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  • #91
    Originally posted by Rory Buszka View Post
    There were some requests for additional information about my DIY "LRAD" portable acoustic hailing demonstration, and the speaker components used for the "acoustic emitter" - the speaker head.

    The drivers used were PRV Audio D4400Ph-Nd phenolic-diaphram neodymium drivers, with a combined weight of 35 lbs of driver in the speaker, plus about 10 more pounds of MDF and hardware. They are mounted to horns from "Blast King", a car audio company with a cheeky name, but they were the right size and the right flare rate, and they had a very solid thick wall construction. The D4400Ph-Nd is about 6" in outer diameter, and they have a 4" diaphragm with a 4" voice coil, so they are the most monstrous midrange-oriented compression driver I could use at a reasonable price to keep the project feasible. (BMS has a dual-diaphragm midrange compression driver but that would be unreasonably expensive.) The emitter was positioned a little less than 6' off the ground using a pro-audio tripod speaker stand.

    Peak sensitivity of the driver is 113dB 2.83V/1m, and the four drivers operate as a coherent 'phased array' summing to provide a voltage sensitivity of 125 dB @ 2.83V/1m, with the impedance dropping to 2 ohms (all four drivers are in parallel). This is no problem for the amp used, which is an auto sound amp with an internal step-up power supply, designed to draw power from a 12V battery. The amp I used for the demonstration was a SounDigital Nano 250.2 supplying 125W into the 2-ohm load, but the plan for future demos is to use a Taramps HD3000 2-ohm variant to supply up to 3kW peak into 2 ohms.

    Frequency response is from 500 Hz at -10dB to 7.5kHz at -10dB (full power operating range 400-8,000 Hz should be no problem), and peak SPL is at 4.5kHz, with smooth-ish response between 1kHz and 5kHz (no big peaks).

    With the amp I used, peak SPL at 4.5kHz/1m should have been around 145 dB, and SPL at the 500' distance of the listening position should have peaked around 100 dB, but for various reasons (including atmospheric loss, windage, ground reflections, power compression, throat distortion, or the lower crest factor of speech compared to tone signals) I suspect I wasn't achieving that level, at least not continuously. There is more testing to be done. With the bigger amp, it should be possible to reach continuous on-axis levels of 154 dB at 1m, and peaks of 158 dB; that's pretty lofty so I'll need to figure out a way to validate that. The guidance from FEMA for designing outdoor warning siren systems uses a -10dB per distance doubled model instead of -6dB for a typical point source, so they are factoring in more losses. Even so, all reports during the demo confirmed there was no lack of volume.

    Thanks for indulging me with the chance to demonstrate this project publicly. There's nothing really patentable here; the design approach is to implement a modular construction with a phased array of 'cells' that provide good efficiency in converting electrical power to acoustic power. They can then be configured in any manner needed to optimize dispersion and suit the application, such as a panel array (imagine 2x4 or 3x3 units in a grid), a circular array of 12 drivers, a hexagonally-packed array on a flat surface, or a ring array (annular array) where very narrow dispersion is needed from a minimum number of sources.

    JR's wife took a video: https://www.youtube.com/watch?v=OhusYx4Dv3Q

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    Very impressive demo. Thanks for sharing.
    SideTowers: http://techtalk.parts-express.com/fo...corundum-build
    Totally Flat: http://techtalk.parts-express.com/fo...5-totally-flat
    Plumber's Delight: http://techtalk.parts-express.com/fo...notech-winners
    Linehopper: http://techtalk.parts-express.com/sh...Esoteric-build

    Comment


    • #92
      Clear as a bell too!

      I will see if i can get EQ's xover to post it. Time has been against me this week to get some post event stuff in order.
      Wolf
      "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
      "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
      "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
      "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

      *InDIYana event website*

      Photobucket pages:
      https://app.photobucket.com/u/wolf_teeth_speaker

      My blog/writeups/thoughts here at PE:
      http://techtalk.parts-express.com/blog.php?u=4102

      Comment


      • #93
        Originally posted by wogg View Post
        That's a great idea! I'll have to post my design and reasoning behind it when I get a chance. Didn't win.. but was in one of the "split the room" votes so I'll take it!

        "Hoping to finish in the top 10" - Billet
        Thanks, Wogg. I'm putting together a set of VituixCad overlay graphs to compare all xovers and plan to post them when I have everything put together. My plan is to do one overlay comparison graph for on-axis FR, one overlay comparison graph for Listening Window, one overlay comparison graph for estimated In-Room Response, and one overlay comparison graph for power response. Should be interesting. We could also compare each xovers NBD (Olive) preference rating scores.

        dcibel helped me set up the model in VituixCad and so far I have collected 7 of the 11 crossovers and have keyed them into VituixCad's variant tabs. Still looking for schematic data on 4 of the crossovers, one of which I think is yours. Thanks again.

        Bill
        SideTowers: http://techtalk.parts-express.com/fo...corundum-build
        Totally Flat: http://techtalk.parts-express.com/fo...5-totally-flat
        Plumber's Delight: http://techtalk.parts-express.com/fo...notech-winners
        Linehopper: http://techtalk.parts-express.com/sh...Esoteric-build

        Comment


        • #94
          I can say for sure mine measured flat too, as we RTA'd them back on voicing day. FWIW, Nick, Chuck, and myself all had a +13mm offset in the model compared to the tweeter.

          I will try and get EQ, Jack's, and more if you need them, Bill.
          Wolf
          "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
          "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
          "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
          "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

          *InDIYana event website*

          Photobucket pages:
          https://app.photobucket.com/u/wolf_teeth_speaker

          My blog/writeups/thoughts here at PE:
          http://techtalk.parts-express.com/blog.php?u=4102

          Comment


          • #95
            Originally posted by Wolf View Post
            I can say for sure mine measured flat too, as we RTA'd them back on voicing day. FWIW, Nick, Chuck, and myself all had a +13mm offset in the model compared to the tweeter.

            I will try and get EQ, Jack's, and more if you need them, Bill.
            Wolf
            Thanks, Ben. I think Wogg's would be #8, so the only ones I still need are EQ (#2), Jack (#9), and Chuck (#11).
            SideTowers: http://techtalk.parts-express.com/fo...corundum-build
            Totally Flat: http://techtalk.parts-express.com/fo...5-totally-flat
            Plumber's Delight: http://techtalk.parts-express.com/fo...notech-winners
            Linehopper: http://techtalk.parts-express.com/sh...Esoteric-build

            Comment


            • #96
              Here you go 4thtry

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              Here's the resulting 6-Pack from VirtuixCAD.
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              There really wasn't much unconventional in the design. The tanked coil in the woofer was my main method to kill breakup to the point of it not being in the chart any longer, and the 3rd order on the tweeter looked like it did the job above Fs just enough. I didn't like that the tweeter distortion was rising prior to the roll off when looking at the data, but didn't want to push the knee any higher based on the power response around 2K looking great. Electrically the cross is just above 2K while acoustically they end up just below 2k. I opted to not do anything with that rising top response of the tweeter, I tend to prefer that as compensation for my own Tinnitus.

              I also did merged responses of the woofer on axis, and modeled the full system in Xsim to validate the baffle step and make sure I wasn't ending up weak in the low end.
              Electronics engineer, woofer enthusiast, and musician.
              Wogg Music
              Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

              Comment


              • #97
                Part selections were tight, used what I had + bargain parts from PE. The caps were selected by value range, so the tweeter ended up with an NPE in series that I normally wouldn't do. The woofer coil was a huge compromise due to availability. I needed 2mH and wanted a low resistance laminate core, but had to settle for a small gauge cheap bobbin on buyout. It ended up in the 0.3 ohm range, costing my maybe 0.5dB in output.

                Construction was a "what do I have already" exercise. I got a new 1/8" HDF panel, but had 1x2 red oak and 1.5" wide aluminum stock on hand to make a little chassis. The oak was slotted by hand holding the board against a fence and running the skill saw down a couple times until the kerf cut was wide enough.

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                Kerf cutting the oak by hand

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                Mostly done

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                Ta Da! Waiting on the second 2mH coil on the left, wrong part mis-haps and re-shipments.

                Wire was also what I had on hand, so pretty small gauge. With short runs, this isn't important.
                Electronics engineer, woofer enthusiast, and musician.
                Wogg Music
                Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

                Comment


                • #98
                  I really like the construction of these, Wogg! You can swap boards and do it again.

                  Mine was made like a proto-board, with a common ground running the perimeter, and jumpers from tweeter to woofer halves. I plan on using them again....
                  Pics to come...
                  Wolf
                  "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                  "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                  "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                  "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                  *InDIYana event website*

                  Photobucket pages:
                  https://app.photobucket.com/u/wolf_teeth_speaker

                  My blog/writeups/thoughts here at PE:
                  http://techtalk.parts-express.com/blog.php?u=4102

                  Comment


                  • #99
                    Nice, neat xover design. Thanks for sharing. We should all post a pic or two of our xovers. I've only seen 4 or 5 of them so far.
                    SideTowers: http://techtalk.parts-express.com/fo...corundum-build
                    Totally Flat: http://techtalk.parts-express.com/fo...5-totally-flat
                    Plumber's Delight: http://techtalk.parts-express.com/fo...notech-winners
                    Linehopper: http://techtalk.parts-express.com/sh...Esoteric-build

                    Comment


                    • 2 pair were virtually identical in construction.
                      Wolf
                      "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                      "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                      "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                      "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                      *InDIYana event website*

                      Photobucket pages:
                      https://app.photobucket.com/u/wolf_teeth_speaker

                      My blog/writeups/thoughts here at PE:
                      http://techtalk.parts-express.com/blog.php?u=4102

                      Comment


                      • Congratulations to Ben and Chuck. Much deserved.


                        I recently did a 3 way design and had two crossovers, both giving on-axis responses of +/- 1dB between 40Hz and 20Khz. And I tried two different tweeters. Just slightly different crossover points between the M-T. But yes, one could they they are both measure “flat”.

                        But they both sound different. And I’m not sure which I prefer, or which others prefer. my guess is that it depends on the room and program material, but a slightly more mellow sound may be more acceptable to the general listening, but may be not for critical listening

                        It’s like when you adjust your resistor for your tweeter. A half dB across the entire tweeter band can make a Goldilocks situation; the difference from “not quite right, but too much” and “just right”
                        Voicing is real thing.

                        Comment


                        • Who let in these guys??
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                          Bill's (Chuck's behind):
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                          John's:
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                          Chuck's:
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                          EQ:
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                          More in a few...
                          Wolf
                          "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                          "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                          "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                          "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                          *InDIYana event website*

                          Photobucket pages:
                          https://app.photobucket.com/u/wolf_teeth_speaker

                          My blog/writeups/thoughts here at PE:
                          http://techtalk.parts-express.com/blog.php?u=4102

                          Comment


                          • Warts 'N' All generic xover for initial audible baseline. No comp of any sort was employed:
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                            Mine:
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                            Jack's:
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                            Later,
                            Wolf
                            "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                            "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                            "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                            "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                            *InDIYana event website*

                            Photobucket pages:
                            https://app.photobucket.com/u/wolf_teeth_speaker

                            My blog/writeups/thoughts here at PE:
                            http://techtalk.parts-express.com/blog.php?u=4102

                            Comment


                            • These are the only additional xover photos I was able to get:

                              Ken's (left) next to dcibels (right):

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                              Billet's:

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                              SideTowers: http://techtalk.parts-express.com/fo...corundum-build
                              Totally Flat: http://techtalk.parts-express.com/fo...5-totally-flat
                              Plumber's Delight: http://techtalk.parts-express.com/fo...notech-winners
                              Linehopper: http://techtalk.parts-express.com/sh...Esoteric-build

                              Comment


                              • So, we're missing one only.
                                We have:
                                Wogg-8/Me-7/Chuck-11/Ken-10/dcibel/Jack-9/EQ-2/Billet/4thtry/JohnH.

                                We need a pic of Nick's.

                                Wolf
                                "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                                "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                                "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                                "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                                *InDIYana event website*

                                Photobucket pages:
                                https://app.photobucket.com/u/wolf_teeth_speaker

                                My blog/writeups/thoughts here at PE:
                                http://techtalk.parts-express.com/blog.php?u=4102

                                Comment

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