Push pull Sono sub?

Discussion in 'Home Theater Projects' started by Mark Wilson, Jun 27, 2003.

  1. Mark Wilson

    Mark Wilson Agent

    Joined:
    Dec 18, 2002
    Messages:
    30
    Likes Received:
    0
    Trophy Points:
    0
    Hi there. I own 2 tempests, only one in use. It's in an adire alignment sonotube. I was originally planning on building a second in the same design, but looking at the size of the beast, I'm not to sure if I'd be able to fit it!

    Plus, reading a thread recently in this forum, about having dual subs in a room and all the nasty cancelation issues and such, I don't have a meter or a BFD to do anything about it.

    It's in my front left corner, and the best 'other' place (for the second) would be either to the left or the right of the couch.

    Now, since I have 2, and I'd like to put both to use, I came to thinking.

    I still have a 8 foot tall section of 20' sonotube to make into whatever I want. I could turn it into a push pull sonosub!

    One on the top sticking with it's magnet to the top, visible to all. (Some may think it'd be ugly, I think it'd look quite.. interesting, no WAF to worry about here) And the bottom driver with the magnet sticking up into the tube. (I think that's right..)

    Would that 'work?' The adire alignment sounds excellent to me. It's the first subwoofer that's actually worked with 'my' taste in music. (Punk, hardrock) Previous, I had a Velodyne CHT 15. It was *very* sloppy sounding compared to this.

    Would I gain any sonic improvement (I really don't see how I could gain any, I'm perfectly happy how it is) More output? Less cone excursion?

    I could either make it sealed, or vented.

    Offer your thoughts, this is all in my head for now, so I haven't even started designing anything yet!

    Thanks!
     
  2. TimForman

    TimForman Supporting Actor

    Joined:
    Dec 4, 2002
    Messages:
    847
    Likes Received:
    0
    Trophy Points:
    0
    I think I'd be tempted to try a dual Tempest transmission line design. I'm fairly impressed with the Shiva TL I slapped together. This is Steve's dual Shiva TL sonosub.
     
  3. Joel X

    Joel X Stunt Coordinator

    Joined:
    Nov 21, 2002
    Messages:
    50
    Likes Received:
    0
    Trophy Points:
    0
    From what I have researched, a transmission-line is a great enclosure. Is there a program that like Winisd that will model a TL?

    Tim, did you add any taper to your TL?
     
  4. TimForman

    TimForman Supporting Actor

    Joined:
    Dec 4, 2002
    Messages:
    847
    Likes Received:
    0
    Trophy Points:
    0
    I totally cheated and found somebody else's numbers. I don't know of a program that runs the numbers for you. TLs have been rather controvertial in the past because there were no firm formulas. Maybe that's changed. I used Nick's numbers. There's some good info at quarter-wave.com though.
     
  5. Mark Wilson

    Mark Wilson Agent

    Joined:
    Dec 18, 2002
    Messages:
    30
    Likes Received:
    0
    Trophy Points:
    0
    I wouldn't even know how to begin building a transmission line in a sonotube. I'd like to keep this fairly easy, if it's at all feasable.
     
  6. Ryan Schnacke

    Ryan Schnacke Supporting Actor

    Joined:
    Feb 5, 2001
    Messages:
    876
    Likes Received:
    0
    Trophy Points:
    0
    If you're mounting a driver on each end of the sonotube, how can you make it vented? You'll have a 20 inch endcap and the Tempest is 15 1/4 in diameter. No room for flares, so you'll probably want at least 20in^2 of port area per woofer. Maybe you could do 3 3inch ports on each endcap but it'd be a tight fit. Easiest would be to just go sealed. You'll have to decide whether you're willing to give up some low-end frequency response.

    With this push-pull alignment you get all the advantages of having 2 sealed woofers - less excursion at a given SPL, higher SPL capability (compared to a single sealed woofer) - plus you cancel out all the even order harmonics. Technically I've heard that the odd-order harmonics are the unpleasant sounding ones, while the even-order harmonics can actually be pleasant sounding. But its distortion nonetheless.

    I'd prefer to mount the drivers in the opposite fashion where the bottom woofer's basket is exposed and the top woofer's cone is exposed.

    Don't forget to wire the woofs out-of-phase.

    An interesting alternative is the isobaric clamshell configuration. Its not often used because it requires twice the amplifier power as a single woofer and doesn't give any more SPL. But the big advantage is that your enclosure size is cut in half for any given alignment. And you still get the even-order harmonics cancellation. Wire out-of-phase for this configuration also.

    With the isobaric you could do a ported EBS alignment in 6 cu ft or an Adire alignment in 3.8 cu ft! You're happy with the performance you're getting now and you already have the 2nd Tempest. So if you'd be interested in making it smaller or trying an EBS without increasing the size, this is the way to go.
     
  7. TimForman

    TimForman Supporting Actor

    Joined:
    Dec 4, 2002
    Messages:
    847
    Likes Received:
    0
    Trophy Points:
    0
    Looking at the dual Shiva TL it seems the only real challenge is determining the Fs for the system from which you calculate the tube length for the 1/4 wave frequency. The rest of the project is about as simple as it gets. Build a box, put the tube on top, stuff and decorate to your taste. I wish there was some quick, easy math formula too. It almost seems like the favorite number is 35 Hz.
     

Share This Page