Variable tuning (port plug) for a Tempest

Discussion in 'Archived Threads 2001-2004' started by KyleGS, Feb 25, 2003.

  1. KyleGS

    KyleGS Second Unit

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    I'm interested in a Tempest design that will allow me to plug a port for low HT bass (20hz) then take out the plug for a high-out application (24hz). Here's what I have come up with... The box will be 194L net with three 4" PVC tubes- all at a length of 21.7". If all three are open- the tuning should be at 24.5 hz with a large bump (~1.2hz) around 30hz-48hz in free space. This would be very loud in that 35hz region. This should be interesting for rock music and surely fun at parties. If one of the ports are plugged- tuning would be right at 20hz which is very much like the SBB4 alignment. Does my math check out?
    Is there anything wrong with a design as such?
    Last question- what the heck do I use as a plug?
     
  2. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    Your math checks out fine, but I'm wondering how you will design three 23" ports to be positioned in a 194L enclosure. The reason I say 23" is because 21.7" appears to be the length of the center tube if you plan to use flared ports.

    There are water pipe plugs sold at home depot for around $5 each. I think it is a rubber o-ring that gets sandwiched between 2 plates by a T-nut and then expands to seal the pipe.

    I have a tempest that is tuned to 24hz and one that is tuned to 15.4hz. Yes they sound quite different, so I think having an adjustable box would be well worth it.

    Personally I don't think there's anything wrong with the design. I do recall that the port displacement must be subtracted from the total volume (194L), thus resulting in a bigger box. So your box will have to add about 0.5cf or 14L for ports.

    Good luck
     
  3. Pete Mazz

    Pete Mazz Supporting Actor

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    And if 2 ports are plugged, ~15 Hz tune.

    I like the idea. Great way to play with different alignments to get a feel for your likes/dislikes.

    Pete
     
  4. KyleGS

    KyleGS Second Unit

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    Thanks for the replies-
    I have a few questions for you guys.



    Chris how do you like the sound of the 24hz box? Do you like it for music or HT? How does it compare to the 15.4hz and/or sealed Tempest designs if you've heard them.

    Pete- do you think I would hear lots of chuffing if I did decide to go with one tube? Seems like a lot of air moving at sub 25hz [​IMG] .

    BTW- I plan on having a 28in tall box and the width will be around 31in. Its a weird shape (plant holder for under a window). The weird shape permits three 4in PVC tubes to line up in a row adjacent the driver. 7cf plant holder [​IMG]
    Its all for the SAF
     
  5. Pete Mazz

    Pete Mazz Supporting Actor

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  6. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    24hz tuning is great for hip hop and rock music. It even sounds great with home theater "booming" bass because it adds some extra chest pounding presence.

    The 15.4hz bass is a lot smoother and easier on the ears. It doesn't have the hump so it loses some kick/punch that I kind of like the bass to have. I feel a smooth bass response loses personality because it becomes neutral when playing everything. I suppose this is a good thing to some people but for some types of music, I just like bass that can knock ppls socks off.

    For movies and dance/rock type music I would definitely pick the higher tuning. For well integrated bass with the mains, and better musical accuracy for playing audiophile music I would choose the lower tuning.
     
  7. KyleGS

    KyleGS Second Unit

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    Thanks Chris- I think I'll try this out. I think 3- 4" tubes tuned to 24.5hz will be plenty loud for parties and weekends and the 20hz should be better for everyday listening.
     

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