Question about the CS Ultra for Ron or Tom?

Discussion in 'Archived Threads 2001-2004' started by Dustin B, Jul 8, 2001.

  1. Dustin B

    Dustin B Producer

    Joined:
    Mar 10, 2001
    Messages:
    3,126
    Likes Received:
    0
    I was just curious why you went with three 3" ports instead of a single 5"-6" port?
    Is there some advantage to multiple smaller ports over a single larger one?
     
  2. John Morris

    John Morris Guest

    Possibly, they could use shorter ports and avoid some of the sonic problems inherent in using very long port-enclosure ratios. Then again, I'm no TV... or even a JG for that matter. [​IMG]
    ------------------
    Take Care,
    merc
     
  3. Julian Data

    Julian Data Second Unit

    Joined:
    Oct 5, 1999
    Messages:
    408
    Likes Received:
    0
    The more ports you add, the longer each length. The bigger the diameter, the more the length.
    The more the ports the lower the airspeed.
    ------------------
     
  4. Dustin B

    Dustin B Producer

    Joined:
    Mar 10, 2001
    Messages:
    3,126
    Likes Received:
    0
    Oops, I thought length was solely dependant on the cross sectional area of the ports. So if you take the cross sectional area of three 3" ports, you find out you need a 5.2" port to have the same cross sectional area. In playing with LspCAD some more I found out that the single 5.2" port needs to be several cm longer than the three 3" ports to achieve the same tune. Is space that tight in the CS Ultra that you couldn't use a single larger port, or are there other reasons?
    While I'm at it, why have you choosen to stick with 12" drivers in all your subs? Will the SS still be a 12"? Do you ever plan to make a 15" or 18" sub?
    Just curious of your opinions since I've delved into the world of DIY subs and still feel like learning more (even though I've already built mine).
     
  5. Doug_B

    Doug_B Screenwriter

    Joined:
    Feb 11, 2001
    Messages:
    1,081
    Likes Received:
    0
     
  6. PeteE

    PeteE Stunt Coordinator

    Joined:
    Nov 30, 2000
    Messages:
    63
    Likes Received:
    0
    The SS sub will use the same driver as the Ultra sub, but will be in a larger tube, about the size of the 16-46.
    ------------------
    [​IMG]
     
  7. Jack Gilvey

    Jack Gilvey Producer

    Joined:
    Mar 13, 1999
    Messages:
    4,948
    Likes Received:
    0
    I can only guess based on some quick WinISD sims, but I'd assume that they wanted to maximize port area with the available flared ports (3",4",6" as far as I know) and given enclosure length. Going from the one 4" port used in the 20-39 to two of them results in a length which wouldn't fit in the box. One 6" port is even longer. The 3 x 3" ports are already pretty long in approx. 4 cu.ft tuned to 19.5 Hz.
    So, I'd conclude that the area provided by three 3" ports is about all that will fit given the required length for 19.5 Hz tuning in 4 cu.ft. They provide about a 70% increase in port cross-sectional area vs. one 4" port, and, according to the numbers TV posted, don't start to compress until very high output.
    There was some discussion on driver size a while ago. (Very) basically, a 15" driver would need a much larger enclosure, which is bad for shipping, etc. The 12" driver in the Ultras exceeds the displacement of most 15" drivers, which is all that really counts.
     
  8. Tom Vodhanel

    Tom Vodhanel Cinematographer

    Joined:
    Sep 4, 1998
    Messages:
    2,215
    Likes Received:
    8
    >>>I was just curious why you went with three 3" ports instead of a single 5"-6" port?Is there some advantage to multiple smaller ports over a single larger one?>>I can only guess based on some quick WinISD sims, but I'd assume that they wanted to maximize port area with the available flared ports (3",4",6" as far as I know) and given enclosure length. Going from the one 4" port used in the 20-39 to two of them results in a length which wouldn't fit in the box. One 6" port is even longer. The 3 x 3" ports are already pretty long in approx. 4 cu.ft tuned to 19.5 Hz.
    So, I'd conclude that the area provided by three 3" ports is about all that will fit given the required length for 19.5 Hz tuning in 4 cu.ft. They provide about a 70% increase in port cross-sectional area vs. one 4" port,
     
  9. Jack Gilvey

    Jack Gilvey Producer

    Joined:
    Mar 13, 1999
    Messages:
    4,948
    Likes Received:
    0
     
  10. Ron Stimpson

    Ron Stimpson Stunt Coordinator

    Joined:
    Jul 19, 1998
    Messages:
    199
    Likes Received:
    0
    Jack,
    We could tell you that, but then we'd have to kill you!
    ;^)
    Ron
     
  11. Jack Gilvey

    Jack Gilvey Producer

    Joined:
    Mar 13, 1999
    Messages:
    4,948
    Likes Received:
    0
    Fair enough. [​IMG] I'll have to wait for TN to get one. [​IMG]
     

Share This Page