Adding bracing for my sealed/ported SW-15 cabinet , +Questions, +Lotsa pic Updates

Discussion in 'Home Theater Projects' started by Joe.Kuta, Sep 21, 2003.

  1. Joe.Kuta

    Joe.Kuta Stunt Coordinator

    Jun 4, 2002
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    This number of pictures might constitute as a separate thread possibly in a different forum, but this is more an update + DIY question thread.

    First I installed the AV15.
    It was only after using 10-32 Hurricane nuts that the driver was fully sealed (using speaker caulk).
    Note :: The person I bought the sub from had put Dynamat and Acoustic Foam on all inside walls,
    which I discovered were useless.
    The Dynamat adds minimal mass, and the Acousic Foam only cancels higher frequencies.
    So I pulled everything out.

    This is the old speaker (sub+main) placement.
    AV15 Installed
    AV15 Installed Closeup
    AV15 Installed Top View

    My entertainment PC is the only source of audio.
    Audio Control (matching)

    I might or might not install this on the top/bottom.
    Precision Port Profile
    Precision Port Top

    Old Driver
    At this point I pulled the driver to properly install it,
    and took some pics comparing the two.
    Stryke Closeup
    Versus Top
    Versus Side
    Further Away

    Next I received the Rythmik amp with some upgrades.
    New Rythmik vs Old Audiosource
    Rythmik Size
    Rythmik Controls
    Rythmik Electronics

    I also took a set of pictures installing the new Rythmik into the old SW-15 cabinet.

    At this point, I realized proper speaker placement was long overdue.
    First, I bought some black shelf supports @ Lowes and threw my JBL S26 speakers high in the sky.
    (yes i know ear-level is best, but i prefer the raised studio look)
    Note the phatty black speaker cable.

    Right Speaker
    Center View of Room
    Left Speaker

    I took pictures of the speakers parallel to the wall,
    because I thought they looked best that way.
    Left Speaker
    Right Speaker
    Right Speaker 2
    Right Room Profile

    Speaker Receiver- Yamaha RX-595 Yesterday I was given a piece of furniture to put this in.

    The subwoofer is currently behind and to the left of my seating.
    The sound is improved, however there are still major dead zones.
    New Sub Placement (Side)
    New Sub Placement (Front)
    Rythmik Mounted

    Bonus Video :: 10Hz Excursion
    Requires DivX 5.05 codec.

    This ends my Show & Tell.

    Main Post
    It is apparent that at louder volumes, my SW-15 cabinet is not capable of containing the AV15's power.
    Much stronger bracing is needed.

    This picture shows the stock bracing.
    2 3" wide sidewalls run the height of the cabinet,
    and are attached using a groove and black glue.

    I need to brace the x,y, and z axis of the sub.
    Using either 1"/1.125"/1.25" round oak dowels, or 1.5" X 1.5" rectangular oak legs/supports.
    The size of the AV15 limits some bracing in the front.

    I can run 1 support between the front-left-top and the mid-brace, another from the midbrace-left-top and the back,
    and then the same for the front-left-bottom, front-right-top, front-right-bottom.
    4 Braces

    Two supports from top to bottom, in the rear section of the cabinet.
    Could also add 2 supports to the existing bracing, and/or 1/2" dowel bracing in front.
    2 or 4 Braces

    2 supports in the back, 2 supports in the front.
    4 Braces


    Assuming I use 12 braces,
    1" dowels would sum to 0.0932 ft^3,
    1.25" dowels = 0.1456 ft^3
    1.5" legs = 0.2670 ft^3

    Here are my questions ::
    1. Would my Front-To-Back bracing be effective?
    How does my bracing plan look?

    2. How much better would the 1.5" rectangular bracing be over dowels?
    I am trying to lose as little volume as possible.

    3. Here is a WinISD graph of Ported Vs Sealed
    Red = Ported, tuned to 25Hz
    Green = Ported, tuned to 22Hz (same port, polyfil added volume)
    Yellow = Sealed


    Right now my sub is sealed.
    It was suggested I use a Linkwitz Transformer,
    however I don't want to lose 5 or 8 or even more decibels, I enjoy a -lot- of bass.

    I have a 4" precision port that can be up to around 15" (16") long,
    which I can install in either the top or bottom of the sub.

    Should I go ahead and do that?
    WinISD says I should.

    /Note!! With 380W, at 30Hz I am just under 26 m/s
    and at 20Hz I am just under 36 m/s, which is just under peak air velocity for all frequencies.
    40Hz is 14.5 m/s, 50Hz is 7.5 m/s, etc

    +wow, that took me about 2hrs to write
  2. Joe.Kuta

    Joe.Kuta Stunt Coordinator

    Jun 4, 2002
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  3. Jack Gilvey

    Jack Gilvey Producer

    Mar 13, 1999
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    First, stop modeling and experiment with what you've actually got. Try all the available eq options on the Rythmic to see what it'll get you as far as extension and output sealed. If that doesn't cut it, add the port and play with the eq filters again. Given your choice of main speaker placement, I'm guessing you're much more concerned with quantity of bass than quality, so the 25Hz porting might make you happiest.
    You're in a position to try all these things, so do it.
  4. Joe.Kuta

    Joe.Kuta Stunt Coordinator

    Jun 4, 2002
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    What about the bracing?
    Would 1.25" dowels be about the same as 1.5" legs?
    Dowels would take up 4.1L while the legs occupy 7.6L,
    a difference of 3.4L.
    I guess that is negligible, and I should just go with the 1.5" legs.

    How does the bracing look?
    I will just try that out as well,
    but wanted to get a feel from here.
  5. Joe.Kuta

    Joe.Kuta Stunt Coordinator

    Jun 4, 2002
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    Low end response is a -lot- better, and I think having the port on the top fills the room better.
    Less of a dead zone @ listening position.

    I used around 1.5lbs/ft^3 density of polyfil, based on my calculations of internal volume.
    This is what was recommended for cabinet volumes up to 3ft^3 here ::
    However he was using a 1.4ft^3 ported cabinet.

    I might be a little high or a little low, for optimal density.
    I need to get my actual tuning frequency in order to find out.
    How do I do that?

    Anyway, on to the bracing, again.
    I didn't brace anything yet.
    I got -plenty- of the 1.5" X 1.5" X 36" Oak supports,
    you can see them in the pictures.
    I tried to cut one of them with a hand saw, and failed miserably.
    I need to find a table saw to do this right.

    Also, there might not be enough room to (without a great deal of aggrivation) stuff 12 supports into that tiny box.
    6-8 might be more realistic.

    I will definately have one support in the back going Left to Right,
    one in the front going Left to Right,
    two in back going Top to Bottom,
    and then I am still not sure if the bracing going from Front to Back would be effective.

    Luckily, porting the enclosure relieved a great deal of stress on the cabinet.

    The port runs perpendicular to the driver.
    The port is a little off center, further to the back (amp) of the cabinet,
    because I wanted to give the T-Yolk's air port a little room to breathe,
    cooling the voice coils.
    I allowed 0.875" breathing room, which is a little over its diameter of 0.75".
    I think this is fine.
    I also think it looks a little better slightly off centre.

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