Announcement

Collapse
No announcement yet.

Curved line array?

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

  • Curved line array?

    I have a bunch of old monsoon planar mids and tweets. Was going to make a line array about 64" tall (sealed back). One of the problems with tall line arrays is they are not time aligned from center to top and center to bottom. On a 64" array, at 14' listening distance the center speakers are 3" closer than the top and bottom creating smear or loss of definition. One of the solutions for this is to send more power to the center speakers and less to toward the top and bottom. But I don't like that idea.
    I could make it curved so that the tops and bottoms are 3" forward from the center drivers.

    ***My concern is that this will point more drivers straight toward the listening position and adversely affect the frequency response due to that direction manipulation***
    Maybe I should build a cheap mock up and try it before making a great looking box that kinda sucks.

    Any thoughts?
    Two very good sociological markers.
    The state of our public wash rooms.
    How we treat each other behind the safety of a monitor and key board.

  • #2
    I did a focused array with 4" full range drivers.
    http://www.diyaudio.com/forums/full-...-arrays-3.html

    definitely play with cardboard b4 cutting wood.

    Comment


    • #3
      An alternative is to use DSP to achieve precise time alignment. I believe neildavis is doing something like that. That's as far as my knowledge on the subject goes though!!

      Comment


      • #4
        This is one of those instances where intuition isn't necessarily correct. Reference this: https://www.parts-express.com/cbt36k...r-kit--301-980
        www.billfitzmaurice.com
        www.billfitzmaurice.info/forum

        Comment


        • #5
          Planar drivers don't radiate like cone or dome drivers. I cover slot/planar/ribbon drivers in my near field line array white paper at:

          http://www.audioroundtable.com/misc/nflawp.pdf

          Planar drivers radiate such that their output narrows toward the aperture length as frequency increases. Don't count on much SPL gain vs. arrays made with cone drivers as the radiated sound from each driver will have minimal overlap.

          Planar drivers should be mounted in a straight line vertical stack. If the array is tall enough (see the WP for near field distance calculation), your ears will integrate the sound as you move up or down the line so that the sound tends to merge and is limited to the space directly in front of you.

          Bottom line: no issues with the sound that you hear from the drivers at the bottom and top at your normal listening distance. Try this if you wish and listen for how it sounds.

          Comment


          • #6
            Originally posted by norman bates View Post
            I did a focused array with 4" full range drivers.
            http://www.diyaudio.com/forums/full-...-arrays-3.html

            definitely play with cardboard b4 cutting wood.
            Thanks for the info. That's a nice build BTW.

            That graph looks very close to what a single driver would measure. That is a good sign if I have understood it correctly.

            Is listening distance pretty flexible for that build?
            Two very good sociological markers.
            The state of our public wash rooms.
            How we treat each other behind the safety of a monitor and key board.

            Comment


            • #7
              Thank you.
              Years in development (thoughts, saving money, finding a builder, etc).

              yes, it sounded really good but lit up the room similar to a line array, but it sounded best at the focus.
              Funny thing was at sweet spot, the sound only seemed to be coming out of the middle 3 4" drivers.

              I learned you need baffle step, micro 6" cubes (within the enclosure) make a peak in response 1-2khz, and an sd equal to a 12" worth of full range driver isn't enough bass for me.

              I found sweet spot at focus was 1' tall, but couch wide (as much as the drivers do horizontal dispersion).
              Someone said to sit 1' closer than the focus, couldn't tell you.

              Those drivers were very revealing, that was one of the best sounds I've ever had.

              Good luck with your build.

              Comment


              • #8
                Norman,

                Have you ever built a line array with planar transducers?

                Try one sometime and likely you would not recommend a concave array with them.

                Likely, he will not be using baffle step with his planars unless they can go into the below 500 Hz area.

                Concave or focused arrays have a very limited listening spot as Norman points out which most people find very limiting. Checkout the arrays you see at concerts and such and you will notice that none of them are concave arrays but straight or at most convex curved.

                The CBT arrays mentioned by Bill are very nice--wide horizontal coverage across the room and near constant volume front to back as well. I have a CBT at my home.

                http://techtalk.parts-express.com/fi...8&d=1531769004



                Jim

                Comment


                • #9
                  Originally posted by scottvalentin View Post
                  An alternative is to use DSP to achieve precise time alignment. I believe neildavis is doing something like that. That's as far as my knowledge on the subject goes though!!
                  It's not just DSP--you need lots of amps: one for each DSP channel. I've got a pair of boards with 3 ADAU1701 DSP chips plus 20 power amps for each board. That's 8 amps for the woofer and 12 amps for the tweeters. They are not very powerful amps, but they are sufficient to fill the room reasonably well. Plus another pair of plate amps for the subs.

                  I had a lot of debugging to get through, but I've got all of the amps working, most of the DSP software working, and a cell phone app to control the apparent curvature. But I only have one array wired up completely, so I can only listen in mono, to one or the other channel. But I'll have stereo in a week or two, and I'll add a lot more info to the project page at: http://www.audiodevelopers.com/10-ca...rray-with-dsp/. Being able to control the curvature electronically is very interesting, but I need to have stereo and set up the EQ before I'll post any more details. Except for this: the "concave" setting of the delay is pretty cool, at least in mono
                  Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

                  Comment


                  • #10
                    Crossover will be around 225hz for the monsoons mids (off of MM 700 computer speakers) There will be between 12 to 16 of them on each speaker depending on how I build it. Tweeters are off of the Mh 500 and will be crossed over at 2000hz which they can handle no problem even a bit lower I think. 12 of the tweets for each speaker. Below this will be 1 EV SP15a for each speaker crossed over at 60hz. After that it's my sub taking over (dual 15 push push, tuned to 14Hz).

                    One option is to build a pivot at each mid (turned sideways so 4 inches tall) and tweeter (5 inches tall) combination (so every 5 inches), so that it could be curved both forward or backward or put straight, and I could play with it for a year or so LOL!
                    Yes that would be difficult build. It would have to have two different sets of stabilising side panels. One for forward concave option and one for backward.

                    I'll change my mind tomorrow.
                    Two very good sociological markers.
                    The state of our public wash rooms.
                    How we treat each other behind the safety of a monitor and key board.

                    Comment


                    • #11
                      If I make it adjustable, I might find a compromise concave ratio. One where smear is limited and yet, sweet spot is larger.
                      Two very good sociological markers.
                      The state of our public wash rooms.
                      How we treat each other behind the safety of a monitor and key board.

                      Comment


                      • #12
                        Originally posted by Jim Griffin View Post
                        Planar drivers don't radiate like cone or dome drivers. I cover slot/planar/ribbon drivers in my near field line array white paper at:

                        http://www.audioroundtable.com/misc/nflawp.pdf

                        Planar drivers radiate such that their output narrows toward the aperture length as frequency increases. Don't count on much SPL gain vs. arrays made with cone drivers as the radiated sound from each driver will have minimal overlap.

                        Planar drivers should be mounted in a straight line vertical stack. If the array is tall enough (see the WP for near field distance calculation), your ears will integrate the sound as you move up or down the line so that the sound tends to merge and is limited to the space directly in front of you.

                        Bottom line: no issues with the sound that you hear from the drivers at the bottom and top at your normal listening distance. Try this if you wish and listen for how it sounds.
                        So what you are saying is. Infinity IRS 5 had it right.
                        Two very good sociological markers.
                        The state of our public wash rooms.
                        How we treat each other behind the safety of a monitor and key board.

                        Comment


                        • #13
                          some planars have such narrow vert dispersion, I think they would work well for a flat array.

                          My only focused array was using 4" (5" frame) full range drivers.

                          Certainly not for everyone (or most actually).

                          Comment


                          • #14
                            Norman,

                            Yes, if we use planars--which have reduced vertical radiation characteristics--then array them as a concave array, we can further reduce any spread of the sound. Pretty soon we will be listening through headphones. Hence, loudspeakers will no longer be needed.

                            Jim

                            Comment


                            • #15
                              My understanding on vertical dispersion in an array is that it is set not by the driver itself but by the height of the array in array application. That being said, point source drivers tend to stop functioning like line array because of their center to center spacing (as frequency increases) which creates a different dispersion characteristic per individual driver compared to the planar driver which does not have a center point.

                              What I'm getting from all this great input is that I should build a quick test unit first or build it adjustable, to find what imperfections I can live with.
                              Try a quick straight up first, or make it so that each 5.25" can be pivoted (safely).

                              This is one option for driver lay out (but with 12 mids and tweets) especially if there are pivot points at each driver section.
                              Attached Files
                              Two very good sociological markers.
                              The state of our public wash rooms.
                              How we treat each other behind the safety of a monitor and key board.

                              Comment

                              Working...
                              X