First Measurements of My Sub..

Collapse
This topic is closed.
X
X
 
  • Time
  • Show
Clear All
new posts
  • Bing Fung
    Ultra Senior Member
    • Aug 2000
    • 6521

    First Measurements of My Sub..

    Measured my sub, and it looks pretty good, except I sure miss that over boosted signal of my energy sub. Seeing all my speakers are now powered by the same type of monoblock amp as the sub, I don't seem to have as much slam in the 30 - 40 Hz range.

    Here are the measured numbers:

    Reference 85dB, 1 octave Pink noise centered @ 125 Hz Uncorrected

    8 Hz 80 dB
    16 Hz 90 dB
    20 Hz 95 dB
    25 Hz 95 dB
    32 Hz 95 dB
    40 Hz 98 dB
    50 Hz 101 dB
    65 Hz 97 dB
    125 Hz 80 dB


    Reference 85dB, 1 octave Pink noise centered @ 125 Hz corrected

    8 Hz 100 dB
    16 Hz 101.5 dB
    20 Hz 100 dB
    25 Hz 100 dB
    32 Hz 98 dB
    40 Hz 100.5 dB
    50 Hz 102.5 dB
    65 Hz 98.5 dB
    125 Hz 81.5 dB

    The frequency steps came from a Sound and Vision test disk.

    Please offer comments on this and any suggestions for more thorough measurements.

    How real are those corrected values?

    Though the sub certainly can reach the low stuff, I now feel as if I can't boost the signal enough to my liking, but if I boost the level to it's maximum value +12, it does sound overall to bassy in the low range. Still I don't have that mid range slam that I like.




    Bing
    Bing
  • ThomasW
    Moderator Emeritus
    • Aug 2000
    • 10934

    #2
    First, I assume by corrected you're referring to the RS meter?

    Second, at what distance are you taking the measurements?

    Something with the measurements is goofy. 100db@8Hz and 101.5@16Hz. That's not possible with the driver and cabinet you have. My big IB is one of only a handful of subs that will do that. You actually probably getting doubling or more of the signal by the driver.

    Refresh my memory, give me the T/S specs and box design so I can model it




    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

    • Bing Fung
      Ultra Senior Member
      • Aug 2000
      • 6521

      #3
      Thomas, that was the one meter on plane to the center of the cone, based on the average of 5 measurement rounds. The RS SP meter was mounted on a small Ultra pod Tripod. The values deviated no more that 2 db per measurement round. The actual measured value at 8Hz was 80dB, as the driver just moved in and out at this slow lopp. The correction factor to add to the RS meter was 20dB @ 10 Hz.... so I just added it on not truely believing the corrected value.



      T/S numbers

      QTS: 0.44
      Vas: 2.941 ft^3
      Fs: 23.32 Hz
      Re: 4 ohm
      Le: 3.05
      Xmax: 14mm
      Z: 4 ohm
      Qms: 10.28
      Qes: 0.46
      SPL: 96 dB
      Pe: 350 W
      BL: 16.90
      Dia: 12"
      Sd: 531 cm^2


      Here is the build spec


      Number of drivers : 1
      Box type : Vented
      Box size : 120.2 l
      Tuning frequency : 21.03 Hz
      Vent : 1 vent(s)
      14.8 in length for each
      4.0 in round

      Here is the predicted response from WinIsd
      Relative
      Freq Gain SPL
      [Hz] [dB] [dB]
      20.00 -2.57 93.43
      25.00 -0.32 95.68
      30.00 -0.15 95.85
      35.00 -0.16 95.84
      40.00 -0.16 95.84
      45.00 -0.15 95.85
      50.00 -0.13 95.87
      55.00 -0.11 95.89
      60.00 -0.10 95.90
      65.00 -0.09 95.91
      70.00 -0.08 95.92
      75.00 -0.07 95.93
      80.00 -0.06 95.94
      85.00 -0.05 95.95
      90.00 -0.05 95.95
      95.00 -0.04 95.96
      100.00 -0.04 95.96




      Bing
      Bing

      Comment

      • ThomasW
        Moderator Emeritus
        • Aug 2000
        • 10934

        #4
        Bing

        First I hope you're wearing ear plugs. 101db @50Hz=ear damage

        Place the meter as close as possible to the dust cap, but don't let it get hit with cone excursions. Then remeasure. You don't need to do it 5 times though.

        The "corrections" can't be right for the lowest frequencies, either that or the woofer is doing what's called doubling. This means that when fed a 15Hz note it is reproducing a 30Hz note, etc.. Pretty standard thing to have happen.

        The 50Hz rise is understandable and is probably a room mode.

        Let me run the numbes through BassBox Pro and see what comes up. Is there damping in the cabinet?




        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

        • Bing Fung
          Ultra Senior Member
          • Aug 2000
          • 6521

          #5
          Damping as in poly fill? No, I haven't stuffed the box yet. I wanted to veneer it before stuffing. Should I just stuff it now? Other than that it is just a 1" MDF box with a 2" double baffle and matrix bracing. One 4"x 14.8" flared port on the same side as the driver.

          Are you serious about the ear plugs? it seems as if this is a different bass than what I'm use to. It is a high quality bass that can be very low, but hardly seems like there is enough of it. Yet there seems to more low bass than is required if the level is turned up. The sub seems very subtile now and doesn't really call attention to it's self unless called for. Is this the way it is suppose to be?

          What mechanism causes this doubling of the frequency? and is this good or bad?

          I'll run the near field test tomorrow as the family is asleep now.

          Thanks




          Bing
          Bing

          Comment

          • ThomasW
            Moderator Emeritus
            • Aug 2000
            • 10934

            #6
            Yes as in polyfill. Ported boxes are lined, not stuffed(filled). Go to the fabric store get "bonded" polyfill(not loose) Line the interior walls with a single layer. Use Scotch 77 spray glue to attach it

            Doubling is just something woofers do when given a signal they can't reproduce. They produce a "multiple" of it. Don't worry your not going to be running across many 8Hz notes :B

            Are you serious about the ear plugs?
            Damn straight! Prolonged exposure (>20min sustained)to 90db or higher levels produces permanent ear damage. Just a little each time, but the results are cumulative!

            The sub seems very subtile now and doesn't really call attention to it's self unless called for. Is this the way it is suppose to be?
            You are not supposed to be aware of the sub. It's supposed to be "invisible" Also my "educated" guess is that you old sub wasn't producing "bass" it was producing "midbass"=bloated sound

            BTW you've got mail!




            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

            • Patrick Sun
              Super Senior Member
              • Aug 2000
              • 1380

              #7
              Bing, what are you using to get the bass tones? Have you considering getting the BassZone CD from www.stryke.com ? Are you using the C-weighted/Slow response setting on your SPL meter (I am using a digital SPL meter, so I don't get the needle quivers).




              PatCave; HT Pix;Gear;DIY Projects;DVDs; LDs
              PatCave; HT Pix;Gear;DIY Projects;DVDs; LDs

              Comment

              • Bing Fung
                Ultra Senior Member
                • Aug 2000
                • 6521

                #8
                I'm using this Sound and Visions Cd test disk. I am using the C weighted, slow setting.

                Ok, I have just finished a near field measurement of my sub, here are the results....

                How does this fit with the 1 meter test?



                Go Here For Pictures Of My Sub




                Bing
                Bing

                Comment

                • ThomasW
                  Moderator Emeritus
                  • Aug 2000
                  • 10934

                  #9
                  Bing

                  These look very good, just about perfect actually Congrats!!!

                  You did a great job!



                  Now just build a crate for it and I'll have FedEx pick everything up in the morning :B




                  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

                  • Andrew Pratt
                    Moderator Emeritus
                    • Aug 2000
                    • 16507

                    #10
                    looks damn fine to me Bing Congrats on a great DIY sub.




                    Comment

                    • Bing Fung
                      Ultra Senior Member
                      • Aug 2000
                      • 6521

                      #11
                      Thanks Thomas & Andrew, it was with all your guidance and teachings that helped me created this vault of a sub. I didn't know nothing about speaker design or building when I started this project, now I know little, enough to be considered dangerous :W Thank You for all your help!

                      I can't wait to finish it off.

                      Thomas, that wool felt you speak of, how does it differ in the damping abilities of the poly fill? It does sound like nice stuff.

                      Is there a way for me to fix that little dip at the 32 Hz point? Should I worry about it?




                      Bing
                      Bing

                      Comment

                      • ThomasW
                        Moderator Emeritus
                        • Aug 2000
                        • 10934

                        #12
                        Bing, our pleasure I'm sure

                        The wool/felt has somewhat better frequency absorbing qualities than the polyfill.

                        The 32Hz dip may be a room null or a standing wave. If the room permits move the sub a few feet one way or another and remeasure to see if the response curve changes. It's only 2db, so it may not be worth the hassle.




                        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

                        • Pat
                          Super Senior Member
                          • Aug 2000
                          • 1637

                          #13
                          Nice Sub Bing!

                          Looks very industrial with the aluminium colored cone and the "vault" like box:B

                          Your graph looks great!

                          Enjoy!




                          Pat's Page
                          Pat's Page

                          Comment

                          • Lexman
                            Super Senior Member
                            • Jun 2000
                            • 1777

                            #14
                            I don't have time to get technical here, as that's Thomas's job anyway, lol.

                            However, I did want to take the time to tell Bing from his post way up there about stuffing,

                            Yes you should STUFF it! hehe.

                            Lex

                            Comment

                            • John Holmes
                              Moderator Emeritus
                              • Aug 2000
                              • 2703

                              #15
                              Nice job Bing! It looks great.




                              "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

                              • Andrew Pratt
                                Moderator Emeritus
                                • Aug 2000
                                • 16507

                                #16
                                Bing the plot you showed us with that slight dip at 32 was nearfield right? Rememeber that you need a 3 dB change in order to percieve a difference in volume so that plot looks very flat. Try running the same plot only at your listening position...I'll bet you'll have much larger dips and peaks since the room will be playing a much larger role in the results you get at your couch. If there are major problems try moving the sub and or the couch...even a foot here or there can make a huge difference




                                Comment

                                • Bing Fung
                                  Ultra Senior Member
                                  • Aug 2000
                                  • 6521

                                  #17
                                  Thanks everyone!, I'll certainly measure the sitting position next...

                                  Lex are you telling me to :F it, or just Stuff it? :B




                                  Bing
                                  Bing

                                  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 "|||"