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  • #46
    Originally posted by johnk... View Post
    You aren't going to get much modulation distortion in the midrange with a woofer crossover at 150 Hz.
    With the second harmonic of 150Hz being 300Hz it doesn't take a lot for a subwoofer crossed that high to be directionally locatable. Crossing at 80Hz keeps the highest second harmonic at 160Hz, so it won't be directionally locatable at moderate levels. It will if the driver is pushed to xmax, and THD jumps, but that's a different concern. One doesn't see that often in home settings, but it's very common in pro-sound, especially with DJs who play too loud with subs that aren't up to the job.

    www.billfitzmaurice.com
    www.billfitzmaurice.info/forum

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    • #47
      Originally posted by billfitzmaurice View Post
      With the second harmonic of 150Hz being 300Hz it doesn't take a lot for a subwoofer crossed that high to be directionally locatable. Crossing at 80Hz keeps the highest second harmonic at 160Hz, so it won't be directionally locatable at moderate levels. It will if the driver is pushed to xmax, and THD jumps, but that's a different concern. One doesn't see that often in home settings, but it's very common in pro-sound, especially with DJs who play too loud with subs that aren't up to the job.
      But a 150 Hz you aren't going to get large excursion even at high SPL for any decent sized woofer, monopole or dipole. In fact, for many open baffle woofers 150Hz would be near the dipole = monopole frequency and the dipole wouldn't produce much more distortion than a monopole woofer. For example, a single, smallish 10" XLS woofer mounted centered on a 2' diameter circular baffle could nominally produce 126.6 dB at max linear excursion. 110 dB would requires only 2mm excursion. Change that to a 15" woofer..... You would have pretty much the same level of distortion as a monopole woofer at 150 Hz. Now, the caveat is that these are single tone considerations. There may be instances with distortion is more significant in a multi tone situation.


      Still don't know what people consider loud, but I have a couple of 10" XLS monopole woofer for my HT system and at the levels I play there is no way distortion, or any other artifact, is signaling their location. Even at 2% distortion the distortion signal would be down more that 30 dB which would be pretty much masked by the fundamental and other content from the main speakers. But in a decent design all these things should be considered.

      DJ's? Who cares. Not hifi.

      John k.... Music and Design NaO dsp Dipole Loudspeakers.

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      • #48
        If anyone is interested in listening to a dipole system and can make it, I will be bringing my latest creation to the Meniscus Audio DIY event, September 20/21, in Grand Rapids Michigan.

        This is an attempt at a 3-way "no baffle" low-cost dipole system. Only the woofer section will have any sort of baffle (it will be an H or M frame) using one or two 15" woofers per side. There is a 15" nude midrange (you read that right), and a back-to-back dome dipole tweeter rounds out the top end. The crossover is done via my usual software DSP (via LADSPA under Linux). It's a very different take on "open baffle".
        Charlie's Audio Pages: http://audio.claub.net

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        • #49
          Originally posted by dlr View Post
          As long as you can have them positioned far enough from the walls, no reason why dipole can't be good in a small room. I've found dipole bass to be better than closed or ported systems in any situation. This is equalized dipole, not passive large, open baffle systems, that is.

          dlr
          Hey man, I have huge respect for your analytic capabilities and speaker analysis chops. I've heard good things about dipole bass from several people, Can you quantify that impression scientifically? Is it group delay, room modes, T60, room gain?

          I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
          "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

          High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
          SB13/Vifa BC25SC06 MTM DCR Galeons-SB13-MTM
          My Voxel min sub Yet-another-Voxel-build

          Tangband W6-sub

          Comment


          • #50
            Originally posted by charlielaub View Post
            If anyone is interested in listening to a dipole system and can make it, I will be bringing my latest creation to the Meniscus Audio DIY event, September 20/21, in Grand Rapids Michigan.

            This is an attempt at a 3-way "no baffle" low-cost dipole system. Only the woofer section will have any sort of baffle (it will be an H or M frame) using one or two 15" woofers per side. There is a 15" nude midrange (you read that right), and a back-to-back dome dipole tweeter rounds out the top end. The crossover is done via my usual software DSP (via LADSPA under Linux). It's a very different take on "open baffle".
            Far out! Wish I could be there.

            I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
            "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

            High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
            SB13/Vifa BC25SC06 MTM DCR Galeons-SB13-MTM
            My Voxel min sub Yet-another-Voxel-build

            Tangband W6-sub

            Comment


            • #51
              Click image for larger version  Name:	 Views:	1 Size:	43.0 KB ID:	1419298Click image for larger version  Name:	 Views:	1 Size:	407.8 KB ID:	1419299Click image for larger version  Name:	 Views:	1 Size:	36.7 KB ID:	1419297

              Some of the most accurate, deep bass I have heard are from my OB speakers. Sure size and placement is an issue but it's an issue with most speakers.
              20hz to 40khz. 15" woofers, 15" midrange and cultured marble 15" AMT per speaker.
              Last edited by Ossidian; 08-13-2019, 07:38 PM.

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              • #52
                Originally posted by donradick View Post
                Hey man, I have huge respect for your analytic capabilities and speaker analysis chops. I've heard good things about dipole bass from several people, Can you quantify that impression scientifically? Is it group delay, room modes, T60, room gain?
                Quantify? No, I don't do extensive room response measurements. It's my empirical experience with dipoles compared to any other systems I've had, commercial and my own designs. I would say it's primarily reduced room modes. I had dipole hybrid ribbons (commercial system) for years in which the closed box bass was the weak part (not in this house, however). My previous designs were closed box or passive radiator bass systems. All suffered from more severe room modes.

                Dipole midrange also has, IMO, a more "open" sound. The off-axis is also reduced as well, so If one were to measure nearby side wall reflections, I would expect smaller reflection magnitudes. But I haven't measured this. The primary concern is the rear wall.

                This relates to the in-room power response being 4.8 db lower than a monopole at low frequencies (see John K. page here). As an aside, I just noticed that John is evidently closing down his web site. It will be sorely missed when we're in these discussions.

                Certainly not group delay vs. closed box, but vs. reflex, yes.

                My system is in my basement, old home, low ceiling, but surprisingly smooth response if I move around whereas my previous closed/PR systems had noticeable changes.

                I'm planning on putting my old 3-way closed system back together and comparing the passive crossover with a DSP version (Ultimate Equalizer) to see how much influence the passive woofer lowpass may have been an issue.

                dlr
                WinPCD - Windows .NET Passive Crossover Designer

                Dave's Speaker Pages

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                • #53
                  Ossidian -- wow, looks awesome, bet it sounds just as good.
                  dlr - thanks bud. That's what I hear from every OB bass head.

                  I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
                  "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

                  High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
                  SB13/Vifa BC25SC06 MTM DCR Galeons-SB13-MTM
                  My Voxel min sub Yet-another-Voxel-build

                  Tangband W6-sub

                  Comment

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