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It’s that time audio enthusiasts! Registration for the 2019 Speaker Design Competition is now open! Visit midwestaudiofest.com for details and to list your speaker project. We are excited to see all returning participants, and look forward to meeting some new designers this year, as well! Be sure your plans include a visit to the Parts Express Tent Sale for the lowest prices of the year, and the Audio Swap Meet where you can buy and trade with other audio fans. We hope to see you this summer! Vivian and Jill
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Speaker directivity in home sized rooms (Earl Geddes)

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  • Speaker directivity in home sized rooms (Earl Geddes)

    "This has been a simplified analysis of some of the problems of small room acoustics, but it does point out one thing very clearly. What we want in source directivity is not the omni-directional response that we get from the extremely common small loudspeaker systems that dominate today’s marketplace. We want a narrow directivity such as can only be achieved with waveguides and/or arrays of transducers." - Earl Geddes

    Geddes argues omni-directional speaker design has led to increased demand for room treatments; directional sound with fewer treatments makes better use of reflections; toe-in directional speakers to achieve at least 10 millisecond first reflection delays.

    https://www.youtube.com/watch?v=fE2nWVwFT9k

    http://www.gedlee.com/downloads/AT/Chapter_8.pdf

  • #2
    As an owner of giant horn speakers in a small room, I have to agree!
    Francis

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    • #3
      Earl is going up against WAF here. I bet I know who will win.
      Francis

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      • #4
        Earl may have some valid points, but judging by pictures of his room Floyd Toole hasn't bought into them.




        www.billfitzmaurice.com
        www.billfitzmaurice.info/forum

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        • #5
          I think sometimes it boils down to preference. I hate reflective rooms, no matter how well they are designed. The Revel Salon room at the JBL center in Times Square drove me nuts with all the reverberance. My girl was annoyed by it too. I notice that they finally added some absorbers on the walls there. Much better!
          Francis

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          • #6
            Originally posted by billfitzmaurice View Post
            Earl may have some valid points, but judging by pictures of his room Floyd Toole hasn't bought into them.
            The question is how wide a beamwidth and how should the beamwidth change with frequency? Many from the studio side look for a fairly narrow beamwidth that is constant with frequency. I have not looked at the Geddes references cited but he is likely to be in this camp. Others look for a wider beamwidth that narrows with increasing frequency. This brings in more reflections that are rolled off with frequency rather than flat. I suspect Toole is more in this camp. An extensive listening test reported on AVL a couple of years ago compared the JBL M2 and the Revel Salon2 which are good example from each of the camps.

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            • #7
              The shame. I don't even know what AVL is and my speakers are little MTMs.

              At least I have an opinion on Geddes.

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              • #8
                More on the first reflections, according to Geddes. In regard to imaging, controlling first reflections is critical. Horizontal reflections aren't critical in in regard to imaging.

                His opinion in this specific instance conflicts with Toole. And it is said in the context of home sized rooms.

                https://www.youtube.com/watch?v=5pdIZcMYD2o

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                • #9
                  I think this gets so deeply into personal preference that you can only make broad statements. Off-axis directivity should be smooth, for example. Other than that, different people like different presentations from speakers. For example a horn guy will probably never like a Bose 901, and vice versa.
                  Francis

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                  • #10
                    Originally posted by djg View Post
                    The shame. I don't even know what AVL is and my speakers are little MTMs.
                    Not surprised since AVL is an institution I had dealings with at work. I meant to type AVS. Link here.

                    Originally posted by djg View Post
                    At least I have an opinion on Geddes.
                    Yes it doesn't take long to form an opinion chatting with him on diyaudio forums.

                    Comment


                    • #11
                      Originally posted by fpitas View Post
                      I think this gets so deeply into personal preference that you can only make broad statements. Off-axis directivity should be smooth, for example. Other than that, different people like different presentations from speakers. For example a horn guy will probably never like a Bose 901, and vice versa.
                      There is certainly personal preference in terms of exchanging a sense of space for imaging. Although subject to the room and recording to some extent, the perceived tonal balance is less about personal preference and more about what is correct. This determines which combinations of beamwidth with frequency work reasonably "correctly" and which are more, possibly attractive, sound effects.

                      Comment


                      • #12
                        Originally posted by andy19191 View Post
                        There is certainly personal preference in terms of exchanging a sense of space for imaging. Although subject to the room and recording to some extent, the perceived tonal balance is less about personal preference and more about what is correct. This determines which combinations of beamwidth with frequency work reasonably "correctly" and which are more, possibly attractive, sound effects.
                        I'll play devil's advocate and say the only "correct" is using the exact speakers the recording engineer used.
                        Francis

                        Comment


                        • #13
                          Originally posted by fpitas View Post
                          As an owner of giant horn speakers in a small room, I have to agree!
                          I share the same experience. As I attempt to learn speaker design, I've noticed that the importance of directivity comes up more than once.

                          At one point I had a pair of SEOS based speakers and an Oris Horns - based system.

                          The SEOS had far better on and off-axis response. The Oris, due to their shape, had a much narrower directivity.

                          Pretty much anyone who heard the two systems preferred the Oris over the SEOS.

                          I think this was likely due to the poor acoustics of the room (highly reflective): hardwood floors, large glass windows, etc.

                          The SEOS horn just excited the room too much.

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                          • #14
                            Floyd Toole's speakers appear to be four way Harman Revel Salon2, $11K each with an $8K three way center channel.

                            https://revelspeakers.com/productdet...ct/salon2.html

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                            • #15
                              What jumps out at me from the esteemed Dr. Toole's room is how asymetrical it it. A sloped ceiling, a large opening on one side wall to an adjacent room, different sized seating flanking the recliners. the marble topped fireplace right next to the bottom of the right speaker, etc. I'm sure a lot of "audiophiles" would scream you could never have good sound in the room.

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