Tempest Design, using lspCAD

Collapse
This topic is closed.
X
X
 
  • Time
  • Show
Clear All
new posts
  • KennyG
    Moderator Emeritus
    • Sep 2000
    • 745

    Tempest Design, using lspCAD

    I am trying to design the 3.25 cu.ft. sub Dan Wiggins is talking about, but I seem to get a flatter response (F3 @ 19.7) using the following perimeters:

    Box Vol 120 l (4.25 cu.ft.)
    Ql 15 (What is this???)
    Qa 100 (What is this???)
    Fill 50%

    PORT
    Length 35.6 cm (14")
    Min Dia 10.2 cm (4")
    Flare inf

    Res Freq 20.2

    I'm missing something here.
  • ThomasW
    Moderator Emeritus
    • Aug 2000
    • 10934

    #2
    Ql=The "Q" of a box as a result of all leakage losses

    Qa= The "Q" of a box as a result of all absorption loss

    I'd stick with Dan's design after all who knows best how this driver works?

    Also remember that there is basically a 10% "fudge factor" with ported designs. And the differences may show in the computer model, but not in the real world especially considering "room gain"




    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

      #3
      Thomas, according to the CAD program, Dan's design starts a gentle roll-off @ 100hz, and has an F3 @ 29hz, this is using one 2" port 10" long...what about using two 2" ports 20" long?
      Max airspeed is <6 ms @ 10hz.
      I'm probably going to build a rectangular cabinet with a 1 X 1.44 X 2 ratio, so it will have a 25" width...a 20" vent will fit.

      Comment

      • ThomasW
        Moderator Emeritus
        • Aug 2000
        • 10934

        #4
        My numbers come up a little different. But, this is my first time playing with LspCAD, and I've got a bad cold, so my brain isn't working all that well

        The 2-2" ports have less area than a single 4". "Chuffing" can be a major problem with 2" ports. Especially with a high output sub. That's why Dan presented the coiled tube idea.

        I think a better idea is using PR's instead of ports. It increases the price, but it makes design and building easier. Since your modeling, do a version using the PR model in LspCAD. Try models using 1, then 2 PR's. I played with this a little last noc in BassBox Pro. It seemed that 2 worked best.




        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

          #5
          Thomas, what's a PR...passive radiator?

          Comment

          • ThomasW
            Moderator Emeritus
            • Aug 2000
            • 10934

            #6
            Yes.




            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

            • DanWiggins
              Junior Member
              • Sep 2000
              • 6

              #7
              Kenny,

              Part of the difference is that I count on room gain. I know some folks don't like to do that, but I've consistently found that I get better final results if I design with some room gain in mind. I think the sound is more natural, and the final results are flatter. That's the whole reason of doing low Q designs. Does it give the best "number"? No, but to my ears, it sounds best.

              Dan Wiggins
              Adire Audio

              Comment

              • KennyG
                Moderator Emeritus
                • Sep 2000
                • 745

                #8
                Hi Dan, looks like I have you comin' and goin'!!!
                I am definintely looking at room gain with everything I model now, I know my Legacy's were designed that way and I absolutely love their sound.
                I'm going to work on that 175L per driver design you mentioned @ HTT.
                Dan would you take a look at this design I have modeled, and give me your professional opinion?

                DRIVER UNIT; tempest
                Iso
                Elec Conn sep source
                Double VC parallell

                BOX;
                Volume 120 l
                Ql 15
                Qa 10?
                Fill 25%

                PORT;
                Length 55.4cm
                Dia. 10.2cm
                Num of vents 1

                MEASURED SET-UP 10 watts (I think that's average to high for my listening habits)

                Anyway, please slam it, or praise it, I just want to know what you think...Thomas I'd value your opinion also...please.

                Comment

                • ThomasW
                  Moderator Emeritus
                  • Aug 2000
                  • 10934

                  #9
                  Kenny


                  The primary issue is the short port length. Load Dan's model, then enter your "box" data. When you get to the port length, watch the curve change when you enter 55.4. Toggle back an forth between this and the 100.2 port length.


                  The rest of design is ok, but it just works better with the longer port.




                  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

                    #10
                    Didn't read above post right, will reply when I finally wake up!
                    I do have a question; Why does source resistance (amp & cabling) have so much to do with the response curve?
                    I realize the drivers motor structure sends induced voltage back at the amp...but, how does that effect the response curve? I can't seem to get a steady resistance reading across my amps output terminals, it keeps changing and is in the Meg ohms range, so I must be charging a capacitor. If this is the case what can I use as a Source resistance? This amp has balanced outputs, I'm not sure if that's got anything to do with it.
                    I may have to call the company.

                    Comment

                    • ThomasW
                      Moderator Emeritus
                      • Aug 2000
                      • 10934

                      #11
                      Kenny :?

                      JonMarsh is going to drop in after a bit and answer your guestion.




                      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

                      • ThomasW
                        Moderator Emeritus
                        • Aug 2000
                        • 10934

                        #12
                        posting error, oops




                        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

                        • JonMarsh
                          Mad Max Moderator
                          • Aug 2000
                          • 15214

                          #13
                          Kenny,

                          Without going into a ton of detail,

                          1) The amplifier has to be "ON" to measure the output impedance.

                          2) It is output impedance, not resistance, which is important- simply put, resistance is the DC ohms law bit, where current is equal to voltage divided by resistance; impedance is a complex frequency dependent variable (in the "real" world, there is various inductive and capcitive reactance parasitic components- for example, for amplifiers with substantial negative feedback, declining feedback with increasing frequecy gives an inductive component to the output impedance, with a rise in impedance with frequency.

                          3) The parameter Qe for a loudspeaker is measured/calculated assuming an essentially zero source impedance. Speakers which depend electrical damping (in general, designs with high BL product, and high Q cone systems (high mass, high compliance) will be very strongly affected by non-ideal source impedance.

                          The affect of this can be seen by raising Qe in the speaker parameter, and seeing the deterioration in Qts, and Qb for a specific design.
                          So, folks, just remember, momma said don't use SET amps for your subwoofers- your Qt won't be anywhere near where you think it should be if you do! This is another reason why it is good to go with biamping with low frequency crossovers- and why I chose to biamp instead of use passive crossovers at 125 Hz for my X1 clones. Even using enormous wire gauges, the inherent Xc of the serious inductor deteriorates the electrical damping in the bass, IMO.

                          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-Saƫns 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

                          • ThomasW
                            Moderator Emeritus
                            • Aug 2000
                            • 10934

                            #14
                            There's a bug in the software, both this and the post below were posted in response to Kenny's last post at 8:31PM and timed before. But were placed above his post by the software :? :?




                            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

                            • ThomasW
                              Moderator Emeritus
                              • Aug 2000
                              • 10934

                              #15
                              Kenny

                              I'm not a "power" LspCAD user. I primarily use BassBox Pro.

                              All I did was take the data file Dan posted to the HTF site, and "plug-in" your box specs. I didn't use any power ratings.

                              So with this method the longer port "modeled" better.

                              Oh BTW, while out and about "surfing", I ran across this link. Maybe you can get some more specific info here http://www.egroups.com/community/lspcad-users




                              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

                              • ThomasW
                                Moderator Emeritus
                                • Aug 2000
                                • 10934

                                #16
                                This is a test post. Time 7:26 MDT so the server should post them as 9:26 not 8:26


                                Kenny

                                In the post above this one there is a response to your post timed at 8:31PM, but for some reason the server/software is placing the replies above your question.


                                I bet it's a daylight savings time change over with the server. Usually it puts the time 2hr difference, due to the time zones, but now its only one hour difference :?

                                Help I'm caught in the twilight zone!!!!






                                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

                                  #17
                                  Thomas, I've been trying to work that longer vent, here's what I'm getting (using SPL room & cabinet graph) 100.2cm long vent; response curve is +/- 1db from 31 to 70hz with F3 @ 21hz, gentle roll off starts @ 40hz.
                                  55.4cm long vent; response curve is +/- 1db from 21.5 to 71hz with F3 @ 16.5, roll off is much sharper.
                                  I'm I entering my perimeters wrong, or is that gentle roll off what is wanted. I had thought the deeper you could go flat, the better.
                                  I have tried to enter a resistance in the "source resistance" box, under measured set-up, but it won't let me input anything close to what I'm measuring (in the M-ohm range) and the higher the number I input the peakier the response curve gets!...it's just to scary!!! 0 resistance looks much better!

                                  Comment

                                  • KennyG
                                    Moderator Emeritus
                                    • Sep 2000
                                    • 745

                                    #18
                                    Jon, thank you very much, I have digested most of your post, and will get the rest with another reading or two My background is electonics...just not audio electronics...hell at the rate I'm going it may soon be.

                                    Thomas, I just started playing with Dan's 3.25 cu.ft. design, I changed two things to match the 4.25 cu.ft. design that haunts me.
                                    He's using a 50% fill, so I changed the Qa to 7 (per manual) and upped the input power to 10 watts (just to match mine)
                                    Setting the graphs up for a 10 to 200hz view, the 3.25's response curve looks alot like the 4.25's with the longer vent you mentioned...but it still doesn't seem as flat or as deep as the 4.25 with the short vent. I believe I'm lost in design hell!!!

                                    Comment

                                    • ThomasW
                                      Moderator Emeritus
                                      • Aug 2000
                                      • 10934

                                      #19
                                      Ok now the server seems to be happy so I'll duplicate the post

                                      Kenny
                                      I'm not a "power" LspCAD user. I primarily use BassBox Pro.

                                      All I did was take the data file Dan posted to the HTF site, and "plug-in" your box specs. I didn't use any power ratings.

                                      So with this method the longer port "modeled" better.

                                      Oh BTW, while out and about "surfing", I ran across this link. Maybe you can get some more specific info here http://www.egroups.com/community/lspcad-users




                                      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

                                        #20
                                        Thanks Thomas this looks promising!

                                        Comment

                                        Working...
                                        😀
                                        😂
                                        🥰
                                        😘
                                        🤢
                                        😎
                                        😞
                                        😡
                                        👍
                                        👎
                                        Searching...Please wait.
                                        An unexpected error was returned: 'Your submission could not be processed because you have logged in since the previous page was loaded.

                                        Please push the back button and reload the previous window.'
                                        An unexpected error was returned: 'Your submission could not be processed because the token has expired.

                                        Please push the back button and reload the previous window.'
                                        An internal error has occurred and the module cannot be displayed.
                                        There are no results that meet this criteria.
                                        Search Result for "|||"