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Any one emember "Billow" ports?

Discussion in 'Amps and Cabs [BG]' started by Wesley R, Nov 28, 2006.


  1. Way back in the later 60's I remember a cab maker (REH?) that had a rear port thatwas a door and hinge assembly. Supposedly the design was somewhat innovative , but developed from some old sound book.

    The theory was something like, ports are for specific freq. ranges to optimize speaker performance by limiting cone excursion or some such. The billow port automatically (from air pressure I guess) opened and closed thereby changing port size to the optimum size for the freq. being played.

    Now that I think about it, the door couldn't possibly react quick enough could it?

    I do know those were the loudest, deepest, smoothest sounding 2x15 JBL cabs I ever heard.


    Best of Luck,
    Wesley R.
     
  2. Standalone

    Standalone

    Jan 17, 2005
    New Haven
    I dunno, but it'd be fun playing with my doors a-flappin' for the whole world to see! :bassist:

    mmm JBL 2x15..... I've got to get back to playing rock soon. very soon.
     
  3. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    The flappin' door would act like a crude passive radiator, with an emphasis on crude.
     
  4. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Actually it resembles the Dynaudio Vario-Vent, a port tightly filled with porous material. Suffice it to say that the technology hasn't swept the industry.
     
  5. The Vario-Vent does indeed work within the application it is designed for.

    It operates the same way as adding a restriction to an open port using a few layers of nylon stockings. Vance Dickason touches on the Vario-Vent in his book.
     
  6. Sounds like a similar thing to the Mesa 'passive radiators' in their Scout cabs (basically a speaker with no voice coil/magnet, etc.)... those cabs sound GREAT... huge low end for their size... not sure how much can be attributed to the passive radiators though. The cabs have 'standard' rear ports, and a passive radiator on the bottom of the cab.
     
  7. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    A passive radiator works in almost precisely the same way as a standard port. What differs is that a drone cone takes up less box volume than a long ducted port, so it's more practical in smaller boxes. On the downside they're more expensive and can't be easily tuned.
     
  8. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    I use one in my car sub. I stuffed the port with foam, to give enough chamber compression to prevent over-excursion.
     
  9. seamonkey

    seamonkey

    Aug 6, 2004
    Do billow ports work best on the front or rear of the cabinet? :bag:
     
  10. Bassflute

    Bassflute

    Jun 24, 2006
    Vancouver
    Endorsing Artist: MTD basses and strings; Bergantino Amps & Cabs
    A TON; pick one up off the floor sometime and see what you get. The thing I don't like about the passive raditor system is just that - it's passive, and you have no control over it.

    Cheers,
    Cameron
     
  11. Bassflute

    Bassflute

    Jun 24, 2006
    Vancouver
    Endorsing Artist: MTD basses and strings; Bergantino Amps & Cabs

    My old Trace 1225 V combo (aluminum pre-amp front, 2x10's and a tweeter) and 15" extension cab had two sets of port stuffers - a set of solid plastic disk as well as a set of pourous 'port bungs' they called them. So you could run it multiple ways, and really tune the cab for the room. Wish more companies had that. It sounded TOTALLY different with the port wide open than stuffed, and since there was two of them in the front, you could do different combinations of them. The deepest was one port with the plastic disk, one wide open. the most 'hi-fi' was both stuffed with the porous stuff. The loudest (but boxiest) was wide open.

    Cheers,
    Cameron
     
  12. The port was in the back and it was relatively small, not big enough to wave around and produce sounn. I m thinking something about 4'-6" hihign and a foot or a little longer wide.

    Truly odd.

    Best of Luck,
    Wesley R.
     

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