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Down Firing Voxel with SA70 Amp

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  • KEtheredge87
    Originally posted by Kevin K. View Post
    Is this on hold until you finish the Heliums or do you need some help??
    Hey Kevin, this isn't on hold. I actually plan to cut all the materials to build the Heliums and this Voxel at the same time. I've been trying to build a cross cut sled for my table saw for the past few days, but I can't get the accuracy where it ought to be. I'm beginning to think I should have used MDF instead of 3/4 ply since I keep finding little places where the surface isn't as flat as I think it is!

    I'm pretty anxious to get cutting on the speaker cabinets, just gotta get all the tools lined up. I hate it when a project takes a lot longer to set up than expected.
    Last edited by KEtheredge87; 11-02-2016, 10:21 AM. Reason: Edited because smartphone text autocorrect isn't all that smart!

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  • Kevin K.
    Is this on hold until you finish the Heliums or do you need some help??

    Leave a comment:

  • KEtheredge87
    The Final Product!

    Click image for larger version

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    Attached Files
    Last edited by KEtheredge87; 01-28-2017, 02:14 AM. Reason: Adding pictures of the new kid on the block...

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  • KEtheredge87
    Driver Measurements, Performance Modeling, and Port Tuning

    At this point, I need to extend a special thanks to forum member Kevin K! Kevin encouraged me to pick up a DATS V2 system in support of this project to make sure I was achieving the same design goals that Paul Carmody set out in his original design. I've learned a lot through a lengthy discussion with Kevin, and I am really appreciative of his support.

    Driver Measurements

    Initial measurements of the TangBand W5-1138SMF subwoofer obtained from DATS V2 after a break-in (30 minutes of reference level sine wave at 50 Hz amplified with Dayton Audio SA70 amplifier, gain turned up until just before audible distortion) Note: The values reported by DATS would change a little bit from run to run, which is why the text output and the graph don't match 100%. The values are still fairly close to the manufacturer's reported specs.

    This data was exported from DATS the Dayton Audio Test System
    Manufacturer: Tang Band
    Model: W5-1138SMF
    Piston Diameter = 104.1 mm
    f(s)= 46.43 Hz
    R(e)= 3.501 Ohms
    Z(max)= 24.21 Ohms
    Q(ms)= 3.95
    Q(es)= 0.6679
    Q(ts)= 0.5713
    V(as)= 4.661 liters (0.1646 cubic feet)
    L(e)= 1.33 mH
    n(0)= 0.06661 %
    SPL= 80.33 1W/1m
    M(ms)= 25.69 grams
    C(ms)= 0.457 mm/N
    BL= 6.268
    K(r)= 0.0531
    X(r)= 0.543
    K(i)= 0.01999
    X(i)= 0.6686
    Click image for larger version

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    Performance Modeling

    Kevin and I did a back to back comparison of BassBox Pro 6 and the latest version of WinISD to model the subwoofer enclosure and see where our port length needed to be. The target tuning frequency was in the low 40s (we went for Vb = 41 hz), which allowed us to have the same F3 of 35 hz on the system. Ultimately there were some differences between BassBox and WinISD, and we had to trust the data from DATS when we measured an impedance sweep.

    Final Port Tuning

    Using DATS V2, I measured an impedance sweep after constructing the port to the first length that was suggested by the programs. I ended up with a Vb of ~38 Hz, which was a bit low of my initial target of 41. After discussing with Kevin, I removed the second straight piece I originally had in my port and remeasuring, which bumped my Vb up to 40.37 Hz. At this point we called it good. Unfortunately this left me with some unpleasant chuffing noises during the testing phase. We redesigned the port length and flares to what is documented today and achieved better results... not 100% perfect, but certainly good enough for my use.

    Using BassBox, I made one final sim of this design as it was finished out. The Vb reads higher than my design, but the net Vb is correct based on subtracting internal driver volume, port volume, and Dayton SA70 volume.

    Click image for larger version

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    Last edited by KEtheredge87; 01-28-2017, 02:06 AM. Reason: Updating the modeling results for the final design.

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  • KEtheredge87
    Click image for larger version

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    Hello Everyone!

    Here are the drawings I generated in the design process. Full drawings for each piece are in the attached PDF.

    Final edits to this design were posted on Jan 28th 2017.

    Attached Files
    Last edited by KEtheredge87; 01-28-2017, 01:54 AM. Reason: Finally completed updates to model based on final design. All documentation complete!

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  • KEtheredge87
    started a topic Down Firing Voxel with SA70 Amp

    Down Firing Voxel with SA70 Amp

    Hi Everyone,

    While searching for a set of designs I could build to replace an old 5.1 home theater in a box, I was directed to Scott Sehlin's Helium design as a satellite speaker and Paul Carmody's Voxel subwoofer designs. A big THANK YOU to both of you for sharing your designs with us!

    With respect to these gentlemen, here are their original design threads:The more I dug into the Voxel design, I realized I was modifying it enough to warrant a build thread, so here it is. My two design goals for this modified Voxel subwoofer are pretty simple. First, I wanted to change the driver arrangement to allow a down firing subwoofer since this will live near a high traffic corner of the living room (no feet accidentally kicking the driver!) Second, I wanted to incorporate the Dayton Audio SA70 plate amplifier into the rear of the cabinet for simplicity of powering the sub, as well as aesthetics. I'll be using the same Tang Band W5-1138SMF subwoofer that Paul used, and doing my best to keep the same ported chamber volume and tuning. We'll see how this turns out!

    Build Photos:
    I'm spending more time working and building rather than documenting, so if anyone wants to follow along, here's the shared google photos album for this build
    Last edited by KEtheredge87; 12-11-2016, 03:25 PM.