Mk II speakers done, but Mk III in the works

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  • JonMarsh
    Mad Max Moderator
    • Aug 2000
    • 15277

    Mk II speakers done, but Mk III in the works

    Some days I feel like Bullwinkle J. Moose.

    You know, "This time for sure!"

    I've been breaking in the second set of my 8" two way project; these using the Eton 8-800 and Accuton C23 tweeter instead of the Focal woofer and MB tweeter of the first set. You do have to bed a speaker in for a while to get to it's final tonality, and fine tuning the relative level of the tweeter (other than basic measurments cofirming the design) would be pretty frustrating.

    I don't really know why this is the case; Chas Hansen used to talk about this issue with the Avalon Eclipse and Ascent; they would change their tonal character as they broke in, sometimes getting bright, sometimes getting dull, then just eventually "gelling". Maybe it's the Eton woofers, maybe it the polypropylene caps. I don't know.



    Mk II version of M8 with Eton and Accuton components


    The one shown above without grille is finished in black; the first set, and the next ones will be "honey" oak.

    The Mk II has been fairly successful- I've learned a bit, too- but it's not quite where I want it to be. The Accuton tweeters were a little bit of a disappointment, not measuring as well as their published specs, and requiring more crossover work than expected, as a result. They sound very detailed, and aren't edgy- with the right electronics. However, the matchup between the two, even using the elliptic/cauer network I dreamed up for this project, could be still a little better. It's odd to describe, some things sound really fabulous, where I'm surprised at what I hear on old CD's I'm quite familiar with, but a few times things don't quite sound right, especially if you're standing in front of them. To some extent, this is an unavoidable byproduct of the stands they're on, and issues with being off the vertical axis.

    With pecussion, piano, and standup bass, as well as complex synth lines, they're very pleasing. Occasionally on a few female vocals I detect a roughness which I'm likely to attribute to the transistion between the two drivers. The 8-800 has a first cone resonance about 1.6 kHz, so the crossover is quite steep at about 1.25 kHz, and it's a little much for the Accuton tweeter- even with what is effectively an 8th order Linkwitz-Riley network, the blend isn't as good as I would like. Yet, I'm listening to Acoustic Alchemy, just having finished a Jacque Loussier album, and both sound very good.

    The Eton woofer has a voicing that works well in the classic "Cardas" positioning, but it will never be mistaken for a "techno" style music woofer on the bottom end- in this alignment, it has a smooth, gradual roll off starting about 75- by gradual, I'm talking about being 4-6 dB down in the low 40's, with output to the mid thirties. Low bass is still there, it's just "polite". On the otherhand, close miked recordings of standup bass, such as Holly Cole, Patricia Barber, and Jacque Loussier, sound totally musical and coherent. No bloat at all; not a "ported" sound; instead, the port reduces the "congestion: compared with a sealed alignment playing near the driver's limits. This is the correct way to use a reflex; not flat anechoically, but overdamped.


    So where does the Mk III come in? Well, it's already in "test box" mode. It's got a little something "back to my roots" (the Focal Td120dx2 tweeter)



    and something brand new for me, a metal cone woofer. Everyone else is working with them, so I though, perhaps lets take a stab at it. But that brings up a point; in general, most metal cone woofers have an absolutely horrendous upper breakup mode- stab is what they do to the ears, unless you take some specific crossover measures. The most widely used series of this type are probably the SEAS magnesium/aluminum drivers, both the standard and Excel versions. However, the upper break up mode is about 15 dB over the nominal midrange level, requiring considerable care. The construction is first class, including a copper coated phase plugs, and copper rings to reduce inductance modulation and resulting distortion. Cost is also first class.

    Revel and some other manufacturers, instead of using cones with modified curvilinear profiles, like SEAS does, have adopted a concave contruction. The Hi-Vi M8a driver follows this path, and seems to have more managable breakup modes than many other types.



    The performance I've measured on the first samples I recieved is quite reasonable; the first breakup mode is at about 2.5 kHz, and the level is modest, by metal cone standards.





    With a version of the EF-LR8 crossover at 1.5 kHz, in room response (no special positioning, lot's of reflecting stuff near by, unfortunately) shows very good supression of the upper resonance- by over 35 dB.



    The predicted bottom end extension is a bit better, looking at a Unibox analysis with the measured T/S parameters, with a predicted F3 of 30 Hz.

    Of course, the final matter is how will it sound- give me a week or two, and I'll report back. Computer predictions are only good for so much.



    "This time for sure!"


    Regards,

    Jon




    Earth First!
    _______________________________
    We'll screw up the other planets later....
    Last edited by ThomasW; 09 October 2004, 22:10 Saturday.
    the AudioWorx
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    In Development...
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    Resistance is not futile, it is Volts divided by Amperes...
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  • Lex
    Moderator Emeritus
    • Apr 2001
    • 27461

    #2
    Nice job on the speakers though, however they sound. Anxious to see those honey oak ones later on!



    Lex
    reply 2000 in Mission Possible! Wow
    Doug
    "I'm out there Jerry, and I'm loving every minute of it!" - Kramer

    Comment

    • JonMarsh
      Mad Max Moderator
      • Aug 2000
      • 15277

      #3
      Thanks, Lex.

      The next set should be done pretty soon- basic cabinets are finished- but evaluating them will *also* require some break-in time for final crossover tweaking.

      It's not at all that this set sound's "bad"; often they make me look up and listen in surprise on what was a familiar CD, to hear something with more clarity and focus, and obviously more "right". It's just that, well, perhaps I'm being hyper critcial here, but there's a little last something that needs to be fixed or improved in the upper mids or presence range. (earlier, while they were breaking in, I thought there was more than a little to be changed, but time, plus the new DAC, perhaps, let the sound really "gell" for me).

      The interesting thing will be going back to my big babies (the X1's) and applying what I've been learning to them. (they're sulking off in a corner right now! ) Then it will be time for the third generation of crossovers- but I'm also probably going to upgrade from the Eton 370 driver to the Eton 7-360. So it will be a little while before I'll be able to foot that expense. Right now, fee coins are going into the semi's for a amp mod I've been working on- something ThomasW is beating me up about!

      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

      • JonMarsh
        Mad Max Moderator
        • Aug 2000
        • 15277

        #4
        For ThomasW and others that inquired about the updated cabinet design, see below for a rough idea.




        This perspective doesn't clearly show changes to the back panel, where an addditinal beveled panel is used for reinforcement and to mount the port (from the backside) further out, so that the entry is farther from an enclosure wall. Tuning is about 30 Hz. The M8 HiVi driver has a higher Xmax than the previously used drivers.

        Also, some interior bracing details are changed, especially around the front panel- most of the front panel will have 3/4" oak behind it in a layer, as was done previously for the tweeter. Again, the tweeter cutout will be completely baffled, so that there is no pressure wave to modulate the tweeter chassis.

        Regards,

        Jon




        Earth First!
        _______________________________
        We'll screw up the other planets later....
        Last edited by ThomasW; 09 October 2004, 22:05 Saturday.
        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

        • David Meek
          Moderator Emeritus
          • Aug 2000
          • 8938

          #5
          Jon, what CAD package are you using? AutoCad, TurboCad?

          BTW those metal woofers are pretty sexy!

          - David -
          .

          David - Trigger-happy HTGuide Admin

          Comment

          • JonMarsh
            Mad Max Moderator
            • Aug 2000
            • 15277

            #6
            Hi David,

            I'm an old time AutoCAD user, all the way back to version 1.4. (think 1983!). Currently at AutoCAD 2000; which is a pretty nice piece of software compared with the early versions!

            Actually, I'm pretty hopeful about the HiVi M8z drivers; the cone is better damped, and they definitely are sexy looking!

            I've got another project in mind for them; dual 8's, a mid and a tweeter. Possibly with a 6" mid driver, or some Accuton 2" inverted dome mids that I have. It might get built in a modified Woodstyle tower enclosure, or something completely from scratch. But Tom's also got me thinking about some possible line array projects, so who knows what will be next! The M8 described here and in other posts should be a great surround speaker, too, though; after I replace what's in my bedroom, that might be the next thing I do.

            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

            • David Meek
              Moderator Emeritus
              • Aug 2000
              • 8938

              #7
              That's cool! In '83 I was cutting my teeth on an old Intergraph mapping system called WMS. It eventually mutated into one of the modules of MicroStation, so that's where my CAD path led me.

              I'm really getting "itchy" to do a set of DIY speakers, but have to finish up my current cabinetry project - I'm building an oak cabinet/storage system for our best friend's 65" Mits 16:9 and components. Once that's complete, I'd like to build a pair of monitors as the starting point for a dedicated music system. Oh well, one of these days. . .

              - David -
              .

              David - Trigger-happy HTGuide Admin

              Comment

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