Cabinet ports

Discussion in 'Amps and Cabs [BG]' started by sixstringer506, Sep 8, 2002.

  1. front port

    29 vote(s)
  2. rear port

    11 vote(s)
  3. slots

    15 vote(s)
  4. somthing else

    2 vote(s)
  1. I was just curious about what type of ports are in everyones cabinets . What are the benifits or disadvantages of different types .
  2. gfab333


    Mar 22, 2000
    Honolulu, Hawaii
    Front slots for me, based on my Eden experience.

    Epifanis sound pretty good with their front port. I played a few gigs through a friend's rig.
  3. Front ports get all dimensions of your sound to the same place where they belong; towards the audience...'nuf said.
  4. I like to "feel the air" rear ports can have issues of some stages, the air will bounce off of walls, posters, lord knows what else. with fronts its always in the same place.

    Counterpoint. Some people think that moving air around the speakers can effect the sound in a bad way,

    Bag end vs. eden if you will. Both are great. but very different cab designs
  5. What difference does front ports vs. front slots make?
  6. At risk of getting flamed again, port location makes no difference at very low frequencies, unless the port is blocked.

    My current sub ports are located in the front, because there is sufficient room for a 6" diameter port.

    I'm currently building a cab for my newly acquired JBL E155 18" driver, and the port will be in the rear, due to having no room on the baffle board. The JBL will be in an SBB4 alignment tuned at 30 Hz with a modest 3" diameter port. The port air velocity is 0.09 MACH at 30 Hz under full power. This isn't a problem, but I will never hit it anyway, as I am moving back to all 4-string basses. Port air velocity is much lower at 41 Hz.

    The intent of the port is tuning the box. It has to have sufficient cross sectional area to avoid high velocity air noises. Shape isn't much of an issue unless it induces eddy currents (noise) in the air flow pattern.

    The larger the port diameter, the longer the duct required to tune it. This can induce organ-pipe resonances. A larger port area has a more linear response and less distortion than a small area port. It is a balancing act.

    The Eden top and bottom slot ports are a brilliant idea. The ports not only tune the box, but provide significant, multiple, reinforcements against buzzing and flexing of the inner cabinet walls.
  7. my Eden 112 has rectangular 'ports' on the bottom, and my ampeg 210 has 2 ports on the back, don't think my ampeg 15 is ported.

  8. Gavin -- I agree technically. With the small exception of sometimes having things behind the cabinet that make it dificult to position the cabinet.

    I once built a 2 x 12 tuned to 45 hz with side ports on a trapaziod box. (car audio) was one of the best boxes I have ever had.
  9. Rockbobmel

    Rockbobmel Supporting Member

    All my Eden cabs have top & bottom ports.

    I really would like to know if I could block up the ports somehow and see if this would tighten up the sound and make it punchier?

    Are any of the smaller Ampeg cabs sealed boxes. The site is do full of advertising, I can't get any important info from it.
    The catalog has nice pictures too, but is equally useless.

    This whole thing is frustrating and making me mental.

    No, I don't want to go with the 8-10.
  10. I believe that the 2 10 HE and 4 10 HE are both sealed cabinets.

    blocking the ports in vented cabs can cause damage to the speakers, as the cabinet and the speakers are designed to work together. Sealed boxes usually use different speakers.
  11. the Ampeg 210HE has 2 ports in the rear (round ones), and i'm guessing the 410 is the same, could be wrong though

  12. The Ampeg 410 HE 15 (H)E and 810 E are all sealed. When you get into the HLF/HL/HLN cabs, those are ported.
  13. Matthias


    May 30, 2000
    Vienna, Austria
    According to their downlodable spec sheets:
    810E: sealed (4 chambers)
    610HLF: 2 sealed, 1 ported chamber
    410HE: sealed
    410HLF: ported
    210HE: ported
    15E: ported
    215E: ported
    1540HE, 810HP: no sheet available
  14. username1


    Dec 28, 2005
    alberta canada
    I prefer rear ports because the mids sound so much smoother, tighter and focused. The reason for this is because the reverberated mids from in the cabinet arent directed directly to your ear garbling up your mid clarity. The rear port acts like a low pass filter and only allows the lows to come from the port to your ear leaving the mids uncluttered. Try them side by side.
  15. tadawson


    Aug 24, 2005
    Lewisville, TX
    One rear ported, one sealed. I frankly don't give a monkeys dork which design I have, just so the sound is what I want. Either can be good or just suck, depending on the cabinet designer.

    - Tim
  16. Petebass


    Dec 22, 2002
    QLD Australia
    Remember the old Trace Elliot cabs that used to come with port plugs? Blocking one port lowers the tuning frequency of the cab. Tonally, this causes the cab to start rolling off at a higher frequency, so you hear less bottom end. Wether or not this sounds "better" is subjective and depends on how much botom end you had to start with.
  17. HMZ

    HMZ Supporting Member

    Dec 21, 2003
    I like the ports facing forward because you can control the sound better. I find rear-firing ports can sound muddy or boomie if you’re in a corner of a room or tight agents a wall.
  18. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    This is only true of poorly engineerd cabs with insufficient internal damping material. A properly lined cab doesn't project mids out the port. A cab that does project mids out the port will also sound like crap in general as the same lining material that prevents this is crucial for smooth response.
  19. username1


    Dec 28, 2005
    alberta canada
    Guess i better stop trusting my ears then. I was always taught to trust my ears and ignore what "the experts" tell me. :meh:
  20. Petebass


    Dec 22, 2002
    QLD Australia
    Have you ever A/B tested the exact same cab where the only difference is the position of the port? I have! Bill's right. Any difference in midrange you're hearing is due to the sonic colouration of the speaker itself and has nothing to do with the porting.