Swan 305 Traditional Subwoofer Design Comments?

Discussion in 'Archived Threads 2001-2004' started by Stephen Hopkins, Aug 22, 2002.

  1. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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    I've been running numbers on doing a sub $200 DIY subwoofer and i think i've made me decision and ironed out my design.

    I'm planning on using a Swan 305 driver, 150w @ 4ohm PE plate amp, and a traditional enclosure made of 3/4" MDF. It will be tuned to 24hz using a PE 4-5/16" Adjustable port at 7". The internal dimensions will be 22.5" x 22.5" x 22.5", 11390.625 cubic inches, 186.7 L.

    I've calculated all this using WinISD. It looks fairly flat until it drops below -3db at 23.9hz. Does anyone see any flaws, or have any suggestions before i start construction?

    I know a sonosub might be a little easier to build, but finding 20" tube in a short length has proven impossible, plus cost wise, a full sheet of MDF is much cheaper. Also, i don't have to build a box for the amp. Also, i can get the MDF cut for free at the cutting stations at home depot or lowes.

    Now all i have to figure out is how to cut my holes for the amp, sub, and port. I may wait until i can get home to kentucky where i have all the necessary tools, but right now i'm in atlanta at college, so if there's anyone in the atlanta area who would like to swing by georgia tech w/ a router, feel free to (or i can come to you)!

    Any feedback would be great.

    Thanks a ton!
     
  2. Brian Bunge

    Brian Bunge Producer

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    Jack,

    I think you can find the specs on the Madisound website.

    Brian
     
  3. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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  4. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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    http://www.madisound.com/swan.html
    here are my WinISD results
    Driver : Swan 305
    Vas : 167.0
    Qts : 0.31
    Fs : 24.53
    SPL : 90.00
    --
    Project by : Stephen Hopkins
    Project for : you
    --
    Number of drivers : 1
    Box type : Vented
    Box size : 186.7 l
    Tuning frequency : 24.00 Hz
    Vent : 1 vent(s)
    0.178 m length for each
    0.110 m round
    Relative
    Freq Gain
    [Hz] [dB]
    20.00 -8.11
    22.00 -4.96
    24.00 -2.92
    26.00 -2.03
    28.00 -1.83
    30.00 -1.91
    32.00 -2.06
    34.00 -2.18
    36.00 -2.26
    38.00 -2.31
    40.00 -2.33
    42.00 -2.32
    44.00 -2.30
    46.00 -2.26
    48.00 -2.21
    50.00 -2.15
    52.00 -2.10
    54.00 -2.03
    56.00 -1.97
    58.00 -1.91
    60.00 -1.84
    62.00 -1.78
    64.00 -1.72
    66.00 -1.66
    68.00 -1.60
    70.00 -1.55
    72.00 -1.49
    74.00 -1.44
    76.00 -1.39
    78.00 -1.34
    80.00 -1.30
    82.00 -1.25
    84.00 -1.21
    86.00 -1.17
    88.00 -1.13
    90.00 -1.09
    92.00 -1.06
    94.00 -1.02
    96.00 -0.99
    98.00 -0.96
    100.00 -0.93
     
  5. Greg Monfort

    Greg Monfort Supporting Actor

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    FWIW, I used a bunch of these back before the Shiva first came out and settled on 5ft^3/20Hz (two 3" dia. vents 16.56" long) as the best overall compromise. Since the published specs haven't changed, neither has my recommendation. [​IMG] Tuned to 24Hz will make it underdamped before any room effects are factored in, so is a bit too high IMO.
    GM
     
  6. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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    With 5ft^3 enclosure, tuned to 22hz, the -3db roll off point would be arond 41hz. Will this produce the last octave bass that i'm looking for?

    What i just posted doesn't roll of 'til below 25hz. What would i gain by going w/ the significantly smaller cabinet that you reccomend?

    Tuning the box, however, doesn't seem to change the roll off point much, so i'm pretty open to any feedback on where i should tune the box to, # of ports, size of ports, and length of ports.

    Thanks
     
  7. Greg Monfort

    Greg Monfort Supporting Actor

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    The 0.31 Qts you're using is way too low unless you've measured one and it's that much different from the listed specs, and the ones I measured years ago. The pic shows the same small magnet so I seriously doubt it's this low. Real world in service Qts will be around 0.45, which will lower F3 considerably and flatten out the response. Sim it again with the higher Qts and see what you think.

    GM
     
  8. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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    Ok, i custom entered all of the driver specs from the madisound website, and there were some differences when compared to the pre entered WinISD info. Working w/ the new number, 5ft^3 internal dimensions, tuned to 20hz, i'm getting a roll off around 26hz. W/ it tuned to 22hz, i don't roll off until 23.9zh.

    I'm going to go w/ a single 4-5/16" adjustable port. This way i can play around w/ the tuning pretty easily and will probably set it somewhere between 20hz and 22hz, whatever sounds best.

    Does this make sense?

    thanks
     
  9. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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    New WinISD Data:
    Driver : Madisound Swan 305
    Vas : 166.5
    Qts : 0.39
    Fs : 22.70
    SPL : 90.00
    --
    Project by : Stephen Hopkins
    Project for : you
    --
    Number of drivers : 1
    Box type : Vented
    Box size : 5.750 ft^3
    Tuning frequency : 22.00 Hz
    Vent : 1 vent(s)
    10.71 in length for each
    4.31 in round
    Relative
    Freq Gain
    [dB] [dB]
    20.00 -5.31
    22.50 -3.00
    25.00 -1.81
    30.00 -1.01
    35.00 -0.79
    40.00 -0.68
    45.00 -0.60
    50.00 -0.52
    55.00 -0.46
    60.00 -0.40
    65.00 -0.36
    70.00 -0.32
    75.00 -0.28
    80.00 -0.25
    85.00 -0.23
    90.00 -0.21
    95.00 -0.19
    100.00 -0.17
    22.50 -3.00 22.50 -3.00
     
  10. Greg Monfort

    Greg Monfort Supporting Actor

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    WINISD doesn't factor in acoustic mass loading of the driver so the 20Hz tuning will yield an F3 around 20Hz, but yeah, sounds like a plan to me. The main thing is to get an in-room response that doesn't excessively overdrive it in the 25-40Hz BW, where there's lots of sustained peaks in movies these days.

    GM
     
  11. BrendanL

    BrendanL Agent

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    I built two of these before the current drivers were out as well. I used a 3.25 cu ft. and a 3x8" port. (I'm going from memory on the port size) Of course, that is not going to get the same extension as the 5+ cu ft enclosures being talked about here.

    They handle 250+ watts in that setup, I have had them over powered by a good amount. Currently I'm powering one of them with one channel of a crown ce-2000 amplifier. I sold one of them to my roommate and he is powering it with the PE 250 watt plate amp.
     
  12. Mark Seaton

    Mark Seaton Supporting Actor

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    Brendan???

    Those aren't the same Swan 305 subwoofers which used to reside at Purdue University? Is that you?
     

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