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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

    Pete, if you have a picture it's not showing up. It would be interesting to compare to a 1" round over.
    John H

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

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

      Originally posted by jhollander View Post
      Pete, if you have a picture it's not showing up. It would be interesting to compare to a 1" round over.
      Not sure why. I see one, but I've added another just in case.

      I really doubt that a 1" roundover in front of the RS28 would have any benefits. It's not wide enough to offer any diffraction control and I'd wager that the vertical wall next to the dome would cause some funky response anomalies.
      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

        Two versions on hand now, one sanded smooth. It only took me 10 minutes to remove the tool marks. Elliptical and circular guides. I'm curious to see the differences. They're both the same width and depth.




        Click image for larger version

Name:	round and elliptical.jpg
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Size:	77.1 KB
ID:	1165103
        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

          I like it a lot and I'm also curious to see the differences between the elliptical and circular guides... Would love to have a set of these but for a Seas 27 series tweeter since I already have a set laying around and I like this tweeter a lot. I would be pretty curious to compare it to my current JBL 2408H driver and JBL 6x6 PT waveguides also...

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

            I forgot to ask how much a set of these would cost?

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

              Originally posted by 300Z View Post
              I like it a lot and I'm also curious to see the differences between the elliptical and circular guides... Would love to have a set of these but for a Seas 27 series tweeter since I already have a set laying around and I like this tweeter a lot. I would be pretty curious to compare it to my current JBL 2408H driver and JBL 6x6 PT waveguides also...
              I happen to have a 27TBFC/G on hand. I'll get some data with it too. It will bolt to the back no problem.

              Click image for larger version

Name:	tbfc.jpg
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Size:	34.1 KB
ID:	1165105
              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

                Very nice. I have the 27TDFC but it would still be very helpful to see data on the 27TBFC/G. Thank you.

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

                  Have you done any measurements on the new baffles yet?

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

                    Originally posted by 300Z View Post
                    Have you done any measurements on the new baffles yet?
                    Was hoping to run a sweep on the TBFC and RS28A today actually.
                    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

                      Awesome!

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

                        Got the measurement rig up and took a few plots. I'll get some off axis too but for now, here's on axis for TBFC in the elliptical and the RS28A in elliptical and circular profiles. All these were taken with the exact same mic position, power level, 300Hz gating.

                        They look very promising indeed. Notice how similar the response of the elliptical and round guides are for the RS28A (elliptical green). The TBFC is a bit more sensitive for sure (blue)!

                        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

                          Thank you.
                          The TBFC is a little more sensitive and also has a little less distortion in it's effective range, but I was hoping for a little more gain down low, still very workable response for my application tho.

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

                            Originally posted by 300Z View Post
                            Thank you.
                            The TBFC is a little more sensitive and also has a little less distortion in it's effective range, but I was hoping for a little more gain down low, still very workable response for my application tho.
                            The natural response dominates in a guide that wide. The TBFC doesn't have the low end extension of the RS28 and no guide can make up for the difference. What you'll get is a better match in directivity when pairing it with a 7" or 8" woofer, along with reduced strain at the lower end of the band. Looks like the guide offers at least an extra 8dB of margin at 1500Hz, 8dB less power at the crossover point with the guide than without it. That's significant. It will allow you to drive the system to much higher levels before stressing the tweeter.

                            The noise floor in my living room isn't that good so the distortion measurements will be better for any signal that has a higher ambient level. Once I put a crossover on them I'll run sweeps at much higher power. These plots are from sweeps starting at 300Hz without anything between the amp and tweeter other than the wires.

                            I only have the single TBFC on hand so I won't be able to voice out a pair of them with the woofers. I'll definitely re-work the RS28A crossover to make use of these new baffles.

                            If you had to pick 300Z, which would you take, the elliptical or round? Looks like either one will work just fine.
                            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 Pete Schumacher View Post
                              The natural response dominates in a guide that wide. The TBFC doesn't have the low end extension of the RS28 and no guide can make up for the difference. What you'll get is a better match in directivity when pairing it with a 7" or 8" woofer, along with reduced strain at the lower end of the band. Looks like the guide offers at least an extra 8dB of margin at 1500Hz, 8dB less power at the crossover point with the guide than without it. That's significant. It will allow you to drive the system to much higher levels before stressing the tweeter.

                              The noise floor in my living room isn't that good so the distortion measurements will be better for any signal that has a higher ambient level. Once I put a crossover on them I'll run sweeps at much higher power. These plots are from sweeps starting at 300Hz without anything between the amp and tweeter other than the wires.

                              I only have the single TBFC on hand so I won't be able to voice out a pair of them with the woofers. I'll definitely re-work the RS28A crossover to make use of these new baffles.

                              If you had to pick 300Z, which would you take, the elliptical or round? Looks like either one will work just fine.
                              Good point, the natural low end response on the RS28 is indeed lower than the TBFC.

                              Me personally I would go with the elliptical waveguide, they measure very similar but with the elliptical the woofer could be mounted closer and I like the looks of the elliptical better... :p
                              I would like to pair them with the FaitalPRO 6FE100 woofers tho because I'm not changing my current B&C/JBL system but I really want to build this for another smaller room that will see much less use so it wouldn't be worth the investment for the B&C woofers.

                              Any ideas on how much a set of baffles would cost with the ellipticals?
                              Last edited by 300Z; 07-13-2019, 03:56 PM.

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

                                I'll definitely re-work the RS28A crossover to make use of these new baffles.
                                By baffles are you talking about the WG/baffle combo? Are you still using the 10"x17" PE dimensioned baffle for this?
                                Thanks,
                                Aaron

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