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Can a tuned cabinet get out of tune?

Discussion in 'Amps and Cabs [BG]' started by Skel, Apr 22, 2006.


  1. Skel

    Skel

    Jun 19, 2005
    Boulder, Colorado
    Just wondering; I read a lot about "hand tuned" ported cabinets. Can these get out of tune, or has anybody ever messed around with the tuning and gotten a better sound than the factory tuning?
     
  2. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    I would assume that "hand tuning" means measuring the port resonant frequency, comparing it to the designed value, and adjusting the length of the port as needed. At least for a DIY'er like me, it is a useful way to avoid screwing up and having a high port resonance that exposes the driver to damage on the lowest notes. But the resonant frequency is independent of the properties of the driver, and would not have to change from one box to the next in a production run.

    Also, from what I have been able to gather, you don't really have a lot of wiggle room on the port tuning -- too much above the lowest fundamental (40 or 30 Hz, choose your poison depending on whether you are a 4- or 5-stringer) and you risk driver damage. Too much below and the port has no beneficial effect. Given the small range that you are working within, I would not expect changes to have much of an effect.

    And unless you are measuring the response, you could end up with a fragile system. (Note that you can measure the response with my free software... click below).

    This is just my guess as a DIY'er, thinking about why I would ever want to try tuning the ports on my own cabs. Hand tuning could be a marketing gimmick -- stranger things have happened ;)
     
  3. To me, hand tuning means running an actual test on the completed cab to see if it is tuned correctly. I don't have any robots building my cabs, so every one of mine are hand tuned.

    :D

    Tuning changes if the cab develops leaks of any kind. The vent can be hacked to change the tuning. The duct length can be altered, and/or the vent area resized. The vent can also be blocked.
     
  4. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    Yes, a speaker cabinet can get out of tune if you work it too hard. I had an Eden 112XLT that I was running a bridged PLX3002 into. One night a chick dancing up by the stage kept pointing at the cabinet which was at about eye level for her. Finally I knelt down to have a look. A big piece of stuffing had come loose on the inside and was flapping back and forth in the port. By the end of the night the port was full of stuffing. Some of it blew out and collected along the bottom between the speaker and the metal grill. I'm sure this affected the cabinet tuning. But fortunately the volume coming out of the PA was so head-splitting loud that no one would know.
     
  5. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The tuning can be disrupted by damage to the cabinet and by aging of the driver; fs goes down as the suspension continues to loosen with use. You can alter the tuning easily, whether it will be an improvement is a subjective judgement.
     
  6. Skel

    Skel

    Jun 19, 2005
    Boulder, Colorado
    Yes, I was just wondering if a cabinet had a "tune" as in a guitar is "tuned" to a standard tuning, and whether the cab could get out of tune, like a bass guitar, for example.

    Also, I assume porting is to provide additional low end. With that said, do cabs with 15" speakers need to be ported?
     
  7. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Good points. I was not considering deterioration of the driver.
     

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