Small speaker enclosure venting?

Discussion in 'The Projects Forum' started by tracecom, Oct 24, 2012.

  1. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    I have assembled a small amplifier and two 2-inch speakers in a small wooden (cigar) box. The enclosure is about 4 inches by 5 inches by 6 inches, and is essentially sealed except for two 1 3/4-inch holes that expose the speaker cones; the speakers are mounted tightly to the back side of the panel.

    I don't need or expect high performance from the speakers. The entire assembly will be used primarily to amplify human speech (podcasts, e.g.) that are stored on my MP3 player.

    My question is whether or not I should port the enclosure. I don't want to boost the bass; I just wonder if the speaker cones would move more freely if the box was vented, and if so, how small a vent can I get by with?

    Thanks.
     
  2. crutschow

    Expert

    Mar 14, 2008
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    It likely won't make much difference for voice frequencies whether the box is vented or not. If the lid is on the opposite side of the speakers, you can open in slightly to see if there's any significant change in the sound.
     
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  3. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Tons of cheap commercial hifis were made with small glue-sealed wooden speaker boxes and one speaker driver(often 4" or 6" driver), and worked reasonably well. I don't think it will matter that much with your two little 2" drivers.
     
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  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    If you know what speakers you exactly got, then there are programs to calculate the bass reflex opening.
     
  5. MrChips

    Moderator

    Oct 2, 2009
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    Every loudspeaker has a natural resonant frequency. If you put the two speakers in a sealed enclosure you will raise the resonant frequency and also attenuate the bass response. If you are not interested in building a bass reflex speaker which dampens the resonant frequency, just vent the enclosure at the back.
     
  6. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    I doubt venting will do anything good. The speaker has to be built for bass reflex, which means heavy magnet assembly and tight cone damping.

    In a sealed enclosure (acoustic suspension) the air actually damps and protects the speaker cone from excessive travel where it bottoms out and kills itself over time.

    I doubt very much any generic 2" speaker was intended for bass reflex. Iw would leave it sealed.
     
  7. MrChips

    Moderator

    Oct 2, 2009
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    I think we're pulling hairs here. With 2" speakers you are not going to rouse the neighbours. Vent or no vent will not make much difference.
     
  8. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    True, it's basically a tweeter and nothing can change that.

    I was just trying to point out that you can't just vent any speaker/enclosure and magically get more bass and/or better sound. The drivers have to be designed for bass reflex usage (typically low Q) to benefit from venting. many drivers, especially smaller ones, actually rely on an airtight enclosure to help limit cone excursion. Opening up the box can make them more likely to fail.
     
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