Initial SPL results for my new Sonosub

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  • Andrew Pratt
    Moderator Emeritus
    • Aug 2000
    • 16507

    Initial SPL results for my new Sonosub

    Okay I didn't get chance to do half the things I intended to tonight but I did manage to run a couple of sine waves through the new tube. Its obvious I've got a couple of deep holes in the response due to the room but I knew that before since the old sonosub showed the same "problems"
    These numbers were obtained by running a cable from my soundcard to the sub input on the Denon 3300's external 6 channel input. I calibrated it to 70 dB with white noise (91 dB at 1KHz) and then started feeding the tube short durations from 100Hz down to 15Hz and writing down the result. The SPL meter was placed 1 meter away from the center of the tube and was flat on the carpet. The sub doesn't fit in the far corner so it was left beside the entertainment unit and against the wall. There is a opening immediatly to the left which goes down a hall way and a short wall beside that so its corner loaded minus the doorway. I then entered the values into an excel spread sheet and corrected them for the known errors the RS SPL meter has. Here are those corrected values. I intend to do some more testing and keep in mind this driver isn't yet broken it at all.

    Hz dB*

    15 73
    18 81
    20 86
    25 90
    30 91
    35 94
    40 96
    45 95
    50 86
    55 90
    60 99
    65 87
    70 95
    75 92
    80 96
    85 95
    90 91
    95 92




  • Lexman
    Super Senior Member
    • Jun 2000
    • 1777

    #2
    Nice Andrew! That's a sonosub with what amp and driver again?

    Lex





    <A HREF="http://www.catcables.com" <IMG SRC="http://www.htguide.com/lexman/other/sm_logo.gif"

    Comment

    • ThomasW
      Moderator Emeritus
      • Aug 2000
      • 10934

      #3
      Andrew

      Try retesting and let's remove some of the variables that are impacting the current results.

      First get the meter up off the floor. This position can cause significant problems.

      Second do "nearfield" measurements, hold or place the meter a couple of inches away from the dust cap. Try 2 different angles, first aim the meter directally at the dust cap, then turn the meter 90 degrees to the dust cap keeping the same distance away.. Compare the differences and use the angle that provides the flattest response. This will eliminate most room induced issues, and give you a better look at what the sub is really doing.

      The driver "break-in" should only effect the lowest frequencies and the overall output level. Other than that not much should change.

      Prompt my memory. What is the configuration and tuning for this sub?




      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

        #4
        You've got room nulls, and I have room humps in the 55-63Hz range (sounds like the roof is about to come off the place sometimes). Thanks for posting the numbers. looks like you're "flat" to about 21-22Hz (room gain/nulls can be a bitch). Have you also done the near field measurements? That would be a good indicator of how the the sub is also performing.




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

        Comment

        • Andrew Pratt
          Moderator Emeritus
          • Aug 2000
          • 16507

          #5
          I do plan on doing nearfield and also with and without the base plate to see if there's any effect there unfortunatly I ran out of time last night. The sub uses the 15" parts express driver and is in a 250 liter tube tuned to 20 Hz using three non flared 4" vents (each 73 cm long) and is powered with a Hafler DH220 so each coil is getting 115 watts (conservative estimate on power)




          Comment

          • Andrew Pratt
            Moderator Emeritus
            • Aug 2000
            • 16507

            #6
            Thomas when I do the nearfield measurements holding it in place is going to be difficult due to clearence b/t the bottom plate and the bottom endcap. There's about 5" of clearence to work with there but that isn't much to play with for the SPL meter. I can try and prop it up with something while its sitting under there...what do you suggest?




            Comment

            • ThomasW
              Moderator Emeritus
              • Aug 2000
              • 10934

              #7
              Andrew

              If it's possible, remove the bottom plate. If that's not possible turn the sub upside down (woofer facing the sky), and make the measurements that way.

              Try attaching the meter to a small stick with tape. Isolate it from the stick with some cloth or a small piece of foam. Then attach the stick to something that will suspend it in the appropriate position in front of the woofer. What you're trying to create is something like a "boom mike stand", with the meter on the end.

              Measuring with the meter near any boundry, either the bottom plate or the floor will screw up the accuracy of the measurements. This is because certain frequencies will "boundry load" and give artificial readings.

              Is there any damping material in the tube? If not try adding some when possible.




              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

                #8
                Andrew, thanks for posting the prelim results.

                Looks like at sitting position you will be flat to 20Hz, that hole at 50 though? How do you fix that?

                It is a first measurement though. Are you going to measure it at sitting position to determine actual room gain, is that how it's done?




                Bing
                Bing

                Comment

                • Andrew Pratt
                  Moderator Emeritus
                  • Aug 2000
                  • 16507

                  #9
                  I can easily remove the bottom plate its only held in place with three screws so that won't be a problem, I'll then turn in upside down so as to get a better idea of whats going on. Its too bad my 30 day copy of Spectraplus is over otherwise I could have used that. Bing I will do measurements at the seat location...if you have holes the only solution is to move either the sub or the seat...peaks can be tames with an eq. but nulls are deep holes that can't be filled no matter how much power you dump into them.




                  Comment

                  • Andrew Pratt
                    Moderator Emeritus
                    • Aug 2000
                    • 16507

                    #10
                    okay I did the near field measurements tonight. See this graph for the results nearfield




                    Comment

                    • Patrick Sun
                      Super Senior Member
                      • Aug 2000
                      • 1380

                      #11
                      Andrew, that's a nicer looking plot. But I think it's time for you (and me) to make a subsonic filter (cut-off around 18Hz) to protect your driver). I have been thinking about making a 4th order high pass subsonic filer for my sub too. Would it be easy to just slap together the correct L's and C's values and sticking them in a little black box with a on-off switch.




                      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

                        #12
                        Andrew, that certainly looks like a nice plot. That port comes in very nicely.

                        Pat, I'm all for this subsonic filter, Can I get in on one as well? What can I do to help. Electrical design, I'm an Idiot...




                        Bing
                        Bing

                        Comment

                        • ThomasW
                          Moderator Emeritus
                          • Aug 2000
                          • 10934

                          #13
                          Andrew

                          Now that looks more like it should.

                          Good job




                          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

                            #14
                            Thanks guys yes that plot looks really nice doesn't it So Thomas whats the best way to protect these beasts as far as adding a low pass crossover on them?




                            Comment

                            • Patrick Sun
                              Super Senior Member
                              • Aug 2000
                              • 1380

                              #15
                              Andrew, you want a HIGH pass filter (passing anything over, say, 18Hz) to protect the sub, and let your receiver's LFE low pass to protect's its high end of the frequency range (80-120Hz).

                              I may have to dig out my EE books and dust them off.




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

                              Comment

                              • ThomasW
                                Moderator Emeritus
                                • Aug 2000
                                • 10934

                                #16
                                Hi Guys

                                I saw these posts last noc and was wondering how to respond. :?

                                Using "subsonic" filtering is manditory for those playing vinyl. It's wierd to watch the woofer cones "pump" in and out during a "quiet" groove on a record. This eats-up TONS of watts for no good reason. But...

                                For anything that's from a digital source, I've yet to see subsonics be a problem. As a matter of fact I think that there is potential gain from not filtering out the subsonics. The reason being that there is a "reasonable" amount of subsonic energy is DVD soundtracks, so why not experience to it?

                                Also not that it would be a significant issue but filtering just adds more "stuff" in the signal path. Generally something to avoid.

                                The only reason to use a filter for digital sources, IMO, is if you have a very small amp, one just big enough for the task. And are concerned about conserving all it's power for the "audible" frequencies.

                                If you are interested in testing to see if there are any audible benefits to "subsonic" filtering, I'd suggest a roll-off beginning at 15Hz.




                                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

                                  #17
                                  Thomas, I think the concern arises from playing discs such as Star wars TMP, blowing drivers due to the extremely low signals. After reading about Obi's adventures with the SVS's, I know I was wanting a subsonic limiter for my homemade sub.

                                  So you don't think it is required?




                                  Bing
                                  Bing

                                  Comment

                                  • ThomasW
                                    Moderator Emeritus
                                    • Aug 2000
                                    • 10934

                                    #18
                                    Hi Bing

                                    Well, I have my doubts about "Obi" in general :roll: Also not knowing ALL the info regarding Obi's situation, it's hard to second quess.

                                    However, I haven't played TPM, JonMarsh bought me a copy for my birthday, LAST APRIL, but hasn't sent it out yet.!


                                    Oops sorry got sidetracked there.

                                    My spin, is a tale of caution. First I don't listen at "reference" levels. I always "gain ride" during DVD movie playback. If I don't know the source material, I play it back at a low to moderate level to make sure there's nothing problematic in the recording. After initial playback, then I open up the throttle :B

                                    Remember I've been doing this audio stuff for almost 40 years and have NEVER blown a speaker. So this method seems to be successful

                                    If you want the peace of mind this may bring then use one. But be advised that it may not have "saved" Obi's sub. The "harmonics" themselves at VERY high volumes can do harm. A subsonic filter wouldn't "catch" those!

                                    It's not really an issue of "how low" it's an issue of "how loud"

                                    As usual YMMV




                                    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

                                      #19
                                      ThomasW, I have TPM LD (AC-3), and it can be awfully stressful on a sub. I got some popping when I under-power it on some LFE heavy scenes, like the bombing of the Jedi ship, and the Pod Race. But I'll be getting a Peavey CS800X amp this week I hope, so I'll see if it's a power issue. Obi's other problem was his LFE output was too high to begin with when he cranked up TPM. Once he calibrated it was better behaved at high SPLs.

                                      The Haunting dts DVD has some scenes with tons of low info in the 5-10Hz range. Tom Vodhanel posted some TPM bass 3-D pix, and there's lots of sub-20Hz info on TPM's LFE track. Thomas, you need to at least take a listen to TPM's soundtrack, the light sabre fights have tons of LFE (though not super low). Of course, I think Joey-Loud is a good test for a sub and TPM.




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

                                      Comment

                                      • ThomasW
                                        Moderator Emeritus
                                        • Aug 2000
                                        • 10934

                                        #20
                                        Patrick

                                        Thanks for the info.

                                        I'll get to hear TPM when Jon sends it out. But he's traveling most of this month including a possible trip to Germany, so it's of no benefit to push him for the LD.

                                        Popping is probably the amp clipping. Many times clipping can have a mechanical sound like bottoming. It takes tremendous amounts of power to actually bottom the Shiva in a properly designed box.

                                        The "Obi" story is too strange! One would think he'd know how to properly set-up a pre/pro by this time :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

                                          #21
                                          Thomas Joey has a copy of TPM on laser so the next time he's over tell him to bring it. I won't be anywhere near ref level for some time so I'm not worried at all about my sub.




                                          Comment

                                          • Bing Fung
                                            Ultra Senior Member
                                            • Aug 2000
                                            • 6521

                                            #22
                                            Thanks Thomas, I too have my reservations, but what do I know? LOL on your comment :B

                                            Okay, I won't sweat it then.

                                            Pl@, how much did the Pevey cost, If you don't mind?




                                            Bing
                                            Bing

                                            Comment

                                            • Patrick Sun
                                              Super Senior Member
                                              • Aug 2000
                                              • 1380

                                              #23
                                              Bing, check your email...




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

                                              Comment

                                              • Eric S
                                                Senior Member
                                                • Sep 2000
                                                • 175

                                                #24
                                                I've been wondering about the benefits/drawbacks of subsonic filtering as well. I have just finished a 135L vented sub with one Mass12 driver. Its tuned to about 19Hz with a 6"ID 36" long vent. I have just ordered the Stryke BassZone test CD, but it hasn't arrived just yet. I am not driving the sub with a whole lot of power right now, probably about 120-150w. Reference levels will not be achieved until we move from our condo and get a house.

                                                Anyhow, I am a little worried about potentially damaging the driver with subsonic material found on a few CDs and DVDs. It seems to be the consensus here that if you are properly calibrated and not pushing ref levels on the first run thought, everything should be fine...

                                                On the other hand, I thought I saw a post where ThomasW had hooked the water heater through a highpass filter...

                                                So which way do I go? Or should I just wait for my test disk to arrive and go from there?
                                                My DIY Theater Projects

                                                Comment

                                                • Andrew Pratt
                                                  Moderator Emeritus
                                                  • Aug 2000
                                                  • 16507

                                                  #25
                                                  Eric i don't think you'll have any problem esp if you're not pushing your sub to really loud levels. Your driver has a lot of Xmax to use up before it will bottom out I think the biggest concern will be you overdriving the amp and it clipping. If that happens no amount of Xmax will help. Still at reasonable levels you're not going to have any problem. Most bass on DVD's centers around 30-45 hz so you're well safe there. Cd's are even safer since there's little really low bass on those unless you're into techno tracks where the bass has been altered etc. DTS Telarc discs can cause real problems though if played loud.




                                                  Comment

                                                  • Patrick Sun
                                                    Super Senior Member
                                                    • Aug 2000
                                                    • 1380

                                                    #26
                                                    Well, even with the new Peavey amp (400W/ch), I can get my Sunosub to pop during some scenes from TPM LD (but I think this LD is the exception). I've been thinking about re-tuning my sub to around 16Hz (I would need to add another 12" to my 24" long 8" wide port). Any ideas? Or should I find/create a subsonic filter and be done with it?




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

                                                    Comment

                                                    • Andrew Pratt
                                                      Moderator Emeritus
                                                      • Aug 2000
                                                      • 16507

                                                      #27
                                                      well a 16" tune will help give you some protections but you are going to give up a lot of bass SPL in the area most used in movies. I wouldn't make that trade off but thats just me. How often does it happen? If its only with the Star wars LD I'd just leave things as they are and back off the sub a bit when watching that movie.




                                                      Comment

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