Announcement

Collapse
No announcement yet.

ultimax 18 box modeling help needed.

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    Re: ultimax 18 box modeling help needed.

    Originally posted by Jwhite View Post
    How does room size effect box design? Do I need a larger box for a larger room or is this something that effects the tuning of the enclosure?

    The tuning, any added EQ, and your room will all affect the response.

    Your room is large enough and open enough that it will not provide much if any "room gain" above the low/mid-20s.

    Somebody designing for a smaller room with cinder block walls (maybe a college dorm room, or a basement room) would be be getting significant room gain further up.

    The subwoofer systems used in those different rooms should be tailored for the application.

    To have flat in-room reponse in the region of interest, I think your subwoofer should exhibit an anechoic response that rolls off in the low/mid 20s and is relatively flat above that.

    "Anechoic" response is the reponse it would have without reflections, without room boundaries, "free field". The modeling tools use anechoic reponse to separate the room considerations from the rest of the design.
    "Our Nation’s interests are best served by fostering a peaceful global system comprised
    of interdependent networks of trade, finance, information, law, people and governance."
    - from the October 2007 U.S. Naval capstone doctrine
    A Cooperative Strategy for 21st Century Seapower
    (a lofty notion since removed in the March 2015 revision)

    Comment


    • #17
      Re: ultimax 18 box modeling help needed.

      I am terribly sorry for asking so many elementary questions. I was under the assumption that this would be the right place for a beginner such as myself to ask questions. Further more we all started off asking elementary questions. Please do tell me if this is the wrong place for a person such as myself trying to expand his knowledge in subwoofer designing and any other audio or electronic devices.

      Comment


      • #18
        Re: ultimax 18 box modeling help needed.

        Originally posted by Jwhite View Post
        I am terribly sorry for asking so many elementary questions. I was under the assumption that this would be the right place for a beginner such as myself to ask questions. Further more we all started off asking elementary questions. Please do tell me if this is the wrong place for a person such as myself trying to expand his knowledge in subwoofer designing and any other audio or electronic devices.
        It is the right place for questions. No worries.

        Good answers might not be immediate.
        "Our Nation’s interests are best served by fostering a peaceful global system comprised
        of interdependent networks of trade, finance, information, law, people and governance."
        - from the October 2007 U.S. Naval capstone doctrine
        A Cooperative Strategy for 21st Century Seapower
        (a lofty notion since removed in the March 2015 revision)

        Comment


        • #19
          Re: ultimax 18 box modeling help needed.

          Originally posted by Jwhite View Post
          I picked up a few sheets of 3/4 birch today and all of the other small parts I thought I may need for the enclosure. How does room size effect box design? Do I need a larger box for a larger room or is this something that effects the tuning of the enclosure?
          The best way to go is to build one of the recommended enclosures described on the UM18-22 product page and place it in your room. The size of your room won't affect the operation of the enclosure the way a small enclosed space like a car might do. Just choose the enclosure design that is tailored to your needs. (Some of the listed enclosure configurations are more recommendable for music or for home theater, but the difference between them is small.)

          Once you select the enclosure design that suits your needs, design a rigid enclosure that is well-braced on the inside and has the same net internal volume as what is recommended. If ports are called for by the design you choose, then install the same number of ports recommended, cut to the recommended length. The Precision Port kits are best if ports are needed. If you need additional length, buy another collar and tube (they are offered a-la-carte). For most rooms, the sealed enclosure designs should be more optimal - only the largest rooms may need a vented enclosure.
          Best Regards,

          Rory Buszka
          Product Manager, Dayton Audio

          The best way to predict the future is to create it.

          Comment


          • #20
            Re: ultimax 18 box modeling help needed.

            Originally posted by Jwhite View Post
            I am terribly sorry for asking so many elementary questions. I was under the assumption that this would be the right place for a beginner such as myself to ask questions.
            It is, but if you don't have the necessary skills and knowledge trying to design your own speaker the first time out of the gate is a recipe for firewood, and you don't acquire those skills and knowledge overnight, or even over a hundred fortnights. The best way to get your feet wet is with a tested design. BTW, rule of thumb for ported versus sealed, if the longest room dimension is 18 feet or less sealed will probably do the job, if longer than that you're better off with ported. Ported is a lot larger, but since the room is a lot larger that shouldn't be a problem.
            www.billfitzmaurice.com
            www.billfitzmaurice.info/forum

            Comment


            • #21
              Re: ultimax 18 box modeling help needed.

              I have built several subwoofer boxes designed by others I want to try to design and build one of my own. Well not entirely my own as we all know I am limited as far as my knowledge of designing. I understand that following a proven design is a safe and easy way to reach satisfying sound and performance but what does it teach me about designing? I am trying to learn how to design an enclosure have I come to the wrong place for that?

              Comment


              • #22
                Re: ultimax 18 box modeling help needed.

                How do my measurements in post #5 look? Do they work with the port size does it need to be changed?

                Comment


                • #23
                  Re: ultimax 18 box modeling help needed.

                  If your goal is to really learn speaker design, then nothing beats a good reference book like "Speakerbuilding 201".

                  Comment


                  • #24
                    Re: ultimax 18 box modeling help needed.

                    Originally posted by Jwhite View Post
                    (post #23)

                    How do my measurements in post #5 look? Do they work with the port size does it need to be changed?



                    Originally posted by Jwhite View Post
                    (post #5)

                    I came up with 60x21x23 for box dimensions which after sub displacement is about 13.9 cubic feet. I came up with 3" wide by 19.5" tall 44" long vent for about 15hertz the displacement for the vent is about .66cubic feet. I dont know how to come up with those graphs you guys use or even how to read most of them but I do understand that is an important part of this process. Can some one help me out in that aspect of this design? I want to be sure this will perform in both movies and music.
                    .

                    Here is a model of your design using Unibox...

                    For two Dayton UM18-22 woofers wired in parallel.
                    For 13.9 cubic feet used 393.6 liters, no fill, no leaks.
                    For 3 inch by 19.5 inch rectangular port used 21.92 cm diameter port, flush one end.
                    For 44 inch long port, adjusted box tuning finding that 14.95 Hz came very close at 11.74 cm port length.
                    Included port resonances, because fundamental is centered at ~142 Hz.

                    Separately included 4th order Linkwitz-Riley (Q=0.5) at 80 Hz active low pass filter to show affect on port resonance SPL.
                    Attached Files
                    Last edited by JRT; 08-13-2014, 11:26 PM.
                    "Our Nation’s interests are best served by fostering a peaceful global system comprised
                    of interdependent networks of trade, finance, information, law, people and governance."
                    - from the October 2007 U.S. Naval capstone doctrine
                    A Cooperative Strategy for 21st Century Seapower
                    (a lofty notion since removed in the March 2015 revision)

                    Comment


                    • #25
                      Re: ultimax 18 box modeling help needed.

                      Here are some more graphics of that same model.
                      Attached Files
                      "Our Nation’s interests are best served by fostering a peaceful global system comprised
                      of interdependent networks of trade, finance, information, law, people and governance."
                      - from the October 2007 U.S. Naval capstone doctrine
                      A Cooperative Strategy for 21st Century Seapower
                      (a lofty notion since removed in the March 2015 revision)

                      Comment


                      • #26
                        Re: ultimax 18 box modeling help needed.

                        The graphics below show what you get with two Dayton UM18-22 and four Acoustic Elegance PR18-1600 passive radiators (no additional mass) in 450 liters net enclosed volume, no leaks, no stuffing.

                        If you divide this in half, using one woofer, two PRs, half the enclosed volume, half of the stereo amplifier (one channel), then response SPL would be -6_dB relative to what is shown below, and excursion remains the same. And a higher output amplifier could be used to drive that half to higher SPLs (note that excursion in the model is well below Xmax where the higher level content exists).



                        Click image for larger version

Name:	Dayton UM18-22.jpg
Views:	1
Size:	151.6 KB
ID:	1159672

                        Click image for larger version

Name:	PR Response Dayton UM18-22.gif
Views:	1
Size:	32.9 KB
ID:	1159673

                        Click image for larger version

Name:	PR Excursion Dayton UM18-22.gif
Views:	1
Size:	35.5 KB
ID:	1159674

                        Click image for larger version

Name:	PR Impedance Dayton UM18-22.gif
Views:	1
Size:	23.2 KB
ID:	1159675

                        Click image for larger version

Name:	Amplifier Peak Voltage Dayton UM18-22.gif
Views:	1
Size:	18.3 KB
ID:	1159676
                        Last edited by JRT; 08-13-2014, 11:32 PM.
                        "Our Nation’s interests are best served by fostering a peaceful global system comprised
                        of interdependent networks of trade, finance, information, law, people and governance."
                        - from the October 2007 U.S. Naval capstone doctrine
                        A Cooperative Strategy for 21st Century Seapower
                        (a lofty notion since removed in the March 2015 revision)

                        Comment


                        • #27
                          Re: ultimax 18 box modeling help needed.

                          Here is what you get with one Dayton UM18-22 (DVCs wired in series) and two Acoustic Elegance PR18-1600 passive radiators (no additional mass) in 225 liters net enclosed volume, no leaks, walls covered, powered at 110.5_V-peak.


                          Click image for larger version

Name:	PR Response Dayton UM18-22 at 1400W.gif
Views:	1
Size:	32.5 KB
ID:	1159677

                          Click image for larger version

Name:	PR Excursion Dayton UM18-22 at 1400W.gif
Views:	1
Size:	35.8 KB
ID:	1159678

                          Click image for larger version

Name:	Amplifier Peak Voltage Dayton UM18-22 at 1400W.gif
Views:	1
Size:	18.5 KB
ID:	1159679

                          Click image for larger version

Name:	PR Impedance Dayton UM18-22 at 1400W.gif
Views:	1
Size:	24.8 KB
ID:	1159685
                          Last edited by JRT; 08-13-2014, 11:33 PM.
                          "Our Nation’s interests are best served by fostering a peaceful global system comprised
                          of interdependent networks of trade, finance, information, law, people and governance."
                          - from the October 2007 U.S. Naval capstone doctrine
                          A Cooperative Strategy for 21st Century Seapower
                          (a lofty notion since removed in the March 2015 revision)

                          Comment


                          • #28
                            Re: ultimax 18 box modeling help needed.

                            The graphics below represent one UM18-22 and three Acoustic Elegance PR18-2100 passive radiators (no additional mass) in 265 liters, with no leaks, walls covered, dual voicecoils wired in series, and flat drive level at 109.5_V-peak.

                            Note that the woofer has a dip in excursion centered at 16.6_Hz tuning. Above tuning the woofer excursion sees a local peak where it rises to 22mm, tangent to X-max lines. Below tuning, the woofer excursion rises thru 22mm at slightly below 15_Hz, and the three PRs are rising thru 30mm also slightly below 15_Hz (and again for emphasis, this is with flat input at 109.5_V-peak).

                            SPL is 118.5_dB in the region around 50_Hz. A pair of these located within 1/4 wavelength separation distance in th frequency range of interest would sum +6_dB.

                            To me this one looks pretty good for a big open room. Opinions vary.
                            Attached Files
                            "Our Nation’s interests are best served by fostering a peaceful global system comprised
                            of interdependent networks of trade, finance, information, law, people and governance."
                            - from the October 2007 U.S. Naval capstone doctrine
                            A Cooperative Strategy for 21st Century Seapower
                            (a lofty notion since removed in the March 2015 revision)

                            Comment


                            • #29
                              Re: ultimax 18 box modeling help needed.

                              Thank you for all of these models. I am having a difficult time understang what all of this means though. I will likely be running only one um-18 for the time being. I have bean reading up on box modeling to further understand what these graphs are telling me. I dont know if my budget will allow the purchase of passive radiators at the moment the wife is still trying to get over the expense so far. I am going to take a picture of what I am trying to replace with this build to get some advice.

                              Comment


                              • #30
                                Re: ultimax 18 box modeling help needed.

                                Originally posted by Jwhite View Post
                                Thank you for all of these models. I am having a difficult time understang what all of this means though. I will likely be running only one um-18 for the time being. I have bean reading up on box modeling to further understand what these graphs are telling me. I dont know if my budget will allow the purchase of passive radiators at the moment the wife is still trying to get over the expense so far. I am going to take a picture of what I am trying to replace with this build to get some advice.
                                Some things to think about...

                                Consider how you dribble a basketball. Very little motion is required from the hand to produce large motion from the ball. Likewise the woofer motion and the air spring enclosed in the box work together to dribble the passive radiator. At tuning, very little motion is required from the woofer to move the PRs, and likewise the PR motion is putting a lot of opposing pressure/vacuum inside the box on the back of the woofer diaphram which reduces the motion of the woofer diaphram. Well away from the tuning frequency the PRs don't move much with a lot of woofer motion, a little like trying to dribble the basketball out of sync.

                                The woofer motion and PR motion are not sharing the same phase across the frequency range, are not marching in step. They hit their zero crossings at different moments in time. So the sum total SPL has to include consideration of the phase of each source in that sum.

                                Look at the last model, the graphic showing frequency response. The summed SPL from the woofer and PRs is the dark blue curve above the others. The red straight line is what the woofer by itself would produce if it was driven at X-max across the range of frequencies. The woofer is not really driven that way, rather the redline just represents a limit at X-max. I set the drive level in that model such that the woofer's output kisses that line in the mid-20s_Hz region without crossing over, so it hits X-max there, but does not exceed X-max there. The black line below is the woofer SPL. The light blue curve that peaks in mid-teens is the SPL from the three PRs. Down towards 10_hz you can see that woofer and PRs are so out of phase that their sum curve is well below the the woofer curve and well below the PR curve.

                                The dark blue sum curve (mentioned above) is the output of the subwoofer system, the whole rather than the individual pieces. It is shown as an anechoic response.
                                "Our Nation’s interests are best served by fostering a peaceful global system comprised
                                of interdependent networks of trade, finance, information, law, people and governance."
                                - from the October 2007 U.S. Naval capstone doctrine
                                A Cooperative Strategy for 21st Century Seapower
                                (a lofty notion since removed in the March 2015 revision)

                                Comment

                                Working...
                                X