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Home/Pro 8" 2-way: RS28A and B&C 8BG51

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  • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

    For what it's worth, at last week's Loudspeaker Design Workshop I gave a presentation on how to get quasi-anechoic frequency response in your room that is completely accurate down to 10Hz with no room interactions at all. It requires taking two measurements that I defined precisely how they are to be taken, and putting them together using a tool that Charlie and I put together. I stated that the conventional method of splicing does not result in an accurate frequency response, and graphs like the one pictured in Joe D's book on Measuring Loudspeakers is incorrect, but I showed that my method produces a correct frequency response that you can verify fairly easily. I need to write this process up in a paper. This new method is one of the special treats I gave the group last week. It was the first time this has been presented anywhere, and I have never seen this methodology presented anywhere I have ever read, online or in a book, so I think what I have is a new twist on the subject.

    Jeff B.
    hi jeff,

    would you mind to elaborate more on this? for those of us who cant attend (especially me, as im half world apart :D ) your seminar

    cheers
    henry

    Comment


    • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

      Originally posted by Jeff B. View Post
      For what it's worth, at last week's Loudspeaker Design Workshop I gave a presentation on how to get quasi-anechoic frequency response in your room that is completely accurate down to 10Hz with no room interactions at all. It requires taking two measurements that I defined precisely how they are to be taken, and putting them together using a tool that Charlie and I put together. I stated that the conventional method of splicing does not result in an accurate frequency response, and graphs like the one pictured in Joe D's book on Measuring Loudspeakers is incorrect, but I showed that my method produces a correct frequency response that you can verify fairly easily. I need to write this process up in a paper. This new method is one of the special treats I gave the group last week. It was the first time this has been presented anywhere, and I have never seen this methodology presented anywhere I have ever read, online or in a book, so I think what I have is a new twist on the subject.

      Jeff B.
      Jeff

      I could not attend your seminar for obvious reason I live in Australia.

      Is it possible you may like to share with me and others your notes(presentations materials) from the seminar, especially the area on how I can perform the measurements you mention above. I would be happy to pay for them.

      Comment


      • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

        Originally posted by ttan98 View Post
        Jeff

        I could not attend your seminar for obvious reason I live in Australia.

        Is it possible you may like to share with me and others your notes(presentations materials) from the seminar, especially the area on how I can perform the measurements you mention above. I would be happy to pay for them.
        Send me an email (not a PM).

        Jeff
        Click here for Jeff Bagby's Loudspeaker Design Software

        Comment


        • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

          Originally posted by davepellegrene View Post
          Do you think the dip at 700 Hz is still from the room even in the gated measurements? I was looking back on post #265 at your close mic measurements and I don't see anything in the tweeter response that could be causing a suck out but I'm not quite sure why the tweeter drops about 15 Dbs from the crossover then flattens out until about 200 Hz then drops off. Is that your noise floor? Looking at the woofer response after crossover and tweeter response after the crossover is what my noise floor looks like when my furnace is running.

          Not trying to point out your warts. I'm just trying to interpret the graphs. Sometimes it's hard to tell when your not taking the measurements. It's been a will since I've used HOLMImpulse and if I remember you can slide the gating back and forth. I think if the gating is moved higher the dip would disappear. Which would indicate it is the room.

          Dave
          The close mic on both woofer and tweeter was done with the woofer and tweeter both hooked up. I could redo them I suppose by disconnecting them and running the sweeps individually. That's the reason the tweeter flattens out; the woofer is showing up in the plot, and I ran the sweep starting at 200Hz.

          I'm pretty sure the 700Hz dip is room related since I don't see any hint of it in the close mic data. Its a lousy room for measuring. I need to see Jeff's method and try it out.
          R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio
          Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51

          95% of Climate Models Agree: The Observations Must be Wrong
          "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

          Comment


          • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

            The close mic on both woofer and tweeter was done with the woofer and tweeter both hooked up. I could redo them I suppose by disconnecting them and running the sweeps individually. That's the reason the tweeter flattens out; the woofer is showing up in the plot, and I ran the sweep starting at 200Hz.

            I'm pretty sure the 700Hz dip is room related since I don't see any hint of it in the close mic data. Its a lousy room for measuring. I need to see Jeff's method and try it out.
            I don't see a reason to pull them apart as you said it's not in the close mic so it must be room related. I just didn't understand what was going on. I didn't know you could get that good of results with both hooked up. Once the speaker is put together its a pain to disconnect one then the other especially when the woofer need the cabinet sealed to get a good measurement. The way you did it tells you what you need without all the work.
            Good to know
            Dave
            http://www.pellegreneacoustics.com/

            Trench Seam Method for MDF
            https://picasaweb.google.com/101632266659473725850

            Comment


            • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

              Dave,

              How far away is your mic when you take measurements?

              Comment


              • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

                Originally posted by Jeff B. View Post
                For what it's worth, at last week's Loudspeaker Design Workshop I gave a presentation on how to get quasi-anechoic frequency response in your room that is completely accurate down to 10Hz with no room interactions at all. It requires taking two measurements that I defined precisely how they are to be taken, and putting them together using a tool that Charlie and I put together. I stated that the conventional method of splicing does not result in an accurate frequency response, and graphs like the one pictured in Joe D's book on Measuring Loudspeakers is incorrect, but I showed that my method produces a correct frequency response that you can verify fairly easily. I need to write this process up in a paper. This new method is one of the special treats I gave the group last week. It was the first time this has been presented anywhere, and I have never seen this methodology presented anywhere I have ever read, online or in a book, so I think what I have is a new twist on the subject.

                Jeff B.
                I had to cancel last minute. My new boat was being delivered to my house Friday evening just before the ice/ snow storm so I had to be there to shoehorn it through my garage door when it arrived. Being 5 hours away in good weather there was no way I was going to be able to make it.

                I'd really like to hear your method. Do you think you will have a right up soon? I don't want to bother you because I'm sure you have more emails to answer then you want to already.

                Dave
                http://www.pellegreneacoustics.com/

                Trench Seam Method for MDF
                https://picasaweb.google.com/101632266659473725850

                Comment


                • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

                  Originally posted by Erich H View Post
                  Dave,

                  How far away are you when you take measurements?
                  I measure from 1 meter using a 5ms gating. Then if I want to see what the woofer is doing I splice a close mic, about 2" away, to the 1 meter response.I have my set up marked on the floor so as I change drivers or bring the mic in close to set the height I can get it set back up the same.

                  I have notices that my close mic woofers top end rolls off a little quicker then the measurement at 1 meter. I'm not sure if this is part of what Jeff is talking about but when I overlay them I see a difference.
                  Dace
                  http://www.pellegreneacoustics.com/

                  Trench Seam Method for MDF
                  https://picasaweb.google.com/101632266659473725850

                  Comment


                  • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

                    Originally posted by henry218 View Post
                    hi jeff,

                    would you mind to elaborate more on this? for those of us who cant attend (especially me, as im half world apart :D ) your seminar

                    cheers
                    henry
                    I will have to write something up. I don't have anything ready to present on this right now. I will try to get to it soon after the New Year.
                    Jeff
                    Click here for Jeff Bagby's Loudspeaker Design Software

                    Comment


                    • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

                      Pete, are your coordinates (in your location) the lat/lon of your "sweet spot"? I figure 6 decimals should get you down to a foot or two, eh?

                      Comment


                      • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

                        Originally posted by Jeff B. View Post
                        I will have to write something up. I don't have anything ready to present on this right now. I will try to get to it soon after the New Year.
                        Jeff
                        thanks Jeff, looking forward to it .

                        Comment


                        • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

                          I haven't paid a lot of attention to this thread until tonight. What a great thread? When we get settled on 7" or so WG, I want a pair. Would love to hear these Pete.

                          Jeff, look forward to the Paper.
                          " To me, the soundstage presentation is more about phase and distortion and less about size. However, when you talk about bass extension, there's no replacement for displacement". Tyger23. 4.2015

                          Quote Originally Posted by hongrn. Oct 2014
                          Do you realize that being an American is like winning the biggest jackpot ever??

                          http://www.midwestaudioclub.com/spot...owell-simpson/
                          http://s413.photobucket.com/albums/pp216/arlis/

                          Comment


                          • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

                            oops
                            " To me, the soundstage presentation is more about phase and distortion and less about size. However, when you talk about bass extension, there's no replacement for displacement". Tyger23. 4.2015

                            Quote Originally Posted by hongrn. Oct 2014
                            Do you realize that being an American is like winning the biggest jackpot ever??

                            http://www.midwestaudioclub.com/spot...owell-simpson/
                            http://s413.photobucket.com/albums/pp216/arlis/

                            Comment


                            • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

                              Originally posted by [email protected] View Post
                              I haven't paid a lot of attention to this thread until tonight. What a great thread? When we get settled on 7" or so WG, I want a pair. Would love to hear these Pete.

                              Jeff, look forward to the Paper.
                              I'm really interested in working with Erich on a guide that replicates what we're getting with the guide Tom fabricated. It's not perfect by any means, but it does an admirable job of getting the RS28 down to a 1KHz crossover point with very little strain. And you can easily get another 5dB from the tweeter if someone wanted to do MTM with these woofers.

                              These woofers would do marvelously well in a tapered TL, and a pair of them would make for quite an authoritative low end.
                              R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio
                              Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51

                              95% of Climate Models Agree: The Observations Must be Wrong
                              "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

                              Comment


                              • Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

                                Curious if you ever got close to exceeding xmax during your jam session? 6.5mm. Like the idea of a Tapered TL
                                Is there enough inductance in the crossover to wire two of these in parallel with a RE of 5.1?
                                " To me, the soundstage presentation is more about phase and distortion and less about size. However, when you talk about bass extension, there's no replacement for displacement". Tyger23. 4.2015

                                Quote Originally Posted by hongrn. Oct 2014
                                Do you realize that being an American is like winning the biggest jackpot ever??

                                http://www.midwestaudioclub.com/spot...owell-simpson/
                                http://s413.photobucket.com/albums/pp216/arlis/

                                Comment

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