DIY side surround dipoles

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  • Bent
    Super Senior Member
    • Sep 2003
    • 1570

    DIY side surround dipoles

    Greetings to all:
    First post here - I'm from the same province as Mr. Pratt, albeit approx 70 km away from him.

    I've been into HT for a coupla three years now, have upgraded a Kenwood VR-309 to a HK AVR-525, have Paradigm Mini-Monitors V.2, CC-350 and Titans as rear surrounds. Since the HK is a seven channel unit, and 2nd Zone doesn't really apeal to me yet, I'm thinking of adding some side surround speakers, Paradigms ADP's seem a tad dear, (and I don't care for their appearance either), so I'm actaully thinking either DIY or a kit...
    Timbre' matching asside, has anyone ever built their own Dipole surrounds? Did it go well, did they integrate well? You know, the usual questions...
  • sfdoddsy
    Senior Member
    • Sep 2000
    • 496

    #2
    I have, and it is actually one of the easiest speakers you could build, at least from a construction point of view. Here's an early version of mine:



    I have it firing at me like a monopole, but you could turn it sideways to sit in the null if you wanted.

    You will need to boost the bass for flat response.

    Here's a link to a design suggestion with crossover:

    Open baffle loudspeaker prototypes with passive equalization and passive crossovers


    Cheers

    Steve




    Steve's DIY Dipoles
    Steve's OB Journey

    Comment

    • Bent
      Super Senior Member
      • Sep 2003
      • 1570

      #3
      Accyually I was thinking along the lines of a sealed unit with matched drivers back-to-back, but what you've proposed is essentially the same thing... the driver does "essentially" operate "out of phase" (I just needed a second to get my head around it).

      I heard a set of DIY monopoles similar to these pictures (OK, they were an open back design) at Creative Audio in Winnipeg 10 years ago, Dan Scrapneck built them, and gave me the opportunity to lesten to them at his store for a good 30 minutes - I couldn't believe how well they not only conveyed both a sense of soundstage, but "depth" as well.

      interesting idea.

      Comment

      • sfdoddsy
        Senior Member
        • Sep 2000
        • 496

        #4
        Yep, the concept is the same, you just use fewer drivers. The big advantage (to me) as opposed to tradition surround dipoles, is that you can if you want simply turn them around to have the drivers facing you and have direct radiating surrounds. Which I prefer both in 5.1 and 7.1 setups.

        Depending in your needs, you could obviously also do them as TMM or MTM, and even have the drivers opposing each other for lowered distortion.

        The danger, of course, is that you may like them more than your mains and end up going dipole (open baffle) all the way.

        Best things is, cheap as all get out to try.
        Cheers

        Steve




        Steve's DIY Dipoles
        Steve's OB Journey

        Comment

        • Hank
          Super Senior Member
          • Jul 2002
          • 1345

          #5
          Well, I built triangular side surrounds a couple of years ago: the Speaker City T62. I bought their drivers and they gave me the outside dimensions and I built the cabinets. I really like the configuration and have had nothing but compliments on their "sound".
          http://www.speakercity.com/ht_rear.shtml

          Comment

          • Bent
            Super Senior Member
            • Sep 2003
            • 1570

            #6
            I've been pondering this for a good while now, and started wondering about one of the things Mr. Linkwitz (sp?) mentioned, he said basicaly that an open box speaker (dipole) isn't as affected my poor room accoustics...

            I have nothing but poor room accoustics, and I'm sure I could build some dipoles for a lot less trouble than I'd have trying to tame a bad room!

            Can anybody offer an explanation as to why these types of dipoles aren't as dependant on room accoustics (in something easy to understand?)

            Thansk much.

            Comment

            • sfdoddsy
              Senior Member
              • Sep 2000
              • 496

              #7
              I'm the simplest one here, so I'll try.

              In simple terms, dipoles have a radiation pattern like a figure eight 8, and monopoles like a sphere 0 (although I'm sure someone will correct me here .

              This means that the areas at right angles to the acoustic center (the skinny bit of the figure eight) receive less acoustic energy than the front and the back.

              If you place this speaker in a room, aimed at the listener, it will excite fewer room resonances to the sides (ie side walls) and also top and bottom (ceiling and floor) because of these nulls.

              The result is greater clarity, especially in the bass. Once you go open back, the others sound slack. I just made that up .

              This is also how dipoles work as surround speakers of course. You deliberately sit in the null so you can't pick the exact source of the sound.

              Cheers

              Steve




              Steve's DIY Dipoles
              Steve's OB Journey

              Comment

              • Bent
                Super Senior Member
                • Sep 2003
                • 1570

                #8
                So, (technical time now) A dipole arrangement gives minimal dispersion to either side, and a D'Appolito can be tuned (via crossover values and Order) to allow limited vertical dispersion... Will a dipole-D'Appolito design work? And ow dramatically does the off- axis response get affected (more than one listener at a time in this house), and in the case of a TM type, is the "lobing" effect any different than a conventional enclosure?

                Comment

                • Bent
                  Super Senior Member
                  • Sep 2003
                  • 1570

                  #9
                  oops, double post.

                  Comment

                  • sfdoddsy
                    Senior Member
                    • Sep 2000
                    • 496

                    #10
                    If you really want technical, this may help with the radiation patterns:

                    The acoustic behavior of rooms at different frequencies. The loudspeaker's polar radiation pattern determines its interaction with the room and the accuracy of sound reproduction. Reverberation time as most important parameter for a room's acoustic behavior.


                    My mains use an MTM configuration above 100Hz, and there are plans for these (or something similar) on the Linkwitz site. Check under Phoenix, but here's a beauty shot.



                    You should also do a search here for Arvo Part, as Jon is designing a similar speaker, but using passive crossovers.

                    As far as off axis goes, mine seem pretty good, both listening and measurements.

                    Linkwitz's new speaker uses a TM arrangement, which he feels has slightly fewer problems vertically.

                    Cheers

                    Steve




                    Steve's DIY Dipoles
                    Steve's OB Journey

                    Comment

                    • Hank
                      Super Senior Member
                      • Jul 2002
                      • 1345

                      #11
                      Once you go open back, the others sound slack.
                      That was too good to not be repeated.
                      Good simple explanation, Steve!
                      Someone is bound to bring up the direct radiating versus dipole issue, but for side surrounds, I still prefer dipole.

                      Comment

                      • sfdoddsy
                        Senior Member
                        • Sep 2000
                        • 496

                        #12
                        You mean I got a technical explanation right?

                        I'm retiring from comments right now.

                        ;zx




                        Steve's DIY Dipoles
                        Steve's OB Journey

                        Comment

                        • Andrew Pratt
                          Moderator Emeritus
                          • Aug 2000
                          • 16507

                          #13
                          Hi Bent nice to see other manitoban's on the board:T You're more then welcome to drop on by if you're in the city (I'm in Crestview near the Grace Hospital)




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