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Does a 2 way, 8" woofer - 1 1/8" tweeter speaker make sense? Could it work?

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  • #31
    The way I see it is this.

    Option A- off centre tweeter until you have a nice smooth on axis. But then off axis goes all over the place and is asymmetrical
    Option B - centred; on axis not ideal but off axis probably not all that bad. And the evidence seems to suggest on axis smoothness and flatness only accounts for between sbout 30-45% of the perceived sound preference.
    (Olive Experiments; Ch 20.2 Sound Reproduction; Toole. Focal Press)
    Option C- centred with round overs. But then only with 3/4” or bigger roundovers make a significant difference. The downside of which makes veneering or painting harder.

    I’ve tried all three and but I’ve never done a controlled blinded listening test to tell if option C was the best, or whether I have a preference. In a sighted test I prefer option A- because I like sharp edged cabinets and tweeters on the inside aka ProAc style...

    Comment


    • #32
      When zaph says "relative to..." I believe that what he's doing is showing the normalized response to the reference. For instance, the graph "Flush mounted tweeter, effects of overlapping woofer w/.12" flange" shows a nearly flat response, but it does not show the absolute driver responses nor the amount of diffraction from the adjacent driver. It is useful to show that overlapping does not change the response much, but does not show the significant diffraction of the tweeter response due to the woofer diaphragm, it simply shows the change from a different driver mounting. Every system I have ever built has had significant midrange/woofer diffraction. I have a 2-way with an Accuton midwoofer, probably one of the worst with regard to diffraction due to the cone shape and material. I put felt in between the drivers to drastically reduce it. The woofer diffraction was worse than the baffle edges in this case. So keep in mind that you will likely see a lot of tweeter irregularity from an 8" woofer, possibly more than than the baffle edges. This will also likely be worst on-axis, whereas baffle edge diffraction varies more with axis.

      dlr
      WinPCD - Windows .NET Passive Crossover Designer

      Dave's Speaker Pages

      Comment


      • #33
        Originally posted by tktran View Post
        The way I see it is this.

        Option A- off centre tweeter until you have a nice smooth on axis. But then off axis goes all over the place and is asymmetrical
        Option B - centred; on axis not ideal but off axis probably not all that bad. And the evidence seems to suggest on axis smoothness and flatness only accounts for between sbout 30-45% of the perceived sound preference.
        (Olive Experiments; Ch 20.2 Sound Reproduction; Toole. Focal Press)
        Option C- centred with round overs. But then only with 3/4” or bigger roundovers make a significant difference. The downside of which makes veneering or painting harder.

        I’ve tried all three and but I’ve never done a controlled blinded listening test to tell if option C was the best, or whether I have a preference. In a sighted test I prefer option A- because I like sharp edged cabinets and tweeters on the inside aka ProAc style...
        Strangely enough, I guess this all comes down to Sean Olive and Floyd Toole. I remember reading an article by them stating asymmetrical frequency response is not ideal - hence the centered tweeter idea. The roundovers (1") are necessary, I believed - until I heard the Revel Concerta2 M16, without roundovers, and finding they sound amazing, and off and on axis they have smooth responses.

        How do they do that? No roundovers, tweeter dead center, no issues.

        I'm trying to replicate that kind of sound, flat on axis, smooth, downard slopes off axis. I cannot see a way to simulate this... I always end up with irregular frequency response, either on or off axis.
        Line Array: IDS-25 Clone, FE-83.
        2-2.5 Way:
        Zaph Audio's winning entry: ZA5+SB29. - Microliths: RS125+RS28. - Small Bangs: TB W4-1658SB+SEAS 27TBFC/G. - Monoliths: Peerless 830884+SEAS 27TBFC/G.
        3-3.5 Way:Miniliths: SEAS P21/CA21REX+Neo8 PDR+Neo3 PDR. - Megaliths: 2xDayton RS270+2xT-B W4-1337SB+SB29. - ZDT3.5 +: 2xDayton RS180+Dayton RS52+Vifa DQ25. Reflexos: OB 4xDayton RS150 + Neo3 PDR.

        Comment


        • #34
          Originally posted by dlr View Post
          When zaph says "relative to..." I believe that what he's doing is showing the normalized response to the reference. For instance, the graph "Flush mounted tweeter, effects of overlapping woofer w/.12" flange" shows a nearly flat response, but it does not show the absolute driver responses nor the amount of diffraction from the adjacent driver. It is useful to show that overlapping does not change the response much, but does not show the significant diffraction of the tweeter response due to the woofer diaphragm, it simply shows the change from a different driver mounting. Every system I have ever built has had significant midrange/woofer diffraction. I have a 2-way with an Accuton midwoofer, probably one of the worst with regard to diffraction due to the cone shape and material. I put felt in between the drivers to drastically reduce it. The woofer diffraction was worse than the baffle edges in this case. So keep in mind that you will likely see a lot of tweeter irregularity from an 8" woofer, possibly more than than the baffle edges. This will also likely be worst on-axis, whereas baffle edge diffraction varies more with axis.

          dlr
          I have decided to flush mount both drivers. Unfortunately, I seem I still can't figure out whether the tightest baffle, tightest baffle with 1" roundovers, or asymmetrical tweetr mounting looks best....

          Line Array: IDS-25 Clone, FE-83.
          2-2.5 Way:
          Zaph Audio's winning entry: ZA5+SB29. - Microliths: RS125+RS28. - Small Bangs: TB W4-1658SB+SEAS 27TBFC/G. - Monoliths: Peerless 830884+SEAS 27TBFC/G.
          3-3.5 Way:Miniliths: SEAS P21/CA21REX+Neo8 PDR+Neo3 PDR. - Megaliths: 2xDayton RS270+2xT-B W4-1337SB+SB29. - ZDT3.5 +: 2xDayton RS180+Dayton RS52+Vifa DQ25. Reflexos: OB 4xDayton RS150 + Neo3 PDR.

          Comment


          • #35
            Originally posted by fjhuerta View Post

            until I heard the Revel Concerta2 M16, without roundovers, and finding they sound amazing, and off and on axis they have smooth responses.

            How do they do that? No roundovers, tweeter dead center, no issues.

            I'm trying to replicate that kind of sound, flat on axis, smooth, downard slopes off axis. I cannot see a way to simulate this... I always end up with irregular frequency response, either on or off axis.
            It’s the waveguided tweeter.

            thanks to dear John, again for explaining how and why:

            reference:
            http://www.zaphaudio.com/Waveguidetmm.html

            ...The waveguide greatly reduces distortion at the low end of the tweeter's range. This particular waveguide layout works by raising the on-axis efficiency in a broad range between 1 and 6kHz. When the response curve is shaped back down to flat, harmonic distortion is reduced compared to a standard tweeter mounted on a flat baffle.

            There are quite a few other benefits to waveguides. The low end of the tweeter's output has a change in directivity that more closely matches the woofer's directivity. The result is very smooth horizontal off axis response, and a power response that does not have the same deep null that a standard speaker would have. Related to the directivity benefit is the fact that a waveguide is not affected by the baffle it's on. Baffle diffraction is a non-issue compared to a standard dome mounted in an enclosure. In a waveguide system, you will not see the lower treble "ripple response" present in typical box systems. Fans of flat baffle dipoles, take note: with no cabinet depth, this is the worst case diffraction ripple. A waveguide is perfect for dipole usage, keeping the lower treble smooth.

            The final benefit of a waveguide is that it moves the acoustic center of the tweeter back. In this case, by about 1.25 inches. This puts the listening axis straight forward in a standard LR2 design, and eliminates the need for a slanted baffle or the increased complexity of a ladder delay network. This combines with other benefits to greatly simplify crossover design. In fact, later on in this article you will be surprised just how simple the crossover can be in this design.

            Comment


            • #36
              Originally posted by tktran View Post

              It’s the waveguided tweeter.

              thanks to dear John, again for explaining how and why:

              reference:
              http://www.zaphaudio.com/Waveguidetmm.html

              ...The waveguide greatly reduces distortion at the low end of the tweeter's range. This particular waveguide layout works by raising the on-axis efficiency in a broad range between 1 and 6kHz. When the response curve is shaped back down to flat, harmonic distortion is reduced compared to a standard tweeter mounted on a flat baffle.

              There are quite a few other benefits to waveguides. The low end of the tweeter's output has a change in directivity that more closely matches the woofer's directivity. The result is very smooth horizontal off axis response, and a power response that does not have the same deep null that a standard speaker would have. Related to the directivity benefit is the fact that a waveguide is not affected by the baffle it's on. Baffle diffraction is a non-issue compared to a standard dome mounted in an enclosure. In a waveguide system, you will not see the lower treble "ripple response" present in typical box systems. Fans of flat baffle dipoles, take note: with no cabinet depth, this is the worst case diffraction ripple. A waveguide is perfect for dipole usage, keeping the lower treble smooth.

              The final benefit of a waveguide is that it moves the acoustic center of the tweeter back. In this case, by about 1.25 inches. This puts the listening axis straight forward in a standard LR2 design, and eliminates the need for a slanted baffle or the increased complexity of a ladder delay network. This combines with other benefits to greatly simplify crossover design. In fact, later on in this article you will be surprised just how simple the crossover can be in this design.
              You have my full attention.

              Comment


              • #37
                Originally posted by tktran View Post

                It’s the waveguided tweeter.

                thanks to dear John, again for explaining how and why:

                reference:
                http://www.zaphaudio.com/Waveguidetmm.html

                ...The waveguide greatly reduces distortion at the low end of the tweeter's range. This particular waveguide layout works by raising the on-axis efficiency in a broad range between 1 and 6kHz. When the response curve is shaped back down to flat, harmonic distortion is reduced compared to a standard tweeter mounted on a flat baffle.

                There are quite a few other benefits to waveguides. The low end of the tweeter's output has a change in directivity that more closely matches the woofer's directivity. The result is very smooth horizontal off axis response, and a power response that does not have the same deep null that a standard speaker would have. Related to the directivity benefit is the fact that a waveguide is not affected by the baffle it's on. Baffle diffraction is a non-issue compared to a standard dome mounted in an enclosure. In a waveguide system, you will not see the lower treble "ripple response" present in typical box systems. Fans of flat baffle dipoles, take note: with no cabinet depth, this is the worst case diffraction ripple. A waveguide is perfect for dipole usage, keeping the lower treble smooth.

                The final benefit of a waveguide is that it moves the acoustic center of the tweeter back. In this case, by about 1.25 inches. This puts the listening axis straight forward in a standard LR2 design, and eliminates the need for a slanted baffle or the increased complexity of a ladder delay network. This combines with other benefits to greatly simplify crossover design. In fact, later on in this article you will be surprised just how simple the crossover can be in this design.
                This is pretty awesome. Thank you so much. It completely explains why I loved my Revels so much, and why my current speakers (Focal Arias) also have quite smooth.off axis response.

                Now I wish I had bought the SEAS DXT instead of the Peerless. Well, I still have time...
                Line Array: IDS-25 Clone, FE-83.
                2-2.5 Way:
                Zaph Audio's winning entry: ZA5+SB29. - Microliths: RS125+RS28. - Small Bangs: TB W4-1658SB+SEAS 27TBFC/G. - Monoliths: Peerless 830884+SEAS 27TBFC/G.
                3-3.5 Way:Miniliths: SEAS P21/CA21REX+Neo8 PDR+Neo3 PDR. - Megaliths: 2xDayton RS270+2xT-B W4-1337SB+SB29. - ZDT3.5 +: 2xDayton RS180+Dayton RS52+Vifa DQ25. Reflexos: OB 4xDayton RS150 + Neo3 PDR.

                Comment


                • #38
                  Speaking of that, why then aren't all tweeters waveguides?
                  Line Array: IDS-25 Clone, FE-83.
                  2-2.5 Way:
                  Zaph Audio's winning entry: ZA5+SB29. - Microliths: RS125+RS28. - Small Bangs: TB W4-1658SB+SEAS 27TBFC/G. - Monoliths: Peerless 830884+SEAS 27TBFC/G.
                  3-3.5 Way:Miniliths: SEAS P21/CA21REX+Neo8 PDR+Neo3 PDR. - Megaliths: 2xDayton RS270+2xT-B W4-1337SB+SB29. - ZDT3.5 +: 2xDayton RS180+Dayton RS52+Vifa DQ25. Reflexos: OB 4xDayton RS150 + Neo3 PDR.

                  Comment


                  • tktran
                    tktran commented
                    Editing a comment
                    I guess it's one way to achieve to directivity match to a large (mid)woofer eg. 7-8" 2 way, or even larger eg. 15" in JBL's M2 is crossed over at 800Hz.

                    But a waveguided tweeter is neither necessary, nor sufficient, to have to achieve a good power response.

                    A typical cone/dome can be integrated in a way that achieves a smooth transition in the power response by choosing appropriate sized drivers, Fc and slope. eg. 8" W 4" M x 3/4' T (or ribbon)

                • #39
                  Waveguides/horns are band pass devices. What you gain in low end response you lose in high end response, so there's a good deal of engineering involved in getting them right.
                  www.billfitzmaurice.com
                  www.billfitzmaurice.info/forum

                  Comment


                  • #40
                    So, if I wanted to be sure that I'd get the best off axis response curves, I should probably go for the DXT drivers, right?
                    Line Array: IDS-25 Clone, FE-83.
                    2-2.5 Way:
                    Zaph Audio's winning entry: ZA5+SB29. - Microliths: RS125+RS28. - Small Bangs: TB W4-1658SB+SEAS 27TBFC/G. - Monoliths: Peerless 830884+SEAS 27TBFC/G.
                    3-3.5 Way:Miniliths: SEAS P21/CA21REX+Neo8 PDR+Neo3 PDR. - Megaliths: 2xDayton RS270+2xT-B W4-1337SB+SB29. - ZDT3.5 +: 2xDayton RS180+Dayton RS52+Vifa DQ25. Reflexos: OB 4xDayton RS150 + Neo3 PDR.

                    Comment


                    • #41
                      Originally posted by tktran View Post
                      There are quite a few other benefits to waveguides. The low end of the tweeter's output has a change in directivity that more closely matches the woofer's directivity. The result is very smooth horizontal off axis response, and a power response that does not have the same deep null that a standard speaker would have.
                      Much depends on the how effective the waveguide is, the crossover Fc and the slope. It's not an absolute guarantee. One such as the DXT has a nominal waveguide, but it's limited at the low end.

                      Related to the directivity benefit is the fact that a waveguide is not affected by the baffle it's on. Baffle diffraction is a non-issue compared to a standard dome mounted in an enclosure.
                      Same as my comment above.

                      Fans of flat baffle dipoles, take note: with no cabinet depth, this is the worst case diffraction ripple.
                      How did you come to this conclusion? If one designs a multi-way dipole system such that each driver's passband is almost exclusively at or below the dipole peak, the diffraction ripple in the upper stopband of each section can be made minimal. See john k's pages on dipoles, he does an excellent job describing this in one of them.

                      A waveguide is perfect for dipole usage, keeping the lower treble smooth.
                      A waveguide cannot be used for a dipole, there is no output to the rear. Now if you mean that a single tweeter used in an otherwise dipole system, then a tweeter can be integrated in a way that provides a smooth transition from midrange or midwoofer to the tweeter, including the off-axis, but again, my first comment above applies. I do precisely this in my 3-way dipole system, using the DXT tweeter. However, there is very little output from the tweeter to the rear much above the Fc point. With the DXT, there will be some output to the rear that will be due to some diffraction around the baffle. The DXT has more output to the side than you might think, but it's better than a standard tweeter.

                      dlr
                      WinPCD - Windows .NET Passive Crossover Designer

                      Dave's Speaker Pages

                      Comment


                      • #42
                        So...

                        I'd assume a DXT tweeter would be better than the Peerless... Right?
                        Line Array: IDS-25 Clone, FE-83.
                        2-2.5 Way:
                        Zaph Audio's winning entry: ZA5+SB29. - Microliths: RS125+RS28. - Small Bangs: TB W4-1658SB+SEAS 27TBFC/G. - Monoliths: Peerless 830884+SEAS 27TBFC/G.
                        3-3.5 Way:Miniliths: SEAS P21/CA21REX+Neo8 PDR+Neo3 PDR. - Megaliths: 2xDayton RS270+2xT-B W4-1337SB+SB29. - ZDT3.5 +: 2xDayton RS180+Dayton RS52+Vifa DQ25. Reflexos: OB 4xDayton RS150 + Neo3 PDR.

                        Comment


                        • #43
                          There are still baffle step and edge diffraction FR changes with wave guided tweeters. It's dependent on the size of the baffle. There's also the on-axis null with wave guide tweeters. The Seas DXT is not similar to the 6.5 horn lens Zaph is using.

                          If you like what the wave guide is doing then add the 6.5 horn lens to the Peerless. I think you are moving away from your original intention to building a simple two way speaker.
                          John H

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

                          Comment


                          • #44
                            Originally posted by fjhuerta View Post
                            So...
                            I'd assume a DXT tweeter would be better than the Peerless... Right?
                            It depends. I chose the DXT partly for what I hoped was less dispersion, thinking to have a high Fc, low slope to integrate with the dipole mid, but the opposite was required. The DXT was a benefit due to its higher sensitivity that allowed for a lower Fc, but to get a smooth off-axis integration it required LR8 at 1200Hz. Anything different resulted in the typical off-axis "bloom". And as I've pointed out, there was significant diffraction to the tweeter, baffle edge and nearby midrange. A midwoofer may be more problematic becoming directive at a lower frequency. That said, my personal opinion is that the DXT will be easier to integrate unless you mount the Peerless in a small waveguide. The additional z-axis offset of the DXT (rather small) or Peerless in a waveguide is a benefit as well, as some have pointed out.

                            dlr
                            WinPCD - Windows .NET Passive Crossover Designer

                            Dave's Speaker Pages

                            Comment


                            • #45
                              Originally posted by fjhuerta View Post
                              So...I'd assume a DXT tweeter would be better than the Peerless... Right?
                              The Visaton Waveguide WG 148 R has been modified for use with the XT25TG30-04 and Dayton Rst28a and are $17ish each plus shipping at Mouser. I think the DA25TX was a little too small in diameter but that was before the DA32TX came out. The opening is 38mm so if you already have the DA32TX you could measure the diameter with surround and see if that off the shelf waveguide might work.

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