Results 1 to 3 of 3

Thread: Port question

  1. #1
    Senior Member LE15-Thumper's Avatar
    Join Date
    Feb 2004
    Location
    Winnipeg, Canada
    Posts
    602

    Port question

    I have noticed that port theory dictates that as a port gets bigger in diam it's length must also get longer. And as it gets smaller, it gets shorter. No puns please !
    Question: why does one need to use a port that is 4" in diameter when a 2" would work and be a lot shorter and hence easier to work with.

    I know that the small port won't move as much air, but there has to be more to it ?
    LE15-Thumper
    "Give me JBL, or give me death"

  2. #2
    Senior Member edgewound's Avatar
    Join Date
    Jun 2005
    Location
    Southern California
    Posts
    2,776
    Has to do with the efficiency of the port itself...a smaller port creates more friction...and chuffing, or wind noise. The JBL Enclosure Design Reference Manual should have a better explanantion.


    Edgewound

  3. #3
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Location
    Berkeley, CA
    Posts
    9,963

    Port noise.

    It's the velocity if the air moving in and out of the port, which should be kept below 0.10 mach (speed of sound in air) at max SPL for the design. Below 0.05 mach is better, even.

    If the port's too small, it will huff and whistle at high volumes. It it's too big (and thus, too long) it'll start resonating like an organ pipe....

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Cabinet size vs. port displacement
    By johnaec in forum Lansing Product Technical Help
    Replies: 12
    Last Post: 08-15-2005, 07:33 PM
  2. Non-Searching Newbie Question solution?
    By Regis in forum Forum Feedback
    Replies: 7
    Last Post: 05-04-2005, 07:12 PM
  3. JBL 3110 crossover question and aftermarket diaphragm report
    By molecularman in forum Lansing Product Technical Help
    Replies: 4
    Last Post: 04-24-2005, 07:51 AM
  4. Port tube availability ?
    By buzzmarr in forum Lansing Product Technical Help
    Replies: 14
    Last Post: 12-30-2004, 01:46 PM
  5. Port size change.
    By vifa32144 in forum Lansing Product Technical Help
    Replies: 9
    Last Post: 03-15-2004, 09:44 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •