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  • Brian Steeves
    Junior Member
    • Nov 2000
    • 24

    Hi Guys

    Just wanted to say hi to you all. This is my first time here. Looks like a great site Lex!




    She said,"you're gonna put that thing WHERE!"
    She said,"you're gonna put that thing WHERE!"
  • Pat
    Super Senior Member
    • Aug 2000
    • 1637

    #2
    Welcome aboard Brian.

    Did you decide on a design for your Tempest yet?




    Pat's Page
    Pat's Page

    Comment

    • Bing Fung
      Ultra Senior Member
      • Aug 2000
      • 6521

      #3
      Welcome Brian!




      Bing
      Bing

      Comment

      • Brian Steeves
        Junior Member
        • Nov 2000
        • 24

        #4
        Pat,

        I think so. I'm pretty sure I'm gonna go with a 240l 17hz tune. The only thing I am concerned about it Xmax. It seems that some others are concerned about this as well. The LspCAD program shows huge amounts of excursion between 25-40hz.




        She said,"you're gonna put that thing WHERE!"
        She said,"you're gonna put that thing WHERE!"

        Comment

        • Andrew Pratt
          Moderator Emeritus
          • Aug 2000
          • 16507

          #5
          Welcome to the guide. I'm not sure if you've seen my site or not but I built a 250 liter sonosub using the PE 15" driver which is a clone of the tempest. There's an SPL plot on the site that might interest you given the similarity b/t our subs. (link to my site is below)




          Comment

          • JonMarsh
            Mad Max Moderator
            • Aug 2000
            • 15209

            #6
            Brian and others;

            Whenever you use an extremely low tuning in order to optimize the output in the 20Hz and below region, (say an Fb of 15-17 Hz)the problem you have is that 1 octave above that frequency the system is acting for all intents and purposes like a sealed box. That means there's little to no port contribution, and in the range from 32 - 45 Hz, the driver has to do all the work. Without the port involved, there's simply no replacement for displacement- a single 12" driver is going to have to work very hard if you're trying to feed it several hundred watts and get 110 dB or so out. Not really practicle. That's why in my mains, the box Fb is 26 Hz, and useful port output doesn't go away until above 50 Hz. This translates into 118 dB per cabinet from 28 Hz to 200 Hz in the bass system, which is an Audax 13" pro and Audax 15.5" pro (it's a bit bigger than a std. 15") driver. When the Tempest's are available (some day, some day!!), then the dual subs with 2 Tempests per cabinet will get built; they'll be crossed over about 35 - 40 Hz, so that there is adequate overlap. Yeah, this is going to look a bit too much like a Greatful Dead PA system when it's done, but when you're not married, and can build odd shaped cabinets (plannig on two corner cabinets with beveled front panels), you have a few more options.

            Regards,

            Jon




            Earth First!
            _______________________________
            We'll screw up the other planets later....
            the AudioWorx
            Natalie P
            M8ta
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            Resistance is not futile, it is Volts divided by Amperes...
            Just ask Mr. Ohm....

            Comment

            • ThomasW
              Moderator Emeritus
              • Aug 2000
              • 10934

              #7
              Brian

              Also see the large signal vs small signal answer I place after your "Thomas you've got mail" post on HTF




              theAudioWorx
              Klone-Audio

              IB subwoofer FAQ page


              "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

              Comment

              • KennyG
                Moderator Emeritus
                • Sep 2000
                • 745

                #8
                Hi Brian, nice to have you on board, for such a small site we alot of DIYers, and beginning DIYers (that's me!) KennyG

                Comment

                • Brian Steeves
                  Junior Member
                  • Nov 2000
                  • 24

                  #9
                  John,
                  Not sure if you realize it or not but I have a Tempest driver for this project, not a Shiva.
                  What's wrong with the idea that in the 40-80hz range the sub acting like a sealed enclosure? I mean wouldn't that be a good thing? And if the amp power is available, and I think it is (850 watts into 4 ohms) this would be the best of both worlds. Good low end extension and tight midbass.
                  Now this is my first attempt at a ported sub, I have made several sealed ones over the years. I have always had good results with them.
                  Dan Wiggins is the one that suggested the volume and tune I mentioned.
                  What would you recommend if you were going to make one and why?




                  She said,"you're gonna put that thing WHERE!"
                  She said,"you're gonna put that thing WHERE!"

                  Comment

                  • Brian Steeves
                    Junior Member
                    • Nov 2000
                    • 24

                    #10
                    Patrick,

                    Why 3 4" ports? Dan says 1-4" flared or 1-6" non flared flared port is enough.

                    I am getting so confused with this port thing!




                    She said,"you're gonna put that thing WHERE!"
                    She said,"you're gonna put that thing WHERE!"

                    Comment

                    • ThomasW
                      Moderator Emeritus
                      • Aug 2000
                      • 10934

                      #11
                      Brian,

                      Jon is talking about 3 different systems

                      1)
                      Whenever you use an extremely low tuning in order to optimize the output in the 20Hz and below region, (say an Fb of 15-17 Hz)the problem you have is that 1 octave above that frequency the system is acting for all intents and purposes like a sealed box. That means there's little to no port contribution, and in the range from 32 - 45 Hz, the driver has to do all the work. Without the port involved, there's simply no replacement for displacement- a single 12" driver is going to have to work very hard if you're trying to feed it several hundred watts and get 110 dB or so out. Not really practical.
                      Here he's discussing generic sub design, and what happens with low FB tunings and the effect they have on driver workload

                      2)
                      That's why in my mains, the box Fb is 26 Hz, and useful port output doesn't go away until above 50 Hz. This translates into 118 dB per cabinet from 28 Hz to 200 Hz in the bass system, which is an Audax 13" pro and Audax 15.5" pro (it's a bit bigger than a std. 15") driver.
                      Here he talking about the bass bins for his Wilson Audio X1-SLAMM clones

                      3)
                      When the Tempest's are available (some day, some day!!), then the dual subs with 2 Tempests per cabinet will get built; they'll be crossed over about 35 - 40 Hz, so that there is adequate overlap. Yeah, this is going to look a bit too much like a Greatful Dead PA system when it's done, but when you're not married, and can build odd shaped cabinets (plannig on two corner cabinets with beveled front panels), you have a few more options.
                      Here he's talking about a corner loaded ported box using 2 Tempests. These will be his subs.

                      The references to "The Grateful Dead" are a result of when Jon custom designed and built equipment for several members of that band.

                      Sorry for any confusion.




                      theAudioWorx
                      Klone-Audio

                      IB subwoofer FAQ page


                      "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

                      Comment

                      • Brian Steeves
                        Junior Member
                        • Nov 2000
                        • 24

                        #12
                        Thomas,

                        I figured he was. But like he said,"Whenever you use an extremely low tuning in order to optimize the output in the 20Hz and below region, (say an Fb of 15-17 Hz)the problem you have is that 1 octave above that frequency the system is acting for all intents and purposes like a sealed box. That means there's little to no port contribution, and in the range from 32 - 45 Hz, the driver has to do all the work. Without the port involved, there's simply no replacement for displacement- a single 12" driver is going to have to work very hard if you're trying to feed it several hundred watts and get 110 dB or so out. Not really practical."

                        Does this apply to a "Tempest" based sub with the design I mentioned?

                        My question,"What's wrong with the idea that in the 40-80hz range the sub acting like a sealed enclosure? I mean wouldn't that be a good thing? And if the amp power is available, and I think it is (850 watts into 4 ohms) this would be the best of both worlds. Good low end extension and tight midbass."

                        Like I said before this will be my first vented sub so all the experience you advanced guys have to offer is very appreciated! I an trying to learn the advantages and disadvantages.

                        "That's why in my mains, the box Fb is 26 Hz, and useful port output doesn't go away until above 50 Hz. This translates into 118 dB per cabinet from 28 Hz to 200 Hz in the bass system"

                        Ok since I will be crossing my Mirage OM10 mains to this sub at the standard 80THX crossover(no other choice at this point) why would the above statement apply to me?
                        She said,"you're gonna put that thing WHERE!"

                        Comment

                        • Andrew Pratt
                          Moderator Emeritus
                          • Aug 2000
                          • 16507

                          #13
                          Brian I'll let the thomas and jon handle the volume questions but I will say that a single 4" vent flared or not is not nearly enough for a tempest driver unless you are only planning on providing it 2-300 watts...even thats a stretch. If you limit the porting it will compress the sub forcing it to act more like a sealed sub so SPL's are limited and you may get nasty chuffing sounds as huge amounts of air try to get through that tiny hole




                          Comment

                          • John Holmes
                            Moderator Emeritus
                            • Aug 2000
                            • 2703

                            #14
                            Hello Brian,
                            I am not a technical guy so I have nothing to add to this discussion but good luck

                            I haven't had the chance to say welcome to the forum so, Welcome!




                            "I came here, to chew bubble gum and kickass. And I'm all out of bubble gum!!!" My DVD's
                            "I have come here, to chew bubblegum and kickass. And I'm all out of bubblegum!!!"

                            Comment

                            • JonMarsh
                              Mad Max Moderator
                              • Aug 2000
                              • 15209

                              #15
                              Hi Brian,

                              If you're doing a tempest system, using a single 4" port would be selling the 15" driver WAY short on the port output- TEMPEST and SHIVA drivers have long excursion, can really work a port hard, and the port velocity and losses will be too high. For a 15" driver, I usually use a 6-1/2" diameter port minium, which is a lot more area than a 4". Otherwise, if you want to tune real low, a PR may be an option to consider. I'm not personally big on PR's, that's just one of my prejudices.
                              If you have a box simulation program, you can look at the driver excusion and power handling, which is a function of thermal effects but especially the excursion limitations of the drive. Everyone seems to want 115 dB plus, but when you tune very low, you have to recognize the limitation in power handling that results if port output goes away for all purposes above 25 Hz. What will happen is a "saddle" in the power handling curve, with a dip in the 25-40 Hz region, and higher cone excursion. Not saying that's a bad tradeoff, but be aware of the ramifications. When goin to sealed or IB type approaches, you can sometimes expect to realistically use 2X to 4X the drivers. That's why ThomasW's "12 Shiva's Dancing" isn't such a totally over the top system- it makes a lot of sense, if you want uniform output down to 15 Hz.

                              Regards,

                              Jon




                              Earth First!
                              _______________________________
                              We'll screw up the other planets later....
                              the AudioWorx
                              Natalie P
                              M8ta
                              Modula Neo DCC
                              Modula MT XE
                              Modula Xtreme
                              Isiris
                              Wavecor Ardent

                              SMJ
                              Minerva Monitor
                              Calliope
                              Ardent D

                              In Development...
                              Isiris Mk II updates- in final test stage!
                              Obi-Wan
                              Saint-Saëns Symphonique/AKA SMJ-40
                              Modula PWB
                              Calliope CC Supreme
                              Natalie P Ultra
                              Natalie P Supreme
                              Janus BP1 Sub


                              Resistance is not futile, it is Volts divided by Amperes...
                              Just ask Mr. Ohm....

                              Comment

                              • Brian Steeves
                                Junior Member
                                • Nov 2000
                                • 24

                                #16
                                What would you guys recommend if you were going to make one and why? i.e. volume, tuning, port size, etc...?




                                She said,"you're gonna put that thing WHERE!"
                                She said,"you're gonna put that thing WHERE!"

                                Comment

                                • ThomasW
                                  Moderator Emeritus
                                  • Aug 2000
                                  • 10934

                                  #17
                                  Brian

                                  If you look at the plots in the link below, you'll see the "notch" or "saddle", Jon is referring to in #2&4






                                  theAudioWorx
                                  Klone-Audio

                                  IB subwoofer FAQ page


                                  "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

                                  Comment

                                  • Lexman
                                    Super Senior Member
                                    • Jun 2000
                                    • 1777

                                    #18
                                    Thanks Brian! Hope you enjoy our little hideout.

                                    Sorry for being late here, but just saw it. It's been a rocky road with PCs at home and very busy at work.

                                    Lex

                                    Comment

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