Port tube ?

Discussion in 'Archived Threads 2001-2004' started by David_Merrow, Nov 13, 2001.

  1. David_Merrow

    David_Merrow Stunt Coordinator

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    I have a friend new to DIY who is looking at building the SBB4 adire design for a Tempest. He would like to know the difference between using flared ports or nonflared? The two tubes he is looking at are from PE. One is $1 and has one end flared (maybe) and the other is a PNR AeroPORT valued at $16.50 each with flares on each end.
    Is there a difference between the two? If so, is it worth $15?
    thank you
     
  2. Dustin B

    Dustin B Producer

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    Flared port ends are supposed to make it so a particular port diameter can sustain a higher port airspeed with out creating port noise (don't know why, but I trust the guys with more fluid dynamics education than me that told me so). Using a tempest and a 4" port I would strongly recommend the flared port ends. Most of us doing ported tempest's are using 6" ports. Although several people, such as Hank F, have had excellent results with the tempest and a 4" flared port.
    ------------------
    Dustin
    [email protected]
    My Adire Tempest Sonosub
     
  3. David_Merrow

    David_Merrow Stunt Coordinator

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    The Adire box blueprint calls for two 3" ports. Would you recommend otherwise (4" or 6")? Why?
    Also, Adire's plans are for 3/4" plywood/particleboard. Is this thick enough? Would you recommend thicker? If so, how do you achieve that thickness? Glue two 3/4" sheets together? or maybe two 1/2" sheets? That box would weigh a ton....
     
  4. Dustin B

    Dustin B Producer

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    With adequit (god i can't spell today) bracing 3/4" ply should be fine, although make sure it's void free ply, otherwise you'd be better off using MDF. If you want to go overkill, then sure, just laminate two 3/4" pieces together and use 1.5".
    As for the ports, there are some other factors, but it really comes down to cross sectional surface area. Two 3" ports have a surface area of 14.1 square inches, while a single 4" port has a surface area of 12.5 square inches. A single 6" port has a surface area of 28.3 square inches. The greater the cross sectional area the lower the port air speed will be at a given output.
    So you have to compromise. Wider ports, need to be longer to tune low. Narrower ports can be shorter to tune low but have a higher port airspeed at a given output. Whether that port airspeed is audible will depend on the output level and whether the port is flared or not. Its safe to say you won't hear any port noise with a 6" port. With twin flared or non flared 3" or a single flared or no flared 4", you may or may not hear port noise. It depends on how much power you feed the tempest, what levels you like to listen at and how sensitive you are to port noise.
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    Dustin
    [email protected]
    My Adire Tempest Sonosub
     
  5. FrankD

    FrankD Stunt Coordinator

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    ............
     

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