fine day to all the rest as well.
    The Dayton Audio Reference Series sets a new standard of value in high-performance loudspeaker drivers. Incorporating a low-distortion motor system with a copper ring, a copper cap, and an aluminum phase plug, the RS75-4 can outperform "boutique" drivers

  • #2
    You can use pvc to get your .75 inner diameter. Use pvc elbows to fit the port in the cabinet. WinISD lets you calculate the port air speed to avoid chuffing. You can also do roundovers at the ends of the port with a router, this helps smooth out chuffing. You would glue the pvc tube to the wood and drill a pilot hole for the router to then do a small roundover. You could probably line the walls of the cabinet with some open cell foam. If you go with polyfill, do a handful and test the sound. Adjust the amount of fill to your liking of the sound. What are you using for an amp? Any crossover filter?

    PE has a 1" inner diameter port, but it's too short for your application https://www.parts-express.com/speake...lared--260-470

    Here's an option to avoid painting pvc
    Attached Files

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    • #3
      I'm using a little chinese bluetooth receiver/amplifier off of Amazon: https://www.amazon.com/gp/product/B01469WQ66
      Amazon.com: SMAKN� Wireless Digital Bluetooth 4.0 Audio Receiver Ampli: Electronics

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      • #4
        I have used a lot of the FormuFit PVC pipe. It cuts great on a table saw to get nice square ends. Great stuff and having black is a real plus. I would highly recommend the KAB-215 amp/BT combo. It is a plug and play unit and has lots of options including battery power. It would be a good fit for the RS-75's. It will have no noise and is backed by PE's 5 year warranty. There really is no better amp/BT system or boom boxes.

        For more low end you might give the PC83 drivers a look. Smooth little driver and it won't break the bank. It will perform better in the low end than the RS75. The great thing is, there are lots of options.
        "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

        The Madeleine
        The Roxster
        Swopes 5.0
        Acoustic Panels
        Living Room Make Over

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        • #5
          Originally posted by Gordy View Post
          I have used a lot of the FormuFit PVC pipe. It cuts great on a table saw to get nice square ends. Great stuff and having black is a real plus. I would highly recommend the KAB-215 amp/BT combo. It is a plug and play unit and has lots of options including battery power. It would be a good fit for the RS-75's. It will have no noise and is backed by PE's 5 year warranty. There really is no better amp/BT system or boom boxes.

          For more low end you might give the PC83 drivers a look. Smooth little driver and it won't break the bank. It will perform better in the low end than the RS75. The great thing is, there are lots of options.

          Thanks! It'll have to be next time. I'm all set with everything here to start building. I'm making two of them for Christmas presents.

          Comment


          • #6
            You may want a contour filter on the driver so that the sound is more balanced, more bass (baffle step correction), and less shouty in the midrange region.

            This is just a quick example -- see pic. You'd get a better sound, but less sensitivity.

            You may also want to consider a tweeter to add to the top end if you're young and can still hear that top octave well (10k to 20kHz). That way the bump from 3k to 5k could be brought down with a crossover and then the tweeter would take over.
            Click image for larger version

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            total cost about $4 per driver

            https://www.parts-express.com/075mh-...ctor--269-2120

            https://www.parts-express.com/dayton...istor--004-4.7

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            • #7
              Originally posted by ceiol View Post
              You may want a contour filter on the driver so that the sound is more balanced, more bass (baffle step correction), and less shouty in the midrange region.
              +1. can be added after the build and a listen ... after the drivers are broken in a bit.

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              • #8
                Originally posted by Matt Clara View Post


                Thanks! It'll have to be next time. I'm all set with everything here to start building. I'm making two of them for Christmas presents.
                To warn you...building as gifts as how it starts. Then it is for a friend. Then you realize that you can actually build a speaker and you will start finding very good reasons to add to or to build your own...thats how it starts. You have been warned.
                "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

                The Madeleine
                The Roxster
                Swopes 5.0
                Acoustic Panels
                Living Room Make Over

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                • #9
                  You could always glue up some wood and drill a 3/4" hole to get your port... That's probably what I'd do.
                  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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                  • #10
                    If PVC is used for the port be aware that 3/4" schedule 40 PVC pipe has an inside diameter of .824 and 1/2" an inside diameter of .622. The area of the 3/4" pipe is .533 sq in while a "real" 3/4" opening has an area of .442 sq in. The actual .824 diameter of the PVC is 120% larger and would lengthen the port. You might be abler to use two 1/2" pieces of PVC but the guys that know what they're doing would need to comment on that option.
                    Attached Files

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                    • #11
                      Click image for larger version

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                      Be aware that 3/4" PVC has an inside diameter of .824 for an area of .533 square inches while the area of 3/4" is .442 square inches. The actual pipe has an area 120% larger than the 3/4" dimension which will have an impact on your port calculation.

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                      • #12


                        Be aware that 3/4" PVC has an inside diameter of .824 for an area of .533 square inches while the area of 3/4" is .442 square inches. The actual pipe has an area 120% larger than the 3/4" dimension which will have an impact on your port calculation.

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                        • #13
                          Thanks everybody for your comments! Real rabbit hole, this speaker design thing, eh? Yes, I'll need to perfect my design--or build something completely different.

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                          • #14
                            If you could make those internal cubes only about 2" larger, you could get another octave and a half of bass using a Dayton ND90-8 (or its AURA NS3 equivalent).
                            Nearly down to 50Hz, instead of 140-150.

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                            • #15
                              Originally posted by Millstonemike View Post

                              +1. can be added after the build and a listen ... after the drivers are broken in a bit.
                              Except they're going to be given away come Christmas morning, so if I'm going to do it, it has to be at assembly time. Are they really just wired in a Y on the positive side? It looks easy enough. What's the preferred method of fastening them down?

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