Any Designs using smaller ribbons?

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  • Ted White
    Junior Member
    • Sep 2002
    • 2

    Any Designs using smaller ribbons?

    Hello, what a great forum you guys have here. Just a quick question as to whether anyone has successfully used smaller ribbon tweeters in their speakers (like Raven sizes).

    Thanks!

    Ted
  • Hank
    Super Senior Member
    • Jul 2002
    • 1345

    #2
    Well, Zalytron has some kits with Raven tweets. Those Ravens are expensive, and of course using one or two does a line source not make.

    Comment

    • JonMarsh
      Mad Max Moderator
      • Aug 2000
      • 15270

      #3
      There is one main and serioius problem with smaller ribbons in a speaker design- dispersion, or lack of it.

      I have experience with the Decca ribbon in an HGD system back in the 70's- it worked OK as a super tweeter only because the size of the speakers and room dictated that no one was listening closer than about 15 feet. Then, it's limited vertical dispersion window has time to spread out.

      Raven's are gorgeous devices, but they will have very narrow vertical dispersion also. If you listening situation is constrained so that you know you have a narrow vertical window requirement (say, a recording studio where the listening position is tightly controlled), then I think they'll work great.

      Or, if you can afford to stack a few of them, then they may work well in a home environment, though I have reservations about going from a line source in the region above 5 kHz to a point source below that point. The fall off with distance is quite different; you'd be able to get a good blend at one distance, but not such an accurate balance at others.

      For that reason I tend to favor high performance dome tweeters in the home environment- like the Focal TC120 or at more moderate cost, the Vifa XT25. Many like the Excel and Scanspeak tweeters also. The real challenge is selecting the lower frequency drivers to be free of cone modes in the pass band, and managing the transistion to the tweeter so that both on axis and off axis response are smooth.

      Ideally, controlled dispersion should be the word of the day.

      An interesting "low dollar" possiblity might be combining Neo3 and two Neo8 in an MTM array; used with woofers, the most logical configuration might be WMTMW. The trick would be how low you could cross over from the Neo3, and the Neo8, so that you don't have line source behavior, but are free from comb filtering in the driver passband.

      Somethign to think about, but I've already got too many something's to think about!

      What's your listening situation, Ted? Would a narrow vertical window work for you? I don't use speakers just sitting down; I like the response to be fairly similar sitting down and standing up at a distance of 10-12 feet or more, and this implies a vertical window going from 3 feet to almost 6 feet; about a +/-20 degree window, unless you design for an upward lobe, or set the ribbon at a height about half way between the seated and standing positions; then narrow dispersion might do- +/- 10 to 15 degrees? But 3" high ribbons don't have that much dispersion at 15 kHz, anymore than three inch diameter dome midranges would.


      Best regards,

      Jon

      Jon




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      Comment

      • Dennis H
        Ultra Senior Member
        • Aug 2002
        • 3791

        #4
        Jon, what's your take on Linkwitz's test of the Vifa? Do you think his bad non-linear distortion results were because of the low test frequency? I think he was using a 1.6KHz tone modulated with a 160Hz tone. Might his results indicate a higher crossover point is required with that driver? The low stored energy part sounds good.



        "Addendum: I recently compared two Vifa XT25TG-30 to the Seas T25CF002-06 and Scanspeak D2905/9700 tweeters. Non-linear 2nd order distortion products of the XT25 were by far the worst of the three, 3rd order products were ok and higher order products were very low. Both units performed well on stored energy, better than the T25CF, which was slightly ahead of the 9700. Overall not a bad performance, but not quite the same as the Seas and Scanspeak, in my ranking, especially when the higher directivity of the XT25 is considered."

        Comment

        • JonMarsh
          Mad Max Moderator
          • Aug 2000
          • 15270

          #5
          Dennis,

          Linkwitz raises valid points, but my choice and usage was dictated by a few points:

          1. 2nd order is relatively high (this is the least offensive sonically, sort of that "vacuum tube" sound), 3rd oder and higher were quite low (these contribute to an edgy or "hard" sound.

          2. Directivity above 12-14 kHz is a problem- take a few points off for the XT-25

          3. Overall frequency response from 1 kHz to 15 kHz on axis is very flat - rear chamber venting design is quite good.

          4. Impedance is low- it's really a 3 ohm tweeter. I wouldn't run it on "weak" amplifiers, though in most cases the energy high up is small enough it won't present a problem.


          In practice, the XT has works the best of any tweeter I've found that is still available for DIY for a "budget" two way system- particularly with a steep crossover network (my filter emulates an 8th order L-R for the 1st 50 dB of attenuation). I'd rather be using the MBTTR-1, but it's no longer available for DIY. Other tweeters I've investigated and built systems with (M8 MkII, for example) include the Accuton C23-6. The latter doesn't seem to be as flat as it's published curves would lead you to believe, and it has HF issues because of the protective grille.

          If you can cross over higher (1.8 to 2 kHz) by using a more expensive driver (SEAS EXCEL 7", for example), then I go with the Focal Tc120dx2. This is the upgrade I'll be implementing on my X1 klones, probably early next year. (They already have the Focals, but are using Eton's for midwoofers).

          But to get comparable total Sd of a single 8.5" driver requires two Excels - we're talking about $340 of woofers, and $80 of tweeter per cabinet. This would be a superior solution to a HiVi M8a and Vifa XT- but the latter will only set you back $150 per cabinet, not $420. There's a reason the SEAS Thor system costs as much as it does...

          The XT25 is being used by a lot of people because it sounds good (less "Hi-Fi" than most tweeters), at a reasonable price.

          What I wish I could get is something built like the Excel Millenium but with the titanium dome from the MBttr-1.

          Regards,

          Jon




          Earth First!
          _______________________________
          We'll screw up the other planets later....
          the AudioWorx
          Natalie P
          M8ta
          Modula Neo DCC
          Modula MT XE
          Modula Xtreme
          Isiris
          Wavecor Ardent

          SMJ
          Minerva Monitor
          Calliope
          Ardent D

          In Development...
          Isiris Mk II updates- in final test stage!
          Obi-Wan
          Saint-Saëns Symphonique/AKA SMJ-40
          Modula PWB
          Calliope CC Supreme
          Natalie P Ultra
          Natalie P Supreme
          Janus BP1 Sub


          Resistance is not futile, it is Volts divided by Amperes...
          Just ask Mr. Ohm....

          Comment

          • Dennis H
            Ultra Senior Member
            • Aug 2002
            • 3791

            #6
            Thanks Jon. Informative as always.

            Comment

            • Ted White
              Junior Member
              • Sep 2002
              • 2

              #7
              Jon,

              Thanks for the reply. The listening environment id a home theater. Two rows of seats with the back row elevated, so overall dispersion is an issue.

              It's not that I wanted to use Ravens, per say, but smaller ribbons like Ravens. It seems that others have ribbons now (GR Research).

              So in an environment like this I would not be able to use ribbons as effectively as dome tweeters?

              Thanks!

              Ted

              Comment

              • JonMarsh
                Mad Max Moderator
                • Aug 2000
                • 15270

                #8
                To do so you'd have to investigate the dispersion characteristics pretty carefully. I haven't seen very comprehensive data published to date for most ribbons- certainly not for vertical dispersion.

                A relatively short ribbon- 3" or so- might be able to do the trick, with controlled dispersion at a specific listening range. Also, as I mention, there are monitor style loudspeakers using ribbons in the 5-6" height region, but at this point you have the vertical dispersion vs. frequency characteristic similar to a 6" midwoofer. Which means a pretty narrow vertical window over 5 kHz. It's almost like a flashlight, for all practical purpose, as regards vertical dispersion. Not to say it's not doable for the right conditions, but it's also easy to wind up with something not very satisfying if it's not carefully planned. Plus, the farfield reverberant sound suffers somewhat because there's a vary different balance between response on axis and response off axis. For this reason I tend to favor either consistent point source technology (which can be variable size- but related to the wavelength - a classic is an WMTMW which decreases in radiating size with increasing frequency), or a wide range line source- such as Mangeplanars, ESL's, or dynamic systems like the line array's discussed in other threads here. It's my experience that you get more overall consistent and pleasing results with one approach or the other, but not trying to mix them partially.

                That said, I would never discourage experimentation and innovation; I'm just trying to be open about some possible pitfalls.

                Best regards,

                Jon




                Earth First!
                _______________________________
                We'll screw up the other planets later....
                the AudioWorx
                Natalie P
                M8ta
                Modula Neo DCC
                Modula MT XE
                Modula Xtreme
                Isiris
                Wavecor Ardent

                SMJ
                Minerva Monitor
                Calliope
                Ardent D

                In Development...
                Isiris Mk II updates- in final test stage!
                Obi-Wan
                Saint-Saëns Symphonique/AKA SMJ-40
                Modula PWB
                Calliope CC Supreme
                Natalie P Ultra
                Natalie P Supreme
                Janus BP1 Sub


                Resistance is not futile, it is Volts divided by Amperes...
                Just ask Mr. Ohm....

                Comment

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