New DIY Subwoofer Project

Discussion in 'Archived Threads 2001-2004' started by Conrad_S, Feb 8, 2002.

  1. Conrad_S

    Conrad_S Stunt Coordinator

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    I'm building 2 Blueprint 1203's in 16" Sonotube. The planned specs are:
    - 33" tall tubes (30" total inside height after endcaps)
    - double thick 3/4" MDF for endcaps
    - 4" flared port 20" length (tuned to 20hz)
    - driver 4" off the ground
    Not sure what amp I'll want to power these two.
    Any comments or suggestions on changes I should make are welcome. [​IMG] (Only things that won't change are the 1203's and the 16" sonotube, since they are already purchased)
     
  2. I sure hope you mean a 1203 per sonotube!...other wise there will be no room for the ports or one of the drivers!

    As designed, you have 3.3ft^3 in that tube. Modeling that, you will need a 22" long 4" port. The plot shows a ~-6db drop around 30hz and it raises to -4.5db right around 20hz. This should be fine with a bit of EQing. you may want to double check your port calculations.

    Also, download the Sonotube construction program that is at the bottom of the sonotube links page. Very helpful.
     
  3. Conrad_S

    Conrad_S Stunt Coordinator

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    Yep, dual 16" diameter 33" tall tubes, each with a single 1203.
     
  4. Conrad_S

    Conrad_S Stunt Coordinator

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    Those specs were recommended to me by Pat Morrissey, the guy in charge at Blueprintdrivers.com. Are you suggesting his calculations were wrong?
     
  5. Jack Gilvey

    Jack Gilvey Producer

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    The way I see it, the whole reason for using the Blueprint -03's is for the massive Xmax/displacement. Using a 4" port with it strangles the driver, I think. In 95L tuned to 20 Hz with a 4" port, you've got the big hump at Fb, and airspeed is insane at 20Hz with only 250 watts. I think the thing calls for PR's in a reflex, personally. Even with 500 watts, the 1203 in that box is only at about half of Xmax, but airspeed is so high the port would probably be glowing.

    Just my $.02.
     
  6. Conrad_S

    Conrad_S Stunt Coordinator

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    Hm, I'm at a bit of a loss now. Should I maintain the 33" high tube and just increase the size of the flared port to 6"? (A flared port will decrease port noise, right?)
     
  7. Jack Gilvey

    Jack Gilvey Producer

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    A 6" port will reduce noise and, more importantly, reduce dynamic compression. It will also be 53" long.

    Herein lies the quandry with trying to vent these high-excursion drivers which like fairly small enclosures. Give them enough vent area so they're able to perform at their capabilities, and the ports become much too long, a problem logistically as well as sonically. As I mentioned, this is what passive radiators are made for.

    This is from the Blueprint website:

     
  8. Conrad_S

    Conrad_S Stunt Coordinator

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    Is there anyway to incorporate a passive radiator into a sonotube design? (On top perhaps?) I'm set on a sonotube since finishing it will be relatively easy and the results should be pretty good. (MDF is much harder, IMHO, to finish properly)

    If that's not an option, what about putting both drivers in one tube?
     
  9. nope...because of the mass of PR's (sometimes as much as 4lbs) and a very soft suspension, PR's HAVE TO BE mounted vertically.
    the 1203 IMO is only good sealed (EQed/LT) or PRed....vents are not an option...unless you like the snorkel look.
    The 1503 on the other hand works vented as well.
    Since you will be getting a parametric EQ like the BFD (I do hope you plan on getting one..right?!!!!) then sealed may be an option for you! Drop them each in a 40L with 500-1000watts each and you are set!
    You could do a 1203 version of mine and Thomas W's 1503 sub. a 16-18" sonotube with a 1203 at each end...something like this:
    [​IMG]
     
  10. Jack Gilvey

    Jack Gilvey Producer

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  11. Brian Bunge

    Brian Bunge Producer

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    Conrad,
    The only way you can use a PR in a sonotube would be to lie the tube on it's side. PR's cannot be mounted horizontally.
    I'm also not sure what you hope to achieve by putting both drivers on a single tube. If you were going to use it sealed and then give it plenty of power (and EQ) that would work. Although, I guess you could put them in a really long tube so that you get proper length for the 6" port. But then a single 6" port would probably not be large enough in diameter to prevent the same issues that Jack mentioned with the single 4" port.
    Brian
    Edit: Well hell, it looks like we were all posting the same time![​IMG]
     
  12. Vince Bray

    Vince Bray Stunt Coordinator

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    Just to elaborate on the PR-never-up/down-firing rule, if you can get hold of a PR designed for low tuning the diapragm is usually 3/4 or 1" mdf. So imagine a piece of 3/4" mdf suspended with the typical surround foam and think what it does when you turn it such that gravity can pull it.
    Anyway, I agree with Jack that the PR in a cube is definitely a good way to go. You could build a box similar to the 15.4. Use your 1203s and some 15" PRs. Also you could use just two of the PR18 from stryke and just build the box an appropriate size. Intuition tells me that 4ft^3 would work fine, just like the 15.2 cube. Maybe someone will sim this, or I will if I get time.
    Another idea I've been kicking around might help get the port down to a manageable length while giving sufficient area. I started working out the details but haven't had time to really nail it down. Imagine a six inch port inside an 8-9" port. The six inch opens to the atmosphere, while the 9" port opens to the inside of the cabinet, but the opening is at the baffle where the 6" port opens to the outside. This folds the port back on itself and gives you effectively twice the port for the length. There are some calculations that need to be done here to make sure that the fold maintains the port area, and that the area between the ports is equivilant to the 6" port. This will not be as desirable as a six inch port straight due to the fold, and increased boundary effect from the outer section, but I think it might work quite well given the space constraint. The idea bothered me until I thought about all the TL designs that bend about many times. I think if done correctly you could really cheat the port longer.
    Now, this would only help you to get one 1203 in a 16" tube and use a decent size port, but a pair of these would be killer. I have noticed that the 8" nominal sonotube they sell at home depot comes in several diameters and they nest together for more efficient storage. This is simple enought to calculate, it just depends on the wall thickness of the 6" tube...
    Vince
     
  13. Pete Mazz

    Pete Mazz Supporting Actor

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    I think it would probably act like a TL at that point. In fact, one TL I saw used dual sonotube, one inside the other, as your port in port is described.
    I think you're in GM territory here.[​IMG] Greg, you out there???
    Pete
     
  14. Conrad_S

    Conrad_S Stunt Coordinator

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    So, it seems my options to get best performance are:
    - Since you will be getting a parametric EQ like the BFD (I do hope you plan on getting one..right?!!!!) then sealed may be an option for you! Drop them each in a 40L with 500-1000watts each and you are set!
    (This may not work since the 1203's are 7 1/4" from the mounting flange.)
    - Anyway, I agree with Jack that the PR in a cube is definitely a good way to go. You could build a box similar to the 15.4. Use your 1203s and some 15" PRs. Also you could use just two of the PR18 from stryke and just build the box an appropriate size. Intuition tells me that 4ft^3 would work fine, just like the 15.2 cube. Maybe someone will sim this, or I will if I get time.
    - Use a 33" sonotube with a bending port
    How much of a performance difference is there between the cube with PR, a sealed sonotube with dual subs, and dual 33" sonotubes with bending ports (to equal 53" in length)? What about sound quality/frequency?
    BTW, Anthony, that's a really slick looking sonotube you have there. [​IMG]
    *edit* Just thought of a 4th option. What about dual sealed sonotubes with a 1203 in each?
     
  15. Vince Bray

    Vince Bray Stunt Coordinator

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    I *think* that what makes a TL different is the lack of an interior volume in the equation. A TL is like a long tube of (more or less) equal cross-section, that extends from directly behind the driver. Imagine a woofer bolted to the end of a piece of PVC. I think the folded port would work, it would just take some effort to ensure the fold maintained the proper cross-section (more or less). You'd need some kind of fillet in the fold to take up the corner volume to some degree. Turbulence would be more, although being inside the pipe it would not be too bad *I think*. Also, you can use a bigger port than 6", maybe an 8" port and just find an outer tube the right size. Hmm, you could fold it more than once if you're slick....
    DIY disclaimer [​IMG] : If you choose this option, remember I haven't tried it yet, but I am considering it as one option to do an 1803. That one may turn out to be a slot that goes from the bottom front and then folds up the back of the cab.
    The PR design is a great simple option, although at more cost. The dual 1203 / PR18 would be unique to my knowledge, and you'd love the result with drivers on all four faces. PR designs are wonderfully un-compressed as Jack has alluded. They love volume, and will impress you with the ability to be dynamic way down low, and at outrageous volumes. Ported designs are somewhat cleaner in transient response but suffer more from compression the harder you push them. IMHO the PR is superior for max-spl HT use as it begs to be driven. The 15.2 kind of mocks you as if to say 'that all you can stand? Won't the volume go up higher?'
    The sealed option would likely be fine, but you'll need more amplifier power to feed an already hungry situation. Think Crown K2 or big Crest amp to be happy, $1k or better. The vented/PR options will probably be happy with 500 watts per driver (maybe a Crest VS900, about $500), whereas I would definitely get 1000 watts per driver if you go sealed.
    Vince
     
  16. Conrad_S

    Conrad_S Stunt Coordinator

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    Small note, these subs are intended for about 90% music and 10% home theater.

    So a sealed enclosure looks like it will cost the most since it will require the most AMP power to drive those 1203s? In its place I should build a dual 1203/dual 18" PR 3/4" MDF box?

    Wouldn't a sealed sonotube acoustically sound best though?
     
  17. Greg P

    Greg P Stunt Coordinator

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    So a sealed enclosure looks like it will cost the most since it will require the most AMP power

    Not necessarily. PRs arent cheap. For the extra $120 you could swing more of the juice you need. However like Vince said if you get a really nice amp high wattage will cost you. Ive been doing a lot of searching for amps and here are some of the best deals Ive found.

    In order:

    Crest LT 1000: Ive heard the crest amps are pretty

    amazing. One member said this class D amp

    put a more expensive (and rated to have

    more watts) Mackie to shame. Has a fan but

    is supposively a quiet one.

    Price: $479 free delivery. If you search

    Lt 1000 on yahoo there is a place

    that is called New England Audio.

    This is the cheapest Ive seen it.

    Retail is about $850.

    Im tryin to find one used, though I

    may just splurge and get this amp.

    QSC 1450: Supposivly these amps have great power

    reserves and are very stout amps. The only

    drawback is the fan is a tad noisy. I bet

    you could do a mod for this amp to resolve

    the fan issue.

    Price: $389. If you find a place that

    gives a best price offer you could

    probobly get it down to around $370.

    Crown CE 1000: Has a pretty good power reserve but some

    have said it doesnt perform as well as the

    the others mentioned. It does however have

    a quiet fan.

    Price: I saw a guy on ebay selling new ones

    for $379 plus shipping. Generally

    the best price on the net is around

    $440.

    If your going to use mostly for music sealed is your best choice. You could build a really tiny sonotube with each 1203 opposing eachother. This would be a lot of bass in a small space.
     
  18. Conrad_S

    Conrad_S Stunt Coordinator

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    Well, I have 12 feet of 16" sonotube to work with here, since the concrete store didn't want to sell it in pieces. I can probably build enclosures for every type of idea here. [​IMG] I suppose I'll give that "mighty midget" sealed idea the first shot.
    Forgive my ignorance, but how do I go about calculating the space needed for dual 1203s in one enclosure? Is it just the same size as if there was only one sub?
     
  19. each sub needs equal volume. Meaning, if you calculate that a single sub needs 40L, the two subs sharing a volume would need a total of 80L to share (40L+40L).
     
  20. Conrad_S

    Conrad_S Stunt Coordinator

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    Throwing one more idea out... what about lowering the tuning frequency of the port to say 25hz to shorten its length for the ported tube? (And at the same time greatly increasing the output)

    *edit* Give a bit more detail as to why I'm building a DIY. I have an SVS 20-39CS paired with a Samson S700. It sounds great, but it really lacks in output. I just want to build something that sounds similar while increasing the output - all for a cheaper/similar price.
     

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