I received my Tempest and the DT300 amp but...

Discussion in 'Home Theater Projects' started by ClaudeL, Jul 2, 2003.

  1. ClaudeL

    ClaudeL Stunt Coordinator

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    but I didnt buy yet the flared ports!!! I had in mind the SBB4 ported design, and Adire recommand to use two 3 inches flared ports but I doubt that it will be enough if I dont want to hear any port noise. Would it be better if I go with THREE 3 inches flared ports? If yes, what would be the center lengh of these ports? In WinISD, I saw like 21 inches but this is with ports with two flares, so I guess that the center tube lengh would be near 17-18 inches...

    I thought about something else too: three 3 inches flared ports with variable tuning. I would use foam plugs to tune the sub like I want. I saw someone in this forum using its Tempest this way... by blocking one port, the sub is tuned to about 25 Hz, with 2 ports blocked the sub is tuned to about 18-20 Hz like the normal SBB4 design. But when I simulated the 194 liter box tuned at 25 Hz (all ports open) with WinISD PRO, the FR curve didnt look too much flat. There was a big bump between 25 and 40 Hz, this is normal of course for that type of woofer... but would the sub sound "bad" because of this?

    Thank you in advance for all your suggestions and answers! :wink:
     
  2. Jonny K

    Jonny K Second Unit

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    Well I'd assume that if Adire (the company who makes the driver) recommends two 3 inch flared ports, odds are those will work well. I'd assume that they know what they're talking about. Also, go ahead and e-mail them and ask your questions. They are happy to help (from my experience). [​IMG]

    I made myself a Tempest using the Adire alignment and two 3" flared ports and guess what? I can feel VERY little air moving in the ports. I think it's one of the properties of a flared port...so no worries.

    Remember, more port is not necessarily better!

    http://www.adireaudio.com/tech_papers/vent_sizing.htm


    Jonny K. [​IMG]
     
  3. ClaudeL

    ClaudeL Stunt Coordinator

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    113 views and only 1 anser? Comon! [​IMG]

    I know that too large would not give a good result... like too small. But you know, all the SVS PC+ still have three 3 inches flared ports and they are long! And you know, my VTF-3 has two 3 inches flared ports and I find that this is really the minimum because I find that I feel quite a lot of air coming from the ports when it is loud. Considering that the Tempest can move like 2 times the amount of air, Im affraid that only two 3 inches flared ports would be enough.

    So I ask this question to all the Tempest owners... if you push your Tempest at its maximum, do you hear any port noise from the two 3 inches flared ports? Im just affraid, I want so much the perfection from my DIY sub [​IMG]

    And do you know any dealers in Canada who sell 3 inches flared ports?

    Thank you again [​IMG]
     
  4. ClaudeL

    ClaudeL Stunt Coordinator

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    Ohhh! I forgot...

    I know that some persons have made their Tempest sub a variable tuning subwoofer with three 3 inches flared ports... what is your feeling about this? Does it sound good when the 3 ports are opened? What are the tuning points?

    And do you gain any considerable output over a sealed Mid-Q design? Because I think about make it sealed too since I didnt buy the flared ports yet...

    Thank you again for all your ansers [​IMG]
     
  5. Seth_L

    Seth_L Screenwriter

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    Just because Adire recommends it doesn't mean it's properly ported. Even SVS subs are under ported. Check the air velocity in a simulation program and use the largest ports you can fit in the box.
     
  6. ClaudeL

    ClaudeL Stunt Coordinator

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    Seth,

    What program do you use to see that? Because with WinISD Pro, you cannot because the software doesnt use FLARED ports...
     
  7. Seth_L

    Seth_L Screenwriter

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    Claude,

    The velocities are still close. The flared mouths only prevent turbulence, but don't reduce the velocities much. At least that's my understanding. I think Unibox can compute flared ports.
     
  8. John Wes

    John Wes Stunt Coordinator

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    I'm using a Tempest with flared ports..the Adair alignment. I feel very little air comming out the ports..and when I'm cranking it, I don't hear any port noise..

    I just built it a couple of weeks ago.
     
  9. ClaudeL

    ClaudeL Stunt Coordinator

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    What would be the center lengh if I use three 3 inches flared port for a 194 liter cabinet tuned to 18.8 Hz? (Tempest SBB4 design). If you use two 3 inches flared ports, the center lengh is 5 inches. By the way, how do you calculate this? I think that I would feel more secure with 3 flared ports instead of 2. Thank you for your inputs! [​IMG]
     
  10. ClaudeL

    ClaudeL Stunt Coordinator

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    Oh! And also something that I dont really understand... The HSU VTF-3 subwoofer has two 3 inches flared ports and displace 2x less air than a Tempest. So is it true to say that a SBB4 vented Tempest may expel 2 times more air from its two 3 inches flared ports near its tuning point (compared to the Hsu sub)?

    So guys, this is why I feel unsafe for the Tempest if I use two 3 inches flared ports. I think constantly that with two 3 inches flared ports, I could hear port noise considering that with the Hsu, I can feel the air coming from the ports when it is pushed real hard (but not hearing it).
     
  11. Justin Ward

    Justin Ward Supporting Actor

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    I built an SBB$ Tempest and used 2 3" PVC ports(non-flared). I only notice port noise when I crank a deep tone like 18hz really loud. I've never noticed it during a movie though. I think my porting may be restricting the Tempest a little though, so I may change boxes later.
     
  12. Allen Ross

    Allen Ross Supporting Actor

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    i got dual 4 inch flared ports and i really only notice a lot of air moving when i am listening to a 25hz note or lower, (aww common who here doesn't sit down and listen to test tones and sweeps for the heck of it [​IMG] ) around 19 or so its really moving, i am always amazed at it.

    if you can get 4 inchers into the box alignment go for it
     
  13. ClaudeL

    ClaudeL Stunt Coordinator

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    For my SBB4 Tempest box, the internal dimensions are:

    23x23x24 (HxWxD) -> 209 liters with the woofer, braces, ports (two 3 inches flared for the moment), and amp but without all of these: 194 liters.

    Two 4 inches flared ports can be a great idea but they would have to be a bit longer than three 3 inches flared ports if Im doing well my math calculations! Two 3 inches flared ports may be good for not hearing any port noise but I saw somewhere Dustin telling that it is not really enough if you want that your tempest works at its best (port compression certainly).

    So yessss, two 4 inches or three 3 inches FLARED ports (at both ends) may be superb but I DONT KNOW how long they must be for my 194L SBB4 box!!! How can you calculate this? Could someone tell me? Im all ready to make the sub... but I just didnt buy the flared ports yet because I dont know to much what to do!!!!!!
     
  14. GeoffM

    GeoffM Agent

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    winisd says 3 3in ports should be roughly 22inches long. That's with straight pipe. Two 4 inch ports should be just under 26 inches. Again that's with straight pipe. I forget how much you take off if using flared ports. I think it's 4/5 inches. Better let someone else chime in as I'm still a newbie [​IMG]

    -Geoff
     
  15. ClaudeL

    ClaudeL Stunt Coordinator

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    Geo,

    This is what I figured out with WinISD PRO! Its why I said that two 4 inches flared ports would have to be longer than two 3 inches flared ports so this might not fit into the cabinet :b If only WinISD could be able to cacluate the lengh of flared ports according to the tuning point of an enclosure! [​IMG]

    I'm always waiting for buying those flared ports [​IMG]
     
  16. Justin Ward

    Justin Ward Supporting Actor

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    I think Adire has 3" ports simply due to space limitations. The 4" ports would come too close to the top to let them work well I think. You could change the cabinet dimensions to make it taller and slimmer, this should allow the 4" ports. Although, the SBB4 is really meant for lots of mid-bass impact, not extension like the EBS design.

    Another question for the port experts out there. Would it be a good idea to roundover the ends of my ports? It would make it look better I think and it might help port noise(which is already almost non-existant). This wouldn't change the tuning of the sub at all would it?
     
  17. ClaudeL

    ClaudeL Stunt Coordinator

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    But with the SBB4 design, your still able to go low very well, down to 18 Hz. I have my hopes on the 4 inches flared ports because if you use two 3 inches flared ports, the tube center lengh is 5 inches for each port. I doubt that the center lengh would be more than 15 or 20 inches for a pair of FP4 vents.

    More I think about it, more the thread title should be like "porting a Tempest SBB4 box" [​IMG] For the moment, I think that the title is a bit misleading...
     
  18. Brian Bunge

    Brian Bunge Producer

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    Guys,

    It's very simple. Simply add 1" to the total length of the port when going from a straight pipe to one of the dual flared ports like Adire, PE, and Madisound sell.
     
  19. ClaudeL

    ClaudeL Stunt Coordinator

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    I finally bought my ports [​IMG] I will tell you what I chose later tonight because I must go to work rigth now. All I can say is that Dan Wiggins from Adire Audio has been really helpfull for my decision. Thank you Dan!!! [​IMG]
     
  20. ClaudeL

    ClaudeL Stunt Coordinator

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    Hi all! As promised, I tell you what ports I bought!

    I chose the pair of 3 inches flared ports after talking to Dan Wiggins. In resume, this is what he said to me on the phone:

    Those who use two 4 inches flared ports are the freaks who want the every last decibel of their subwoofer. Sure, you would be a tad better with two 4 inches flared ports because in that case, you wouldnt have to worry about port compression. They might not fit in your enclosre if you keep the same dimensions. You would have most likely to change the depth and the height of your subwoofer in your case if you want to fit the 4 inches flared ports. BUT even with two 3 inches flared ports you would be just FINE! You would loose like 0.5 dB of performance in that case because of some port compression that may occur with some materials and I CHALLENGE YOU to detect this difference. 0.5 dB is really not a huge margin. Moreover, there are not so many movies or music which demand a lot of low 16 Hz bass so you should not hear any port noise. You may hear port noise if you listen to a straight very low test tone but in the other cases, with two 3 inches flared ports, you should be just fine! This is what we recommand in our plans and this is not for nothing... we have tested a lot of enclosure in our labs to determine this.

    So a big thank you to Dan Wiggins and I hope that other people who are worried about how to port their Tempest have read this message. Two 4 inches flared ports may be better, especially if you have a larger enclosure (I think about the EBS alignment) so you can fit them in it. But you are still fine if you go with two 3 inches flared ports. Effectively, Ive calculated the lengh of two 4 inches flared ports (thank you Brian) and for my enclosure, they are just too long and I want to keep the same dimensions.

    Now, I just have to wait for my ports and I immediatly begin to build that box! I predict that the sub will be built before the end of this week... hopefully [​IMG]
     

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