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RST28F-4 and RS150-4 2-Way Build

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  • RST28F-4 and RS150-4 2-Way Build

    I want to build some bookshelves for a friend with these drivers but cannot find any existing builds online. This will basically be a smaller version of the Samba with a 6" instead of a 7" woofer. Has anyone designed a crossover for these speakers yet? This will be a gift so I'd rather not fumble through this on my own. I'm comfortable building but not designing yet!

    I've got a few specific restrictions but still have some flexibility with the design.

    - The maximum size is an 8"x7.5"x14" cabinet with 1/2" baltic birch ply. My calculations put this at about 11 liters or .4ft3.
    - The metal grill on the RST28F is a major reason for choosing them as these speakers will be near a well-trafficked area but I'd rather not mess with making a fabric grill. I'd like to use the RS150 or RS150P but I'm open to other woofers that are all black and fit in an 11-liter cabinet.
    - They will be a few inches from a wall in a 20x20 room and I'd like to use a front port.
    - One of the requests was Bluetooth compatible and I've used some bluetooth boards in the past, but the Lepai LP40PA https://tinyurl.com/2p9fnd74 seems to check all of my boxes. Bluetooth, aux-in for a record player, the power switch for ease of mind. Will this be enough power for modest volume levels?
    - Under $300

    Any input would be greatly appreciated!

    Thanks!
    Last edited by DinoRhinoDance; 12-08-2021, 10:56 AM.

  • #2
    Tyger23 did a speaker names the Arias that used the RS-150-4 and the neo version of the XT25. I heard them at the Lone Star Audio Conference and was impressed. I built a pair and donated to a local Hot Springs local radio station who seemed very happy with them. They were not a big cabinet but I don't remember the dimensions. You might have to make adjustments to the crossover placing them so close to a wall. Good luck.

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    • #3
      Here is the original post.

      https://techtalk.parts-express.com/f...-4-xt25sc90-04

      Comment


      • #4
        IF those dims are outside, then you've only got 0.35cf INside (not 0.40). Personally, I'd not go that thin for a box that size.
        The better news is that the paper cone should be able to almost get down to 50Hz in that size box, using a 1-1/2"id by 4" long port (the Al cone would be more like 60).
        They'll be X-max limited to about 25wRMS.

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        • #5
          The late Jeff Bagby did a RS150 design, the Dreydels.

          cjd has a RS150 design at HTguide forum.

          Neither use your tweeter.

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          • #6
            I recently designed and built a small pair of ported book shelf speakers that are that exact size and use the RS150P-8. They sound fantastic and a friend is using them in his studio to mix tracks. Unfortunately that design uses the no longer available RS28A. I'm sure the crossovers could be massaged to for the RST28F without too much trouble. I'm way too busy at work and with other projects to commit to helping though.
            Craig

            I drive way too fast to worry about cholesterol.

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            • #7
              There is also my "Jonquils" design that is in that same sized box and uses the RS150P-8 and SB26STCN tweeter. Many folks here heard them at InDIYana a few years ago and I received very positive compliments. Unfortunately those tweeters don't have a protective metal screen.
              Craig

              I drive way too fast to worry about cholesterol.

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              • #8
                About a year ago I built a full home theater system for someone and used the RS150-4 and RST28A-4 for the surrounds. My design was specifically built as a surround, so I built them to be installed somewhat high on the wall and angled down. I also designed the crossover with very little to no baffle step compensation, knowing that they would receive LF reinforcement from the wall. The front baffle was 8" wide x 13.5" tall and I had about a 1/2" roundover on all edges of the baffle. Since they were used in a HT with subwoofers, I built them sealed with an internal volume of about 0.18 cu ft. As long as you build speakers with similar front baffle dimensions, you should achieve similar response to what I had in the mid and high frequencies. Again, my measurements show the drop in LF response due to the baffle step, but since I installed them on the wall, that baffle step would be filled in.

                FYI, the dashed yellow line in the frequency response is the measured response of the finished speaker, to be able to compare to the simulation.

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                • #9
                  Originally posted by DinoRhinoDance View Post

                  ... an 8"x7.5"x14" cabinet with 1/2" baltic birch ply. My calculations put this at about 11 liters or .4ft3.
                  When you model the alignment for the little midwoofer, remember that the net enclosed volume utilized in the model equals the gross internal volume of the box less the volume displaced by the driver and port and any internal bracing (if not already included in your gross internal volume calculations).

                  "Our Nation’s interests are best served by fostering a peaceful global system comprised
                  of interdependent networks of trade, finance, information, law, people and governance."
                  - from the October 2007 U.S. Naval capstone doctrine
                  A Cooperative Strategy for 21st Century Seapower
                  (a lofty notion since removed in the March 2015 revision)

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                  • djg
                    djg commented
                    Editing a comment
                    I get .34 cu ft.

                • #10
                  You guys are right, I didn't consider all of the extra components in my volume calculations. This will put me closer to 9.5 liters. Fortunately, it looks like this woofer should be okay in a smaller box, similar to the Arias. I already have 1/2" birch so I'm going to use a window brace and stick with what I have.

                  Ben, that crossover is incredibly helpful. I'd be happy to use the aluminum woofer and tweeter since I've got the RS180P and RST28F on my desktop build.

                  The final speakers will be about a foot from the wall, so a little further away than your build. Do you think that warrants some baffle step compensation? I'd rather err on the side of too much bass for this project.

                  I plugged the woofer into WinISD with a 9.5 liter cabinet and tuned it to 50hz. Seems like it should work with a 1.5"x 4.5" port. I'd like to place the port on the front so I'll need to bump the drives up a little bit on the baffle.

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                  • djg
                    djg commented
                    Editing a comment
                    My .34 cu ft was just from your dimensions, not extra components.

                • #11
                  Thanks for sticking with me djg, math is NOT one of my strengths! I found a conversion error in my calculations so now with bracing, drivers, and port included I'm down to 9.1 liters.

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                  • djg
                    djg commented
                    Editing a comment
                    My "old math" is slow but it gets me there.

                • #12
                  I made some adjustments to a resistor and a capacitor in the crossover to add some baffle step compensation. I'm not sure why my tweeter looks different in the simulation, it drops off around 15k. Everything else seems in order. Does anyone see flaws in my changes? I'm venturing out into deeper waters here and don't want to mess this up!

                  Thanks!

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