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  • Bedrails Project

    I figured it's time to start my project's own thread so I can document and ask questions in one place rather than cluttering things up with threads for each question. The goal for this project and series of prototype speakers is for me to learn-by-doing as I'm brand new to designing and building from scratch. I plan on building a series that will hopefully sound decent and get me to a point where I can be confident in using better drivers and taking a step up. I've taken the forum's advice to heart that the best way is to start out with a proven design and built a pair of C-notes with a textured rattle can finish, then move on to projects that will be learning experiences (this series), and eventually ones using better drivers that will sound good and look decent. I started out with minimal power tools (a 40 year old circular saw with an equally old 24 teeth blade, a cordless drill and clamps) and have been slowly trying to acquire things through craigslist, Home Depot and Harbor Freight. This is a shoestring budget project because $ are tight due to COIVD and it is called the Bedrails because the prototypes are made out of wood from my youngest son's bed. A few months back he came to me and said "My bed broke" which is his translation of he was jumping off the side bedrail one too many times and broke it. Aha - I know what I can use that for! Bed had survived 2 other kids and was almost 15 years old, and it's a great supply of MDF of varying thickness and width. My measurement rig is a very cheap jig for ARTA and REW based on the plans here and elsewhere, and a Dayton IMM-6. It's what I've got on-hand and can afford right now, and hopefully it will be good enough.

    I bought 4 of the Visaton W130s-4 5" and a BC25TG15-4, as well as a DX20BF00-4 and a Tectonic TEMB46C20M. Current plan is to start out with the Visaton and Peerless making a sealed TM and then port it; make a floorstanding vented MTM that can be plugged it desired (and possibly a TMM), then finish with a 3-way center channel using the DX20 and BMR as the mid. I selected the W130s-4 largely on cost and availability (back in July when driver stock was challenging), bearing in mind sensitivity and a driver that could be used either ported or sealed. I bought some 1' x 4' 3/4 MDF shelving (so much cheaper than sheets right now - sheesh) to have a stock when I get to finishing. I plan on that being a learning experience as well trying the MDF staining tobacco burst method that I saw here for a cabinet or two and then probably veneering, neither of which I've tried before.

    The speakers will go in an irregularly shaped smallish room for gaming, HT and hopefully some music listening. Width between speakers will be about 7' and listening position at the couch (against a back wall) will be ~7.5' - 9'. Speakers will come out 5"-10" from the wall with the TV, which is angled about 30 degrees. Room dimensions are ~12' x 13' if the angle wasn't there on the 12' wall. I'm guessing the ones I eventually finish cabinets for will be floorstanding MTMs.

    So far I've burned in the drivers, taken T/S parameters, and done some measurements in the prototype box I built. Unfortunately I've had some issues with the formatting of the FRD files for those but the FR measurements seem very close to the manufacturers specs in nearfield and at one meter. The T/S parameters for the W130s we're a good bit higher in Fs and Qts from Visaton's. Visaton had a a recommended TM size of 0.25 cf and I wound up with .44 cf or 12.5 liters. The idea for the first TM sealed was a surround use case with an F3 of approx 80 Hz. Even though 0.44 to me is too big for a surround I went forward with it anyway just to complete the design and then tear it down. Below are the T/S parameters for the first W130s and the rest are practically the same - very consistent but higher in Fs and Qts.

    Fs = 63.83 Hz
    Re = 3.70 ohm[dc]
    Le = 102.49 uH
    L2 = 124.39 uH
    R2 = 6.18 ohm
    L3 = 320.73 uH
    R3 = 1.72 ohm
    Qt = 0.53
    Qes = 0.62
    Qms = 3.82
    Mms = 7.23 grams
    Rms = 0.749310 kg/s
    Cms = 0.859898 mm/N
    Vas = 6.33 liters
    Sd= 72.38 cm^2
    Bl = 4.170500 Tm
    ETA = 0.26 %
    Lp(2.83V/1m) = 89.54 dB

    Added Mass - Constant Bl Method:
    Driver unbaffled
    Added mass = 6.25 grams
    Membrane Diameter= 9.60 cm

    Hopefully I will get the FRD and measurements in box situation worked out but I've got enough to go on for ordering a bunch of parts for a crossover and various possibilities (thanks to help in another thread on full and partial BSC) and will post more on that in the future. In the meantime, folks can have a laugh at my prototype TM box that was cut with a circular saw and drivers eventually flush mounted with a craigslist router (homemade circle jig and freehand). It's not remotely square in the back (I caulked the heck out of it internally and gave it a couple days to cure), but I measured the internal volume carefully and it is .44. As you can see I've got far to go in all aspects! I'll be back once I get the crossover parts and can measure again. It'll be interesting to see if the box size turns out to be too big. Thanks for folks generosity and patience with my questions - experienced insight is invaluable!

  • #2
    If it's any consolation, some people go to great effort to make non-square cabinets
    Francis

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    • Colonel7
      Colonel7 commented
      Editing a comment
      Good reminder - a work of art it is not.😎

  • #3
    I made some speaker stands from some old bedframe rails and a 2 x 12. Don't give up just because your first effort is not perfect.

    Comment


    • Colonel7
      Colonel7 commented
      Editing a comment
      Thanks for the words of encouragement. No intention of giving up. I'm not good at doing things the first time but persistence and repetition will help a lot. For the bedrails one of the pieces will be perfect for a future clamped router table fence

  • #4
    This is where I would be tempted to use the belt-sander to "trim" the edges flush so it looks like everything lined up really well...then let folks try to figure out if the edges/angles look a little weird because of the camera's perspective or wonder if they're too tired to be looking at speaker pictures on the internet right now. :D
    My first 2way build

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    • #5
      Originally posted by LOUT View Post
      This is where I would be tempted to use the belt-sander to "trim" the edges flush so it looks like everything lined up really well...then let folks try to figure out if the edges/angles look a little weird because of the camera's perspective or wonder if they're too tired to be looking at speaker pictures on the internet right now. :D
      That's how I routinely make cabinets: leave just a little edge protruding, then come back once it's all assembled and trim the edges with a file and sander. Then I pretend I'm really good at lining things up!
      Francis

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