Upward firing and port questions

Discussion in 'Archived Threads 2001-2004' started by Han, Nov 20, 2002.

  1. Han

    Han Second Unit

    Jan 13, 2001
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    Sorry, I've searched around, but most sub FAQs only seem to cover downward vs. side firing subs...

    I'm thinking of experimenting with a sonosub with the driver on top firing upwards. What characteristics, advantages, and limitations will this give me?

    On the bottom, I'm flexible with either sealed, or even multiple ports. My other question is, do the ports have to be aligned in any sort of symmetrical configuration pointing towards the driver?

    Oh, and other dumb questions: Do the sum of multiple ports equal one long port? ie, 2x(4"dia) 12" ports = 1x(4"dia) 24" port? And does port diameter matter as long as volume is the same (3" dia vs. 4" dia both having the same volume)?
  2. Patrick Sun

    Patrick Sun Moderator

    Jun 30, 1999
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    Most people worry about driver damage if you leave it in an upward firing position exposed to careless people/kids. If a driver can be used in a downfire position, then upfiring should be okay. But remember that some drivers can only be used in a sidefire position to the sag of the cone over time.

    As long as the ports have adequate air around the openings, it should be okay, some people avoid putting the port pointing towards the driver, but SVS does this with apparently little ill-effect in the sound quality of the bass.

    Length of port has more to do with the cross-sectional area of the opening of the port. So you just have to see how many port openings would sum for the needed cross-sectional area of the port opening for a given design.

    For example, if you wanted to use two 3" wide ports, that's same as solving for the length for 1 port (using WinISD, or LspCAD) that has the same cross-section area as two 3" wide circles, which is 4.243" wide (radius of 2.1215"). That's how it's done.
  3. Greg.K

    Greg.K Screenwriter

    Sep 15, 1998
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    Greg K.
    Multiple ports require TWICE the length of a single port for the same tuning. 1 4x24 port is equivalant to 2 4x48 ports - because you are doubling the area you have to double the length to achieve the same tuning.

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