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  • #16
    Originally posted by Chris Roemer View Post
    Most modern (non-"pro") designs today will use a (maybe "soft") dome tweeter - about 1" in dia.
    Your ADVE\TS used the "fried egg" tweeter, which was kinda like a "hybrid" between a small dome (was it about 5/8" ?) and an old-fashioned "cone" tweeter - due to its large half-roll (paper?) surround - giving it the area of maybe a 3" cone?
    That tweeter was crossed much lower than almost any dome can be crossed today (I think they claimed 1500Hz, maybe even as low as 1000?).
    Brand new to me with my Original Large Advent find ... my first thought seeing the "fried egg" was ring radiator.

    And the directivity, now I understand why many "stacked" them tweeters in the middle.


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    • #17
      Originally posted by Millstonemike View Post
      And the directivity, now I understand why many "stacked" them tweeters in the middle.
      AFAIK the first to do so was Henry Kloss, making a pair of Large Advents into an W-T-T-W. He had that setup in his office where I met with him a few times just prior to my six month vacation in beautiful Southeast Asia.
      www.billfitzmaurice.com
      www.billfitzmaurice.info/forum

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      • #18
        Originally posted by billfitzmaurice View Post
        There's importance, and there's importance. I deal with this all the time in pro-sound, and if you think that crossing over from an eight to an one inch dome at 3kHz or so is bad consider going from a fifteen to a horn loaded tweeter at 4kHz, which isn't at all uncommon. Not that I'd ever put my name on a speaker of that sort, but I've designed more than a few for companies because that's what they wanted, and the one who signs the check has the final say. As I already said I'd rather a pair of 6.5s in an MTM to one eight, but one eight will still sound pretty good, and the off-axis dip at the upper end of the eight's range will look far worse on a chart than it will sound.
        On this board we're not dealing with companies demanding that a design be a certain way, we're dealing with DIYers that want to learn the details to make optimal decisions. I appreciate that you have to do things that you might not like to satisfy a customer, but don't let that influence your commentary to someone here looking for help in design. The fact is that an 8" midwoofer with a 1" tweeter is going to require compromises and those compromises should be made clear, the off-axis possibly being the most significant. No one has said that they can't sound good, but they don't sound that way by accident..
        dlr
        WinPCD - Windows .NET Passive Crossover Designer

        Dave's Speaker Pages

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        • #19
          There are several possible reasons why speakers can sound good with a large woofer two way design. Some woofers have a relatively smooth cone breakup that sounds acceptable to many people. I think paper and poly woofers tend to have a relatively smooth cone break up.

          My previous main speakers were a 15" coaxial two way. The woofer has paper cone with those old school ridges that I believe were intended to create a controlled cone breakup. They were crossed over to a 1.4" compression tweeter around 2-3 kHz. In the past, I would have said from looking at them that they MUST sound terrible, but in fact they sounded rather nice. Sure, they were flaws with the design, but they had a very clean overall sound. In my opinion, they had enough strengths to easily offset the flaws. They did not have much of a stereo image in my room, but the mid bass through the lower mid range was especially good. I enjoy listening to them.

          My current main system uses two 6.5" paper woofers and a 0.8" tweeter. The woofers have a smooth breakup with good response up to 7 kHz or so. I used a contour filter to flatten their response and the tweeter is crossed in at around 7 kHz, first order. After much tweaking, these sound really excellent to me. The high crossover gives me nice phase and power response through the critical range from upper bass throughout the entire mid range. These two items are design priorities to me and I will happily sacrifice other traits to achieve them.

          I agree that a speaker system design is an exercise in compromise. There is more than enough good to offset the not so good in any well designed system.

          As far as theoretical vs real world sound, I have been using WinPCD to get my designs looking good on paper. Then I always do final voicing by ear in my listening room. I usually make changes and then enter the final result back into WinPCD to see what the effects are on paper. I am concerned that if I voice something that has major amplitude or phase issues, then it may sound good at that moment, but become tiring over time.

          In general, if it sound good to me, with my music, and in my room, then it is good.

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          • #20
            Originally posted by ernperkins View Post

            +1. Look at the work of Toole and Olive on this importance.
            To the best of my knowledge, they haven't ranked or assigned any multipliers to the variables they've found important through their empirical tests.

            It is entirely possible, that a speaker that breaks every single rule but extends to 20-Hz, would outperform a speaker that observes every other rule but can't play below 60-Hz.

            I keep going back to that because back in the 70's I think, Julian Hirsch mentioned a paper where they found the single greatest factor in loudspeaker acceptance in blind testing, was extended bass. This paper (I think the research was from a university) had attempted to rank what matters to people in blind testing, and bass was it.

            So I think we need to be a little careful in treating every aspect equally.

            How much an 8" two-way influences power response depends a lot on the design. But how much power response influences a blind listeners preferences is another matter that I don't think is in evidence?

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            • #21
              Originally posted by dlr View Post
              On this board we're not dealing with companies demanding that a design be a certain way, we're dealing with DIYers that want to learn the details to make optimal decisions...
              Always figured that was a major ( though not solitary ) reason that DIY existed; personal control of outcome, such as cost vs performance.

              "Not a Speaker Designer - Not even on the Internet"
              “Pride is your greatest enemy, humility is your greatest friend.”
              "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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              • #22
                Not sure if this was previously mentioned, but Troels G. attempted to build a 2-way utilizing an 8" + tweeter. See link below.

                http://www.troelsgravesen.dk/8555-7100.htm

                Overall, Troels does not advise going from an 8" to a 1". Beyond the off-axis response issue, to him, the sound is a little un-natural going from such a large radiating surface to a significantly smaller radiating surface.

                He does agree that its certainly not impossible to design a good 8"/1" - the above showcases one of his successful designs. He adds that certain cone material has a much more manageable cone-break up.

                Personally, I'm very much interested in a 1"/8" design. Not saying that off-axis response does not matter to me, but I rarely listen to my system severally off axis. And when I am listening off-axis, I'm so far off axis that I'm not even paying attention to what I'm listening to - its just background music.

                I feel that going to an 8" might allow me to enjoy a more "full-range" sound that its otherwise not possible with a small compact monitor. I'm also still trying to learn about a simple TM so TMW is totally out of the question for me.

                I do have a really dump question though: Is there ever an instance that a woofer's/mid's beaming property be utilized as a benefit? In other words, assuming a listening room with no room treatment, could it ever be advantageous to utilize a slightly higher crossover point, so the speaker has good on-axis response (and +/- 15 degree) and the beaming property helps reduce reflections at the listening position?





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                • #23
                  Originally posted by dkalsi View Post
                  Not sure if this was previously mentioned, but Troels G. attempted to build a 2-way utilizing an 8" + tweeter. See link below.

                  http://www.troelsgravesen.dk/8555-7100.htm

                  Overall, Troels does not advise going from an 8" to a 1". Beyond the off-axis response issue, to him, the sound is a little un-natural going from such a large radiating surface to a significantly smaller radiating surface.

                  He does agree that its certainly not impossible to design a good 8"/1" - the above showcases one of his successful designs. He adds that certain cone material has a much more manageable cone-break up.

                  Personally, I'm very much interested in a 1"/8" design. Not saying that off-axis response does not matter to me, but I rarely listen to my system severally off axis. And when I am listening off-axis, I'm so far off axis that I'm not even paying attention to what I'm listening to - its just background music.

                  I feel that going to an 8" might allow me to enjoy a more "full-range" sound that its otherwise not possible with a small compact monitor. I'm also still trying to learn about a simple TM so TMW is totally out of the question for me.

                  I do have a really dump question though: Is there ever an instance that a woofer's/mid's beaming property be utilized as a benefit? In other words, assuming a listening room with no room treatment, could it ever be advantageous to utilize a slightly higher crossover point, so the speaker has good on-axis response (and +/- 15 degree) and the beaming property helps reduce reflections at the listening position?




                  A great solution to the transition of 8" to 1" is the use of a waveguide. The waveguide makes the off axis response much more uniform with angle and that keeps the reflected sound comparable to the on axis sound so the overall tonal balance remains consistent. Hopefully the new RS28 is compatible with the Denovo SEOS-8 and we can re-do a version of Marksman.
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                  • #24
                    Originally posted by billfitzmaurice View Post
                    . . . I met with him a few times just prior to my six month vacation in beautiful Southeast Asia.
                    Enlisted or drafted to Vietnam?

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                    • #25
                      Originally posted by philthien View Post

                      To the best of my knowledge, they haven't ranked or assigned any multipliers to the variables they've found important through their empirical tests.

                      It is entirely possible, that a speaker that breaks every single rule but extends to 20-Hz, would outperform a speaker that observes every other rule but can't play below 60-Hz.

                      I keep going back to that because back in the 70's I think, Julian Hirsch mentioned a paper where they found the single greatest factor in loudspeaker acceptance in blind testing, was extended bass. This paper (I think the research was from a university) had attempted to rank what matters to people in blind testing, and bass was it.

                      So I think we need to be a little careful in treating every aspect equally.

                      How much an 8" two-way influences power response depends a lot on the design. But how much power response influences a blind listeners preferences is another matter that I don't think is in evidence?

                      In their "Audio Engineering Society Convention Paper 6190" they define an overall preference rating equation:

                      Pref. Rating= 6.04−0. 67* AAD_ON− 1. 28* LFX −0. 66* LFQ+ 4. 02* SM_ON+ 3.58* SM_SP

                      Also from the paper:

                      The variables related to the smoothness (SM) and average absolute deviation (AAD) of the on-axis curve have a combined weighting of 45% in our model. This tells us that the flatness and smoothness of the direct sound is an important factor in predicting sound quality. The next largest contributor is the smoothness of the sound power (SM_SP) weighted at 30%. The remaining two variables related to low frequency deviations contribute a combined 25% to our model (LFQ=17%, LFX=6%).

                      Here's a summary slide from on of Toole's speeches.
                      Click image for larger version

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                      Last edited by ernperkins; 03-11-2018, 11:17 AM. Reason: Readability
                      "Everything is nothing without a high sound quality." (Sure Electronics)

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                      • #26
                        Thanks for posting that, emperkins.

                        I stand corrected!

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                        • #27
                          What is the DI ?

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                          • #28
                            Originally posted by philthien View Post
                            ...a speaker that breaks every single rule but extends to 20-Hz...
                            That ignores the problem of infra-Schroeder modal response in small room acoustics, which includes domestic consumer applications. The vast majority of homes, mine included, do not have a room with architectural design optimized for use as a mastering studio. In optimizing audio playback in these compromized domestic rooms, with optimized practical placement of listener(s), the optimized practicable placement of tweeters and upper midranges (where ray tracing models apply above the trans-Schroeder frequencies) might be poor locations for woofers, as the biggest problem at lower frequencies is in the interference sum that includes the infra-Schroeder eigentones, the fundamental frequencies and low order harmonics associated with the room's modal response. A multilocation/multisource low frequency subsystem can significantly help in improving performance in double digit frequencies, and with use of a separate low frequency subsystem the mains might not contribute much in the contra and sub-contra octaves.
                            Last edited by JRT; 03-11-2018, 02:30 PM.
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                            • #29
                              Originally posted by Billet View Post
                              What is the DI ?

                              It stands for Directivity Index. They use two different directivity indices that represent the early reflections (ERDI) and sound power (SPDI). In broad terms the two indices represent the off axis response of the speaker.
                              "Everything is nothing without a high sound quality." (Sure Electronics)

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