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

    Originally posted by mzisserson View Post








    But really....



    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.

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    • Re: 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


        I start with the volume at -45, pretty loud in the seated position. Gotta be over 90dB, and I'm 3m away from each monitor. Well before the end of the song, the volume setting had moved up over 10dB. And I want it even louder. Basically, here's me during that song.



        Wow, these pro woofers could easily get addictive!!!

        The sound was HUGE, clean, defined. I couldn't believe how the vocalist stayed front and center, in between the speakers, not in front, not behind. Just right THERE. Didn't matter how loud it played, the sound stage was massive. Chest pounding. Exhilarating. Goosebumps!
        For some reason after reading this I felt like standing up and high-fiving someone! Must be that smell of victory!

        Well done,
        chuck

        Comment


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

          Pete,
          How much do you think the fact that this is a bookshelf/monitor style box play into the imaging of the speaker. These type boxes have always bested floorstanders in this department, IMO.

          Comment


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

            Pete,

            Getting more and more interested in this project as it continues to unfold. I am curious about pics and polars, not that either one are super critical but I am curious about how you have decided to finish the baffle and how everything looks in that PE cabinet and with the waveguide integrated into the baffle. Also, I am very curious about the waveguide directivity at crossover point and how that lines up with the woofer. I am not a strict follower of Geddes on this stuff but I do take his work and contributions to DIY very seriously so I am always looking to see how his priorities line up with listening experience, and of course, nothing but respect to you, Pellegrene, Bagby and others... I like taking a little bit from everyone and see how it might come together with my own bias/preference.

            I am glad to hear that the RS28A is such a strong unit, I have always been a bit hesitant to give this one a try given the other options that get raves around here, such as Transducer Labs and CSS, at least when it comes to waveguide use. Still curious about Dave's experience with the Audax tweeter and then how all of these domes would stack up against the AC aero striction in a waveguide and the TPL-150H, at some point I might start on thread on that and hope I can get a bunch of folks to chime in. Also looking at options for 8-10 inch midwoofers as I think this diameter size is the ideal match for dome oriented waveguides 7-9 inches running down to 1-1.6 kHz. Volt and Audax are high on my list, along some more pro sound stuff like the B&C you chose here.

            Anyways, the above musings are really geared around a future high end project, and what is more important is what you have created here, as it looks like you have possibly hit the absolute sweet spot in performance/value for many folks. My home studio still needs a decent monitor (more midfield than near field I suppose) and your project is still at the top of my list. Keep the info flowing as you can, much appreciated.

            Regards,

            Greg Jensen
            Last edited by Greggo; 12-03-2013, 11:24 AM.

            Comment


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

              In all seriousness, Nice work Pete. I like to see a concept work. It is a very godo example if when to WG, it is exectuted very well, has a specific purpose and fill that purpose with ease.

              Let's not forget it IS NOT a cheap, low skill, or budget build and you have some serious metal in that crossover, so the ROI needed to be exceptional. And from what I can see it is. I would love to get these on my 500WPC Carver Ref. Signature and open em' up

              Oh, and thanks for the new Pony GIF!!!!!! :D
              .

              Comment


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

                ...This will be an 8 Ohm system, and I'm guessing at around 87dB overall sensitivity after baffle step, with F3 about 47Hz, and should be able to produce over 110dB from 50Hz on up...
                I realize it wasn't ever part of your plan but did you consider going w/ a sealed enclosure? I can do the modeling but I was wondering if you modeled the same size box (sealed) w/ a more gradual 12dB roll off, for use specifically with a sub.

                Just thinking out loud mostly.
                Thanks,
                Aaron

                Comment


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

                  Originally posted by Greggo View Post
                  Pete,

                  Getting more and more interested in this project as it continues to unfold. I am curious about pics and polars, not that either one are super critical but I am curious about how you have decided to finish the baffle and how everything looks in that PE cabinet and with the waveguide integrated into the baffle. Also, I am very curious about the waveguide directivity at crossover point and how that lines up with the woofer. I am not a strict follower of Geddes on this stuff but I do take his work and contributions to DIY very seriously so I am always looking to see how his priorities line up with listening experience, and of course, nothing but respect to you, Pellegrene, Bagby and others... I like taking a little bit from everyone and see how it might come together with my own bias/preference.

                  I am glad to hear that the RS28A is such a strong unit, I have always been a bit hesitant to give this one a try given the other options that get raves around here, such as Transducer Labs and CSS, at least when it comes to waveguide use. Still curious about Dave's experience with the Audax tweeter and then how all of these domes would stack up against the AC aero striction in a waveguide and the TPL-150H, at some point I might start on thread on that and hope I can get a bunch of folks to chime in. Also looking at options for 8-10 inch midwoofers as I think this diameter size is the ideal match for dome oriented waveguides 7-9 inches running down to 1-1.6 kHz. Volt and Audax are high on my list, along some more pro sound stuff like the B&C you chose here.

                  Anyways, the above musings are really geared around a future high end project, and what is more important is what you have created here, as it looks like you have possibly hit the absolute sweet spot in performance/value for many folks. My home studio still needs a decent monitor (more midfield than near field I suppose) and your project is still at the top of my list. Keep the info flowing as you can, much appreciated.

                  Regards,

                  Greg Jensen
                  In a comparison between the AeroStriction tweeters/AMTs and domes, I'd take the AST/AMTs. They are more natural sounding to me. But they need to be HUGE in order to cross as low as this 28mm dome tweeter. The bigger the AMT, the narrower their vertical directivity, which may or may not be an issue. I love the TPL150H, but there is a big difference between sitting and standing in the upper couple octaves. But when you're in the sweet spot, their dynamics are very hard to surpass. I've not heard any dome that sounds like a good AMT. Dave Pellegrene has put the AST2560 into a custom guide and achieved excellent results. That approach is certainly an option for a two-way like this. Even more expensive though, but a step up in terms of high end resolution and dynamics. Maybe I can talk Dave into making me a baffle set up for the AST2560 that allows me to mount it to the PE .75cf TM cabinet. Not sure if the 8BG51 can be coaxed into a smooth XO at 2KHz.

                  Hmmmmm . . .

                  As for 10" woofers that would work with this tweeter, I'd LOVE to try the Acoustic Elegance TD10S. I'm unsure of their smoothness of response to 1KHz, but from the data I've seen on their 12" versions, a 10" should work very well. That woofer would allow you to create a very powerful monitor/small floor stander.
                  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

                    Originally posted by aarond View Post
                    I realize it wasn't ever part of your plan but did you consider going w/ a sealed enclosure? I can do the modeling but I was wondering if you modeled the same size box (sealed) w/ a more gradual 12dB roll off, for use specifically with a sub.

                    Just thinking out loud mostly.
                    You could easily seal this up to use with a sub. Just jam a rolled up hand towel into the rear port and you're all set. But if you're going to do that, I'd opt for a different model B&C that has a more controlled upper midrange region since you're not focused as much on extension to 40Hz. Of all the 8" woofers from B&C, this one modeled the best for the target cabinet in terms of usable bass for most music without needing a sub. To get this performance, B&Cs design choices resulted in a woofer that really shouldn't be used above 1KHz due to cone/edge issues where the response goes through some serious bumps. Nothing shows up in the distortion data, just frequency response irregularities. But up to 1KHz, this woofer has some serious teeth.
                    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

                      Originally posted by mzisserson View Post
                      In all seriousness, Nice work Pete. I like to see a concept work. It is a very godo example if when to WG, it is exectuted very well, has a specific purpose and fill that purpose with ease.

                      Let's not forget it IS NOT a cheap, low skill, or budget build and you have some serious metal in that crossover, so the ROI needed to be exceptional. And from what I can see it is. I would love to get these on my 500WPC Carver Ref. Signature and open em' up

                      Oh, and thanks for the new Pony GIF!!!!!! :D
                      Well, I finally had the SPL meter on hand so I can at least calibrate SPL to volume setting. At -40, the 1m SPL via noise signal was 90.7dB. I don't know what power level that is for sure but I'm assuming between 2W and 4W.

                      Knowing that information, I can finally calibrate the plot below to actual SPL levels.



                      The top trace is at just over 100dB. Distortion is flirting with 1%. The mess around 350Hz is related to floor bounce and some low level noise in the sound card. That would make the top trace between 20W and 40W.
                      So, I sat down in the listening spot and held up the meter while I played back that Alter Bridge cut, at the same volume setting. With both speakers playing, levels hovered at just over 100dB at the seated position, so I gave it another couple dB on the volume control allowing an occasional peak of 103dB, and one peak at 105dB. I figure that's about it for the 120W amp with music. Any more power and the onset of clipping might begin. All I know is, my guesses about how loud it was made me feel pretty good when the meter told me what they actually were.

                      There is no hint of compression in the above plots. I could probably crank the volume even further, another 5dB before the amp limit is reached. I hesitate because it is already so dang loud. Distortion appears to be rising with power in a pretty linear fashion. Another 5dB of distortion is probably becoming audible if your hearing isn't already overwhelmed by the sheer volume. But the lack of compression is what I really like to see.


                      They'll be dismantled now to get the paint job on the baffle done. The crossover goes into the cabinet. Once the paint job is complete, pictures.

                      Piano White baffle and Piano Black cabinet? Or should it be another black baffle to hide the drivers?

                      When they're finally assembled, I'll get a series of off axis measurements to get an idea of the polar response.
                      Attached Files
                      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

                        They'll be dismantled now to get the paint job on the baffle done. The crossover goes into the cabinet. Once the paint job is complete, pictures.

                        Piano White baffle and Piano Black cabinet? Or should it be another black baffle to hide the drivers?

                        When they're finally assembled, I'll get a series of off axis measurements to get an idea of the polar response.
                        Nice work Pete, I look forward to hearing them.

                        Black is so dated, you may want to try Kona, or Obsidian
                        John H

                        Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

                        Comment


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

                          Dave Pellegrene has put the AST2560 into a custom guide and achieved excellent results. That approach is certainly an option for a two-way like this. Even more expensive though, but a step up in terms of high end resolution and dynamics. Maybe I can talk Dave into making me a baffle set up for the AST2560 that allows me to mount it to the PE .75cf TM cabinet. Not sure if the 8BG51 can be coaxed into a smooth XO at 2KHz.

                          Hmmmmm . . .
                          In my testing with the AST2560 I found from about 10' back above about 6'-5" off the floor is where you could hear the difference in the vertical axis. I had to stand on a stool to get there so not a problem for me. I did test it thought because the person I was building the speaker for was 6'-4" tall.
                          I do have the octagon pattern cut out for the 8" B&C drivers so a couple baffles would be pretty simple to make up.
                          Let me know if you want to pursue it. Rear mounting may be a good option so a universal baffle could be made to swap out woofers. The pro woofers I've been looking at all seem to fit with a 7-1/4" cut out for rear mounting.

                          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

                            Pete,
                            How "sufficient" do you think the bass will be in a small room, about 12 x 14. The speakers will go on the 12' wall and are generally pulled out about a meter from back wall and have about 1.5meters between them. Listening position is 1 meter, but is adjustable, of course. Ceiling is vaulted behind them, but is still 8'.

                            Comment


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

                              Pete,

                              I would vote for white or stone like finish... anything with a nice contrast.... anything but black in this case.

                              PM on the way.

                              Regards,

                              Greg Jensen

                              Comment


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

                                Originally posted by buzzforb View Post
                                Pete,
                                How "sufficient" do you think the bass will be in a small room, about 12 x 14. The speakers will go on the 12' wall and are generally pulled out about a meter from back wall and have about 1.5meters between them. Listening position is 1 meter, but is adjustable, of course. Ceiling is vaulted behind them, but is still 8'.
                                In my larger room right now, there's plenty of bass to get the heart pumping. For some music a sub would help, but only for the octave between 20 and 40Hz, which is outside most musical genres. So in your smaller space, these should really get you rockin'.

                                And for John H, when they're finished, you could stop by Ryan's again and hear them in the nice listening room.

                                Dave, not sure when, but I may take you up on the offer!
                                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

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