designing and building a subwoofer

Discussion in 'Home Theater Projects' started by Ryan_Mk, May 23, 2003.

  1. Ryan_Mk

    Ryan_Mk Extra

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    Hey, I'm interested in building a subwoofer with a driver I have. Though I'm not sure where to find good software for designing it or even where to really begin. Please help.

    Here are the specs.

    Bumper 450 watt speaker

    Qes: 6.34843
    Qms: 3.61839
    Qts: 0.31782
    Vas: 5.85 cubic feet

    fs = 24.15Hz
    Diameter is 15inchs and the diaphragm is 12 inches

    With the Qts value its has to be a ported box, and I'm not really sure what to do though.

    Would a 300watt RMS amp be sufficient?


    Any help would be appreciated


    btw would a sonotube work good?
     
  2. TimForman

    TimForman Supporting Actor

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    Sure wish you had some more specs, especially Xmax. I plugged the numbers you provided into WinISD and it's showing a 2.72 cu. ft. enclosure tuned to 30.61 Hz with a 4" vent 10 inches long. Should be easy to do with Sonotube and I'm sure 300 W would be plenty. One thing that confuses me though, and this could have a big effect on the numbers, is you say the diameter is 15" and the cone is 12". That makes it sound like the frame is 1 1/2" thick. I don't think I've seen that before.
     
  3. Ryan_Mk

    Ryan_Mk Extra

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    Well its total diameter is 15inches. The diameter of just the diaphragm is 12 inches. The surrounding is 15 inches including the diaphragm.

    After going to a couple hardware stores and finding out I'd have to make out a special order to get an 18inch diameter sonotube I've been looking into different possibilities.

    Possibly a 21.75x21.75x15.75 incher, keeping in mind 1 inch insulation throughout the speaker.

    Does this sound good?? Here's a CAD I drew up to visualize it.


    [​IMG]
     
  4. TimForman

    TimForman Supporting Actor

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    What is the response you're getting on the Sonotube? The stuff comes many sizes. I had to do a bit of searching and a few phone calls but I finally found a place that could get any size I wanted. There's been many Sono-subs built with 24" 'tube. That's probably too big for your app but 18" or 20" would work. Check places that sell construction supplies, after all, Sonotube is a concrete mold. If that fails, you could build the box in your drawing. Looks ok to me. In that case, you might think about using Poly-fil rather than just lining the box.
     
  5. Ryan_Mk

    Ryan_Mk Extra

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    I found a distributor of sonotubing and I'm going to get a 18 inch diameter by 19.5 inch tube.

    I have calculated the space the driver will take in the box and compensated.

    Btw, should I make this subwoofer downfiring? As well, would this sub need insulation? Can the port be on the top if its downfiring? Would I hear the air moving?
     
  6. TimForman

    TimForman Supporting Actor

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    A very common design is to have the driver fire down and the port on top (SVS for example). One thing you have to consider is that not all drivers are made to compensate for gravity pulling them in one direction more than another. Quality drivers are designed to be mounted in any direction. You may find you have to have it fire horizontally rather than vertical. Most loudspeakers benefit in some fashion from having fiber or batting inside. For sonosub probably some batting glued to the inside of the tube will be good.
     
  7. Ryan_Mk

    Ryan_Mk Extra

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    I contacted the company for the second time. I don't have the model number but every single measurement I could make on the darn thing, and they still couldn't help me.

    "We have over 600 different speakers.. blah blah..."

    He said there was no way he would be able to help me without a model number, which was scratched off the speaker... The place I bought it has no idea what model number it is. Argh! Last time I get a dam Bumper Speaker from a second rate dealer who couldn't help me and just said yea, the speaker is good for anything you want!


    Its a single magnet, about 6.5in by 1 inch.
    The speaker cone is 12 inches in diameter with a 15 inch surrounding area.

    Bumper 450 watt speaker

    Qes: 6.34843
    Qms: 3.61839
    Qts: 0.31782
    Vas: 5.85 cubic feet
    Xmax about 5 mm
    fs = 24.15Hz

    I have two finished designs, but would rather use the sonotubing and a downfiring design. Risk it?

    btw: thanks a great deal for your help Tim. You are what makes this forum great [​IMG]
     
  8. TimForman

    TimForman Supporting Actor

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    Go for it! If nothing else it'll be a great experience. The nice thing about sonotube is that it's not that tough to tear it down and try something else.
     
  9. Ryan_Mk

    Ryan_Mk Extra

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    Thanks for all your help. I'll let you know how it turns out.
     
  10. Andrew Low

    Andrew Low Extra

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    Wait a second. Xmax of about 5mm?

    Hopefully you didn't pay very much for this. Based on the power handling of this driver, I'd suspect its not a very efficient driver.

    This Adire Shiva (approx. $180 canadian from creativesound.ca) has a 31mm Xmax and power handling of ~500W?.

    Now, its not all about Xmax. I built a cheapo car subwoofer using some $20USD 8" drivers from parts express, and they had 4mm of Xmax. However, compared to my Shiva.. wait, there is no comparison.

    If you have $250 to spend on an amp, dump that other driver if it really has 5mm of Xmax. Buy a Tempest (~$224 canadian) and buy an old receiver from a pawn shop or a friend $50. A buddy of mine built a sealed shiva and is driving it with an old 45w receiver (dual voice coils). It rocks. Maybe not as strong as my Shiva backed with 350Watts of pro-amp.. but still.. amazing feel it inside bass.

    Roo
     
  11. TimForman

    TimForman Supporting Actor

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    Yeah, I was trying to spare the bad news. If this driver cost more than $50 US then...anyway, I'm trying to be positive here. Chances are this is more suitable to car audio than home theater. You've already got the thing. Build the sonotube, play around with it, then put it in your car or sell it to somebody and reinvest the money into a quality driver. Live and learn. Lord knows I've done that more than once.
     
  12. Ryan_Mk

    Ryan_Mk Extra

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    I gave the sub to a buddy so he can try and sell it on Ebay for me.

    Thinking about an adire shiva with a vented SBB4 size enclosure...

    Could you tell me what program you used to find the port size?

    I already bought the ava250 PE amplifier and had spent $130 canadian on the driver. I figure I might as well get a good driver if I'm going to spend $300 canadian on an amp.

    The xmax could at the most be 7mm I believe for that 450 Bumper woofer.
     
  13. TimForman

    TimForman Supporting Actor

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    The Adire website will have all the measurements for you. If you like to play around with different numbers to see what happens you can download WinISD enter your numbers and see what you get. Sorry about the Bumper driver but you're on the way to a truly great performing sub.
     
  14. Andrew Low

    Andrew Low Extra

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  15. TimForman

    TimForman Supporting Actor

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    Ryan,
    Check out Andrew's website. He's graciously provided many of the tools to help you get the correct measurements if you want to use Adire's volume and port numbers converted for sonotube use.
     

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