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  • Build log: first design

  • jrand

    Member
    May 1, 2022 at 6:59 am

    Hello everyone,

    this is going to be a post for my journey while designing and building my first pair of speakers. I did build a pair of DINAS, but in this case I am also doing all the design efforts.

    My objectives are to build a pair of speakers specified for music, although I will be using them as well for my own living room, so TV output. I would like them to have a nice presence, accuracy and hopefully, to get as close to 30 Hz as possible.

    This all started after seeing what Toids did with the RS180 and RST28-F as a nice pair of floor standing speakers. At first I thought of trying to replicate his design, but as I delved deeper into the design process, I decided to step up the speakers.

    Now, the speakers will be a 3-way design with the following drivers:
    Woofer: RS225-8
    Mid: RS100-8
    Tweeter: RST28F-4

    In reality the RS100-8 is only a small bridge between the woofer and tweeter and maybe it is not the most appropriate driver for the design, but I had it lying around, so I will go with it for now.

    So, in WinISD I was able to get the RS225 to hit 31 Hz with a 48L (~1.7ft³) enclosure which should, in principle, be able to go all the way to 52W RMS. Trying to balance first port resonance with air velocity was quite hard, and I ended up compromising, going for a 70mm diameter port, tuned to 30.25 Hz.

    After thinking about where I would like to place the speakers, and also due to the fact that long cabinets will support lower frequencies as resonant modes (I might be wrong on this), I decided to go for a down-firing port on a dedicated stand. I want to be able to put them flush to a wall and like this also limit the height of the cabinet.

    I tried to account with all things that will be inside the cabinet reducing its net volume, and ended up with the design in the attached photo.

    There is some inspiration on the Wharfdale Linton speakers in terms of the stand, except I open a big hole on the top shelf to vent the port.

    The front baffle will be made with 22mm MDF. I was considering a double baffle, as I thought the point of the double baffle, even if for example considering 2x 1/2″ VS 1″ MDF, would be to have a baffle with a glue layer in between which might help with rigidity, but it seems that everywhere I looked the most important aspect was thickness and so, I decided instead to go for a single layer baffle. The rest of the enclosure will made of 19mm MDF, including the window brace. Below the RS225 there will be 2x 12 mm braces which will connect the front, side and back walls of the enclosure. The RS100 will have its own full box also made with 12mm MDF, that will then be glued only to the front baffle, instead of running the width of the cabinet. Although it uses 3 more parts than simply running a box along the top corner of the main enclosure, I think this will be much easier to build.

    I already ordered the parts of the box (I want to limit woodworking as much as possible as I can only work in my apartment) and will build it and start testing the speakers to then work on the crossover. I already have some preliminary designs, but only after having one box built, will I finish the crossover design.

    As it stands the speakers will be 277 x ~1040 x 378 mm³ (~10.9″ x ~40.95″ x ~14.9″ w:h:d) including the stand. They are only approximately 1.04m in height because I still did not decide about feet. They are a bit deeper than I would have liked, but its not too bad either. The main cabinet will be 720mm in height (28.35″).

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